From: Paolo Bonzini <pbonzini@redhat.com>
To: Sean Christopherson <seanjc@google.com>,
Maxim Levitsky <mlevitsk@redhat.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>,
Cathy Avery <cavery@redhat.com>,
Emanuele Giuseppe Esposito <eesposit@redhat.com>,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Subject: Re: [PATCH RFC] KVM: nSVM: Fix L1 state corruption upon return from SMM
Date: Wed, 23 Jun 2021 22:37:53 +0200 [thread overview]
Message-ID: <82327cd1-92ca-9f6b-3af0-8215e9d21eae@redhat.com> (raw)
In-Reply-To: <YNNfnLsc+3qMsdlN@google.com>
On 23/06/21 18:21, Sean Christopherson wrote:
> On Wed, Jun 23, 2021, Sean Christopherson wrote:
>> And I believe this hackery is necessary only because nested_svm_vmexit() isn't
>> following the architcture in the first place. I.e. using vmcb01 to restore
>> host state is flat out wrong.
>
> Ah, that's not true, using vmcb01 is allowed by "may store some or all host state
> in hidden on-chip memory".
And also, "Different implementations may choose to save the hidden parts
of the host’s segment registers as well as the selectors".
> From a performance perspective, I do like the SMI/RSM shenanigans. I'm not
> totally opposed to the trickery since I think it will break a guest if and only
> if the L1 guest is also violating the APM. And we're not fudging the spec thaat
> much :-)
Yeah, that was my reasoning as well. Any reference to "hidden on-chip
memory", plus the forbidding modifications of the host save area, sort
of implies that the processor can actually flush that hidden on-chip
memory for whatever reason (such as on some sleep states?!?).
Paolo
next prev parent reply other threads:[~2021-06-23 20:38 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-23 7:44 [PATCH RFC] KVM: nSVM: Fix L1 state corruption upon return from SMM Vitaly Kuznetsov
2021-06-23 9:39 ` Paolo Bonzini
2021-06-23 11:39 ` Maxim Levitsky
2021-06-23 12:00 ` Paolo Bonzini
2021-06-23 13:01 ` Maxim Levitsky
2021-06-23 13:07 ` Maxim Levitsky
2021-06-23 13:32 ` Vitaly Kuznetsov
2021-06-23 14:41 ` Maxim Levitsky
2021-06-23 16:10 ` Sean Christopherson
2021-06-23 16:21 ` Sean Christopherson
2021-06-23 20:37 ` Paolo Bonzini [this message]
2021-06-24 7:41 ` Vitaly Kuznetsov
2021-06-24 8:20 ` Maxim Levitsky
2021-06-24 10:38 ` Paolo Bonzini
2021-06-24 14:32 ` Tom Lendacky
2021-06-24 15:36 ` Maxim Levitsky
2021-06-23 13:21 ` Paolo Bonzini
2021-06-23 14:06 ` Maxim Levitsky
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