From: Paolo Bonzini <pbonzini@redhat.com>
To: Quan Xu <quan.xu0@gmail.com>, Rik van Riel <riel@redhat.com>,
"quan.xu04@gmail.com" <quan.xu04@gmail.com>
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
david@redhat.com, borntraeger@de.ibm.com, tglx@linutronix.de,
rkrcmar@redhat.com
Subject: Re: [PATCH 1/2] x86,kvm: move qemu/guest FPU switching out to vcpu_run
Date: Thu, 16 Nov 2017 14:39:50 +0100 [thread overview]
Message-ID: <756023cd-5ba5-bb31-c7cc-7c91b6201632@redhat.com> (raw)
In-Reply-To: <e3cf353c-a62f-8e1c-685d-3a971605590a@gmail.com>
On 16/11/2017 14:35, Quan Xu wrote:
> but we introduce another method:
>
> -- When the VCPU thread is scheduled back in, the context
> switch code will restore current->thread.fpu to the FPU
> registers.
>
>
> there is still a window to restore current->thread.fpu to the FPU
> registers before enter guest mode and
>
> preempt_disable().
That will always use the host PKRU. The guest PKRU is _never_ visible
to the context switch code, because it's only ever used in a section
that runs with preemption disabled.
It's actually much simpler than before.
Paolo
> on target machine, after migration, the pkru value is source_host_pkru
> in current->thread.fpu.
>
> in case,
>
> source_host_pkru_value != guest_pkru_value,
> target_host_pkru_value == guest_pkru_value..
>
> source_host_pkru_value may be restored to PKRU.. make pkru status
> inconsistent..
next prev parent reply other threads:[~2017-11-16 13:40 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-14 21:54 [PATCH v2 0/2] x86,kvm: move qemu/guest FPU switching out to kvm_arch_vcpu_ioctl_run riel
2017-11-14 21:54 ` [PATCH 1/2] x86,kvm: move qemu/guest FPU switching out to vcpu_run riel
2017-11-15 0:47 ` Wanpeng Li
2017-11-15 3:03 ` Rik van Riel
2017-11-15 4:33 ` Wanpeng Li
2017-11-15 14:40 ` Rik van Riel
2017-11-16 5:54 ` Wanpeng Li
2017-11-15 6:53 ` quan.xu04
2017-11-15 14:43 ` Rik van Riel
2017-11-15 15:09 ` Paolo Bonzini
2017-11-16 2:50 ` Quan Xu
2017-11-16 4:21 ` Rik van Riel
2017-11-16 5:06 ` Quan Xu
2017-11-16 10:21 ` Paolo Bonzini
2017-11-16 12:12 ` Quan Xu
2017-11-16 12:18 ` Paolo Bonzini
2017-11-16 13:35 ` Quan Xu
2017-11-16 13:39 ` Paolo Bonzini [this message]
[not found] ` <d67cef62-3165-50cd-36e8-be7c555dc79e@gmail.com>
2017-11-16 17:50 ` Paolo Bonzini
2017-11-17 2:54 ` Quan Xu
2017-11-14 21:54 ` [PATCH 2/2] x86,kvm: remove KVM emulator get_fpu / put_fpu riel
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