From: Sean Christopherson <seanjc@google.com>
To: Thomas Prescher <thomas.prescher@cyberus-technology.de>
Cc: "pbonzini@redhat.com" <pbonzini@redhat.com>,
"x86@kernel.org" <x86@kernel.org>,
"dave.hansen@linux.intel.com" <dave.hansen@linux.intel.com>,
"hpa@zytor.com" <hpa@zytor.com>,
Julian Stecklina <julian.stecklina@cyberus-technology.de>,
"tglx@linutronix.de" <tglx@linutronix.de>,
"bp@alien8.de" <bp@alien8.de>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"kvm@vger.kernel.org" <kvm@vger.kernel.org>,
"mingo@redhat.com" <mingo@redhat.com>
Subject: Re: [PATCH 1/2] KVM: nVMX: fix CR4_READ_SHADOW when L0 updates CR4 during a signal
Date: Wed, 17 Apr 2024 09:28:38 -0700 [thread overview]
Message-ID: <Zh_4tsd5rAo4G1Lv@google.com> (raw)
In-Reply-To: <Zh_0sJPPoHKce5Ky@google.com>
On Wed, Apr 17, 2024, Sean Christopherson wrote:
> On Wed, Apr 17, 2024, Thomas Prescher wrote:
> > On Tue, 2024-04-16 at 11:07 -0700, Sean Christopherson wrote:
> > > Hur dur, I forgot that KVM provides a "guest_mode" stat. Userspace can do
> > > KVM_GET_STATS_FD on the vCPU FD to get a file handle to the binary stats,
> > > and then you wouldn't need to call back into KVM just to query guest_mode.
> > >
> > > Ah, and I also forgot that we have kvm_run.flags, so adding
> > > KVM_RUN_X86_GUEST_MODE would also be trivial (I almost suggested it
> > > earlier, but didn't want to add a new field to kvm_run without a very good
> > > reason).
> >
> > Thanks for the pointers. This is really helpful.
> >
> > I tried the "guest_mode" stat as you suggested and it solves the
> > immediate issue we have with VirtualBox/KVM.
>
> Note,
Gah, got distracted. I was going to say that we should add KVM_RUN_X86_GUEST_MODE,
because stats aren't guaranteed ABI[*], i.e. relying on guest_mode could prove
problematic in the long run (though that's unlikely).
[*] https://lore.kernel.org/all/CABgObfZ4kqaXLaOAOj4aGB5GAe9GxOmJmOP+7kdke6OqA35HzA@mail.gmail.com
next prev parent reply other threads:[~2024-04-17 16:28 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-16 12:35 [PATCH 1/2] KVM: nVMX: fix CR4_READ_SHADOW when L0 updates CR4 during a signal Julian Stecklina
2024-04-16 12:35 ` [PATCH 2/2] KVM: nVMX: remove unnecessary CR4_READ_SHADOW write Julian Stecklina
2024-04-16 14:35 ` [PATCH 1/2] KVM: nVMX: fix CR4_READ_SHADOW when L0 updates CR4 during a signal Sean Christopherson
2024-04-16 15:08 ` Thomas Prescher
2024-04-16 15:17 ` Sean Christopherson
2024-04-16 17:31 ` Thomas Prescher
2024-04-16 18:07 ` Sean Christopherson
2024-04-17 13:05 ` Thomas Prescher
2024-04-17 16:11 ` Sean Christopherson
2024-04-17 16:28 ` Sean Christopherson [this message]
2024-04-18 13:48 ` Thomas Prescher
2024-04-18 18:28 ` Sean Christopherson
2024-05-08 13:27 ` Thomas Prescher
2024-04-18 13:46 ` Thomas Prescher
2024-04-18 18:36 ` Sean Christopherson
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