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Groups > linux.kernel > #1698174
| From | Paolo Bonzini <pbonzini@redhat.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH v2 1/3] kvm: svm: Add support for additional SVM NPF error codes |
| Date | 2017-07-27 18:40 +0200 |
| Message-ID | <u7TZn-8rK-1@gated-at.bofh.it> (permalink) |
| References | <sGNTP-2bH-3@gated-at.bofh.it> <u7TZn-8rK-3@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On 23/11/2016 18:01, Brijesh Singh wrote:
>
> + /*
> + * Before emulating the instruction, check if the error code
> + * was due to a RO violation while translating the guest page.
> + * This can occur when using nested virtualization with nested
> + * paging in both guests. If true, we simply unprotect the page
> + * and resume the guest.
> + *
> + * Note: AMD only (since it supports the PFERR_GUEST_PAGE_MASK used
> + * in PFERR_NEXT_GUEST_PAGE)
> + */
> + if (error_code == PFERR_NESTED_GUEST_PAGE) {
> + kvm_mmu_unprotect_page(vcpu->kvm, gpa_to_gfn(cr2));
> + return 1;
> + }
What happens if L1 is mapping some memory that is read only in L0? That
is, the L1 nested page tables make it read-write, but the L0 shadow
nested page tables make it read-only.
Accessing it would cause an NPF, and then my guess is that the L1 guest
would loop on the failing instruction instead of just dropping the write.
Paolo
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Re: [PATCH v2 1/3] kvm: svm: Add support for additional SVM NPF error codes Paolo Bonzini <pbonzini@redhat.com> - 2017-07-27 18:40 +0200
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