From: Paolo Bonzini <pbonzini@redhat.com>
To: Gleb Natapov <gleb@redhat.com>
Cc: kvm@vger.kernel.org, Kashyap Chamarthy <kashyap.cv@gmail.com>
Subject: Re: [PATCH] KVM: nVMX: fix shadow on EPT
Date: Wed, 09 Oct 2013 18:19:52 +0200 [thread overview]
Message-ID: <52558228.9010602@redhat.com> (raw)
In-Reply-To: <20131009161319.GO3574@redhat.com>
Il 09/10/2013 18:13, Gleb Natapov ha scritto:
> 72f857950f6f19 broke shadow on EPT. This patch reverts it and fixes PAE
> on nEPT (which reverted commit fixed) in other way.
>
> Shadow on EPT is now broken because while L1 builds shadow page table
> for L2 (which is PAE while L2 is in real mode) it never loads L2's
> GUEST_PDPTR[0-3]. They do not need to be loaded because without nested
> virtualization HW does this during guest entry if EPT is disabled,
> but in our case L0 emulates L2's vmentry while EPT is enables, so we
> cannot rely on vmcs12->guest_pdptr[0-3] to contain up-to-date values
> and need to re-read PDPTEs from L2 memory. This is what kvm_set_cr3()
> is doing, but by clearing cache bits during L2 vmentry we drop values
> that kvm_set_cr3() read from memory.
>
> So why the same code does not work for PAE on nEPT? kvm_set_cr3()
> reads pdptes into vcpu->arch.walk_mmu->pdptrs[]. walk_mmu points to
> vcpu->arch.nested_mmu while nested guest is running, but ept_load_pdptrs()
> uses vcpu->arch.mmu which contain incorrect values. Fix that by using
> walk_mmu in ept_(load|save)_pdptrs.
>
> Signed-off-by: Gleb Natapov <gleb@redhat.com>
The new fix also looks much more obvious.
Applied to queue, thanks.
Paolo
next prev parent reply other threads:[~2013-10-09 16:19 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-10-09 16:13 [PATCH] KVM: nVMX: fix shadow on EPT Gleb Natapov
2013-10-09 16:19 ` Paolo Bonzini [this message]
2013-10-09 16:35 ` Gleb Natapov
2013-10-09 16:38 ` Paolo Bonzini
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