From: Greg KH <gregkh@linuxfoundation.org>
To: Marc Orr <marcorr@google.com>
Cc: linux-kernel@vger.kernel.org, stable@vger.kernel.org,
iommu@lists.linux-foundation.org, robin.murphy@arm.com,
hch@lst.de, jxgao@google.com
Subject: Re: [PATCH] dma: mark unmapped DMA scatter/gather invalid
Date: Mon, 11 Jan 2021 17:15:59 +0100 [thread overview]
Message-ID: <X/x5v4Gjretp4lii@kroah.com> (raw)
In-Reply-To: <20210111154335.23388-1-marcorr@google.com>
On Mon, Jan 11, 2021 at 07:43:35AM -0800, Marc Orr wrote:
> This patch updates dma_direct_unmap_sg() to mark each scatter/gather
> entry invalid, after it's unmapped. This fixes two issues:
>
> 1. It makes the unmapping code able to tolerate a double unmap.
> 2. It prevents the NVMe driver from erroneously treating an unmapped DMA
> address as mapped.
>
> The bug that motivated this patch was the following sequence, which
> occurred within the NVMe driver, with the kernel flag `swiotlb=force`.
>
> * NVMe driver calls dma_direct_map_sg()
> * dma_direct_map_sg() fails part way through the scatter gather/list
> * dma_direct_map_sg() calls dma_direct_unmap_sg() to unmap any entries
> succeeded.
> * NVMe driver calls dma_direct_unmap_sg(), redundantly, leading to a
> double unmap, which is a bug.
>
> With this patch, a hadoop workload running on a cluster of three AMD
> SEV VMs, is able to succeed. Without the patch, the hadoop workload
> suffers application-level and even VM-level failures.
>
> Tested-by: Jianxiong Gao <jxgao@google.com>
> Tested-by: Marc Orr <marcorr@google.com>
> Reviewed-by: Jianxiong Gao <jxgao@google.com>
> Signed-off-by: Marc Orr <marcorr@google.com>
> ---
> kernel/dma/direct.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
<formletter>
This is not the correct way to submit patches for inclusion in the
stable kernel tree. Please read:
https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
for how to do this properly.
</formletter>
_______________________________________________
iommu mailing list
iommu@lists.linux-foundation.org
https://lists.linuxfoundation.org/mailman/listinfo/iommu
WARNING: multiple messages have this Message-ID (diff)
From: Greg KH <gregkh@linuxfoundation.org>
To: Marc Orr <marcorr@google.com>
Cc: hch@lst.de, m.szyprowski@samsung.com, robin.murphy@arm.com,
jxgao@google.com, iommu@lists.linux-foundation.org,
linux-kernel@vger.kernel.org, stable@vger.kernel.org
Subject: Re: [PATCH] dma: mark unmapped DMA scatter/gather invalid
Date: Mon, 11 Jan 2021 17:15:59 +0100 [thread overview]
Message-ID: <X/x5v4Gjretp4lii@kroah.com> (raw)
In-Reply-To: <20210111154335.23388-1-marcorr@google.com>
On Mon, Jan 11, 2021 at 07:43:35AM -0800, Marc Orr wrote:
> This patch updates dma_direct_unmap_sg() to mark each scatter/gather
> entry invalid, after it's unmapped. This fixes two issues:
>
> 1. It makes the unmapping code able to tolerate a double unmap.
> 2. It prevents the NVMe driver from erroneously treating an unmapped DMA
> address as mapped.
>
> The bug that motivated this patch was the following sequence, which
> occurred within the NVMe driver, with the kernel flag `swiotlb=force`.
>
> * NVMe driver calls dma_direct_map_sg()
> * dma_direct_map_sg() fails part way through the scatter gather/list
> * dma_direct_map_sg() calls dma_direct_unmap_sg() to unmap any entries
> succeeded.
> * NVMe driver calls dma_direct_unmap_sg(), redundantly, leading to a
> double unmap, which is a bug.
>
> With this patch, a hadoop workload running on a cluster of three AMD
> SEV VMs, is able to succeed. Without the patch, the hadoop workload
> suffers application-level and even VM-level failures.
>
> Tested-by: Jianxiong Gao <jxgao@google.com>
> Tested-by: Marc Orr <marcorr@google.com>
> Reviewed-by: Jianxiong Gao <jxgao@google.com>
> Signed-off-by: Marc Orr <marcorr@google.com>
> ---
> kernel/dma/direct.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
<formletter>
This is not the correct way to submit patches for inclusion in the
stable kernel tree. Please read:
https://www.kernel.org/doc/html/latest/process/stable-kernel-rules.html
for how to do this properly.
</formletter>
next prev parent reply other threads:[~2021-01-11 16:14 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-11 15:43 [PATCH] dma: mark unmapped DMA scatter/gather invalid Marc Orr
2021-01-11 15:43 ` Marc Orr via iommu
2021-01-11 16:08 ` Robin Murphy
2021-01-11 16:08 ` Robin Murphy
2021-01-11 18:03 ` Marc Orr
2021-01-11 18:03 ` Marc Orr via iommu
2021-01-11 20:39 ` Robin Murphy
2021-01-11 20:39 ` Robin Murphy
2021-01-11 21:36 ` Marc Orr via iommu
2021-01-11 21:36 ` Marc Orr
2021-01-11 16:15 ` Greg KH [this message]
2021-01-11 16:15 ` Greg KH
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=X/x5v4Gjretp4lii@kroah.com \
--to=gregkh@linuxfoundation.org \
--cc=hch@lst.de \
--cc=iommu@lists.linux-foundation.org \
--cc=jxgao@google.com \
--cc=linux-kernel@vger.kernel.org \
--cc=marcorr@google.com \
--cc=robin.murphy@arm.com \
--cc=stable@vger.kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.