Re: [Xen-devel] [PATCH] VMX: fix realmode emulation SReg handling

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 28.10.16 at 17:29, <andrew.cooper3@xxxxxxxxxx> wrote:
> On 28/10/16 16:24, Jan Beulich wrote:
>> --- a/xen/arch/x86/hvm/vmx/vmx.c
>> +++ b/xen/arch/x86/hvm/vmx/vmx.c
>> @@ -1499,18 +1499,18 @@ static void vmx_update_guest_cr(struct v
>>              /* Entering or leaving real mode: adjust the segment registers.
>>               * Need to read them all either way, as realmode reads can 
>> update
>>               * the saved values we'll use when returning to prot mode. */
>> -            for ( s = x86_seg_cs ; s <= x86_seg_tr ; s++ )
>> +            for ( s = 0; s <= x86_seg_tr ; s++ )
> 
> As you are changing these lines, mind dropping the space between tr and ; ?

How did I not notice them?

> Alternatively, swapping x86_seg_tr for ARRAY_SIZE(reg) so the indices
> never get out of sync?
> 
> Finally, perhaps an extra BUILD_BUG_ON(x86_seg_tr != x86_seg_gs + 1), to
> cover the expectation of this bit of code?

Done both. v2 coming after another smoke test.

Jan


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