linux-kernel - Re: [PATCH 3/6] x86, kvm: use kernel_fpu_begin/end() in kvm_load/put_guest

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Message-ID: <505AE6C8.90905@redhat.com>
Date:	Thu, 20 Sep 2012 12:50:00 +0300
From:	Avi Kivity <avi@...hat.com>
To:	Suresh Siddha <suresh.b.siddha@...el.com>
CC:	hpa@...or.com, mingo@...nel.org, torvalds@...ux-foundation.org,
	andreas.herrmann3@....com, bp@...64.org, robert.richter@....com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/6] x86, kvm: use kernel_fpu_begin/end() in kvm_load/put_guest_fpu()

On 09/20/2012 03:10 AM, Suresh Siddha wrote:
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index b06737d..8ff328b 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -1493,7 +1493,8 @@ static void __vmx_load_host_state(struct vcpu_vmx *vmx)
>  #ifdef CONFIG_X86_64
>  	wrmsrl(MSR_KERNEL_GS_BASE, vmx->msr_host_kernel_gs_base);
>  #endif
> -	if (user_has_fpu())
> +	/* Did the host task or the guest vcpu has FPU restored lazily? */
> +	if (!use_eager_fpu() && (user_has_fpu() || vmx->vcpu.guest_fpu_loaded))
>  		clts();

Why do the clts() if guest_fpu_loaded()?

An interrupt might arrive after this, look at TS
(interrupted_kernel_fpu_idle()), and stomp on the the guest's fpu.

-- 
error compiling committee.c: too many arguments to function
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