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From: Juan Quintela <quintela@redhat.com>
In-Reply-To: <20170106182823.1960-5-dgilbert@redhat.com> (David Alan Gilbert's
	message of "Fri, 6 Jan 2017 18:28:12 +0000")
References: <20170106182823.1960-1-dgilbert@redhat.com>
	<20170106182823.1960-5-dgilbert@redhat.com>
Reply-To: quintela@redhat.com
Date: Wed, 25 Jan 2017 11:08:00 +0100
Message-ID: <87sho778qn.fsf@emacs.mitica>
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Subject: Re: [Qemu-devel] [PATCH 04/15] Fold postcopy_ram_discard_range into
 ram_discard_range
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To: "Dr. David Alan Gilbert (git)" <dgilbert@redhat.com>
Cc: qemu-devel@nongnu.org, amit.shah@redhat.com, aarcange@redhat.com

"Dr. David Alan Gilbert (git)" <dgilbert@redhat.com> wrote:
> From: "Dr. David Alan Gilbert" <dgilbert@redhat.com>
>
> I'd created this weird pair of:
>   ram_discard_range   that lived in migration/ram.c
>      Which is built target-dependent so can access the insides of
>      RAMBlock
>
>   postcopy_ram_discard_range
>      Which actually does the discard.
>
> Flatten these down into ram_discard_range, this relies on the
> CONFIG_MADVISE check to be sure we have the real DONTNEED madvise
> rather than the posix variant that isn't guaranteed to discard pages.
>
> Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>

Reviewed-by: Juan Quintela <quintela@redhat.com>

> @@ -1877,7 +1879,15 @@ int ram_discard_range(MigrationIncomingState *mis,
>                           host_endaddr);
>              goto err;
>          }
> -        ret = postcopy_ram_discard_range(mis, host_startaddr, length);
> +        errno = ENOTSUP;
> +#if defined(CONFIG_MADVISE)
> +        ret = qemu_madvise(host_startaddr, length, QEMU_MADV_DONTNEED);
> +#endif

This really looks weird, we shouldn't arrive here if CONFIG_MADVISE is
not configured, no?

Later, Juan.