6.1-stable review patch. If anyone has any objections, please let me know.
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From: Sean Christopherson seanjc@google.com
[ Upstream commit 80c64c7afea1da6a93ebe88d3d29d8a60377ef80 ]
Instruct vendor code to load the guest's DR6 into hardware via a new KVM_RUN flag, and remove kvm_x86_ops.set_dr6(), whose sole purpose was to load vcpu->arch.dr6 into hardware when DR6 can be read/written directly by the guest.
Note, TDX already WARNs on any run_flag being set, i.e. will yell if KVM thinks DR6 needs to be reloaded. TDX vCPUs force KVM_DEBUGREG_AUTO_SWITCH and never clear the flag, i.e. should never observe KVM_RUN_LOAD_GUEST_DR6.
Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20250610232010.162191-4-seanjc@google.com Signed-off-by: Sean Christopherson seanjc@google.com [sean: account for lack of vmx/main.c] Signed-off-by: Sean Christopherson seanjc@google.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/x86/include/asm/kvm-x86-ops.h | 1 - arch/x86/include/asm/kvm_host.h | 2 +- arch/x86/kvm/svm/svm.c | 10 ++++++---- arch/x86/kvm/vmx/vmx.c | 10 +++------- arch/x86/kvm/x86.c | 2 +- 5 files changed, 11 insertions(+), 14 deletions(-)
diff --git a/arch/x86/include/asm/kvm-x86-ops.h b/arch/x86/include/asm/kvm-x86-ops.h index 0e5ae3b0c867..c068565fe954 100644 --- a/arch/x86/include/asm/kvm-x86-ops.h +++ b/arch/x86/include/asm/kvm-x86-ops.h @@ -47,7 +47,6 @@ KVM_X86_OP(set_idt) KVM_X86_OP(get_gdt) KVM_X86_OP(set_gdt) KVM_X86_OP(sync_dirty_debug_regs) -KVM_X86_OP(set_dr6) KVM_X86_OP(set_dr7) KVM_X86_OP(cache_reg) KVM_X86_OP(get_rflags) diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 1383f5e5238a..c8fc4f2acf69 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -1458,6 +1458,7 @@ static inline u16 kvm_lapic_irq_dest_mode(bool dest_mode_logical)
enum kvm_x86_run_flags { KVM_RUN_FORCE_IMMEDIATE_EXIT = BIT(0), + KVM_RUN_LOAD_GUEST_DR6 = BIT(1), };
struct kvm_x86_ops { @@ -1504,7 +1505,6 @@ struct kvm_x86_ops { void (*get_gdt)(struct kvm_vcpu *vcpu, struct desc_ptr *dt); void (*set_gdt)(struct kvm_vcpu *vcpu, struct desc_ptr *dt); void (*sync_dirty_debug_regs)(struct kvm_vcpu *vcpu); - void (*set_dr6)(struct kvm_vcpu *vcpu, unsigned long value); void (*set_dr7)(struct kvm_vcpu *vcpu, unsigned long value); void (*cache_reg)(struct kvm_vcpu *vcpu, enum kvm_reg reg); unsigned long (*get_rflags)(struct kvm_vcpu *vcpu); diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c index dc8a1b72d8ec..5a6bd9d5cceb 100644 --- a/arch/x86/kvm/svm/svm.c +++ b/arch/x86/kvm/svm/svm.c @@ -4052,10 +4052,13 @@ static __no_kcsan fastpath_t svm_vcpu_run(struct kvm_vcpu *vcpu, u64 run_flags) svm_hv_update_vp_id(svm->vmcb, vcpu);
/* - * Run with all-zero DR6 unless needed, so that we can get the exact cause - * of a #DB. + * Run with all-zero DR6 unless the guest can write DR6 freely, so that + * KVM can get the exact cause of a #DB. Note, loading guest DR6 from + * KVM's snapshot is only necessary when DR accesses won't exit. */ - if (likely(!(vcpu->arch.switch_db_regs & KVM_DEBUGREG_WONT_EXIT))) + if (unlikely(run_flags & KVM_RUN_LOAD_GUEST_DR6)) + svm_set_dr6(vcpu, vcpu->arch.dr6); + else if (likely(!(vcpu->arch.switch_db_regs & KVM_DEBUGREG_WONT_EXIT))) svm_set_dr6(vcpu, DR6_ACTIVE_LOW);
clgi(); @@ -4822,7 +4825,6 @@ static struct kvm_x86_ops svm_x86_ops __initdata = { .set_idt = svm_set_idt, .get_gdt = svm_get_gdt, .set_gdt = svm_set_gdt, - .set_dr6 = svm_set_dr6, .set_dr7 = svm_set_dr7, .sync_dirty_debug_regs = svm_sync_dirty_debug_regs, .cache_reg = svm_cache_reg, diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 382f42200688..60d1ff3fca45 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -5530,12 +5530,6 @@ static void vmx_sync_dirty_debug_regs(struct kvm_vcpu *vcpu) set_debugreg(DR6_RESERVED, 6); }
-static void vmx_set_dr6(struct kvm_vcpu *vcpu, unsigned long val) -{ - lockdep_assert_irqs_disabled(); - set_debugreg(vcpu->arch.dr6, 6); -} - static void vmx_set_dr7(struct kvm_vcpu *vcpu, unsigned long val) { vmcs_writel(GUEST_DR7, val); @@ -7251,6 +7245,9 @@ static fastpath_t vmx_vcpu_run(struct kvm_vcpu *vcpu, u64 run_flags) vmcs_writel(GUEST_RIP, vcpu->arch.regs[VCPU_REGS_RIP]); vcpu->arch.regs_dirty = 0;
+ if (run_flags & KVM_RUN_LOAD_GUEST_DR6) + set_debugreg(vcpu->arch.dr6, 6); + /* * Refresh vmcs.HOST_CR3 if necessary. This must be done immediately * prior to VM-Enter, as the kernel may load a new ASID (PCID) any time @@ -8208,7 +8205,6 @@ static struct kvm_x86_ops vmx_x86_ops __initdata = { .set_idt = vmx_set_idt, .get_gdt = vmx_get_gdt, .set_gdt = vmx_set_gdt, - .set_dr6 = vmx_set_dr6, .set_dr7 = vmx_set_dr7, .sync_dirty_debug_regs = vmx_sync_dirty_debug_regs, .cache_reg = vmx_cache_reg, diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 83e5e823cbae..9d66830d594c 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -10833,7 +10833,7 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu) set_debugreg(vcpu->arch.eff_db[3], 3); /* When KVM_DEBUGREG_WONT_EXIT, dr6 is accessible in guest. */ if (unlikely(vcpu->arch.switch_db_regs & KVM_DEBUGREG_WONT_EXIT)) - static_call(kvm_x86_set_dr6)(vcpu, vcpu->arch.dr6); + run_flags |= KVM_RUN_LOAD_GUEST_DR6; } else if (unlikely(hw_breakpoint_active())) { set_debugreg(0, 7); }