From: David Matlack <dmatlack@google.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: "kvm list" <kvm@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"Jim Mattson" <jmattson@google.com>,
"Radim Krčmář" <rkrcmar@redhat.com>
Subject: Re: [PATCH 1/4] KVM: nVMX: support restore of VMX capability MSRs
Date: Tue, 29 Nov 2016 09:42:43 -0800 [thread overview]
Message-ID: <CALzav=dtkhEOcOP5jFM5Vw1Yf-pY-JUbBbz28xGEQzxCFzDGVQ@mail.gmail.com> (raw)
In-Reply-To: <1141665457.516897.1480406475749.JavaMail.zimbra@redhat.com>
On Tue, Nov 29, 2016 at 12:01 AM, Paolo Bonzini <pbonzini@redhat.com> wrote:
>> On Mon, Nov 28, 2016 at 2:48 PM, Paolo Bonzini <pbonzini@redhat.com> wrote:
>> > On 28/11/2016 22:11, David Matlack wrote:
>> >> > PINBASED_CTLS, PROCBASED_CTLS, EXIT_CTLS and ENTRY_CTLS can be derived
>> >> > from their "true" counterparts, so I think it's better to remove the
>> >> > "non-true" ones from struct nested_vmx (and/or add the "true" ones when
>> >> > missing) and make them entirely computed. But it can be done on top.
>> >>
>> >> Good point. And that would mean userspace does not need to restore the
>> >> non-true MSRs, right?
>> >
>> > Yes, sorry for being a bit too concise. :)
>>
>> I'll include this cleanup in the next version of the patchset since it
>> affects which MSRs userspace will restore. It looks like a pretty
>> simple patch.
>
> Don't bother removing the "non-true" registers from nested_vmx; you only
> need to adjust the userspace API.
I already wrote the patch, so unless there's an argument against
removing them I'll include it in the next patchset. Thanks!
>
>> >
>> >> KVM does not emulate MSR_IA32_VMX_BASIC[55]=0,
>> >> and will probably never want to.
>> >
>> > That's a separate question, MSR_IA32_VMX_BASIC[55]=0 basically means
>> > that the "true" capabilities are the same as the "default" capabilities.
>> > If userspace wanted to set it that way, KVM right now would not hide
>> > the "true" capability MSR, but on the other hand the nested hypervisor
>> > should not even notice the difference.
>>
>> KVM would also need to use the non-true MSR in place of the true MSRs
>> when checking VMCS12 during VM-entry.
>
> It's not necessary, userspace would set the relevant bits to 1 in the true
> MSRs, for both the low and high parts. If it doesn't, it's garbage in
> garbage out.
>
> Paolo
next prev parent reply other threads:[~2016-11-29 17:43 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-23 1:14 [PATCH 0/4] VMX Capability MSRs David Matlack
2016-11-23 1:14 ` [PATCH 1/4] KVM: nVMX: support restore of VMX capability MSRs David Matlack
2016-11-23 11:44 ` Paolo Bonzini
2016-11-28 21:11 ` David Matlack
2016-11-28 22:48 ` Paolo Bonzini
2016-11-28 22:57 ` David Matlack
2016-11-29 8:01 ` Paolo Bonzini
2016-11-29 17:42 ` David Matlack [this message]
2016-11-23 1:14 ` [PATCH 2/4] KVM: nVMX: fix checks on CR{0,4} during virtual VMX operation David Matlack
2016-11-23 11:31 ` Paolo Bonzini
2016-11-28 19:51 ` David Matlack
2016-11-23 1:14 ` [PATCH 3/4] KVM: nVMX: accurate emulation of MSR_IA32_CR{0,4}_FIXED1 David Matlack
2016-11-23 9:06 ` Paolo Bonzini
2016-11-23 19:16 ` David Matlack
2016-11-23 19:24 ` Paolo Bonzini
2016-11-23 22:07 ` David Matlack
2016-11-23 22:11 ` Paolo Bonzini
2016-11-23 23:28 ` David Matlack
2016-11-28 21:51 ` David Matlack
2016-11-23 1:14 ` [PATCH 4/4] KVM: nVMX: load GUEST_EFER after GUEST_CR0 during emulated VM-entry David Matlack
2016-11-23 11:45 ` [PATCH 0/4] VMX Capability MSRs Paolo Bonzini
2016-11-28 17:44 ` David Matlack
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