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From: | Alex Bligh |
Subject: | Re: [Qemu-devel] [Xen-devel] [PATCHv3] QEMU(upstream): Disable xen's use of O_DIRECT by default as it results in crashes. |
Date: | Sun, 31 Mar 2013 19:53:28 +0000 |
Stefano,--On 29 March 2013 17:19:26 +0000 Stefano Stabellini <address@hidden> wrote:
I think so. blkfront reads "sectors" when QEMU moves to XenbusStateConnected, in blkfront_connect. blk_connect is called from xen_be_try_initialise, which moves to XenbusStateConnected on success. So, QEMU's blk_connect will always be called before blkfront's blkfront_connect.Alex, do you have any updates on this patch?
Sorry, I've been snowed under with other stuff. I got to the speed bump below, then didn't get back to it after Paolo's reply. I'll see if I can get some time tomorrow. -- Alex Bligh ---------- Forwarded Message ---------- Date: 20 March 2013 10:26:21 +0100 From: Paolo Bonzini <address@hidden> To: Alex Bligh <address@hidden>CC: Stefano Stabellini <address@hidden>, George Dunlap <address@hidden>, Ian Campbell <address@hidden>, Ian Jackson <address@hidden>, address@hidden, xen-devel <address@hidden>, Anthony Liguori <address@hidden> Subject: Re: [Xen-devel] [PATCHv3] QEMU(upstream): Disable xen's use of O_DIRECT by default as it results in crashes.
Il 20/03/2013 09:33, Alex Bligh ha scritto:
Stefano, --On 19 March 2013 15:13:29 +0000 Stefano Stabellini <address@hidden> wrote:Therefore I think that the current change is not safe, but it is pretty easy to make it safe. You just need to move the call to blk_open from blk_init to blk_connect. Actually you can move most of blk_init to blk_connect, you just need to keep the 4 xenstore_write_be_int at the end of the function.The final of these 4 writes in blk_init is: xenstore_write_be_int(&blkdev->xendev, "sectors", blkdev->file_size / blkdev->file_blk); and blkdev->filesize comes from bdrv_getlength(blkdev->bs), and that requires (I think) bdrv_open to have been called. Can these 4 writes move safely to blk_connect? Or can we write the sectors count as (say) 0 here and fix it later in blk_connect? The remainder look ok.
I think so. blkfront reads "sectors" when QEMU moves to XenbusStateConnected, in blkfront_connect. blk_connect is called from xen_be_try_initialise, which moves to XenbusStateConnected on success. So, QEMU's blk_connect will always be called before blkfront's blkfront_connect. Paolo ---------- End Forwarded Message ----------
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