Hi Jason, Am 26.07.2012 21:40, schrieb Jason Baron: > While testing q35, which has its cdrom attached to the ahci controller, I > found > that the Fedora 17 install would panic on boot. The panic occurs while > squashfs is trying to read from the cdrom. The errors are: > > [ 8.622711] SQUASHFS error: xz_dec_run error, data probably corrupt > [ 8.625180] SQUASHFS error: squashfs_read_data failed to read block > 0x20be48a > > I was also able to produce corrupt data reads using an installed piix based > qemu machine, using 'dd'. I found that the corruptions were only occuring when > the read size was greater than 128k. For example, the following command > results in corrupted reads: > > dd if=/dev/sr0 of=/tmp/blah bs=256k iflag=direct > > The > 128k size reads exercise a different code path than 128k and below. In > ide_atapi_cmd_read_dma_cb() s->io_buffer_size is capped at 128k. Thus, > ide_atapi_cmd_read_dma_cb() is called a second time when the read is > 128k. > However, ahci_dma_rw_buf() restart the read from offset 0, instead of at 128k. > Thus, resulting in a corrupted read. > > To fix this, I've introduced 'io_buffer_offset' field in IDEState to keep > track of the offset. I've also modified ahci_populate_sglist() to take a new > 3rd offset argument, so that the sglist is property initialized. > > I've tested this patch using 'dd' testing, and Fedora 17 now correctly boots > and installs on q35 with the cdrom ahci controller. > > Signed-off-by: Jason Baron <jba...@redhat.com>
Tested-by: Andreas Färber <afaer...@suse.de> This also fixes my test case of running the "Check Installation Media" boot menu option on, e.g., openSUSE-12.1-GNOME-LiveCD-x86_64.iso with ich9-ahci (BNC#725008). Thanks a lot for finding the root cause! If you resubmit, please cc qemu-sta...@nongnu.org, I would very much like to backport this bugfix to stable-0.15 branch. Regards, Andreas -- SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer; HRB 16746 AG Nürnberg
