From: Daniel Gomez <da.gomez@kernel.org>
To: Jesper Wendel Devantier <foss@defmacro.it>
Cc: qemu-devel@nongnu.org, Paolo Bonzini <pbonzini@redhat.com>,
Peter Xu <peterx@redhat.com>,
Philippe Mathieu-Daudé <philmd@mailo.com>,
Keith Busch <kbusch@kernel.org>, Klaus Jensen <its@irrelevant.dk>,
Klaus Jensen <k.jensen@samsung.com>,
qemu-block@nongnu.org, Daniel Gomez <da.gomez@samsung.com>,
GOST <gost.dev@samsung.com>
Subject: Re: [PATCH v2 1/7] dma-helpers: fix unaligned discard_back
Date: Wed, 9 Sep 2026 14:17:07 +0200 [thread overview]
Message-ID: <20260907222356.1-da.gomez@kernel.org> (raw)
In-Reply-To: <20260904235516.2-foss@defmacro.it>
On 2026-09-04T23:57:16+02:00, Jesper Wendel Devantier <foss@defmacro.it> wrote:
>
>
> On 2026-08-19T17:24:03+02:00, Daniel Gomez <da.gomez@kernel.org> wrote:
> > From: Daniel Gomez <da.gomez@samsung.com>
> It is obviously locally correct.
>
> (I am more confused by the code, broadly. How come the IO isn't rejected
> if unaligned?).
IOs were never unaligned from nvme side. However, chunking introduces an
unalignment case that patch 2 fixes by ensuring that each IOV_MAX chunk
boundary is sector-aligned (not present in v1), which is what led me to
this fio test and unalignment check.
But your question made me look at the discard path more closely. And
looking at the commit introducing it, 58f423fbd5f7 "dma-helpers: Fix too
long qiov", it was meant to fix something unrelated: "This fixes the IDE
qtest case /x86_64/ide/bmdma/short_prdt." So, I guess it's fine for that
case.
I will drop the reproducer from the commit message as it belongs to
patch 2.
next prev parent reply other threads:[~2026-09-09 12:18 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-19 15:24 [PATCH v2 0/7] hw/nvme: lift IOV_MAX limit in DMA path Daniel Gomez
2026-08-19 15:24 ` [PATCH v2 1/7] dma-helpers: fix unaligned discard_back Daniel Gomez
2026-09-04 21:57 ` Jesper Wendel Devantier
2026-09-09 12:17 ` Daniel Gomez [this message]
2026-08-19 15:24 ` [PATCH v2 2/7] dma-helpers: ensure IOV_MAX chunks end aligned Daniel Gomez
2026-08-19 15:24 ` [PATCH v2 3/7] dma-helpers: cap iovec allocation at IOV_MAX Daniel Gomez
2026-09-04 21:57 ` Jesper Wendel Devantier
2026-08-19 15:24 ` [PATCH v2 4/7] dma-helpers: chunk dma_blk_cb " Daniel Gomez
2026-09-04 21:58 ` Jesper Wendel Devantier
2026-08-19 15:24 ` [PATCH v2 5/7] hw/nvme: clamp mdts and zasl shifts Daniel Gomez
2026-09-04 21:58 ` Jesper Wendel Devantier
2026-08-19 15:24 ` [PATCH v2 6/7] hw/nvme: drop DMA-path IOV_MAX guard Daniel Gomez
2026-09-04 21:59 ` Jesper Wendel Devantier
2026-08-19 15:24 ` [PATCH v2 7/7] hw/nvme: cap mdts for CMB/PMR-only Daniel Gomez
2026-09-04 22:02 ` Jesper Wendel Devantier
2026-09-09 12:35 ` Daniel Gomez
2026-09-04 22:00 ` [PATCH v2 0/7] hw/nvme: lift IOV_MAX limit in DMA path Keith Busch
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