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From: "Jan Beulich" <JBeulich@suse.com>
To: David Vrabel <david.vrabel@citrix.com>
Cc: Andrew Cooper <andrew.cooper3@citrix.com>,
	xen-devel@lists.xenproject.org
Subject: Re: [PATCHv2 2/3] x86/fpu: Add a per-domain field to set the width of FIP/FDP
Date: Tue, 23 Feb 2016 08:24:02 -0700	[thread overview]
Message-ID: <56CC87A202000078000D546A@prv-mh.provo.novell.com> (raw)
In-Reply-To: <1456225539-9162-3-git-send-email-david.vrabel@citrix.com>

>>> On 23.02.16 at 12:05, <david.vrabel@citrix.com> wrote:
> @@ -292,17 +296,17 @@ void xsave(struct vcpu *v, uint64_t mask)
>              asm volatile ( "fnstenv %0" : "=m" (fpu_env) );
>              ptr->fpu_sse.fip.sel = fpu_env.fcs;
>              ptr->fpu_sse.fdp.sel = fpu_env.fds;
> -            word_size = 4;
> +            fip_width = 4;
>          }
> +        else
> +            fip_width = 8;
>      }
>      else
>      {
>          XSAVE("");
> -        word_size = 4;
>      }
>  #undef XSAVE
> -    if ( word_size >= 0 )
> -        ptr->fpu_sse.x[FPU_WORD_SIZE_OFFSET] = word_size;
> +    ptr->fpu_sse.x[FPU_WORD_SIZE_OFFSET] = fip_width;
>  }

There's actually a pre-existing bug here that I think should get
fixed at once: The 64-bit save path avoided to update
ptr->fpu_sse.x[FPU_WORD_SIZE_OFFSET] when FPU state
didn't get saved (by setting word_size to -1), which continues to be
the case due to patch 1's changes. The 32-bit code path violated
this even before your change. I.e. the last else visible above
should get extended to return when !(mask & XSTATE_FP).

Jan

  parent reply	other threads:[~2016-02-23 15:24 UTC|newest]

Thread overview: 20+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-02-23 11:05 [PATCHv2 0/3] x86: workaround inability to fully restore FPU state David Vrabel
2016-02-23 11:05 ` [PATCHv2 1/3] x86/fpu: improve check for XSAVE* not writing FIP/FDP fields David Vrabel
2016-02-23 11:18   ` Andrew Cooper
2016-02-23 11:54     ` David Vrabel
2016-02-23 14:07       ` Jan Beulich
2016-02-23 14:59   ` Jan Beulich
2016-02-23 17:42     ` David Vrabel
2016-02-24  7:51       ` Jan Beulich
2016-02-24 10:37         ` Tian, Kevin
2016-02-24 10:49           ` Jan Beulich
2016-03-18 18:23             ` Lai, Paul C
2016-02-23 11:05 ` [PATCHv2 2/3] x86/fpu: Add a per-domain field to set the width of FIP/FDP David Vrabel
2016-02-23 11:10   ` Andrew Cooper
2016-02-23 11:53     ` David Vrabel
2016-02-23 15:24   ` Jan Beulich [this message]
2016-02-23 16:27     ` David Vrabel
2016-02-23 16:39       ` Jan Beulich
2016-02-23 11:05 ` [PATCHv2 3/3] x86/hvm: add HVM_PARAM_X87_FIP_WIDTH David Vrabel
2016-02-23 11:20   ` Andrew Cooper
2016-02-24 11:51     ` Wei Liu

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