Am 07.02.2023 um 10:19 hat Cédric Le Goater geschrieben: > On 2/7/23 09:38, Kevin Wolf wrote: > > Am 06.02.2023 um 16:54 hat Cédric Le Goater geschrieben: > > > On 1/20/23 13:25, Kevin Wolf wrote: > > > > From: Xiang Zheng <zhengxia...@huawei.com> > > > > > > > > Currently we fill the VIRT_FLASH memory space with two 64MB NOR images > > > > when using persistent UEFI variables on virt board. Actually we only use > > > > a very small(non-zero) part of the memory while the rest significant > > > > large(zero) part of memory is wasted. > > > > > > > > So this patch checks the block status and only writes the non-zero part > > > > into memory. This requires pflash devices to use sparse files for > > > > backends. > > > > > > > > Signed-off-by: Xiang Zheng <zhengxia...@huawei.com> > > > > > > > > [ kraxel: rebased to latest master ] > > > > > > > > Signed-off-by: Gerd Hoffmann <kra...@redhat.com> > > > > Message-Id: <20221220084246.1984871-1-kra...@redhat.com> > > > > Reviewed-by: Daniel P. Berrangé <berra...@redhat.com> > > > > Reviewed-by: Kevin Wolf <kw...@redhat.com> > > > > Signed-off-by: Kevin Wolf <kw...@redhat.com> > > > > > > This newly merged patch introduces a "regression" when booting an Aspeed > > > machine. The following extra m25p80 patch (not yet merged) is required > > > for the issue to show: > > > > > > > > > https://lore.kernel.org/qemu-devel/20221115151000.2080833-1-...@kaod.org/ > > > > > > U-Boot fails to find the filesystem in that case. > > > > > > It can be easily reproduced with the witherspoon-bmc machine and seems > > > to be related to the use of a UBI filesystem. Other Aspeed machines not > > > using UBI are not impacted. > > > > > > Here is a tentative fix. I don't know enough the block layer to explain > > > what is happening :/ > > > > I was puzzled for a moment, but... > > > > > @@ -39,7 +39,7 @@ static int blk_pread_nonzeroes(BlockBack > > > return ret; > > > } > > > if (!(ret & BDRV_BLOCK_ZERO)) { > > > - ret = bdrv_pread(bs->file, offset, bytes, > > > > 'bs->file' rather than 'bs' really looks wrong. I think replacing that > > would already fix the bug you're seeing. > > > > Just to be sure, how did you configure the block backend? bs->file would > > happen to work more or less with raw over file-posix (which is probably > > what Gerd tested), but I think it breaks with anything else. > > The command is : > > $ qemu-system-arm -M witherspoon-bmc -net user \ > -drive file=/path/to/file.mtd,format=raw,if=mtd \ > -nographic -serial mon:stdio -snapshot > > If I remove '-snapshot', all works fine.
Ok, that makes sense then. -snapshot creates a temporary qcow2 overlay, and then what your guest sees with bs->file is not the virtual disk content of the qcow2 image, but the qcow2 file itself. Kevin
