>>> On 09.08.18 at 11:09, <paul.durr...@citrix.com> wrote:
>> -----Original Message-----
>> From: Jan Beulich [mailto:jbeul...@suse.com]
>> Sent: 09 August 2018 09:02
>> To: xen-devel <xen-devel@lists.xenproject.org>
>> Cc: Andrew Cooper <andrew.coop...@citrix.com>; Paul Durrant
>> <paul.durr...@citrix.com>; George Dunlap <george.dun...@citrix.com>
>> Subject: [PATCH RFC] x86/HVM: meet xentrace's expectations on emulation
>> event data
>>
>> According to the logic in hvm_mmio_assist_process(), 64 bits of data are
>> expected with 64-bit addresses, and 32 bits of data with 32-bit ones. I
>> don't think this is very reasonable, but I'm also not going to touch the
>> consumer side, the more that it is anyway not very helpful for the code
>> here to only ever supply 32 bits of data (despite the field being 64
>> bits wide, and having been even in the 32-bit days of Xen).
>
> I suspect the data field was 64 bits so it could hold addresses, and no-one
> thought about 64 bits of immediate data (which of course you can only get
> with MMIO) whereas you can have 64-bit addresses even with PIO. Anyway the
> change LGTM...
>
>>
>> Signed-off-by: Jan Beulich <jbeul...@suse.com>
>
> Reviewed-by: Paul Durrant <paul.durr...@citrix.com>
Thanks.
George, strictly speaking I could put this in with just this, but
considering ...
>> ---
>> RFC: Untested; solely based on the observation of "(no data)" in a trace
>> where it was entirely unclear why no data would have been available.
>> I just so happened that the guest had more than 4Gb of memory, and
>> hence addresses were not representable as 32-bit values.
... this I'd prefer to have your consent.
Jan
>> --- a/xen/arch/x86/hvm/emulate.c
>> +++ b/xen/arch/x86/hvm/emulate.c
>> @@ -30,7 +30,7 @@ struct hvmemul_cache
>> static void hvmtrace_io_assist(const ioreq_t *p)
>> {
>> unsigned int size, event;
>> - unsigned char buffer[12];
>> + unsigned char buffer[16];
>>
>> if ( likely(!tb_init_done) )
>> return;
>> @@ -47,8 +47,11 @@ static void hvmtrace_io_assist(const ior
>>
>> if ( !p->data_is_ptr )
>> {
>> - *(uint32_t *)&buffer[size] = p->data;
>> - size += 4;
>> + if ( size == 4 )
>> + *(uint32_t *)&buffer[size] = p->data;
>> + else
>> + *(uint64_t *)&buffer[size] = p->data;
>> + size *= 2;
>> }
>>
>> trace_var(event, 0/*!cycles*/, size, buffer);
>>
>>
>>
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