[Xen-devel] Re: Avoid alloc for xsave before xsave_init

[Keir Fraser <keir@xxxxxxx>]

On 13/01/2011 20:21, "Huang2, Wei" <Wei.Huang2@xxxxxxx> wrote:

> Hi Gang,
> 
> Was the issue caused by the uninitialized variable xsave_cntxt_size,
> triggering problem for _xmalloc()? If so, one solution is to set
> xsave_cntxt_size=576 (the default value after reset) as a default value. When
> xsave_alloc_save_area() is called for idel VCPU, _xmalloc() will initialize
> 576 bytes. Idle domain doesn't change xcr0 from my understanding. So its xcr0
> is XSTATE_FP_SSE all the time.

Idle domain isn't using FPU,SSE,AVX or any such extended state and doesn't
need it saved. Xsave_{alloc,free}_save_area() should test-and-exit on
is_idle_vcpu(), and our context switch code should not be doing XSAVE when
switching out an idle vcpu (I hope this is the case already, as it would be
a pointless waste of time).

 -- Keir

> Best,
> -Wei
> 
> -----Original Message-----
> From: xen-devel-bounces@xxxxxxxxxxxxxxxxxxx
> [mailto:xen-devel-bounces@xxxxxxxxxxxxxxxxxxx] On Behalf Of Wei, Gang
> Sent: Thursday, January 13, 2011 12:49 PM
> To: xen-devel@xxxxxxxxxxxxxxxxxxx
> Cc: Keir Fraser; Wei, Gang
> Subject: [Xen-devel] Avoid alloc for xsave before xsave_init
> 
> While debugging some weird booting failure bugs, just found currently,
> xsave_alloc_save_area will be called in
> init_idle_domain->scheduler_init->alloc_vcpu->vcpu_initialise calls, it is
> earlier than xsave_init called in identity_cpu(). This may causing buffer
> overflow on xmem_pool. I am thinking about how to fix it.
> 
> Jimmy
> 
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> http://lists.xensource.com/xen-devel
> 
> 



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