* [PATCH 0/2] x86/HVM: XSA-267 follow-ups
@ 2018-06-15 8:47 Jan Beulich
2018-06-15 8:58 ` [PATCH 1/2] x86/HVM: account for fully eager FPU mode in emulation Jan Beulich
` (2 more replies)
0 siblings, 3 replies; 8+ messages in thread
From: Jan Beulich @ 2018-06-15 8:47 UTC (permalink / raw)
To: xen-devel; +Cc: Juergen Gross, Andrew Cooper, Paul Durrant
As both XenRT and osstest have found, the XSA-267 patches overlooked a
special case in HVM insn emulation. While looking into this I've also noticed
an omission in the sibling function to the one needing to be changed. At
least patch 1 should be strongly considered for 4.11; patch 2 will need
backporting as well, but doesn't look as urgent.
1: account for fully eager FPU mode in emulation
2: attempts to emulate FPU insns need to set fpu_initialised
Jan
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^ permalink raw reply [flat|nested] 8+ messages in thread
* [PATCH 1/2] x86/HVM: account for fully eager FPU mode in emulation
2018-06-15 8:47 [PATCH 0/2] x86/HVM: XSA-267 follow-ups Jan Beulich
@ 2018-06-15 8:58 ` Jan Beulich
2018-06-15 8:58 ` [PATCH 2/2] x86/HVM: attempts to emulate FPU insns need to set fpu_initialised Jan Beulich
2018-06-15 9:27 ` [PATCH 0/2] x86/HVM: XSA-267 follow-ups Andrew Cooper
2 siblings, 0 replies; 8+ messages in thread
From: Jan Beulich @ 2018-06-15 8:58 UTC (permalink / raw)
To: xen-devel; +Cc: Juergen Gross, Andrew Cooper, Paul Durrant
In fully eager mode we must not clear fpu_dirtied, set CR0.TS, or invoke
the fpu_leave() hook. Instead do what the mode's name says: Restore
state right away.
Signed-off-by: Jan Beulich <jbeulich@suse.com>
--- a/xen/arch/x86/hvm/emulate.c
+++ b/xen/arch/x86/hvm/emulate.c
@@ -2139,13 +2139,20 @@ static void hvmemul_put_fpu(
if ( backout == X86EMUL_FPU_fpu )
{
/*
- * To back out changes to the register file simply adjust state such
- * that upon next FPU insn use by the guest we'll reload the state
- * saved (or freshly loaded) by hvmemul_get_fpu().
+ * To back out changes to the register file
+ * - in fully eager mode, restore original state immediately,
+ * - in lazy mode, simply adjust state such that upon next FPU insn
+ * use by the guest we'll reload the state saved (or freshly loaded)
+ * by hvmemul_get_fpu().
*/
- curr->fpu_dirtied = false;
- stts();
- hvm_funcs.fpu_leave(curr);
+ if ( curr->arch.fully_eager_fpu )
+ vcpu_restore_fpu_eager(curr);
+ else
+ {
+ curr->fpu_dirtied = false;
+ stts();
+ hvm_funcs.fpu_leave(curr);
+ }
}
}
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^ permalink raw reply [flat|nested] 8+ messages in thread
* [PATCH 2/2] x86/HVM: attempts to emulate FPU insns need to set fpu_initialised
2018-06-15 8:47 [PATCH 0/2] x86/HVM: XSA-267 follow-ups Jan Beulich
2018-06-15 8:58 ` [PATCH 1/2] x86/HVM: account for fully eager FPU mode in emulation Jan Beulich
@ 2018-06-15 8:58 ` Jan Beulich
2018-06-22 10:52 ` Ping: " Jan Beulich
2018-06-15 9:27 ` [PATCH 0/2] x86/HVM: XSA-267 follow-ups Andrew Cooper
2 siblings, 1 reply; 8+ messages in thread
From: Jan Beulich @ 2018-06-15 8:58 UTC (permalink / raw)
To: xen-devel; +Cc: Juergen Gross, Andrew Cooper, Paul Durrant
My original way of thinking here was that this would be set anyway at
the point state gets reloaded after the adjustments hvmemul_put_fpu()
does, but the flag should already be set before that - after all the
guest may never again touch the FPU before e.g. getting migrated/saved.
Signed-off-by: Jan Beulich <jbeulich@suse.com>
--- a/xen/arch/x86/hvm/emulate.c
+++ b/xen/arch/x86/hvm/emulate.c
@@ -2053,6 +2053,7 @@ static int hvmemul_get_fpu(
* masking of all exceptions by FNSTENV.)
*/
save_fpu_enable();
+ curr->fpu_initialised = true;
curr->fpu_dirtied = true;
if ( (fpu_ctxt->fcw & 0x3f) != 0x3f )
{
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^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH 0/2] x86/HVM: XSA-267 follow-ups
2018-06-15 8:47 [PATCH 0/2] x86/HVM: XSA-267 follow-ups Jan Beulich
2018-06-15 8:58 ` [PATCH 1/2] x86/HVM: account for fully eager FPU mode in emulation Jan Beulich
2018-06-15 8:58 ` [PATCH 2/2] x86/HVM: attempts to emulate FPU insns need to set fpu_initialised Jan Beulich
@ 2018-06-15 9:27 ` Andrew Cooper
2018-06-15 9:55 ` Jan Beulich
2 siblings, 1 reply; 8+ messages in thread
From: Andrew Cooper @ 2018-06-15 9:27 UTC (permalink / raw)
To: Jan Beulich, xen-devel; +Cc: Juergen Gross, Paul Durrant
On 15/06/18 09:47, Jan Beulich wrote:
> As both XenRT and osstest have found, the XSA-267 patches overlooked a
> special case in HVM insn emulation. While looking into this I've also noticed
> an omission in the sibling function to the one needing to be changed. At
> least patch 1 should be strongly considered for 4.11; patch 2 will need
> backporting as well, but doesn't look as urgent.
>
> 1: account for fully eager FPU mode in emulation
> 2: attempts to emulate FPU insns need to set fpu_initialised
Both Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
At this point, I'm tempted to suggest that we reissue the XSA-267
advisory to include patch 1.
~Andrew
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^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH 0/2] x86/HVM: XSA-267 follow-ups
2018-06-15 9:27 ` [PATCH 0/2] x86/HVM: XSA-267 follow-ups Andrew Cooper
@ 2018-06-15 9:55 ` Jan Beulich
0 siblings, 0 replies; 8+ messages in thread
From: Jan Beulich @ 2018-06-15 9:55 UTC (permalink / raw)
To: Andrew Cooper; +Cc: Juergen Gross, xen-devel, Paul Durrant
>>> On 15.06.18 at 11:27, <andrew.cooper3@citrix.com> wrote:
> On 15/06/18 09:47, Jan Beulich wrote:
>> As both XenRT and osstest have found, the XSA-267 patches overlooked a
>> special case in HVM insn emulation. While looking into this I've also
> noticed
>> an omission in the sibling function to the one needing to be changed. At
>> least patch 1 should be strongly considered for 4.11; patch 2 will need
>> backporting as well, but doesn't look as urgent.
>>
>> 1: account for fully eager FPU mode in emulation
>> 2: attempts to emulate FPU insns need to set fpu_initialised
>
> Both Reviewed-by: Andrew Cooper <andrew.cooper3@citrix.com>
>
> At this point, I'm tempted to suggest that we reissue the XSA-267
> advisory to include patch 1.
Yes, I think we should do this. But let me first see how far this change
is needed, and whether on older versions nothing else is needed in its
stead.
Jan
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^ permalink raw reply [flat|nested] 8+ messages in thread
* Ping: [PATCH 2/2] x86/HVM: attempts to emulate FPU insns need to set fpu_initialised
2018-06-15 8:58 ` [PATCH 2/2] x86/HVM: attempts to emulate FPU insns need to set fpu_initialised Jan Beulich
@ 2018-06-22 10:52 ` Jan Beulich
2018-06-25 7:20 ` Paul Durrant
0 siblings, 1 reply; 8+ messages in thread
From: Jan Beulich @ 2018-06-22 10:52 UTC (permalink / raw)
To: Paul Durrant; +Cc: Juergen Gross, Andrew Cooper, xen-devel
>>> On 15.06.18 at 10:58, <JBeulich@suse.com> wrote:
> My original way of thinking here was that this would be set anyway at
> the point state gets reloaded after the adjustments hvmemul_put_fpu()
> does, but the flag should already be set before that - after all the
> guest may never again touch the FPU before e.g. getting migrated/saved.
>
> Signed-off-by: Jan Beulich <jbeulich@suse.com>
>
> --- a/xen/arch/x86/hvm/emulate.c
> +++ b/xen/arch/x86/hvm/emulate.c
> @@ -2053,6 +2053,7 @@ static int hvmemul_get_fpu(
> * masking of all exceptions by FNSTENV.)
> */
> save_fpu_enable();
> + curr->fpu_initialised = true;
> curr->fpu_dirtied = true;
> if ( (fpu_ctxt->fcw & 0x3f) != 0x3f )
> {
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^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: Ping: [PATCH 2/2] x86/HVM: attempts to emulate FPU insns need to set fpu_initialised
2018-06-22 10:52 ` Ping: " Jan Beulich
@ 2018-06-25 7:20 ` Paul Durrant
0 siblings, 0 replies; 8+ messages in thread
From: Paul Durrant @ 2018-06-25 7:20 UTC (permalink / raw)
To: 'Jan Beulich'; +Cc: Juergen Gross, Andrew Cooper, xen-devel
> -----Original Message-----
> From: Jan Beulich [mailto:JBeulich@suse.com]
> Sent: 22 June 2018 11:53
> To: Paul Durrant <Paul.Durrant@citrix.com>
> Cc: Andrew Cooper <Andrew.Cooper3@citrix.com>; xen-devel <xen-
> devel@lists.xenproject.org>; Juergen Gross <jgross@suse.com>
> Subject: Ping: [PATCH 2/2] x86/HVM: attempts to emulate FPU insns need to
> set fpu_initialised
>
> >>> On 15.06.18 at 10:58, <JBeulich@suse.com> wrote:
> > My original way of thinking here was that this would be set anyway at
> > the point state gets reloaded after the adjustments hvmemul_put_fpu()
> > does, but the flag should already be set before that - after all the
> > guest may never again touch the FPU before e.g. getting migrated/saved.
> >
> > Signed-off-by: Jan Beulich <jbeulich@suse.com>
> >
> > --- a/xen/arch/x86/hvm/emulate.c
> > +++ b/xen/arch/x86/hvm/emulate.c
> > @@ -2053,6 +2053,7 @@ static int hvmemul_get_fpu(
> > * masking of all exceptions by FNSTENV.)
> > */
> > save_fpu_enable();
> > + curr->fpu_initialised = true;
> > curr->fpu_dirtied = true;
> > if ( (fpu_ctxt->fcw & 0x3f) != 0x3f )
> > {
>
Apologies for the delay...
Acked-by: Paul Durrant <paul.durrant@citrix.com>
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^ permalink raw reply [flat|nested] 8+ messages in thread
* Re: [PATCH 0/2] x86/HVM: XSA-267 follow-ups
[not found] <5B237D0B02000078001CB837@suse.com>
@ 2018-06-15 9:29 ` Juergen Gross
0 siblings, 0 replies; 8+ messages in thread
From: Juergen Gross @ 2018-06-15 9:29 UTC (permalink / raw)
To: Jan Beulich, xen-devel; +Cc: Andrew Cooper, Paul Durrant
On 15/06/18 10:47, Jan Beulich wrote:
> As both XenRT and osstest have found, the XSA-267 patches overlooked a
> special case in HVM insn emulation. While looking into this I've also noticed
> an omission in the sibling function to the one needing to be changed. At
> least patch 1 should be strongly considered for 4.11; patch 2 will need
> backporting as well, but doesn't look as urgent.
>
> 1: account for fully eager FPU mode in emulation
> 2: attempts to emulate FPU insns need to set fpu_initialised
For both:
Release-acked-by: Juergen Gross <jgross@suse.com>
Juergen
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2018-06-15 8:47 [PATCH 0/2] x86/HVM: XSA-267 follow-ups Jan Beulich
2018-06-15 8:58 ` [PATCH 1/2] x86/HVM: account for fully eager FPU mode in emulation Jan Beulich
2018-06-15 8:58 ` [PATCH 2/2] x86/HVM: attempts to emulate FPU insns need to set fpu_initialised Jan Beulich
2018-06-22 10:52 ` Ping: " Jan Beulich
2018-06-25 7:20 ` Paul Durrant
2018-06-15 9:27 ` [PATCH 0/2] x86/HVM: XSA-267 follow-ups Andrew Cooper
2018-06-15 9:55 ` Jan Beulich
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