March 2025 - Linux-stable-mirror

FAILED: patch "[PATCH] KVM: x86: Snapshot the host's DEBUGCTL in common x86" failed to apply to 6.1-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 6.1-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y git checkout FETCH_HEAD git cherry-pick -x fb71c795935652fa20eaf9517ca9547f5af99a76 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2025031034-latitude-stinking-09c1@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ From fb71c795935652fa20eaf9517ca9547f5af99a76 Mon Sep 17 00:00:00 2001 From: Sean Christopherson <seanjc(a)google.com> Date: Thu, 27 Feb 2025 14:24:08 -0800 Subject: [PATCH] KVM: x86: Snapshot the host's DEBUGCTL in common x86 Move KVM's snapshot of DEBUGCTL to kvm_vcpu_arch and take the snapshot in common x86, so that SVM can also use the snapshot. Opportunistically change the field to a u64. While bits 63:32 are reserved on AMD, not mentioned at all in Intel's SDM, and managed as an "unsigned long" by the kernel, DEBUGCTL is an MSR and therefore a 64-bit value. Reviewed-by: Xiaoyao Li <xiaoyao.li(a)intel.com> Cc: stable(a)vger.kernel.org Reviewed-and-tested-by: Ravi Bangoria <ravi.bangoria(a)amd.com> Link: https://lore.kernel.org/r/20250227222411.3490595-4-seanjc@google.com Signed-off-by: Sean Christopherson <seanjc(a)google.com> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 0b7af5902ff7..32ae3aa50c7e 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -780,6 +780,7 @@ struct kvm_vcpu_arch { u32 pkru; u32 hflags; u64 efer; + u64 host_debugctl; u64 apic_base; struct kvm_lapic *apic; /* kernel irqchip context */ bool load_eoi_exitmap_pending; diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 6c56d5235f0f..3b92f893b239 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -1514,16 +1514,12 @@ void vmx_vcpu_load_vmcs(struct kvm_vcpu *vcpu, int cpu, */ void vmx_vcpu_load(struct kvm_vcpu *vcpu, int cpu) { - struct vcpu_vmx *vmx = to_vmx(vcpu); - if (vcpu->scheduled_out && !kvm_pause_in_guest(vcpu->kvm)) shrink_ple_window(vcpu); vmx_vcpu_load_vmcs(vcpu, cpu, NULL); vmx_vcpu_pi_load(vcpu, cpu); - - vmx->host_debugctlmsr = get_debugctlmsr(); } void vmx_vcpu_put(struct kvm_vcpu *vcpu) @@ -7458,8 +7454,8 @@ fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu, bool force_immediate_exit) } /* MSR_IA32_DEBUGCTLMSR is zeroed on vmexit. Restore it if needed */ - if (vmx->host_debugctlmsr) - update_debugctlmsr(vmx->host_debugctlmsr); + if (vcpu->arch.host_debugctl) + update_debugctlmsr(vcpu->arch.host_debugctl); #ifndef CONFIG_X86_64 /* diff --git a/arch/x86/kvm/vmx/vmx.h b/arch/x86/kvm/vmx/vmx.h index 8b111ce1087c..951e44dc9d0e 100644 --- a/arch/x86/kvm/vmx/vmx.h +++ b/arch/x86/kvm/vmx/vmx.h @@ -340,8 +340,6 @@ struct vcpu_vmx { /* apic deadline value in host tsc */ u64 hv_deadline_tsc; - unsigned long host_debugctlmsr; - /* * Only bits masked by msr_ia32_feature_control_valid_bits can be set in * msr_ia32_feature_control. FEAT_CTL_LOCKED is always included diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 02159c967d29..5c6fd0edc41f 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -4968,6 +4968,7 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu) /* Save host pkru register if supported */ vcpu->arch.host_pkru = read_pkru(); + vcpu->arch.host_debugctl = get_debugctlmsr(); /* Apply any externally detected TSC adjustments (due to suspend) */ if (unlikely(vcpu->arch.tsc_offset_adjustment)) {

6 months, 1 week

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FAILED: patch "[PATCH] KVM: SVM: Set RFLAGS.IF=1 in C code, to get VMRUN out of the" failed to apply to 5.10-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 5.10-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.10.y git checkout FETCH_HEAD git cherry-pick -x be45bc4eff33d9a7dae84a2150f242a91a617402 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2025031025-hurry-muster-0e93@gregkh' --subject-prefix 'PATCH 5.10.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ From be45bc4eff33d9a7dae84a2150f242a91a617402 Mon Sep 17 00:00:00 2001 From: Sean Christopherson <seanjc(a)google.com> Date: Mon, 24 Feb 2025 08:54:41 -0800 Subject: [PATCH] KVM: SVM: Set RFLAGS.IF=1 in C code, to get VMRUN out of the STI shadow Enable/disable local IRQs, i.e. set/clear RFLAGS.IF, in the common svm_vcpu_enter_exit() just after/before guest_state_{enter,exit}_irqoff() so that VMRUN is not executed in an STI shadow. AMD CPUs have a quirk (some would say "bug"), where the STI shadow bleeds into the guest's intr_state field if a #VMEXIT occurs during injection of an event, i.e. if the VMRUN doesn't complete before the subsequent #VMEXIT. The spurious "interrupts masked" state is relatively benign, as it only occurs during event injection and is transient. Because KVM is already injecting an event, the guest can't be in HLT, and if KVM is querying IRQ blocking for injection, then KVM would need to force an immediate exit anyways since injecting multiple events is impossible. However, because KVM copies int_state verbatim from vmcb02 to vmcb12, the spurious STI shadow is visible to L1 when running a nested VM, which can trip sanity checks, e.g. in VMware's VMM. Hoist the STI+CLI all the way to C code, as the aforementioned calls to guest_state_{enter,exit}_irqoff() already inform lockdep that IRQs are enabled/disabled, and taking a fault on VMRUN with RFLAGS.IF=1 is already possible. I.e. if there's kernel code that is confused by running with RFLAGS.IF=1, then it's already a problem. In practice, since GIF=0 also blocks NMIs, the only change in exposure to non-KVM code (relative to surrounding VMRUN with STI+CLI) is exception handling code, and except for the kvm_rebooting=1 case, all exception in the core VM-Enter/VM-Exit path are fatal. Use the "raw" variants to enable/disable IRQs to avoid tracing in the "no instrumentation" code; the guest state helpers also take care of tracing IRQ state. Oppurtunstically document why KVM needs to do STI in the first place. Reported-by: Doug Covelli <doug.covelli(a)broadcom.com> Closes: https://lore.kernel.org/all/CADH9ctBs1YPmE4aCfGPNBwA10cA8RuAk2gO7542DjMZgs4… Fixes: f14eec0a3203 ("KVM: SVM: move more vmentry code to assembly") Cc: stable(a)vger.kernel.org Reviewed-by: Jim Mattson <jmattson(a)google.com> Link: https://lore.kernel.org/r/20250224165442.2338294-2-seanjc@google.com Signed-off-by: Sean Christopherson <seanjc(a)google.com> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index a713c803a3a3..0d299f3f921e 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -4189,6 +4189,18 @@ static noinstr void svm_vcpu_enter_exit(struct kvm_vcpu *vcpu, bool spec_ctrl_in guest_state_enter_irqoff(); + /* + * Set RFLAGS.IF prior to VMRUN, as the host's RFLAGS.IF at the time of + * VMRUN controls whether or not physical IRQs are masked (KVM always + * runs with V_INTR_MASKING_MASK). Toggle RFLAGS.IF here to avoid the + * temptation to do STI+VMRUN+CLI, as AMD CPUs bleed the STI shadow + * into guest state if delivery of an event during VMRUN triggers a + * #VMEXIT, and the guest_state transitions already tell lockdep that + * IRQs are being enabled/disabled. Note! GIF=0 for the entirety of + * this path, so IRQs aren't actually unmasked while running host code. + */ + raw_local_irq_enable(); + amd_clear_divider(); if (sev_es_guest(vcpu->kvm)) @@ -4197,6 +4209,8 @@ static noinstr void svm_vcpu_enter_exit(struct kvm_vcpu *vcpu, bool spec_ctrl_in else __svm_vcpu_run(svm, spec_ctrl_intercepted); + raw_local_irq_disable(); + guest_state_exit_irqoff(); } diff --git a/arch/x86/kvm/svm/vmenter.S b/arch/x86/kvm/svm/vmenter.S index 2ed80aea3bb1..0c61153b275f 100644 --- a/arch/x86/kvm/svm/vmenter.S +++ b/arch/x86/kvm/svm/vmenter.S @@ -170,12 +170,8 @@ SYM_FUNC_START(__svm_vcpu_run) mov VCPU_RDI(%_ASM_DI), %_ASM_DI /* Enter guest mode */ - sti - 3: vmrun %_ASM_AX 4: - cli - /* Pop @svm to RAX while it's the only available register. */ pop %_ASM_AX @@ -340,12 +336,8 @@ SYM_FUNC_START(__svm_sev_es_vcpu_run) mov KVM_VMCB_pa(%rax), %rax /* Enter guest mode */ - sti - 1: vmrun %rax - -2: cli - +2: /* IMPORTANT: Stuff the RSB immediately after VM-Exit, before RET! */ FILL_RETURN_BUFFER %rax, RSB_CLEAR_LOOPS, X86_FEATURE_RSB_VMEXIT

6 months, 1 week

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FAILED: patch "[PATCH] KVM: SVM: Set RFLAGS.IF=1 in C code, to get VMRUN out of the" failed to apply to 5.15-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 5.15-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.15.y git checkout FETCH_HEAD git cherry-pick -x be45bc4eff33d9a7dae84a2150f242a91a617402 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2025031024-bootleg-parkway-393c@gregkh' --subject-prefix 'PATCH 5.15.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ From be45bc4eff33d9a7dae84a2150f242a91a617402 Mon Sep 17 00:00:00 2001 From: Sean Christopherson <seanjc(a)google.com> Date: Mon, 24 Feb 2025 08:54:41 -0800 Subject: [PATCH] KVM: SVM: Set RFLAGS.IF=1 in C code, to get VMRUN out of the STI shadow Enable/disable local IRQs, i.e. set/clear RFLAGS.IF, in the common svm_vcpu_enter_exit() just after/before guest_state_{enter,exit}_irqoff() so that VMRUN is not executed in an STI shadow. AMD CPUs have a quirk (some would say "bug"), where the STI shadow bleeds into the guest's intr_state field if a #VMEXIT occurs during injection of an event, i.e. if the VMRUN doesn't complete before the subsequent #VMEXIT. The spurious "interrupts masked" state is relatively benign, as it only occurs during event injection and is transient. Because KVM is already injecting an event, the guest can't be in HLT, and if KVM is querying IRQ blocking for injection, then KVM would need to force an immediate exit anyways since injecting multiple events is impossible. However, because KVM copies int_state verbatim from vmcb02 to vmcb12, the spurious STI shadow is visible to L1 when running a nested VM, which can trip sanity checks, e.g. in VMware's VMM. Hoist the STI+CLI all the way to C code, as the aforementioned calls to guest_state_{enter,exit}_irqoff() already inform lockdep that IRQs are enabled/disabled, and taking a fault on VMRUN with RFLAGS.IF=1 is already possible. I.e. if there's kernel code that is confused by running with RFLAGS.IF=1, then it's already a problem. In practice, since GIF=0 also blocks NMIs, the only change in exposure to non-KVM code (relative to surrounding VMRUN with STI+CLI) is exception handling code, and except for the kvm_rebooting=1 case, all exception in the core VM-Enter/VM-Exit path are fatal. Use the "raw" variants to enable/disable IRQs to avoid tracing in the "no instrumentation" code; the guest state helpers also take care of tracing IRQ state. Oppurtunstically document why KVM needs to do STI in the first place. Reported-by: Doug Covelli <doug.covelli(a)broadcom.com> Closes: https://lore.kernel.org/all/CADH9ctBs1YPmE4aCfGPNBwA10cA8RuAk2gO7542DjMZgs4… Fixes: f14eec0a3203 ("KVM: SVM: move more vmentry code to assembly") Cc: stable(a)vger.kernel.org Reviewed-by: Jim Mattson <jmattson(a)google.com> Link: https://lore.kernel.org/r/20250224165442.2338294-2-seanjc@google.com Signed-off-by: Sean Christopherson <seanjc(a)google.com> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index a713c803a3a3..0d299f3f921e 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -4189,6 +4189,18 @@ static noinstr void svm_vcpu_enter_exit(struct kvm_vcpu *vcpu, bool spec_ctrl_in guest_state_enter_irqoff(); + /* + * Set RFLAGS.IF prior to VMRUN, as the host's RFLAGS.IF at the time of + * VMRUN controls whether or not physical IRQs are masked (KVM always + * runs with V_INTR_MASKING_MASK). Toggle RFLAGS.IF here to avoid the + * temptation to do STI+VMRUN+CLI, as AMD CPUs bleed the STI shadow + * into guest state if delivery of an event during VMRUN triggers a + * #VMEXIT, and the guest_state transitions already tell lockdep that + * IRQs are being enabled/disabled. Note! GIF=0 for the entirety of + * this path, so IRQs aren't actually unmasked while running host code. + */ + raw_local_irq_enable(); + amd_clear_divider(); if (sev_es_guest(vcpu->kvm)) @@ -4197,6 +4209,8 @@ static noinstr void svm_vcpu_enter_exit(struct kvm_vcpu *vcpu, bool spec_ctrl_in else __svm_vcpu_run(svm, spec_ctrl_intercepted); + raw_local_irq_disable(); + guest_state_exit_irqoff(); } diff --git a/arch/x86/kvm/svm/vmenter.S b/arch/x86/kvm/svm/vmenter.S index 2ed80aea3bb1..0c61153b275f 100644 --- a/arch/x86/kvm/svm/vmenter.S +++ b/arch/x86/kvm/svm/vmenter.S @@ -170,12 +170,8 @@ SYM_FUNC_START(__svm_vcpu_run) mov VCPU_RDI(%_ASM_DI), %_ASM_DI /* Enter guest mode */ - sti - 3: vmrun %_ASM_AX 4: - cli - /* Pop @svm to RAX while it's the only available register. */ pop %_ASM_AX @@ -340,12 +336,8 @@ SYM_FUNC_START(__svm_sev_es_vcpu_run) mov KVM_VMCB_pa(%rax), %rax /* Enter guest mode */ - sti - 1: vmrun %rax - -2: cli - +2: /* IMPORTANT: Stuff the RSB immediately after VM-Exit, before RET! */ FILL_RETURN_BUFFER %rax, RSB_CLEAR_LOOPS, X86_FEATURE_RSB_VMEXIT

6 months, 1 week

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FAILED: patch "[PATCH] KVM: SVM: Set RFLAGS.IF=1 in C code, to get VMRUN out of the" failed to apply to 6.1-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 6.1-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.1.y git checkout FETCH_HEAD git cherry-pick -x be45bc4eff33d9a7dae84a2150f242a91a617402 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2025031023-dodge-ungodly-172a@gregkh' --subject-prefix 'PATCH 6.1.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ From be45bc4eff33d9a7dae84a2150f242a91a617402 Mon Sep 17 00:00:00 2001 From: Sean Christopherson <seanjc(a)google.com> Date: Mon, 24 Feb 2025 08:54:41 -0800 Subject: [PATCH] KVM: SVM: Set RFLAGS.IF=1 in C code, to get VMRUN out of the STI shadow Enable/disable local IRQs, i.e. set/clear RFLAGS.IF, in the common svm_vcpu_enter_exit() just after/before guest_state_{enter,exit}_irqoff() so that VMRUN is not executed in an STI shadow. AMD CPUs have a quirk (some would say "bug"), where the STI shadow bleeds into the guest's intr_state field if a #VMEXIT occurs during injection of an event, i.e. if the VMRUN doesn't complete before the subsequent #VMEXIT. The spurious "interrupts masked" state is relatively benign, as it only occurs during event injection and is transient. Because KVM is already injecting an event, the guest can't be in HLT, and if KVM is querying IRQ blocking for injection, then KVM would need to force an immediate exit anyways since injecting multiple events is impossible. However, because KVM copies int_state verbatim from vmcb02 to vmcb12, the spurious STI shadow is visible to L1 when running a nested VM, which can trip sanity checks, e.g. in VMware's VMM. Hoist the STI+CLI all the way to C code, as the aforementioned calls to guest_state_{enter,exit}_irqoff() already inform lockdep that IRQs are enabled/disabled, and taking a fault on VMRUN with RFLAGS.IF=1 is already possible. I.e. if there's kernel code that is confused by running with RFLAGS.IF=1, then it's already a problem. In practice, since GIF=0 also blocks NMIs, the only change in exposure to non-KVM code (relative to surrounding VMRUN with STI+CLI) is exception handling code, and except for the kvm_rebooting=1 case, all exception in the core VM-Enter/VM-Exit path are fatal. Use the "raw" variants to enable/disable IRQs to avoid tracing in the "no instrumentation" code; the guest state helpers also take care of tracing IRQ state. Oppurtunstically document why KVM needs to do STI in the first place. Reported-by: Doug Covelli <doug.covelli(a)broadcom.com> Closes: https://lore.kernel.org/all/CADH9ctBs1YPmE4aCfGPNBwA10cA8RuAk2gO7542DjMZgs4… Fixes: f14eec0a3203 ("KVM: SVM: move more vmentry code to assembly") Cc: stable(a)vger.kernel.org Reviewed-by: Jim Mattson <jmattson(a)google.com> Link: https://lore.kernel.org/r/20250224165442.2338294-2-seanjc@google.com Signed-off-by: Sean Christopherson <seanjc(a)google.com> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index a713c803a3a3..0d299f3f921e 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -4189,6 +4189,18 @@ static noinstr void svm_vcpu_enter_exit(struct kvm_vcpu *vcpu, bool spec_ctrl_in guest_state_enter_irqoff(); + /* + * Set RFLAGS.IF prior to VMRUN, as the host's RFLAGS.IF at the time of + * VMRUN controls whether or not physical IRQs are masked (KVM always + * runs with V_INTR_MASKING_MASK). Toggle RFLAGS.IF here to avoid the + * temptation to do STI+VMRUN+CLI, as AMD CPUs bleed the STI shadow + * into guest state if delivery of an event during VMRUN triggers a + * #VMEXIT, and the guest_state transitions already tell lockdep that + * IRQs are being enabled/disabled. Note! GIF=0 for the entirety of + * this path, so IRQs aren't actually unmasked while running host code. + */ + raw_local_irq_enable(); + amd_clear_divider(); if (sev_es_guest(vcpu->kvm)) @@ -4197,6 +4209,8 @@ static noinstr void svm_vcpu_enter_exit(struct kvm_vcpu *vcpu, bool spec_ctrl_in else __svm_vcpu_run(svm, spec_ctrl_intercepted); + raw_local_irq_disable(); + guest_state_exit_irqoff(); } diff --git a/arch/x86/kvm/svm/vmenter.S b/arch/x86/kvm/svm/vmenter.S index 2ed80aea3bb1..0c61153b275f 100644 --- a/arch/x86/kvm/svm/vmenter.S +++ b/arch/x86/kvm/svm/vmenter.S @@ -170,12 +170,8 @@ SYM_FUNC_START(__svm_vcpu_run) mov VCPU_RDI(%_ASM_DI), %_ASM_DI /* Enter guest mode */ - sti - 3: vmrun %_ASM_AX 4: - cli - /* Pop @svm to RAX while it's the only available register. */ pop %_ASM_AX @@ -340,12 +336,8 @@ SYM_FUNC_START(__svm_sev_es_vcpu_run) mov KVM_VMCB_pa(%rax), %rax /* Enter guest mode */ - sti - 1: vmrun %rax - -2: cli - +2: /* IMPORTANT: Stuff the RSB immediately after VM-Exit, before RET! */ FILL_RETURN_BUFFER %rax, RSB_CLEAR_LOOPS, X86_FEATURE_RSB_VMEXIT

6 months, 1 week

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FAILED: patch "[PATCH] KVM: SVM: Set RFLAGS.IF=1 in C code, to get VMRUN out of the" failed to apply to 6.6-stable tree

by gregkh＠linuxfoundation.org

The patch below does not apply to the 6.6-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <stable(a)vger.kernel.org>. To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y git checkout FETCH_HEAD git cherry-pick -x be45bc4eff33d9a7dae84a2150f242a91a617402 # <resolve conflicts, build, test, etc.> git commit -s git send-email --to '<stable(a)vger.kernel.org>' --in-reply-to '2025031022-debunk-winner-e8fe@gregkh' --subject-prefix 'PATCH 6.6.y' HEAD^.. Possible dependencies: thanks, greg k-h ------------------ original commit in Linus's tree ------------------ From be45bc4eff33d9a7dae84a2150f242a91a617402 Mon Sep 17 00:00:00 2001 From: Sean Christopherson <seanjc(a)google.com> Date: Mon, 24 Feb 2025 08:54:41 -0800 Subject: [PATCH] KVM: SVM: Set RFLAGS.IF=1 in C code, to get VMRUN out of the STI shadow Enable/disable local IRQs, i.e. set/clear RFLAGS.IF, in the common svm_vcpu_enter_exit() just after/before guest_state_{enter,exit}_irqoff() so that VMRUN is not executed in an STI shadow. AMD CPUs have a quirk (some would say "bug"), where the STI shadow bleeds into the guest's intr_state field if a #VMEXIT occurs during injection of an event, i.e. if the VMRUN doesn't complete before the subsequent #VMEXIT. The spurious "interrupts masked" state is relatively benign, as it only occurs during event injection and is transient. Because KVM is already injecting an event, the guest can't be in HLT, and if KVM is querying IRQ blocking for injection, then KVM would need to force an immediate exit anyways since injecting multiple events is impossible. However, because KVM copies int_state verbatim from vmcb02 to vmcb12, the spurious STI shadow is visible to L1 when running a nested VM, which can trip sanity checks, e.g. in VMware's VMM. Hoist the STI+CLI all the way to C code, as the aforementioned calls to guest_state_{enter,exit}_irqoff() already inform lockdep that IRQs are enabled/disabled, and taking a fault on VMRUN with RFLAGS.IF=1 is already possible. I.e. if there's kernel code that is confused by running with RFLAGS.IF=1, then it's already a problem. In practice, since GIF=0 also blocks NMIs, the only change in exposure to non-KVM code (relative to surrounding VMRUN with STI+CLI) is exception handling code, and except for the kvm_rebooting=1 case, all exception in the core VM-Enter/VM-Exit path are fatal. Use the "raw" variants to enable/disable IRQs to avoid tracing in the "no instrumentation" code; the guest state helpers also take care of tracing IRQ state. Oppurtunstically document why KVM needs to do STI in the first place. Reported-by: Doug Covelli <doug.covelli(a)broadcom.com> Closes: https://lore.kernel.org/all/CADH9ctBs1YPmE4aCfGPNBwA10cA8RuAk2gO7542DjMZgs4… Fixes: f14eec0a3203 ("KVM: SVM: move more vmentry code to assembly") Cc: stable(a)vger.kernel.org Reviewed-by: Jim Mattson <jmattson(a)google.com> Link: https://lore.kernel.org/r/20250224165442.2338294-2-seanjc@google.com Signed-off-by: Sean Christopherson <seanjc(a)google.com> diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index a713c803a3a3..0d299f3f921e 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -4189,6 +4189,18 @@ static noinstr void svm_vcpu_enter_exit(struct kvm_vcpu *vcpu, bool spec_ctrl_in guest_state_enter_irqoff(); + /* + * Set RFLAGS.IF prior to VMRUN, as the host's RFLAGS.IF at the time of + * VMRUN controls whether or not physical IRQs are masked (KVM always + * runs with V_INTR_MASKING_MASK). Toggle RFLAGS.IF here to avoid the + * temptation to do STI+VMRUN+CLI, as AMD CPUs bleed the STI shadow + * into guest state if delivery of an event during VMRUN triggers a + * #VMEXIT, and the guest_state transitions already tell lockdep that + * IRQs are being enabled/disabled. Note! GIF=0 for the entirety of + * this path, so IRQs aren't actually unmasked while running host code. + */ + raw_local_irq_enable(); + amd_clear_divider(); if (sev_es_guest(vcpu->kvm)) @@ -4197,6 +4209,8 @@ static noinstr void svm_vcpu_enter_exit(struct kvm_vcpu *vcpu, bool spec_ctrl_in else __svm_vcpu_run(svm, spec_ctrl_intercepted); + raw_local_irq_disable(); + guest_state_exit_irqoff(); } diff --git a/arch/x86/kvm/svm/vmenter.S b/arch/x86/kvm/svm/vmenter.S index 2ed80aea3bb1..0c61153b275f 100644 --- a/arch/x86/kvm/svm/vmenter.S +++ b/arch/x86/kvm/svm/vmenter.S @@ -170,12 +170,8 @@ SYM_FUNC_START(__svm_vcpu_run) mov VCPU_RDI(%_ASM_DI), %_ASM_DI /* Enter guest mode */ - sti - 3: vmrun %_ASM_AX 4: - cli - /* Pop @svm to RAX while it's the only available register. */ pop %_ASM_AX @@ -340,12 +336,8 @@ SYM_FUNC_START(__svm_sev_es_vcpu_run) mov KVM_VMCB_pa(%rax), %rax /* Enter guest mode */ - sti - 1: vmrun %rax - -2: cli - +2: /* IMPORTANT: Stuff the RSB immediately after VM-Exit, before RET! */ FILL_RETURN_BUFFER %rax, RSB_CLEAR_LOOPS, X86_FEATURE_RSB_VMEXIT

6 months, 1 week

1
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[PATCH v2 0/2] R-Car CANFD fixes

by Biju Das

This patch series addresses 2 issues 1) Fix typo in pattern properties for R-Car V4M. 2) Fix page entries in the AFL list. v1->v2: * Split fixes patches as separate series. * Added Rb tag from Geert for binding patch. * Added the tag Cc:stable@vger.kernel.org Biju Das (2): dt-bindings: can: renesas,rcar-canfd: Fix typo in pattern properties for R-Car V4M can: rcar_canfd: Fix page entries in the AFL list .../bindings/net/can/renesas,rcar-canfd.yaml | 2 +- drivers/net/can/rcar/rcar_canfd.c | 17 ++++++++++------- 2 files changed, 11 insertions(+), 8 deletions(-) -- 2.43.0

6 months, 1 week

4
15
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[PATCH V3] drm/sched: Fix fence reference count leak

by Qianyi Liu

From: qianyi liu <liuqianyi125(a)gmail.com> The last_scheduled fence leaked when an entity was being killed and adding its callback failed. Decrement the reference count of prev when dma_fence_add_callback() fails, ensuring proper balance. Cc: stable(a)vger.kernel.org Fixes: 2fdb8a8f07c2 ("drm/scheduler: rework entity flush, kill and fini") Signed-off-by: qianyi liu <liuqianyi125(a)gmail.com> --- v2 -> v3: Rework commit message (Markus) v1 -> v2: Added 'Fixes:' tag and clarified commit message (Philipp and Matthew) --- drivers/gpu/drm/scheduler/sched_entity.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/drivers/gpu/drm/scheduler/sched_entity.c b/drivers/gpu/drm/scheduler/sched_entity.c index 69bcf0e99d57..1c0c14bcf726 100644 --- a/drivers/gpu/drm/scheduler/sched_entity.c +++ b/drivers/gpu/drm/scheduler/sched_entity.c @@ -259,9 +259,12 @@ static void drm_sched_entity_kill(struct drm_sched_entity *entity) struct drm_sched_fence *s_fence = job->s_fence; dma_fence_get(&s_fence->finished); - if (!prev || dma_fence_add_callback(prev, &job->finish_cb, - drm_sched_entity_kill_jobs_cb)) + if (!prev || + dma_fence_add_callback(prev, &job->finish_cb, + drm_sched_entity_kill_jobs_cb)) { + dma_fence_put(prev); drm_sched_entity_kill_jobs_cb(NULL, &job->finish_cb); + } prev = &s_fence->finished; } -- 2.25.1

6 months, 1 week

2
4
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[PATCH v4 0/2] Allow non-coherent video capture buffers on Rockchip ISP V1

by Mikhail Rudenko

This small series adds support for non-coherent video capture buffers on Rockchip ISP V1. Patch 1 fixes cache management for dmabuf's allocated by dma-contig allocator. Patch 2 allows non-coherent allocations on the rkisp1 capture queue. Some timing measurements are provided in the commit message of patch 2. Signed-off-by: Mikhail Rudenko <mike.rudenko(a)gmail.com> --- Changes in v4: - rebase to media/next - use `direction` instead of `buf->dma_dir` in dma_sync_sgtable_* - Link to v3: https://lore.kernel.org/r/20250128-b4-rkisp-noncoherent-v3-0-baf39c997d2a@g… Changes in v3: - ignore skip_cache_sync_* flags in vb2_dc_dmabuf_ops_{begin,end}_cpu_access - invalidate/flush kernel mappings as appropriate if they exist - use dma_sync_sgtable_* instead of dma_sync_sg_* - Link to v2: https://lore.kernel.org/r/20250115-b4-rkisp-noncoherent-v2-0-0853e1a24012@g… Changes in v2: - Fix vb2_dc_dmabuf_ops_{begin,end}_cpu_access() for non-coherent buffers. - Add cache management timing information to patch 2 commit message. - Link to v1: https://lore.kernel.org/r/20250102-b4-rkisp-noncoherent-v1-1-bba164f7132c@g… --- Mikhail Rudenko (2): media: videobuf2: Fix dmabuf cache sync/flush in dma-contig media: rkisp1: Allow non-coherent video capture buffers .../media/common/videobuf2/videobuf2-dma-contig.c | 22 ++++++++++++++++++++++ .../platform/rockchip/rkisp1/rkisp1-capture.c | 1 + 2 files changed, 23 insertions(+) --- base-commit: b2c4bf0c102084e77ed1b12090d77a76469a6814 change-id: 20241231-b4-rkisp-noncoherent-ad6e7c7a68ba Best regards, -- Mikhail Rudenko <mike.rudenko(a)gmail.com>

6 months, 1 week

3
6
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[PATCH 1/1] mcb: fix a double free bug in chameleon_parse_gdd()

by Johannes Thumshirn

From: Haoxiang Li <haoxiang_li2024(a)163.com> In chameleon_parse_gdd(), if mcb_device_register() fails, 'mdev' would be released in mcb_device_register() via put_device(). Thus, goto 'err' label and free 'mdev' again causes a double free. Just return if mcb_device_register() fails. Fixes: 3764e82e5150 ("drivers: Introduce MEN Chameleon Bus") Cc: stable(a)vger.kernel.org Signed-off-by: Haoxiang Li <haoxiang_li2024(a)163.com> Signed-off-by: Johannes Thumshirn <jth(a)kernel.org> --- drivers/mcb/mcb-parse.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/mcb/mcb-parse.c b/drivers/mcb/mcb-parse.c index 02a680c73979..bf0d7d58c8b0 100644 --- a/drivers/mcb/mcb-parse.c +++ b/drivers/mcb/mcb-parse.c @@ -96,7 +96,7 @@ static int chameleon_parse_gdd(struct mcb_bus *bus, ret = mcb_device_register(bus, mdev); if (ret < 0) - goto err; + return ret; return 0; -- 2.43.0

6 months, 1 week

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Re: Patch "fs/pipe: Read pipe->{head,tail} atomically outside pipe->mutex" has been added to the 5.10-stable tree

by Linus Torvalds

Note that this was a real fix, but the fix only matters if commit aaec5a95d596 ("pipe_read: don't wake up the writer if the pipe is still full") is in the tree. Now, the bug was pre-existing, and *maybe* it could be hit without that commit aaec5a95d596, but nobody has ever reported it, so it's very very unlikely. Also, this fix then had some fall-out, and while I think you've queued all the fallout fixes too, I think it might be a good idea to wait for more reports from the development tree before considering these for stable. Put another way: this fix caused some pain. It might not be worth back-porting to stable at all, and if it is, it might be worth waiting to see that there's no other fallout. Linus On Sun, 9 Mar 2025 at 09:52, Sasha Levin <sashal(a)kernel.org> wrote: > > This is a note to let you know that I've just added the patch titled > > fs/pipe: Read pipe->{head,tail} atomically outside pipe->mutex

6 months, 1 week

2
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