2024-05-07 16:15:28

by Paolo Bonzini

Subject: [PATCH 12/17] KVM: x86/mmu: Explicitly disallow private accesses to emulated MMIO

From: Sean Christopherson <[email protected]>

Explicitly detect and disallow private accesses to emulated MMIO in
kvm_handle_noslot_fault() instead of relying on kvm_faultin_pfn_private()
to perform the check. This will allow the page fault path to go straight
to kvm_handle_noslot_fault() without bouncing through __kvm_faultin_pfn().

Signed-off-by: Sean Christopherson <[email protected]>
Message-ID: <[email protected]>
Signed-off-by: Paolo Bonzini <[email protected]>
---
arch/x86/kvm/mmu/mmu.c | 5 +++++
1 file changed, 5 insertions(+)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index a8e14c2b68a7..fdae6d19e72b 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -3262,6 +3262,11 @@ static int kvm_handle_noslot_fault(struct kvm_vcpu *vcpu,
{
gva_t gva = fault->is_tdp ? 0 : fault->addr;

+ if (fault->is_private) {
+ kvm_mmu_prepare_memory_fault_exit(vcpu, fault);
+ return -EFAULT;
+ }
+
vcpu_cache_mmio_info(vcpu, gva, fault->gfn,
access & shadow_mmio_access_mask);

--
2.43.0

2024-05-13 06:26:28

by Xiaoyao Li

Subject: Re: [PATCH 12/17] KVM: x86/mmu: Explicitly disallow private accesses to emulated MMIO

On 5/7/2024 11:58 PM, Paolo Bonzini wrote:
> From: Sean Christopherson <[email protected]>
>
> Explicitly detect and disallow private accesses to emulated MMIO in
> kvm_handle_noslot_fault() instead of relying on kvm_faultin_pfn_private()
> to perform the check. This will allow the page fault path to go straight
> to kvm_handle_noslot_fault() without bouncing through __kvm_faultin_pfn().
>
> Signed-off-by: Sean Christopherson <[email protected]>
> Message-ID: <[email protected]>
> Signed-off-by: Paolo Bonzini <[email protected]>

Reviewed-by: Xiaoyao Li <[email protected]>

> ---
> arch/x86/kvm/mmu/mmu.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index a8e14c2b68a7..fdae6d19e72b 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -3262,6 +3262,11 @@ static int kvm_handle_noslot_fault(struct kvm_vcpu *vcpu,
> {
> gva_t gva = fault->is_tdp ? 0 : fault->addr;
>
> + if (fault->is_private) {
> + kvm_mmu_prepare_memory_fault_exit(vcpu, fault);
> + return -EFAULT;
> + }
> +
> vcpu_cache_mmio_info(vcpu, gva, fault->gfn,
> access & shadow_mmio_access_mask);
>