Re: [Qemu-devel] [PATCH 3/6] hypertrace: [*-user] Add QEMU-side proxy to "guest_hypertrace" event

From: "Lluís Vilanova" <vilanova@ac.upc.edu>
To: Eric Blake <eblake@redhat.com>
Cc: qemu-devel@nongnu.org, Riku Voipio <riku.voipio@iki.fi>,
	Stefan Hajnoczi <stefanha@redhat.com>
Subject: Re: [Qemu-devel] [PATCH 3/6] hypertrace: [*-user] Add QEMU-side proxy to "guest_hypertrace" event
Date: Mon, 08 Aug 2016 15:08:06 +0200	[thread overview]
Message-ID: <87h9av8l3d.fsf@fimbulvetr.bsc.es> (raw)
In-Reply-To: <57A4CB91.6050405@redhat.com> (Eric Blake's message of "Fri, 5 Aug 2016 11:23:29 -0600")

Eric Blake writes:

> On 08/05/2016 10:59 AM, Lluís Vilanova wrote:
>> QEMU detects when the guest uses 'mmap' on hypertrace's control channel
>> file, and then uses 'mprotect' to detect accesses to it, which are used
>> to trigger traceing event "guest_hypertrace".

> s/traceing/tracing/

> I'll probably leave the technical review to others, though

Thanks.

>> +++ b/bsd-user/mmap.c
>> @@ -21,6 +21,7 @@
>> #include "qemu.h"
>> #include "qemu-common.h"
>> #include "bsd-mman.h"
>> +#include "hypertrace/user.h"
>> 
>> //#define DEBUG_MMAP
>> 
>> @@ -407,6 +408,7 @@ abi_long target_mmap(abi_ulong start, abi_ulong len, int prot,
>> }
>> }
>> the_end1:
>> +    hypertrace_guest_mmap(fd, (void *)g2h(start));

> Why is the cast to void* needed?

That's unnecessary, my bad.

Thanks,
  Lluis