From: Andrew Cooper <andrew.cooper3@citrix.com>
To: Jan Beulich <jbeulich@suse.com>
Cc: "Roger Pau Monné" <roger.pau@citrix.com>, "Wei Liu" <wl@xen.org>,
Xen-devel <xen-devel@lists.xenproject.org>
Subject: Re: [PATCH v2 04/12] x86/hvm: Reduce stack usage from HVMTRACE_ND()
Date: Tue, 21 Sep 2021 16:38:17 +0100 [thread overview]
Message-ID: <f85e82e9-b75f-5b49-b1a4-86fc90ebde84@citrix.com> (raw)
In-Reply-To: <1ec8d289-5c34-412c-c683-189cd5506600@suse.com>
On 21/09/2021 12:00, Jan Beulich wrote:
> On 20.09.2021 19:25, Andrew Cooper wrote:
>> v2:
>> * Adjust callers of HVMTRACE_ND() too
> What does this refer to? The sole difference to v1 that I can spot
> is ...
Oh - its me who was confused.
I thought I had failed to include the changes in vmx.c/svm.c in v1. In
which case, no change to that in v2.
>> * Drop _d[] for the 0 case.
> ... the one corresponding to this line, i.e. ...
>
>> --- a/xen/include/asm-x86/hvm/trace.h
>> +++ b/xen/include/asm-x86/hvm/trace.h
>> @@ -67,38 +67,30 @@
>> #define TRACE_2_LONG_4D(_e, d1, d2, d3, d4, ...) \
>> TRACE_6D(_e, d1, d2, d3, d4)
>>
>> -#define HVMTRACE_ND(evt, modifier, cycles, count, d1, d2, d3, d4, d5, d6) \
>> +#define HVMTRACE_ND(evt, modifier, cycles, ...) \
>> do { \
>> if ( unlikely(tb_init_done) && DO_TRC_HVM_ ## evt ) \
>> { \
>> - struct { \
>> - u32 d[6]; \
>> - } _d; \
>> - _d.d[0]=(d1); \
>> - _d.d[1]=(d2); \
>> - _d.d[2]=(d3); \
>> - _d.d[3]=(d4); \
>> - _d.d[4]=(d5); \
>> - _d.d[5]=(d6); \
>> + uint32_t _d[] = { __VA_ARGS__ }; \
>> __trace_var(TRC_HVM_ ## evt | (modifier), cycles, \
>> - sizeof(*_d.d) * count, &_d); \
>> + sizeof(_d), sizeof(_d) ? _d : NULL); \
> ... the addition of a conditional operator here (which I assume was
> something a particular compiler didn't like in v1).
And was covered in the commit message:
> The 0 case needs a little help. All object in C must have a unique address
> and _d is passed by pointer. Explicitly permit the optimiser to drop the
> array.
> FAOD - I'm fine
> with the change, but I fear I'm overlooking something (again).
Thanks,
~Andrew
next prev parent reply other threads:[~2021-09-21 15:38 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-20 17:25 [PATCH v2 00/12] xen/trace: Fix leakage of uninitialised stack into the tracebuffer Andrew Cooper
2021-09-20 17:25 ` [PATCH v2 01/12] xen/trace: Don't over-read trace objects Andrew Cooper
2021-09-21 6:53 ` Jan Beulich
2021-09-21 17:51 ` Andrew Cooper
2021-09-22 7:01 ` Jan Beulich
2021-09-22 12:58 ` Andrew Cooper
2021-09-22 13:32 ` Jan Beulich
2021-09-24 14:35 ` Dario Faggioli
2021-09-24 14:51 ` Dario Faggioli
2021-09-27 7:51 ` Jan Beulich
2021-09-30 8:07 ` Dario Faggioli
2021-12-03 16:29 ` Andrew Cooper
2021-09-20 17:25 ` [PATCH v2 02/12] xen/memory: Remove tail padding from TRC_MEM_* records Andrew Cooper
2021-09-24 16:50 ` Dario Faggioli
2021-09-20 17:25 ` [PATCH v2 03/12] xen/credit2: Remove tail padding from TRC_CSCHED2_* records Andrew Cooper
2021-09-24 16:54 ` Dario Faggioli
2021-09-20 17:25 ` [PATCH v2 04/12] x86/hvm: Reduce stack usage from HVMTRACE_ND() Andrew Cooper
2021-09-21 11:00 ` Jan Beulich
2021-09-21 15:38 ` Andrew Cooper [this message]
2021-09-21 15:40 ` Jan Beulich
2021-09-20 17:25 ` [PATCH v2 05/12] x86/hvm: Remove duplicate calls caused by tracing Andrew Cooper
2021-09-21 12:18 ` Jan Beulich
2021-09-21 18:04 ` Andrew Cooper
2021-09-20 17:25 ` [PATCH v2 06/12] xen/credit2: Clean up trace handling Andrew Cooper
2021-09-24 16:55 ` Dario Faggioli
2021-09-20 17:25 ` [PATCH v2 07/12] xen/rt: " Andrew Cooper
2021-09-24 16:56 ` Dario Faggioli
2021-09-20 17:25 ` [PATCH v2 08/12] xen/sched: " Andrew Cooper
2021-09-24 16:57 ` Dario Faggioli
2021-09-20 17:25 ` [PATCH v2 09/12] xen/trace: Minor code cleanup Andrew Cooper
2021-09-21 11:03 ` Jan Beulich
2021-09-24 15:16 ` Dario Faggioli
2021-09-20 17:25 ` [PATCH v2 10/12] x86/pv: Move x86/trace.c to x86/pv/trace.c Andrew Cooper
2021-09-21 15:58 ` Jan Beulich
2021-09-20 17:25 ` [PATCH v2 11/12] xen/arch: Drop asm-*/trace.h Andrew Cooper
2021-09-21 16:01 ` Jan Beulich
2021-10-12 12:31 ` Julien Grall
2021-09-20 17:25 ` [PATCH v2 12/12] x86/trace: Clean up trace handling Andrew Cooper
2021-09-21 16:08 ` Jan Beulich
2021-09-21 18:34 ` Andrew Cooper
2021-09-20 19:29 ` [PATCH v2.1 13/12] xen/trace: Introduce new API Andrew Cooper
2021-09-24 13:21 ` Jan Beulich
2021-09-20 19:32 ` [PATCH v2.1 14/12] xen: Switch to new TRACE() API Andrew Cooper
2021-09-24 13:34 ` Jan Beulich
2021-09-24 15:30 ` Dario Faggioli
2021-09-20 19:33 ` [PATCH v2.1 15/12] xen/trace: Drop old trace macros Andrew Cooper
2021-09-24 13:31 ` Jan Beulich
2021-09-20 19:40 ` [PATCH v2.1 16/12] xen/trace: Restrict CONFIG_TRACEBUFFER to x86 PV Andrew Cooper
2021-09-21 1:10 ` Julien Grall
2021-09-21 20:08 ` [PATCH v2.1 RFC 17/12] xen/trace: Drop cycles parameter Andrew Cooper
2021-09-22 7:03 ` Jan Beulich
2021-09-22 9:38 ` Andrew Cooper
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