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SubjectRe: [PATCH 1/4] KVM: MMU: fix permission_fault()
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On 25/03/2016 14:19, Xiao Guangrong wrote:
> kvm-unit-tests complained about the PFEC is not set properly, e.g,:
> test pte.rw pte.d pte.nx pde.p pde.rw pde.pse user fetch: FAIL: error code 15
> expected 5
> Dump mapping: address: 0x123400000000
> ------L4: 3e95007
> ------L3: 3e96007
> ------L2: 2000083

What's the command line for the reproducer?

> diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
> index b70df72..81bffd1 100644
> --- a/arch/x86/kvm/mmu.h
> +++ b/arch/x86/kvm/mmu.h
> @@ -154,7 +154,7 @@ static inline u8 permission_fault(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
> unsigned pfec)
> {
> int cpl = kvm_x86_ops->get_cpl(vcpu);
> - unsigned long rflags = kvm_x86_ops->get_rflags(vcpu);
> + unsigned long errcode, rflags = kvm_x86_ops->get_rflags(vcpu);
>
> /*
> * If CPL < 3, SMAP prevention are disabled if EFLAGS.AC = 1.
> @@ -175,7 +175,7 @@ static inline u8 permission_fault(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
> bool fault = (mmu->permissions[index] >> pte_access) & 1;
>
> WARN_ON(pfec & (PFERR_PK_MASK | PFERR_RSVD_MASK));
> - pfec |= PFERR_PRESENT_MASK;
> + errcode = PFERR_PRESENT_MASK;

So is this patch doing the same as "KVM: MMU: precompute page fault
error code"? It was necessary after all. :)

Paolo

>
> if (unlikely(mmu->pkru_mask)) {
> u32 pkru_bits, offset;
> @@ -193,11 +193,11 @@ static inline u8 permission_fault(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu,
> ((pte_access & PT_USER_MASK) << (PFERR_RSVD_BIT - PT_USER_SHIFT));
>
> pkru_bits &= mmu->pkru_mask >> offset;
> - pfec |= -pkru_bits & PFERR_PK_MASK;
> + errcode |= -pkru_bits & PFERR_PK_MASK;
> fault |= (pkru_bits != 0);
> }
>
> - return -(uint32_t)fault & pfec;
> + return -(uint32_t)fault & errcode;
> }
>
> void kvm_mmu_invalidate_zap_all_pages(struct kvm *kvm);
> diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
> index 1d971c7..bc019f7 100644
> --- a/arch/x86/kvm/paging_tmpl.h
> +++ b/arch/x86/kvm/paging_tmpl.h
> @@ -360,7 +360,7 @@ retry_walk:
> goto error;
>
> if (unlikely(is_rsvd_bits_set(mmu, pte, walker->level))) {
> - errcode |= PFERR_RSVD_MASK | PFERR_PRESENT_MASK;
> + errcode = PFERR_RSVD_MASK | PFERR_PRESENT_MASK;
> goto error;
> }
>

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