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Re: [PATCH v3 2/6] x86/debugger: separate Xen and guest debugging debugger_trap_* functions

  • To: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
  • From: Jan Beulich <jbeulich@xxxxxxxx>
  • Date: Tue, 24 Aug 2021 15:07:36 +0200
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  • Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Volodymyr Babchuk <Volodymyr_Babchuk@xxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Elena Ufimtseva <elena.ufimtseva@xxxxxxxxxx>, Jun Nakajima <jun.nakajima@xxxxxxxxx>, Kevin Tian <kevin.tian@xxxxxxxxx>, George Dunlap <george.dunlap@xxxxxxxxxx>, Ian Jackson <iwj@xxxxxxxxxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx, Bobby Eshleman <bobby.eshleman@xxxxxxxxx>
  • Delivery-date: Tue, 24 Aug 2021 13:07:45 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On 24.08.2021 14:41, Andrew Cooper wrote:
> On 24/08/2021 13:16, Jan Beulich wrote:
>> On 18.08.2021 22:29, Bobby Eshleman wrote:
>>> Unlike debugger_trap_fatal() and debugger_trap_immediate(),
>>> debugger_trap_entry() is specific to guest debugging and *NOT* the
>>> debugging of Xen itself. That is, it is part of gdbsx functionality and
>>> not the Xen gdstub. This is evidenced by debugger_trap_fatal()'s usage
>>> of domain_pause_for_debugger(). Because of this, debugger_trap_entry()
>>> does not belong alongside the generic Xen debugger functionality.
>> I'm not convinced this is what the original intentions were. Instead I
>> think this was meant to be a generic hook function which initially
>> only cared to deal with the gdbsx needs.
> It doesn't exactly matter what the original intentions where - what we
> currently have is unused and and a clear source of confusion between two
> unrelated subsystems.
> It is unclear that the gdbstub is even usable, given at least a decade
> of bitrot.
> Keeping an empty static inline in the enabled case is nonsense, because
> at the point you need to edit Xen to insert some real debugging, there
> are better ways to do it in something which isn't even a catch-all
> despite appearing to be one.

Perhaps I should have said explicitly that my remark isn't an objection
to the code change, but a suggestion to weaken the claims made in the




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