Linux-Renesas-SoC Archive on lore.kernel.org
 help / color / Atom feed
From: Robin Murphy <robin.murphy@arm.com>
To: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>,
	joro@8bytes.org, axboe@kernel.dk, ulf.hansson@linaro.org,
	wsa+renesas@sang-engineering.com
Cc: linux-renesas-soc@vger.kernel.org, linux-mmc@vger.kernel.org,
	linux-block@vger.kernel.org, iommu@lists.linux-foundation.org,
	hch@lst.de
Subject: Re: [RFC PATCH v6 3/5] block: add a helper function to merge the segments by an IOMMU
Date: Fri, 14 Jun 2019 10:54:38 +0100
Message-ID: <039d7388-ed24-c7e7-dd6a-656c719a5ed9@arm.com> (raw)
In-Reply-To: <1560421215-10750-4-git-send-email-yoshihiro.shimoda.uh@renesas.com>

On 13/06/2019 11:20, Yoshihiro Shimoda wrote:
> This patch adds a helper function whether a queue can merge
> the segments by an IOMMU.
> 
> Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
> ---
>   block/blk-settings.c   | 28 ++++++++++++++++++++++++++++
>   include/linux/blkdev.h |  2 ++
>   2 files changed, 30 insertions(+)
> 
> diff --git a/block/blk-settings.c b/block/blk-settings.c
> index 45f2c52..4e4e13e 100644
> --- a/block/blk-settings.c
> +++ b/block/blk-settings.c
> @@ -4,9 +4,11 @@
>    */
>   #include <linux/bio.h>
>   #include <linux/blkdev.h>
> +#include <linux/device.h>
>   #include <linux/gcd.h>
>   #include <linux/gfp.h>
>   #include <linux/init.h>
> +#include <linux/iommu.h>
>   #include <linux/jiffies.h>
>   #include <linux/kernel.h>
>   #include <linux/lcm.h>
> @@ -831,6 +833,32 @@ void blk_queue_write_cache(struct request_queue *q, bool wc, bool fua)
>   }
>   EXPORT_SYMBOL_GPL(blk_queue_write_cache);
>   
> +/**
> + * blk_queue_can_use_iommu_merging - configure queue for merging segments.
> + * @q:		the request queue for the device
> + * @dev:	the device pointer for dma
> + *
> + * Tell the block layer about the iommu merging of @q.
> + */
> +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.

Robin.

> +		return false;
> +
> +	domain = iommu_get_domain_for_dev(dev);
> +	/* No need to update max_segment_size. see blk_queue_virt_boundary() */
> +	blk_queue_virt_boundary(q, iommu_get_minimum_page_size(domain) - 1);
> +
> +	return true;
> +}
> +
>   static int __init blk_settings_init(void)
>   {
>   	blk_max_low_pfn = max_low_pfn - 1;
> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
> index 592669b..4d1f7dc 100644
> --- a/include/linux/blkdev.h
> +++ b/include/linux/blkdev.h
> @@ -1091,6 +1091,8 @@ extern void blk_queue_dma_alignment(struct request_queue *, int);
>   extern void blk_queue_update_dma_alignment(struct request_queue *, int);
>   extern void blk_queue_rq_timeout(struct request_queue *, unsigned int);
>   extern void blk_queue_write_cache(struct request_queue *q, bool enabled, bool fua);
> +extern bool blk_queue_can_use_iommu_merging(struct request_queue *q,
> +					    struct device *dev);
>   
>   /*
>    * Number of physical segments as sent to the device.
> 

  parent reply index

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 [this message]
2019-06-17  6:29     ` Yoshihiro Shimoda
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

Reply instructions:

You may reply publically 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=039d7388-ed24-c7e7-dd6a-656c719a5ed9@arm.com \
    --to=robin.murphy@arm.com \
    --cc=axboe@kernel.dk \
    --cc=hch@lst.de \
    --cc=iommu@lists.linux-foundation.org \
    --cc=joro@8bytes.org \
    --cc=linux-block@vger.kernel.org \
    --cc=linux-mmc@vger.kernel.org \
    --cc=linux-renesas-soc@vger.kernel.org \
    --cc=ulf.hansson@linaro.org \
    --cc=wsa+renesas@sang-engineering.com \
    --cc=yoshihiro.shimoda.uh@renesas.com \
    /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

Linux-Renesas-SoC Archive on lore.kernel.org

Archives are clonable:
	git clone --mirror https://lore.kernel.org/linux-renesas-soc/0 linux-renesas-soc/git/0.git

	# If you have public-inbox 1.1+ installed, you may
	# initialize and index your mirror using the following commands:
	public-inbox-init -V2 linux-renesas-soc linux-renesas-soc/ https://lore.kernel.org/linux-renesas-soc \
		linux-renesas-soc@vger.kernel.org linux-renesas-soc@archiver.kernel.org
	public-inbox-index linux-renesas-soc


Newsgroup available over NNTP:
	nntp://nntp.lore.kernel.org/org.kernel.vger.linux-renesas-soc


AGPL code for this site: git clone https://public-inbox.org/ public-inbox