Re: [Xen-devel] [PATCH] x86/HVM: correct notion of new CPL in task switch emulation

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 06/06/17 07:42, Jan Beulich wrote:
>>>> On 05.06.17 at 15:06, <andrew.cooper3@xxxxxxxxxx> wrote:
>> On 01/06/17 13:11, Jan Beulich wrote:
>>> Commit aac1df3d03 ("x86/HVM: introduce hvm_get_cpl() and respective
>>> hook") went too far in one aspect: When emulating a task switch we
>>> really shouldn't be looking at what hvm_get_cpl() returns, as we're
>>> switching all segment registers.
>>>
>>> However, instead of reverting the relevant parts of that commit, have
>>> the caller tell the segment loading function what the new CPL is. This
>>> at once fixes ES being loaded before CS so far having had its checks
>>> done against the old CPL.
>>>
>>> Reported-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
>>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
>> On further consideration, wouldn't it be better to audit all segment
>> registers, before updating any of them in the vmcs/vmcb?  This would
>> leave us with a far lower chance of other vmentry failures.
> Overall yes (and I did make a not on my todo list), but I think we
> want to address the regression with no meaningful re-work right
> now.

Entirely reasonable.

~Andrew

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