From: konrad.wilk@oracle•com (Konrad Rzeszutek Wilk)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH v8 18/19] swiotlb-xen: no need to do execute two bus_to_phys translations in a row
Date: Wed, 23 Oct 2013 10:01:50 -0400 [thread overview]
Message-ID: <20131023140150.GB27771@phenom.dumpdata.com> (raw)
In-Reply-To: <1382031814-8782-18-git-send-email-stefano.stabellini@eu.citrix.com>
On Thu, Oct 17, 2013 at 06:43:33PM +0100, Stefano Stabellini wrote:
> xen_unmap_single calls xen_bus_to_phys, then passes dev_addr to
> is_xen_swiotlb_buffer that calls xen_bus_to_phys again.
It does?
I see it call mfn_to_local_pfn which calls pfn_to_mfn and
get_phys_to_machine (which I presume is going to be a slow
operation on ARM).
> xen_bus_to_phys is potentially a slow operation that might involve
> walking a tree.
> We can avoid calling xen_bus_to_phys twice by removing the
> is_xen_swiotlb_buffer call and doing the check directly in
> xen_unmap_single using the physical address.
>
> Signed-off-by: Stefano Stabellini <stefano.stabellini@eu•citrix.com>
Have you tested this with a PFN that is in a foreign domain?
I am bit uncomfortable with this - I recall when developing this
that I had hit some odd cases of doing DMA of a page to a guest
and it not always working. It was the case of not detecting whether
the pfn was foreign or not. Sadly I can't recall the details.
I would think that this problem would also be present with ARM?
But perhaps all the new changes in the pfn_to_mfn that had lately
been done have fixed this?
> ---
> drivers/xen/swiotlb-xen.c | 4 ++--
> 1 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
> index 4d50058..6d9ca61 100644
> --- a/drivers/xen/swiotlb-xen.c
> +++ b/drivers/xen/swiotlb-xen.c
> @@ -426,8 +426,8 @@ static void xen_unmap_single(struct device *hwdev, dma_addr_t dev_addr,
>
> xen_dma_unmap_page(hwdev, paddr, size, dir, attrs);
>
> - /* NOTE: We use dev_addr here, not paddr! */
> - if (is_xen_swiotlb_buffer(dev_addr)) {
> + if (paddr >= virt_to_phys(xen_io_tlb_start) &&
> + paddr < virt_to_phys(xen_io_tlb_end)) {
> swiotlb_tbl_unmap_single(hwdev, paddr, size, dir);
> return;
> }
> --
> 1.7.2.5
>
next prev parent reply other threads:[~2013-10-23 14:01 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-10-17 17:42 [PATCH v8 0/19] enable swiotlb-xen on arm and arm64 Stefano Stabellini
2013-10-17 17:43 ` [PATCH v8 01/19] arm: make SWIOTLB available Stefano Stabellini
2013-10-18 15:56 ` Stefano Stabellini
2013-10-17 17:43 ` [PATCH v8 02/19] arm64: define DMA_ERROR_CODE Stefano Stabellini
2013-10-17 17:43 ` [PATCH v8 03/19] arm/xen,arm64/xen: introduce p2m Stefano Stabellini
2013-10-17 17:43 ` [PATCH v8 04/19] xen/x86: allow __set_phys_to_machine for autotranslate guests Stefano Stabellini
2013-10-17 17:43 ` [PATCH v8 05/19] xen: make xen_create_contiguous_region return the dma address Stefano Stabellini
2013-10-17 17:43 ` [PATCH v8 06/19] xen/arm,arm64: enable SWIOTLB_XEN Stefano Stabellini
2013-10-17 17:43 ` [PATCH v8 07/19] swiotlb-xen: introduce xen_swiotlb_set_dma_mask Stefano Stabellini
2013-10-17 17:43 ` [PATCH v8 08/19] arm/xen: get_dma_ops: return xen_dma_ops if we are running as xen_initial_domain Stefano Stabellini
2013-10-18 12:22 ` Stefano Stabellini
2013-10-18 15:42 ` Russell King - ARM Linux
2013-10-18 15:46 ` Stefano Stabellini
2013-10-18 15:48 ` Russell King - ARM Linux
2013-10-18 15:59 ` Stefano Stabellini
2013-10-17 17:43 ` [PATCH v8 09/19] arm64/xen: " Stefano Stabellini
2013-10-17 17:43 ` [PATCH v8 10/19] xen: introduce xen_alloc/free_coherent_pages Stefano Stabellini
2013-10-17 17:43 ` [PATCH v8 11/19] swiotlb-xen: use xen_alloc/free_coherent_pages Stefano Stabellini
2013-10-17 17:43 ` [PATCH v8 12/19] xen: introduce xen_dma_map/unmap_page and xen_dma_sync_single_for_cpu/device Stefano Stabellini
2013-10-17 17:43 ` [PATCH v8 13/19] swiotlb-xen: use xen_dma_map/unmap_page, xen_dma_sync_single_for_cpu/device Stefano Stabellini
2013-10-23 14:09 ` Konrad Rzeszutek Wilk
2013-10-23 17:20 ` Stefano Stabellini
2013-10-23 19:51 ` Konrad Rzeszutek Wilk
2013-10-24 10:44 ` Stefano Stabellini
2013-10-24 13:11 ` Stefano Stabellini
2013-10-25 20:46 ` Konrad Rzeszutek Wilk
2013-10-25 20:44 ` Konrad Rzeszutek Wilk
2013-10-17 17:43 ` [PATCH v8 14/19] ASoC: Samsung: Rename dma_ops by samsung_dma_ops Stefano Stabellini
2013-10-23 14:39 ` Julien Grall
2013-10-17 17:43 ` [PATCH v8 15/19] swiotlb: print a warning when the swiotlb is full Stefano Stabellini
2013-10-17 17:43 ` [PATCH v8 16/19] arm, arm64: do not always merge biovec if we are running on Xen Stefano Stabellini
2013-10-18 12:23 ` [PATCH v8 16/19] arm,arm64: " Stefano Stabellini
2013-10-18 14:07 ` Catalin Marinas
2013-10-17 17:43 ` [PATCH v8 17/19] grant-table: call set_phys_to_machine after mapping grant refs Stefano Stabellini
2013-10-23 14:04 ` Konrad Rzeszutek Wilk
2013-10-23 17:15 ` Stefano Stabellini
2013-10-17 17:43 ` [PATCH v8 18/19] swiotlb-xen: no need to do execute two bus_to_phys translations in a row Stefano Stabellini
2013-10-23 14:01 ` Konrad Rzeszutek Wilk [this message]
2013-10-23 17:34 ` Stefano Stabellini
2013-10-23 19:53 ` Konrad Rzeszutek Wilk
2013-10-24 10:32 ` Stefano Stabellini
2013-10-17 17:43 ` [PATCH v8 19/19] swiotlb-xen: static inline xen_phys_to_bus, xen_bus_to_phys, xen_virt_to_bus and range_straddles_page_boundary Stefano Stabellini
2013-10-23 14:15 ` [PATCH v8 0/19] enable swiotlb-xen on arm and arm64 Konrad Rzeszutek Wilk
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