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From: Gerd Hoffmann <kraxel@redhat.com>
To: Michael Tokarev <mjt@tls.msk.ru>
Cc: Anthony PERARD <anthony.perard@citrix.com>,
	qemu-trivial@nongnu.org, Alon Levy <alevy@redhat.com>,
	QEMU-devel <qemu-devel@nongnu.org>,
	qemu-stable <qemu-stable@nongnu.org>
Subject: Re: [Qemu-trivial] [PATCH] qxl: Fix QXLRam initialisation.
Date: Tue, 18 Jun 2013 07:37:30 +0200	[thread overview]
Message-ID: <51BFF21A.7050008@redhat.com> (raw)
In-Reply-To: <51BFCDA1.8040507@msgid.tls.msk.ru>

  Hi,

>> If memory is set to 0xc2c2.., it leads to a spice-critical error when
>> trying to start qxl.

> But maybe instead of doing it this way, we should just memset the
> whole thing to 0, to avoid similar bugs in the future?  Are there
> any arches out there which have cpu_to_le32(0) != 0 ?

On qemu + kvm guest memory (including pci device memory where this lives
in) _is_ zero initialized.

IIRC xen has a debug mode where it fills memory with non-zero values
instead, for debugging / testing purposes, and this is where things blow up.

So while the fix is clearly correct, the patch isn't as critical as it
initially looks like.

Reviewed-by: Gerd Hoffmann <kraxel@redhat.com>

cheers,
  Gerd



WARNING: multiple messages have this Message-ID (diff)
From: Gerd Hoffmann <kraxel@redhat.com>
To: Michael Tokarev <mjt@tls.msk.ru>
Cc: Anthony PERARD <anthony.perard@citrix.com>,
	qemu-trivial@nongnu.org, Alon Levy <alevy@redhat.com>,
	QEMU-devel <qemu-devel@nongnu.org>,
	qemu-stable <qemu-stable@nongnu.org>
Subject: Re: [Qemu-devel] [Qemu-trivial] [PATCH] qxl: Fix QXLRam initialisation.
Date: Tue, 18 Jun 2013 07:37:30 +0200	[thread overview]
Message-ID: <51BFF21A.7050008@redhat.com> (raw)
In-Reply-To: <51BFCDA1.8040507@msgid.tls.msk.ru>

  Hi,

>> If memory is set to 0xc2c2.., it leads to a spice-critical error when
>> trying to start qxl.

> But maybe instead of doing it this way, we should just memset the
> whole thing to 0, to avoid similar bugs in the future?  Are there
> any arches out there which have cpu_to_le32(0) != 0 ?

On qemu + kvm guest memory (including pci device memory where this lives
in) _is_ zero initialized.

IIRC xen has a debug mode where it fills memory with non-zero values
instead, for debugging / testing purposes, and this is where things blow up.

So while the fix is clearly correct, the patch isn't as critical as it
initially looks like.

Reviewed-by: Gerd Hoffmann <kraxel@redhat.com>

cheers,
  Gerd

  reply	other threads:[~2013-06-18  7:15 UTC|newest]

Thread overview: 10+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2013-06-17 16:38 [Qemu-trivial] [PATCH] qxl: Fix QXLRam initialisation Anthony PERARD
2013-06-17 16:38 ` [Qemu-devel] " Anthony PERARD
2013-06-18  3:01 ` [Qemu-trivial] " Michael Tokarev
2013-06-18  3:01   ` [Qemu-devel] " Michael Tokarev
2013-06-18  5:37   ` Gerd Hoffmann [this message]
2013-06-18  5:37     ` Gerd Hoffmann
2013-06-18 12:42     ` Anthony PERARD
2013-06-18 12:42       ` [Qemu-devel] " Anthony PERARD
2013-06-19  7:45 ` Michael Tokarev
2013-06-19  7:45   ` [Qemu-devel] " Michael Tokarev

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