This is a note to let you know that I've just added the patch titled
KVM: nVMX: fix HOST_CR3/HOST_CR4 cache
to the 4.9-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...
The filename of the patch is: kvm-nvmx-fix-host_cr3-host_cr4-cache.patch and it can be found in the queue-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.
From 44889942b6eb356eab27ce25fe10701adfec7776 Mon Sep 17 00:00:00 2001
From: Ladi Prosek lprosek@redhat.com Date: Fri, 22 Sep 2017 07:53:15 +0200 Subject: KVM: nVMX: fix HOST_CR3/HOST_CR4 cache
From: Ladi Prosek lprosek@redhat.com
commit 44889942b6eb356eab27ce25fe10701adfec7776 upstream.
For nested virt we maintain multiple VMCS that can run on a vCPU. So it is incorrect to keep vmcs_host_cr3 and vmcs_host_cr4, whose purpose is caching the value of the rarely changing HOST_CR3 and HOST_CR4 VMCS fields, in vCPU-wide data structures.
Hyper-V nested on KVM runs into this consistently for me with PCID enabled. CR3 is updated with a new value, unlikely(cr3 != vmx->host_state.vmcs_host_cr3) fires, and the currently loaded VMCS is updated. Then we switch from L2 to L1 and the next exit reverts CR3 to its old value.
Fixes: d6e41f1151fe ("x86/mm, KVM: Teach KVM's VMX code that CR3 isn't a constant") Signed-off-by: Ladi Prosek lprosek@redhat.com Signed-off-by: Paolo Bonzini pbonzini@redhat.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- arch/x86/kvm/vmx.c | 16 ++++++++-------- 1 file changed, 8 insertions(+), 8 deletions(-)
--- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -191,6 +191,8 @@ struct loaded_vmcs { struct vmcs *shadow_vmcs; int cpu; int launched; + unsigned long vmcs_host_cr3; /* May not match real cr3 */ + unsigned long vmcs_host_cr4; /* May not match real cr4 */ struct list_head loaded_vmcss_on_cpu_link; };
@@ -573,8 +575,6 @@ struct vcpu_vmx { int gs_ldt_reload_needed; int fs_reload_needed; u64 msr_host_bndcfgs; - unsigned long vmcs_host_cr3; /* May not match real cr3 */ - unsigned long vmcs_host_cr4; /* May not match real cr4 */ } host_state; struct { int vm86_active; @@ -4871,12 +4871,12 @@ static void vmx_set_constant_host_state( */ cr3 = read_cr3(); vmcs_writel(HOST_CR3, cr3); /* 22.2.3 FIXME: shadow tables */ - vmx->host_state.vmcs_host_cr3 = cr3; + vmx->loaded_vmcs->vmcs_host_cr3 = cr3;
/* Save the most likely value for this task's CR4 in the VMCS. */ cr4 = cr4_read_shadow(); vmcs_writel(HOST_CR4, cr4); /* 22.2.3, 22.2.5 */ - vmx->host_state.vmcs_host_cr4 = cr4; + vmx->loaded_vmcs->vmcs_host_cr4 = cr4;
vmcs_write16(HOST_CS_SELECTOR, __KERNEL_CS); /* 22.2.4 */ #ifdef CONFIG_X86_64 @@ -8874,15 +8874,15 @@ static void __noclone vmx_vcpu_run(struc vmcs_writel(GUEST_RIP, vcpu->arch.regs[VCPU_REGS_RIP]);
cr3 = __get_current_cr3_fast(); - if (unlikely(cr3 != vmx->host_state.vmcs_host_cr3)) { + if (unlikely(cr3 != vmx->loaded_vmcs->vmcs_host_cr3)) { vmcs_writel(HOST_CR3, cr3); - vmx->host_state.vmcs_host_cr3 = cr3; + vmx->loaded_vmcs->vmcs_host_cr3 = cr3; }
cr4 = cr4_read_shadow(); - if (unlikely(cr4 != vmx->host_state.vmcs_host_cr4)) { + if (unlikely(cr4 != vmx->loaded_vmcs->vmcs_host_cr4)) { vmcs_writel(HOST_CR4, cr4); - vmx->host_state.vmcs_host_cr4 = cr4; + vmx->loaded_vmcs->vmcs_host_cr4 = cr4; }
/* When single-stepping over STI and MOV SS, we must clear the
Patches currently in stable-queue which might be from lprosek@redhat.com are
queue-4.9/kvm-nvmx-fix-host_cr3-host_cr4-cache.patch queue-4.9/virtio-balloon-use-actual-number-of-stats-for-stats-queue-buffers.patch queue-4.9/virtio_balloon-prevent-uninitialized-variable-use.patch