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Re: Help with Understanding vcpu xstate restore error during vm migration
- To: Fonyuy-Asheri Caleb <fonyuy-asheri.caleb@xxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Fri, 12 Jul 2024 12:48:52 +0200
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- Cc: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
- Delivery-date: Fri, 12 Jul 2024 10:49:02 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 12.07.2024 11:08, Fonyuy-Asheri Caleb wrote:
>>> I was able to locate the failure point to the file
>>> xen/arch/x86/domctl.c with the following check.
>>>
>>> if( evc->size<PV_XSAVE_HDR_SIZE||
>>> evc->size>PV_XSAVE_SIZE(xfeature_mask) )
>>> gotovcpuextstate_out;
>>
>> It is certainly more complicated than that.
>>
>> What that's saying is that Xen doesn't think that the size of the blob
>> matches expectations. That said - I'm in the middle of rewriting this
>> logic because lots of it is subtly wrong.
>
>
> Following from the check above, I have this other check in the same code
> block.
>
> if ( evc->size == PV_XSAVE_HDR_SIZE )
> ; /* Nothing to restore. */
> else if ( evc->size < PV_XSAVE_HDR_SIZE + XSTATE_AREA_MIN_SIZE )
> ret = -EINVAL; /* Can't be legitimate data. */
> else if ( xsave_area_compressed(_xsave_area) )
> ret = -EOPNOTSUPP; /* Don't support compressed data. */
> else if ( evc->size != PV_XSAVE_SIZE(_xcr0_accum) )
> ret = -EINVAL; /* Not legitimate data. */
>
>
> What do you consider here as legitimate / non-legitimate data ?
In the first case (first "else if"): Simply too small. In the last case:
Size not matching accumulated features.
Jan
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