Re: [PATCH] kvm/x86/mmu: use the correct inherited permissions to get shadow page

From: Lai Jiangshan
Date: Mon Nov 30 2020 - 20:32:16 EST


On Tue, Dec 1, 2020 at 1:41 AM Sean Christopherson <seanjc@xxxxxxxxxx> wrote:

>
> Hmm, yes, KVM would incorrectly handle this scenario. But, the proposed patch
> would not address the issue as KVM always maps non-leaf shadow pages with full
> access permissions.
>

Is it possible to exactly copy the access permissions from the guest
for non-leaf
shadow pages? Any protection from hypervisor (such as dirty track,
rmap_write_protect)
can only play on the leaf shadow ptes.

> Can we have a testcase in kvm-unit-tests? It's okay of course if it
> only fails with ept=0.

Yes, it may have a flaw with ept=0. I don't get what "It's okay of course"
means. Is it related to kvm-unit-tests? Or no cloud provider uses
ept=0?