Re: [Xen-devel] [PATCH] vm_event: Record FS_BASE/GS_BASE during events

[Tamas K Lengyel <tamas.k.lengyel@xxxxxxxxx>]

On Thu, Feb 11, 2016 at 1:13 PM, Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx> wrote:

On 02/11/2016 10:04 PM, Andrew Cooper wrote:
> On 11/02/16 20:00, Razvan Cojocaru wrote:
>> On 02/11/2016 09:55 PM, Andrew Cooper wrote:
>>> On 11/02/16 19:54, Razvan Cojocaru wrote:
>>>> On 02/11/2016 09:51 PM, Tamas K Lengyel wrote:
>>>>> While the public vm_event header specifies fs_base/gs_base as registers that
>>>>> should be recorded for each event, that hasn't actually been the case. In
>>>>> this patch we remedy the issue.
>>>>>
>>>>> Signed-off-by: Tamas K Lengyel <tlengyel@xxxxxxxxxxx>
>>>>> Cc: Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>
>>>>> Cc: Keir Fraser <keir@xxxxxxx>
>>>>> Cc: Jan Beulich <jbeulich@xxxxxxxx>
>>>>> Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
>>>>> ---
>>>>>Â xen/arch/x86/hvm/event.c | 9 ++++++++-
>>>>>Â 1 file changed, 8 insertions(+), 1 deletion(-)
>>>> Fair enough.
>>>>
>>>> Acked-by: Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>
>>> Oops.
>>>
>>> Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
>> This has actually been intentional, in that we've only needed those
>> fields for EPT events, and thought that not filling what's not needed
>> until it's needed would save a tiny bit of hypervisor processing time.
>> They are being filled in only for page fault events at the moment.
>>
>> I believe it's been discussed at the time. We still don't need those
>> coming with the events that use hvm_event_fill_regs(), but if Tamas
>> needs them then by all means.
>
> The public header file does suggest that all of vm_event_regs_x86 will
> be complete. Are there any other fields currently missing?

There are. p2m_vm_event_fill_regs() fills everything in (in
xen/arch/x86/mm/p2m.c). hvm_event_fill_regs() still does not, even after
Tamas' patch.

Ah, that makes sense. Yea, I would prefer if all registers would get filled in for all events so I'll just consolidate these two functions into one.

Tamas

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