From: Xiao Guangrong <guangrong.xiao@linux.intel.com>
To: Paolo Bonzini <pbonzini@redhat.com>,
Andy Lutomirski <luto@amacapital.net>
Cc: David Matlack <dmatlack@google.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
X86 ML <x86@kernel.org>, kvm list <kvm@vger.kernel.org>,
Ingo Molnar <mingo@redhat.com>,
Andrew Lutomirski <luto@kernel.org>,
"H. Peter Anvin" <hpa@zytor.com>,
Eric Northup <digitaleric@google.com>
Subject: Re: [PATCH 1/1] KVM: don't allow irq_fpu_usable when the VCPU's XCR0 is loaded
Date: Wed, 16 Mar 2016 11:55:05 +0800 [thread overview]
Message-ID: <56E8D919.7080002@linux.intel.com> (raw)
In-Reply-To: <56E86366.10403@redhat.com>
On 03/16/2016 03:32 AM, Paolo Bonzini wrote:
>
>
> On 15/03/2016 19:27, Andy Lutomirski wrote:
>> On Mon, Mar 14, 2016 at 6:17 AM, Paolo Bonzini <pbonzini@redhat.com> wrote:
>>>
>>>
>>> On 11/03/2016 22:33, David Matlack wrote:
>>>>> Is this better than just always keeping the host's XCR0 loaded outside
>>>>> if the KVM interrupts-disabled region?
>>>>
>>>> Probably not. AFAICT KVM does not rely on it being loaded outside that
>>>> region. xsetbv isn't insanely expensive, is it? Maybe to minimize the
>>>> time spent with interrupts disabled it was put outside.
>>>>
>>>> I do like that your solution would be contained to KVM.
>>>
>>> I agree with Andy. We do want a fix for recent kernels because of the
>>> !eager_fpu case that Guangrong mentioned.
Relying on interrupt is not easy as XCR0 can not be automatically saved/loaded
by VMCS... Once interrupt happens, it will use guest's XCR0 anyway.
next prev parent reply other threads:[~2016-03-16 3:55 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-03-11 20:47 [PATCH 0/1] KVM: x86: using the fpu in interrupt context with a guest's xcr0 David Matlack
2016-03-11 20:47 ` [PATCH 1/1] KVM: don't allow irq_fpu_usable when the VCPU's XCR0 is loaded David Matlack
2016-03-11 21:14 ` Andy Lutomirski
2016-03-11 21:33 ` David Matlack
2016-03-14 13:17 ` Paolo Bonzini
2016-03-15 18:27 ` Andy Lutomirski
2016-03-15 19:32 ` Paolo Bonzini
2016-03-16 3:55 ` Xiao Guangrong [this message]
2016-03-16 12:01 ` Paolo Bonzini
2016-03-14 7:46 ` [PATCH 0/1] KVM: x86: using the fpu in interrupt context with a guest's xcr0 Xiao Guangrong
2016-03-15 19:01 ` David Matlack
2016-03-16 3:43 ` Xiao Guangrong
2016-03-16 3:48 ` Andy Lutomirski
2016-03-16 17:11 ` David Matlack
2016-03-16 17:09 ` David Matlack
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