[PATCH] KVM: VMX: Add VMCS to CPU's loaded VMCSs before VMPTRLD

[PATCH] KVM: VMX: Add VMCS to CPU's loaded VMCSs before VMPTRLD

[Jim Mattson]

Kexec needs to know the addresses of all VMCSs that are active on
each CPU, so that it can flush them from the VMCS caches. It is
safe to record superfluous addresses that are not associated with
an active VMCS, but it is not safe to omit an address associated
with an active VMCS.

After a call to vmcs_load, the VMCS that was loaded is active on
the CPU. The VMCS should be added to the CPU's list of active
VMCSs before it is loaded.

Signed-off-by: Jim Mattson <jmattson@google.com>
---
 arch/x86/kvm/vmx.c | 26 +++++++++++++++-----------
 1 file changed, 15 insertions(+), 11 deletions(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 7758680..f3d9995 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -2121,22 +2121,14 @@ static void vmx_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
 	u64 phys_addr = __pa(per_cpu(vmxarea, cpu));
+	bool already_loaded = vmx->loaded_vmcs->cpu == cpu;
 
 	if (!vmm_exclusive)
 		kvm_cpu_vmxon(phys_addr);
-	else if (vmx->loaded_vmcs->cpu != cpu)
+	else if (!already_loaded)
 		loaded_vmcs_clear(vmx->loaded_vmcs);
 
-	if (per_cpu(current_vmcs, cpu) != vmx->loaded_vmcs->vmcs) {
-		per_cpu(current_vmcs, cpu) = vmx->loaded_vmcs->vmcs;
-		vmcs_load(vmx->loaded_vmcs->vmcs);
-	}
-
-	if (vmx->loaded_vmcs->cpu != cpu) {
-		struct desc_ptr *gdt = this_cpu_ptr(&host_gdt);
-		unsigned long sysenter_esp;
-
-		kvm_make_request(KVM_REQ_TLB_FLUSH, vcpu);
+	if (!already_loaded) {
 		local_irq_disable();
 		crash_disable_local_vmclear(cpu);
 
@@ -2151,6 +2143,18 @@ static void vmx_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 			 &per_cpu(loaded_vmcss_on_cpu, cpu));
 		crash_enable_local_vmclear(cpu);
 		local_irq_enable();
+	}
+
+	if (per_cpu(current_vmcs, cpu) != vmx->loaded_vmcs->vmcs) {
+		per_cpu(current_vmcs, cpu) = vmx->loaded_vmcs->vmcs;
+		vmcs_load(vmx->loaded_vmcs->vmcs);
+	}
+
+	if (!already_loaded) {
+		struct desc_ptr *gdt = this_cpu_ptr(&host_gdt);
+		unsigned long sysenter_esp;
+
+		kvm_make_request(KVM_REQ_TLB_FLUSH, vcpu);
 
 		/*
 		 * Linux uses per-cpu TSS and GDT, so set these when switching
-- 
2.8.0.rc3.226.g39d4020

Re: [PATCH] KVM: VMX: Add VMCS to CPU's loaded VMCSs before VMPTRLD

[Radim Krčmář]

2016-07-29 18:56-0700, Jim Mattson:
> Kexec needs to know the addresses of all VMCSs that are active on
> each CPU, so that it can flush them from the VMCS caches. It is
> safe to record superfluous addresses that are not associated with
> an active VMCS, but it is not safe to omit an address associated
> with an active VMCS.
> 
> After a call to vmcs_load, the VMCS that was loaded is active on
> the CPU. The VMCS should be added to the CPU's list of active
> VMCSs before it is loaded.
> 
> Signed-off-by: Jim Mattson <jmattson@google.com>
> ---

Applied to kvm/queue, thanks.

I have tentatively kept the patch without "Cc: stable@..." as VMX might
not write to the in-memory VMCS unless the cached VMCS has been dirtied.

>  arch/x86/kvm/vmx.c | 26 +++++++++++++++-----------
>  1 file changed, 15 insertions(+), 11 deletions(-)
> 
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 7758680..f3d9995 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -2121,22 +2121,14 @@ static void vmx_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
>  {
>  	struct vcpu_vmx *vmx = to_vmx(vcpu);
>  	u64 phys_addr = __pa(per_cpu(vmxarea, cpu));
> +	bool already_loaded = vmx->loaded_vmcs->cpu == cpu;
>  
>  	if (!vmm_exclusive)
>  		kvm_cpu_vmxon(phys_addr);
> -	else if (vmx->loaded_vmcs->cpu != cpu)
> +	else if (!already_loaded)
>  		loaded_vmcs_clear(vmx->loaded_vmcs);
>  
> -	if (per_cpu(current_vmcs, cpu) != vmx->loaded_vmcs->vmcs) {
> -		per_cpu(current_vmcs, cpu) = vmx->loaded_vmcs->vmcs;
> -		vmcs_load(vmx->loaded_vmcs->vmcs);
> -	}
> -
> -	if (vmx->loaded_vmcs->cpu != cpu) {
> -		struct desc_ptr *gdt = this_cpu_ptr(&host_gdt);
> -		unsigned long sysenter_esp;
> -
> -		kvm_make_request(KVM_REQ_TLB_FLUSH, vcpu);
> +	if (!already_loaded) {
>  		local_irq_disable();
>  		crash_disable_local_vmclear(cpu);
>  
> @@ -2151,6 +2143,18 @@ static void vmx_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
>  			 &per_cpu(loaded_vmcss_on_cpu, cpu));
>  		crash_enable_local_vmclear(cpu);
>  		local_irq_enable();
> +	}
> +
> +	if (per_cpu(current_vmcs, cpu) != vmx->loaded_vmcs->vmcs) {
> +		per_cpu(current_vmcs, cpu) = vmx->loaded_vmcs->vmcs;
> +		vmcs_load(vmx->loaded_vmcs->vmcs);
> +	}
> +
> +	if (!already_loaded) {
> +		struct desc_ptr *gdt = this_cpu_ptr(&host_gdt);
> +		unsigned long sysenter_esp;
> +
> +		kvm_make_request(KVM_REQ_TLB_FLUSH, vcpu);
>  
>  		/*
>  		 * Linux uses per-cpu TSS and GDT, so set these when switching
> -- 
> 2.8.0.rc3.226.g39d4020
> 
> --
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