From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:60604) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XP96M-0002J3-7t for qemu-devel@nongnu.org; Wed, 03 Sep 2014 07:51:59 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XP96D-0007U4-62 for qemu-devel@nongnu.org; Wed, 03 Sep 2014 07:51:50 -0400 Received: from mail-qc0-x230.google.com ([2607:f8b0:400d:c01::230]:36135) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XP96D-0007U0-18 for qemu-devel@nongnu.org; Wed, 03 Sep 2014 07:51:41 -0400 Received: by mail-qc0-f176.google.com with SMTP id m20so8287710qcx.7 for ; Wed, 03 Sep 2014 04:51:40 -0700 (PDT) Sender: Paolo Bonzini Message-ID: <540700C7.4080701@redhat.com> Date: Wed, 03 Sep 2014 13:51:35 +0200 From: Paolo Bonzini MIME-Version: 1.0 References: <1404926602-11494-1-git-send-email-kwolf@redhat.com> In-Reply-To: <1404926602-11494-1-git-send-email-kwolf@redhat.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH for-2.1] dma-helpers: Fix too long qiov List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Kevin Wolf , qemu-devel@nongnu.org Cc: stefanha@redhat.com Il 09/07/2014 19:23, Kevin Wolf ha scritto: > If the size of the scatter/gather list isn't a multiple of 512, the > number of sectors for the block layer request is rounded down, resulting > in a qiov that doesn't match the request length. Truncate the qiov to the > new length of the request. > > This fixes the IDE qtest case /x86_64/ide/bmdma/short_prdt. > > Signed-off-by: Kevin Wolf > --- > dma-helpers.c | 4 ++++ > include/qemu-common.h | 1 + > util/iov.c | 13 +++++++++++++ > 3 files changed, 18 insertions(+) > > diff --git a/dma-helpers.c b/dma-helpers.c > index 53cbe92..499b52b 100644 > --- a/dma-helpers.c > +++ b/dma-helpers.c > @@ -170,6 +170,10 @@ static void dma_bdrv_cb(void *opaque, int ret) > return; > } > > + if (dbs->iov.size & ~BDRV_SECTOR_MASK) { > + qemu_iovec_discard_back(&dbs->iov, dbs->iov.size & ~BDRV_SECTOR_MASK); > + } This is right for read/write, but not for discard. Also, it is wrong if you got a misaligned request that straddles a page boundary, and the second half is from a MMIO device. Do you think this works: - add an alignment argument to dma_bdrv_io, and use it instead of 0 in the "if (dbs->iov.size == 0)" conditional - only do the qemu_iovec_discard_back if the SG list has been processed entirely. Paolo > dbs->acb = dbs->io_func(dbs->bs, dbs->sector_num, &dbs->iov, > dbs->iov.size / 512, dma_bdrv_cb, dbs); > assert(dbs->acb); > diff --git a/include/qemu-common.h b/include/qemu-common.h > index ae76197..6ef8282 100644 > --- a/include/qemu-common.h > +++ b/include/qemu-common.h > @@ -329,6 +329,7 @@ size_t qemu_iovec_memset(QEMUIOVector *qiov, size_t offset, > int fillc, size_t bytes); > ssize_t qemu_iovec_compare(QEMUIOVector *a, QEMUIOVector *b); > void qemu_iovec_clone(QEMUIOVector *dest, const QEMUIOVector *src, void *buf); > +void qemu_iovec_discard_back(QEMUIOVector *qiov, size_t bytes); > > bool buffer_is_zero(const void *buf, size_t len); > > diff --git a/util/iov.c b/util/iov.c > index 2b4f46d..24566c8 100644 > --- a/util/iov.c > +++ b/util/iov.c > @@ -550,3 +550,16 @@ size_t iov_discard_back(struct iovec *iov, unsigned int *iov_cnt, > > return total; > } > + > +void qemu_iovec_discard_back(QEMUIOVector *qiov, size_t bytes) > +{ > + size_t total; > + unsigned int niov = qiov->niov; > + > + assert(qiov->size >= bytes); > + total = iov_discard_back(qiov->iov, &niov, bytes); > + assert(total == bytes); > + > + qiov->niov = niov; > + qiov->size -= bytes; > +} >