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KVM: nVMX: Use kvm_{read,write}_guest_cached() for shadow_vmcs12

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Using kvm_vcpu_map() for reading from the guest is entirely gratuitous,
when all we do is a single memcpy and unmap it again. Fix it up to use
kvm_read_guest()... but in fact I couldn't bring myself to do that
without also making it use a gfn_to_hva_cache for both that *and* the
copy in the other direction.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Message-Id: <20211115165030.7422-5-dwmw2@infradead.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
David Woodhouse 2021-11-15 16:50:24 +00:00 committed by Paolo Bonzini
parent 4e8436479a
commit 297d597a6d
2 changed files with 20 additions and 9 deletions
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24
arch/x86/kvm/vmx/nested.c
View File

@ -670,33 +670,39 @@ static inline bool nested_vmx_prepare_msr_bitmap(struct kvm_vcpu *vcpu,
static void nested_cache_shadow_vmcs12(struct kvm_vcpu *vcpu,
struct vmcs12 *vmcs12)
{
struct kvm_host_map map;
struct vmcs12 *shadow;
struct vcpu_vmx *vmx = to_vmx(vcpu);
struct gfn_to_hva_cache *ghc = &vmx->nested.shadow_vmcs12_cache;
if (!nested_cpu_has_shadow_vmcs(vmcs12) ||
vmcs12->vmcs_link_pointer == INVALID_GPA)
return;
shadow = get_shadow_vmcs12(vcpu);
if (kvm_vcpu_map(vcpu, gpa_to_gfn(vmcs12->vmcs_link_pointer), &map))
if (ghc->gpa != vmcs12->vmcs_link_pointer &&
kvm_gfn_to_hva_cache_init(vcpu->kvm, ghc,
vmcs12->vmcs_link_pointer, VMCS12_SIZE))
return;
memcpy(shadow, map.hva, VMCS12_SIZE);
kvm_vcpu_unmap(vcpu, &map, false);
kvm_read_guest_cached(vmx->vcpu.kvm, ghc, get_shadow_vmcs12(vcpu),
VMCS12_SIZE);
}
static void nested_flush_cached_shadow_vmcs12(struct kvm_vcpu *vcpu,
struct vmcs12 *vmcs12)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
struct gfn_to_hva_cache *ghc = &vmx->nested.shadow_vmcs12_cache;
if (!nested_cpu_has_shadow_vmcs(vmcs12) ||
vmcs12->vmcs_link_pointer == INVALID_GPA)
return;
kvm_write_guest(vmx->vcpu.kvm, vmcs12->vmcs_link_pointer,
get_shadow_vmcs12(vcpu), VMCS12_SIZE);
if (ghc->gpa != vmcs12->vmcs_link_pointer &&
kvm_gfn_to_hva_cache_init(vcpu->kvm, ghc,
vmcs12->vmcs_link_pointer, VMCS12_SIZE))
return;
kvm_write_guest_cached(vmx->vcpu.kvm, ghc, get_shadow_vmcs12(vcpu),
VMCS12_SIZE);
}
/*

5
arch/x86/kvm/vmx/vmx.h
View File

@ -141,6 +141,11 @@ struct nested_vmx {
*/
struct vmcs12 *cached_shadow_vmcs12;
/*
* GPA to HVA cache for accessing vmcs12->vmcs_link_pointer
*/
struct gfn_to_hva_cache shadow_vmcs12_cache;
/*
* Indicates if the shadow vmcs or enlightened vmcs must be updated
* with the data held by struct vmcs12.