On Wed, Nov 15, 2023 at 10:53:45AM +0900, AKASHI Takahiro wrote:
The current implementation may cause BUG_ON() in blkfront_aio() BUG_ON(n > BLKIF_MAX_SEGMENTS_PER_REQUEST);
In pvblock_iop(), a read/write operation will be split into smaller chunks of data so that the size in one access (aio_nbytes) is limited to, at the maximum, BLKIF_MAX_SEGMENTS_PER_REQUEST * PAGE_SIZE
But this works only if when the *buffer* passed in to pvblock_io() is page-aligned. If not, the given data region may stand across (BLKIF_MAX_SEGMENTS_PER_REQUEST + 1) pages. See the logic in blkfront_aio(): start = (uintptr_t)aiocbp->aio_buf & PAGE_MASK; end = ((uintptr_t)aiocbp->aio_buf + aiocbp->aio_nbytes + PAGE_SIZE - 1) & PAGE_MASK; Then this will lead to BUG_ON() above.
This can be fixed by decreasing the maximum size of aio_nbytes.
Signed-off-by: AKASHI Takahiro takahiro.akashi@linaro.org Fixes: commit 3a739cc6c948 ("xen: pvblock: Implement front-back protocol and do IO")
Applied to u-boot/next, thanks!