From: Maxim Levitsky <mlevitsk@redhat.com>
To: Paolo Bonzini <pbonzini@redhat.com>, kvm@vger.kernel.org
Cc: Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
Borislav Petkov <bp@alien8.de>,
Thomas Gleixner <tglx@linutronix.de>,
"H. Peter Anvin" <hpa@zytor.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
"open list:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
<linux-kernel@vger.kernel.org>,
"maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)"
<x86@kernel.org>, Ingo Molnar <mingo@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Sean Christopherson <sean.j.christopherson@intel.com>
Subject: Re: [PATCH 8/8] KVM: nSVM: read only changed fields of the nested guest data area
Date: Thu, 20 Aug 2020 13:26:57 +0300 [thread overview]
Message-ID: <76c13e7d8f3c26583411fc6d42f50c98e92ebc1c.camel@redhat.com> (raw)
In-Reply-To: <be88aaae-c776-32d2-fa69-00c6aace787d@redhat.com>
On Thu, 2020-08-20 at 12:18 +0200, Paolo Bonzini wrote:
> On 20/08/20 12:05, Maxim Levitsky wrote:
> > > You probably should set clean to 0 also if the guest doesn't have the
> > > VMCBCLEAN feature (so, you first need an extra patch to add the
> > > VMCBCLEAN feature to cpufeatures.h). It's probably best to cache the
> > > guest vmcbclean in struct vcpu_svm, too.
> > Right, I totally forgot about this one.
> >
> > One thing why I made this patch optional, is that I can instead drop it,
> > and not 'read back' the saved area on vmexit, this will probably be faster
> > that what this optimization does. What do you think? Is this patch worth it?
> > (I submitted it because I already implemented this and wanted to hear opinion
> > on this).
>
> Yeah, good point. It's one copy either way, either on vmexit (and
> partly on vmentry depending on clean bits) or on vmentry. I had not
> considered the need to copy from vmcb02 to the cached vmcb12 on vmexit. :(
>
> Let's shelve this for a bit, and revisit it once we have separate vmcb01
> and vmcb02. Then we might still use the clean bits to avoid copying
> data from vmcb12 to vmcb02, including avoiding consistency checks
> because we know the vmcb02 data is legit.
It makes sense I guess. The vmcb02 would then play the role of the cache of
vmcb12
>
> Patches 1-5 are still worthwhile, so you can clean them up and send them.
>
> Paolo
OK, on it now.
Best regards,
Maxim Levitsky
>
prev parent reply other threads:[~2020-08-20 10:57 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-08-20 9:13 [PATCH 0/8] KVM: nSVM: ondemand nested state allocation + nested guest state caching Maxim Levitsky
2020-08-20 9:13 ` [PATCH 1/8] KVM: SVM: rename a variable in the svm_create_vcpu Maxim Levitsky
2020-08-20 9:13 ` [PATCH 2/8] KVM: nSVM: rename nested 'vmcb' to vmcb_gpa in few places Maxim Levitsky
2020-08-20 9:56 ` Paolo Bonzini
2020-08-20 10:00 ` Maxim Levitsky
2020-08-20 10:19 ` Paolo Bonzini
2020-08-20 10:23 ` Maxim Levitsky
2020-08-20 10:56 ` Paolo Bonzini
2020-08-20 11:52 ` Maxim Levitsky
2020-08-20 9:13 ` [PATCH 3/8] KVM: SVM: refactor msr permission bitmap allocation Maxim Levitsky
2020-08-20 9:13 ` [PATCH 4/8] KVM: x86: allow kvm_x86_ops.set_efer to return a value Maxim Levitsky
2020-08-20 9:13 ` [PATCH 5/8] KVM: nSVM: implement ondemand allocation of the nested state Maxim Levitsky
2020-08-20 9:58 ` Paolo Bonzini
2020-08-20 10:02 ` Maxim Levitsky
2020-08-20 9:13 ` [PATCH 6/8] SVM: nSVM: cache whole nested vmcb instead of only its control area Maxim Levitsky
2020-08-20 9:13 ` [PATCH 7/8] KVM: nSVM: implement caching of nested vmcb save area Maxim Levitsky
2020-08-20 9:13 ` [PATCH 8/8] KVM: nSVM: read only changed fields of the nested guest data area Maxim Levitsky
2020-08-20 9:55 ` Paolo Bonzini
2020-08-20 9:57 ` Maxim Levitsky
2020-08-20 10:01 ` Paolo Bonzini
2020-08-20 10:05 ` Maxim Levitsky
2020-08-20 10:18 ` Paolo Bonzini
2020-08-20 10:26 ` Maxim Levitsky [this message]
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