From: Paolo Bonzini <pbonzini@redhat.com>
To: Jim Mattson <jmattson@google.com>, kvm list <kvm@vger.kernel.org>
Cc: Sean Christopherson <sean.j.christopherson@intel.com>
Subject: Re: PAE mode save/restore broken
Date: Thu, 4 Jun 2020 16:51:39 +0200 [thread overview]
Message-ID: <48454efb-455f-5505-f92c-7f78836d5b91@redhat.com> (raw)
In-Reply-To: <CALMp9eS2UtMazBew2yndKVXC0QnnBW2bvbU_d+27Hp7Fw2NXFg@mail.gmail.com>
On 02/06/20 02:11, Jim Mattson wrote:
> I can only assume that no one cares that KVM_GET_SREGS/KVM_SET_SREGS
> is broken for PAE mode guests (i.e. KVM_GET_SREGS doesn't capture the
> PDPTRs and KVM_SET_SREGS re-reads them from memory).
>
> Presumably, since AMD's nested paging is broken for PAE mode guests,
> the kvm community has made the decision not to get things right for
> Intel either. Can anyone confirm? This was all before my time.
Yes, pretty much. The PDPTRs are not part of the saved state, we just
treat them as a small third level in the radix tree. Of course, for
nested VMX they are properly synced to the VMCS12 and serialized by
KVM_SET_NESTED_STATE.
Out of curiosity are there OSes that rely on the PDPTRs remaining cached
until the next CR3 load?
Paolo
next prev parent reply other threads:[~2020-06-04 14:51 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-06-02 0:11 PAE mode save/restore broken Jim Mattson
2020-06-04 14:51 ` Paolo Bonzini [this message]
2020-06-04 16:27 ` Jim Mattson
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