Re: [Xen-devel] [PATCH] x86emul: don't allow INVLPG in real mode

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 22.04.16 at 18:08, <andrew.cooper3@xxxxxxxxxx> wrote:
> On 22/04/16 15:17, Jan Beulich wrote:
>> As both INVLPG and INVLPGA have basically the same exception rules
>> (leaving aside that INVLPGA requires SVME enabled, which so far isn't
>> being taken care of,
> 
> We also don't appear to handle the ASID in %ecx correctly either.  Yet
> another item on the TODO list for nested virt.
> 
>>  and that INVLPG requires ModRM.mod != 3), fold
>> the handling of the two as much as possible alongside achieving the
>> goal of the patch (at once doing the #UD checks pror to the #GP one,
>> which ought to be more in line with how hardware does things).
>>
>> But please note that AMD and Intel disagree on what exceptions INVLPG
>> may raise, and the more reasonable Intel variant is being followed.
> 
> Which differences?
> 
> You introduce the !in_protmode() check to the `invlpg` path.  However,
> both manuals agree that it should work in real mode (subject to the lock
> prefix not being in use).  I presume the difference is to whether it is
> eligible for use in vm86 mode, where indeed Intel is stricter than AMD.

Oh, indeed - I must have mixed things up badly. Withdrawing
the patch.

Jan


_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel