From: Gleb Natapov <gleb@redhat.com>
To: Marcelo Tosatti <mtosatti@redhat.com>
Cc: avi@redhat.com, aarcange@redhat.com, kvm@vger.kernel.org
Subject: Re: [patch 2/3] KVM: dont require read-only host ptes
Date: Tue, 5 Oct 2010 15:43:01 +0200 [thread overview]
Message-ID: <20101005134301.GQ11145@redhat.com> (raw)
In-Reply-To: <20101005121555.827500635@redhat.com>
On Tue, Oct 05, 2010 at 08:55:00AM -0300, Marcelo Tosatti wrote:
> gfn_to_pfn requires a writable host pte, failing otherwise.
>
> Change it to fallback to read-only "acquision', informing the callers.
>
> Hopefully the ptes are cache-hot so the overhead is minimal.
>
> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
>
> Index: kvm/arch/ia64/kvm/kvm-ia64.c
> ===================================================================
> --- kvm.orig/arch/ia64/kvm/kvm-ia64.c
> +++ kvm/arch/ia64/kvm/kvm-ia64.c
> @@ -1589,7 +1589,7 @@ int kvm_arch_prepare_memory_region(struc
> return -ENOMEM;
>
> for (i = 0; i < npages; i++) {
> - pfn = gfn_to_pfn(kvm, base_gfn + i);
> + pfn = gfn_to_pfn(kvm, base_gfn + i, NULL);
> if (!kvm_is_mmio_pfn(pfn)) {
> kvm_set_pmt_entry(kvm, base_gfn + i,
> pfn << PAGE_SHIFT,
> Index: kvm/arch/x86/kvm/mmu.c
> ===================================================================
> --- kvm.orig/arch/x86/kvm/mmu.c
> +++ kvm/arch/x86/kvm/mmu.c
> @@ -2273,6 +2273,7 @@ static int nonpaging_map(struct kvm_vcpu
> {
> int r;
> int level;
> + int writable;
> pfn_t pfn;
> unsigned long mmu_seq;
>
> @@ -2289,10 +2290,10 @@ static int nonpaging_map(struct kvm_vcpu
>
> mmu_seq = vcpu->kvm->mmu_notifier_seq;
> smp_rmb();
> - pfn = gfn_to_pfn(vcpu->kvm, gfn);
> + pfn = gfn_to_pfn(vcpu->kvm, gfn, &writable);
>
> /* mmio */
> - if (is_error_pfn(pfn))
> + if (is_error_pfn(pfn) || !writable)
> return kvm_handle_bad_page(vcpu->kvm, gfn, pfn);
>
> spin_lock(&vcpu->kvm->mmu_lock);
> @@ -2581,6 +2582,8 @@ static int tdp_page_fault(struct kvm_vcp
> pfn_t pfn;
> int r;
> int level;
> + int writable;
> + int write = error_code & PFERR_WRITE_MASK;
> gfn_t gfn = gpa >> PAGE_SHIFT;
> unsigned long mmu_seq;
>
> @@ -2597,15 +2600,14 @@ static int tdp_page_fault(struct kvm_vcp
>
> mmu_seq = vcpu->kvm->mmu_notifier_seq;
> smp_rmb();
> - pfn = gfn_to_pfn(vcpu->kvm, gfn);
> - if (is_error_pfn(pfn))
> + pfn = gfn_to_pfn(vcpu->kvm, gfn, &writable);
> + if (is_error_pfn(pfn) || !writable)
Why would we fail read only access to read only memory? Shouldn't we
check access type here?
--
Gleb.
next prev parent reply other threads:[~2010-10-05 13:43 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-10-05 11:54 [patch 0/3] allow read-only memory mappings Marcelo Tosatti
2010-10-05 11:54 ` [patch 1/3] KVM: VMX: remove setting of shadow_base_ptes for EPT Marcelo Tosatti
2010-10-05 11:55 ` [patch 2/3] KVM: dont require read-only host ptes Marcelo Tosatti
2010-10-05 13:43 ` Gleb Natapov [this message]
2010-10-05 13:47 ` Marcelo Tosatti
2010-10-05 11:55 ` [patch 3/3] KVM: handle " Marcelo Tosatti
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