[v1] KVM: x86/mmu: Page fault and MMIO cleanups

[PATCH 14/16] KVM: x86/mmu: Set kvm_page_fault.hva to KVM_HVA_ERR_BAD for "no slot" faults

Posted by Sean Christopherson 9 months ago

Explicitly set fault->hva to KVM_HVA_ERR_BAD when handling a "no slot"
fault to ensure that KVM doesn't use a bogus virtual address, e.g. if
there *was* a slot but it's unusable (APIC access page), or if there
really was no slot, in which case fault->hva will be '0' (which is a
legal address for x86).

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 arch/x86/kvm/mmu/mmu.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 4dee0999a66e..43f24a74571a 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -3325,6 +3325,7 @@ static int kvm_handle_noslot_fault(struct kvm_vcpu *vcpu,
 	fault->slot = NULL;
 	fault->pfn = KVM_PFN_NOSLOT;
 	fault->map_writable = false;
+	fault->hva = KVM_HVA_ERR_BAD;
 
 	/*
 	 * If MMIO caching is disabled, emulate immediately without
-- 
2.44.0.278.ge034bb2e1d-goog

Re: [PATCH 14/16] KVM: x86/mmu: Set kvm_page_fault.hva to KVM_HVA_ERR_BAD for "no slot" faults

Posted by Huang, Kai 8 months, 3 weeks ago


On 28/02/2024 3:41 pm, Sean Christopherson wrote:
> Explicitly set fault->hva to KVM_HVA_ERR_BAD when handling a "no slot"
> fault to ensure that KVM doesn't use a bogus virtual address, e.g. if
> there *was* a slot but it's unusable (APIC access page), or if there
> really was no slot, in which case fault->hva will be '0' (which is a
> legal address for x86).
> 
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> ---
>   arch/x86/kvm/mmu/mmu.c | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 4dee0999a66e..43f24a74571a 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -3325,6 +3325,7 @@ static int kvm_handle_noslot_fault(struct kvm_vcpu *vcpu,
>   	fault->slot = NULL;
>   	fault->pfn = KVM_PFN_NOSLOT;
>   	fault->map_writable = false;
> +	fault->hva = KVM_HVA_ERR_BAD;
>   
>   	/*
>   	 * If MMIO caching is disabled, emulate immediately without

Not sure why this cannot be merged to the previous one?

Anyway,

Reviewed-by: Kai Huang <kai.huang@intel.com>

Re: [PATCH 14/16] KVM: x86/mmu: Set kvm_page_fault.hva to KVM_HVA_ERR_BAD for "no slot" faults

Posted by Sean Christopherson 8 months, 3 weeks ago

On Thu, Mar 07, 2024, Kai Huang wrote:
> 
> 
> On 28/02/2024 3:41 pm, Sean Christopherson wrote:
> > Explicitly set fault->hva to KVM_HVA_ERR_BAD when handling a "no slot"
> > fault to ensure that KVM doesn't use a bogus virtual address, e.g. if
> > there *was* a slot but it's unusable (APIC access page), or if there
> > really was no slot, in which case fault->hva will be '0' (which is a
> > legal address for x86).
> > 
> > Signed-off-by: Sean Christopherson <seanjc@google.com>
> > ---
> >   arch/x86/kvm/mmu/mmu.c | 1 +
> >   1 file changed, 1 insertion(+)
> > 
> > diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> > index 4dee0999a66e..43f24a74571a 100644
> > --- a/arch/x86/kvm/mmu/mmu.c
> > +++ b/arch/x86/kvm/mmu/mmu.c
> > @@ -3325,6 +3325,7 @@ static int kvm_handle_noslot_fault(struct kvm_vcpu *vcpu,
> >   	fault->slot = NULL;
> >   	fault->pfn = KVM_PFN_NOSLOT;
> >   	fault->map_writable = false;
> > +	fault->hva = KVM_HVA_ERR_BAD;
> >   	/*
> >   	 * If MMIO caching is disabled, emulate immediately without
> 
> Not sure why this cannot be merged to the previous one?

Purely because (before the previous patch) kvm_faultin_pfn() only paved over pfn,
slot, and map_writable.  I highly doubt clobbering hva will break anything, but
just in case...