From: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
To: Robin Murphy <robin.murphy@arm.com>
Cc: "axboe@kernel.dk" <axboe@kernel.dk>,
"linux-block@vger.kernel.org" <linux-block@vger.kernel.org>,
"ulf.hansson@linaro.org" <ulf.hansson@linaro.org>,
"linux-mmc@vger.kernel.org" <linux-mmc@vger.kernel.org>,
"linux-renesas-soc@vger.kernel.org"
<linux-renesas-soc@vger.kernel.org>,
"wsa+renesas@sang-engineering.com"
<wsa+renesas@sang-engineering.com>,
"iommu@lists.linux-foundation.org"
<iommu@lists.linux-foundation.org>, "hch@lst.de" <hch@lst.de>
Subject: RE: [RFC PATCH v6 3/5] block: add a helper function to merge the segments by an IOMMU
Date: Mon, 17 Jun 2019 06:29:31 +0000 [thread overview]
Message-ID: <OSBPR01MB3590A1AA199894E8220777EFD8EB0@OSBPR01MB3590.jpnprd01.prod.outlook.com> (raw)
In-Reply-To: <039d7388-ed24-c7e7-dd6a-656c719a5ed9@arm.com>
Hi Robin,
> From: Robin Murphy, Sent: Friday, June 14, 2019 6:55 PM
>
> On 13/06/2019 11:20, Yoshihiro Shimoda wrote:
<snip>
> > +bool blk_queue_can_use_iommu_merging(struct request_queue *q,
> > + struct device *dev)
> > +{
> > + struct iommu_domain *domain;
> > +
> > + /*
> > + * If the device DMA is translated by an IOMMU, we can assume
> > + * the device can merge the segments.
> > + */
> > + if (!device_iommu_mapped(dev))
>
> Careful here - I think this validates the comment I made when this
> function was introduced, in that that name doesn't necesarily mean what
> it sounds like it might mean - "iommu_mapped" was as close as we managed
> to get to a convenient shorthand for "performs DMA through an
> IOMMU-API-enabled IOMMU". Specifically, it does not imply that
> translation is *currently* active; if you boot with "iommu=pt" or
> equivalent this will still return true even though the device will be
> using direct/SWIOTLB DMA ops without any IOMMU translation.
Thank you for your comments. I understood the mean of "iommu_mapped" and
this patch's condition causes a problem on iommu=pt.
So, I'll add and additional condition like
"domain->type == IOMMU_DOMAIN_DMA" to check whether the translation is
currently active on the domain or not.
Best regards,
Yoshihiro Shimoda
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next prev parent reply other threads:[~2019-06-17 6:29 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-13 10:20 [RFC PATCH v6 0/5] treewide: improve R-Car SDHI performance Yoshihiro Shimoda
2019-06-13 10:20 ` [RFC PATCH v6 1/5] iommu: add an exported function to get minimum page size for a domain Yoshihiro Shimoda
2019-06-13 19:37 ` Wolfram Sang
2019-06-14 7:16 ` Christoph Hellwig
2019-06-17 5:08 ` Yoshihiro Shimoda
2019-06-14 9:41 ` Robin Murphy
2019-06-17 5:23 ` Yoshihiro Shimoda
2019-06-13 10:20 ` [RFC PATCH v6 2/5] block: sort headers on blk-setting.c Yoshihiro Shimoda
2019-06-13 19:40 ` Wolfram Sang
2019-06-13 10:20 ` [RFC PATCH v6 3/5] block: add a helper function to merge the segments by an IOMMU Yoshihiro Shimoda
2019-06-14 7:22 ` Christoph Hellwig
2019-06-14 9:54 ` Robin Murphy
2019-06-17 6:29 ` Yoshihiro Shimoda [this message]
2019-06-13 10:20 ` [RFC PATCH v6 4/5] mmc: tmio: Use dma_max_mapping_size() instead of a workaround Yoshihiro Shimoda
2019-06-13 19:45 ` Wolfram Sang
2019-06-17 4:25 ` Yoshihiro Shimoda
2019-06-13 20:35 ` Geert Uytterhoeven
2019-06-14 7:18 ` Christoph Hellwig
2019-06-14 7:27 ` Geert Uytterhoeven
2019-06-17 4:54 ` Yoshihiro Shimoda
2019-06-17 6:23 ` Geert Uytterhoeven
2019-06-17 6:54 ` Yoshihiro Shimoda
2019-06-13 10:20 ` [RFC PATCH v6 5/5] mmc: queue: Use bigger segments if IOMMU can merge the segments Yoshihiro Shimoda
2019-06-13 19:58 ` Wolfram Sang
2019-06-17 6:38 ` Yoshihiro Shimoda
2019-06-14 7:24 ` Christoph Hellwig
2019-06-14 10:42 ` Wolfram Sang
2019-06-17 6:46 ` Yoshihiro Shimoda
2019-06-17 6:53 ` Christoph Hellwig
2019-06-17 7:02 ` Yoshihiro Shimoda
2019-06-13 19:36 ` [RFC PATCH v6 0/5] treewide: improve R-Car SDHI performance Wolfram Sang
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