Re: [Xen-devel] [PATCH v2] SVM: limit GIF=0 region

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 29.08.18 at 01:06, <andrew.cooper3@xxxxxxxxxx> wrote:
> On 15/08/18 07:09, Jan Beulich wrote:
>> @@ -96,13 +101,12 @@ __UNLIKELY_END(nsvm_hap)
>>          SPEC_CTRL_ENTRY_FROM_HVM    /* Req: b=curr %rsp=regs/cpuinfo, Clob: 
>> acd */
>>          /* WARNING! `ret`, `call *`, `jmp *` not safe before this point. */
>>  
>> -        STGI
>> -GLOBAL(svm_stgi_label)
>> +        sti
> 
> Nack.  As indicated in v1, moving this breaks SPEC_CTRL_ENTRY_FROM_HVM
> (Even if there is an unexpected bug on the VT-x side of things which
> needs fixing differently).

Well, this increases the pressure to fix the issue. I very much
expect that fix to also take care of the code here. It was
therefore intentional that I did only the technically necessary
adjustments in v2.

I would, btw, likely have tried to find time to look into fixing
that issue, but so far I was under the impression that you are
planning to, and since you've written the code I thought you'd
likely also be in a better position to do so.

> Furthermore, to fix LBR handling, the first thing I'd have to do is
> revert this, so please leave it as it is.

Mind being a little more specific as to the whys here? From a
purely formal pov, Boris'es R-b allows me to put the change in
as is. I'm not overly happy to do the requested change, but I
certainly will, provided - once again - I understand the reason.

Furthermore, please don't forget that the more we delay
especially #MC, the more likely it becomes that a system will
crash in a far less obvious way than by logging an #MC.

Jan



_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxxxxxxxxx
https://lists.xenproject.org/mailman/listinfo/xen-devel