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Re: [PATCH v2 1/2] x86/fpu: Combine fpu_ctxt and xsave_area in arch_vcpu
- To: Alejandro Vallejo <alejandro.vallejo@xxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Mon, 12 Aug 2024 17:16:32 +0200
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- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Mon, 12 Aug 2024 15:16:56 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 08.08.2024 15:41, Alejandro Vallejo wrote:
> --- a/xen/arch/x86/domctl.c
> +++ b/xen/arch/x86/domctl.c
> @@ -1344,7 +1344,10 @@ void arch_get_info_guest(struct vcpu *v,
> vcpu_guest_context_u c)
> #define c(fld) (c.nat->fld)
> #endif
>
> - memcpy(&c.nat->fpu_ctxt, v->arch.fpu_ctxt, sizeof(c.nat->fpu_ctxt));
> + memcpy(&c.nat->fpu_ctxt, &v->arch.xsave_area->fpu_sse,
> + sizeof(c.nat->fpu_ctxt));
> + BUILD_BUG_ON(sizeof(c.nat->fpu_ctxt) != sizeof(fpusse_t));
While it may seem unlikely that it would change going forward, I think
that such build-time checks should make no implications at all. I.e.
here the right side ought to be sizeof(v->arch.xsave_area->fpu_sse)
even if that's longer.
Personally I also think that BUILD_BUG_ON(), just like BUG_ON(), would
better live ahead of the construct they're for.
Same again in at least one more place.
Jan
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