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From: Andrea Arcangeli <aarcange@redhat.com>
To: "Daniel P. Berrange" <berrange@redhat.com>
Cc: qemu-devel@nongnu.org, Michal Privoznik <mprivozn@redhat.com>,
	Jitendra Kolhe <jitendra.kolhe@hpe.com>,
	Stefan Hajnoczi <stefanha@redhat.com>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Eric Blake <eblake@redhat.com>
Subject: Re: [Qemu-devel] [PATCH v3] os: don't corrupt pre-existing memory-backend data with prealloc
Date: Fri, 3 Mar 2017 17:10:39 +0100	[thread overview]
Message-ID: <20170303161039.GB7496@redhat.com> (raw)
In-Reply-To: <20170303113255.28262-1-berrange@redhat.com>

On Fri, Mar 03, 2017 at 11:32:55AM +0000, Daniel P. Berrange wrote:
> When using a memory-backend object with prealloc turned on, QEMU
> will memset() the first byte in every memory page to zero. While
> this might have been acceptable for memory backends associated
> with RAM, this corrupts application data for NVDIMMs.
> 
> Instead of setting every page to zero, read the current byte
> value and then just write that same value back, so we are not
> corrupting the original data. Directly write the value instead
> of memset()ing it, since there's no benefit to memset for a
> single byte write.
> 
> Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
> ---
> 
> Changed in v3:

Reviewed-by: Andrea Arcangeli <aarcange@redhat.com>

Thanks,
Andrea

  parent reply	other threads:[~2017-03-03 16:10 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-03-03 11:32 [Qemu-devel] [PATCH v3] os: don't corrupt pre-existing memory-backend data with prealloc Daniel P. Berrange
2017-03-03 11:38 ` no-reply
2017-03-03 16:10 ` Andrea Arcangeli [this message]
2017-03-10  4:27 ` Stefan Hajnoczi
2017-03-10  4:30 ` Stefan Hajnoczi
2017-03-10  8:34   ` Paolo Bonzini

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