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[Qemu-devel] virtio-blk.c handling of i/o which is not a 512 multiple
From: |
Conor Murphy |
Subject: |
[Qemu-devel] virtio-blk.c handling of i/o which is not a 512 multiple |
Date: |
Wed, 30 Mar 2011 08:48:18 +0000 (UTC) |
User-agent: |
Loom/3.14 (http://gmane.org/) |
Hi,
I'm trying to write a virtio-blk driver for Solaris. I've gotten it to the point
where Solaris can see the device and create a ZFS file system on it.
However when I try and create a UFS filesystem on the device, the VM crashed
with the error
*** glibc detected *** /usr/bin/qemu-kvm: double free or corruption (!prev):
0x00007f2d38000a00 ***
I can reproduce the problem with a simple dd, i.e.
dd if=/dev/zero of=/dev/rdsk/c2d10p0 bs=5000 count=1
My driver will create a virtio-blk request with two elements in the sg list, one
for the first 4096 byes and the other for the remaining 904.
>From stepping through with gdb, virtio_blk_handle_write will sets n_sectors to
>9
(5000 / 512). Later on the code, n_sectors is used the calculate the size of the
buffer required but 9 * 512 is too small and so when the request is process it
ends up writing past the end of the buffer and I guest this triggers the glibc
error.
Is there a requirement for virtio-blk guest drivers that all i/o requests are
sized in multiples of 512 bytes?
Thanks,
Conor
- [Qemu-devel] virtio-blk.c handling of i/o which is not a 512 multiple,
Conor Murphy <=