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Re: [PATCH v5 2/6] x86/gdbsx: Rename debug.c to gdbsx.c


  • To: Jan Beulich <jbeulich@xxxxxxxx>
  • From: Andrew Cooper <Andrew.Cooper3@xxxxxxxxxx>
  • Date: Thu, 21 Apr 2022 17:29:35 +0000
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  • Cc: Bobby Eshleman <bobby.eshleman@xxxxxxxxx>, Roger Pau Monne <roger.pau@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
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  • Thread-topic: [PATCH v5 2/6] x86/gdbsx: Rename debug.c to gdbsx.c

On 21/04/2022 14:06, Jan Beulich wrote:
> On 20.04.2022 16:13, Andrew Cooper wrote:
>> From: Bobby Eshleman <bobby.eshleman@xxxxxxxxx>
>>
>> debug.c contains only dbg_rw_mem().  Rename it to gdbsx.c.
>>
>> Move gdbsx_guest_mem_io(), and the prior setup of iop->remain, from domctl.c
>> to gdbsx.c, merging it with dbg_rw_mem().
>>
>> Signed-off-by: Bobby Eshleman <bobby.eshleman@xxxxxxxxx>
>> Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>

Thanks.

>
>> The semantics are rather broken.  XEN_DOMCTL_gdbsx_guestmemio only sets
>> copyback when there's nothing to copy back, and skips copying back in the
>> -EFAULT case when the iop->remain field is relevant.  Furthermore, it can be
>> asked to move up to 4GB in one go, with no continuability whatsoever.
> The last point perhaps isn't overly much of a problem for this specific
> operation.

It's also not terribly hard to fix, but I really don't have time to get
bogged down in "make the gdbsx hypercalls sane". 
XEN_DOMCTL_gdbsx_domstatus is a disaster, and there are far better ways
of doing this.  https://www.youtube.com/watch?v=osZeioYKsxA is one which
was presented at XenSummit in 2019.

~Andrew

 


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