From: Christoph Hellwig <hch@lst.de>
To: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: "Christoph Hellwig" <hch@lst.de>,
"Marek Marczykowski-Górecki" <marmarek@invisiblethingslab.com>,
"Juergen Gross" <jgross@suse.com>,
"Stefano Stabellini" <sstabellini@kernel.org>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Ingo Molnar" <mingo@redhat.com>,
"Borislav Petkov" <bp@alien8.de>,
"Dave Hansen" <dave.hansen@linux.intel.com>,
x86@kernel.org, "H. Peter Anvin" <hpa@zytor.com>,
"Ben Skeggs" <bskeggs@redhat.com>,
"Karol Herbst" <kherbst@redhat.com>,
"Lyude Paul" <lyude@redhat.com>,
xen-devel@lists.xenproject.org, iommu@lists.linux.dev,
linux-kernel@vger.kernel.org, nouveau@lists.freedesktop.org
Subject: Re: [PATCH 2/4] x86: always initialize xen-swiotlb when xen-pcifront is enabling
Date: Sat, 20 May 2023 08:21:03 +0200 [thread overview]
Message-ID: <20230520062103.GA1225@lst.de> (raw)
In-Reply-To: <20230519125857.GA6994@lst.de>
On Fri, May 19, 2023 at 02:58:57PM +0200, Christoph Hellwig wrote:
> On Fri, May 19, 2023 at 01:49:46PM +0100, Andrew Cooper wrote:
> > > The alternative would be to finally merge swiotlb-xen into swiotlb, in
> > > which case we might be able to do this later. Let me see what I can
> > > do there.
> >
> > If that is an option, it would be great to reduce the special-cashing.
>
> I think it's doable, and I've been wanting it for a while. I just
> need motivated testers, but it seems like I just found at least two :)
So looking at swiotlb-xen it does these off things where it takes a value
generated originally be xen_phys_to_dma, then only does a dma_to_phys
to go back and call pfn_valid on the result. Does this make sense, or
is it wrong and just works by accident? I.e. is the patch below correct?
diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
index 67aa74d201627d..3396c5766f0dd8 100644
--- a/drivers/xen/swiotlb-xen.c
+++ b/drivers/xen/swiotlb-xen.c
@@ -90,9 +90,7 @@ static inline int range_straddles_page_boundary(phys_addr_t p, size_t size)
static int is_xen_swiotlb_buffer(struct device *dev, dma_addr_t dma_addr)
{
- unsigned long bfn = XEN_PFN_DOWN(dma_to_phys(dev, dma_addr));
- unsigned long xen_pfn = bfn_to_local_pfn(bfn);
- phys_addr_t paddr = (phys_addr_t)xen_pfn << XEN_PAGE_SHIFT;
+ phys_addr_t paddr = xen_dma_to_phys(dev, dma_addr);
/* If the address is outside our domain, it CAN
* have the same virtual address as another address
@@ -234,7 +232,7 @@ static dma_addr_t xen_swiotlb_map_page(struct device *dev, struct page *page,
done:
if (!dev_is_dma_coherent(dev) && !(attrs & DMA_ATTR_SKIP_CPU_SYNC)) {
- if (pfn_valid(PFN_DOWN(dma_to_phys(dev, dev_addr))))
+ if (pfn_valid(PFN_DOWN(phys)))
arch_sync_dma_for_device(phys, size, dir);
else
xen_dma_sync_for_device(dev, dev_addr, size, dir);
@@ -258,7 +256,7 @@ static void xen_swiotlb_unmap_page(struct device *hwdev, dma_addr_t dev_addr,
BUG_ON(dir == DMA_NONE);
if (!dev_is_dma_coherent(hwdev) && !(attrs & DMA_ATTR_SKIP_CPU_SYNC)) {
- if (pfn_valid(PFN_DOWN(dma_to_phys(hwdev, dev_addr))))
+ if (pfn_valid(PFN_DOWN(paddr)))
arch_sync_dma_for_cpu(paddr, size, dir);
else
xen_dma_sync_for_cpu(hwdev, dev_addr, size, dir);
@@ -276,7 +274,7 @@ xen_swiotlb_sync_single_for_cpu(struct device *dev, dma_addr_t dma_addr,
phys_addr_t paddr = xen_dma_to_phys(dev, dma_addr);
if (!dev_is_dma_coherent(dev)) {
- if (pfn_valid(PFN_DOWN(dma_to_phys(dev, dma_addr))))
+ if (pfn_valid(PFN_DOWN(paddr)))
arch_sync_dma_for_cpu(paddr, size, dir);
else
xen_dma_sync_for_cpu(dev, dma_addr, size, dir);
@@ -296,7 +294,7 @@ xen_swiotlb_sync_single_for_device(struct device *dev, dma_addr_t dma_addr,
swiotlb_sync_single_for_device(dev, paddr, size, dir);
if (!dev_is_dma_coherent(dev)) {
- if (pfn_valid(PFN_DOWN(dma_to_phys(dev, dma_addr))))
+ if (pfn_valid(PFN_DOWN(paddr)))
arch_sync_dma_for_device(paddr, size, dir);
else
xen_dma_sync_for_device(dev, dma_addr, size, dir);
next prev parent reply other threads:[~2023-05-20 6:25 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-18 13:42 unexport swiotlb_active Christoph Hellwig
2023-05-18 13:42 ` [PATCH 1/4] x86: move a check out of pci_xen_swiotlb_init Christoph Hellwig
2023-05-18 13:42 ` [PATCH 2/4] x86: always initialize xen-swiotlb when xen-pcifront is enabling Christoph Hellwig
2023-05-18 18:18 ` Marek Marczykowski-Górecki
2023-05-19 4:04 ` Christoph Hellwig
2023-05-19 10:10 ` Marek Marczykowski-Górecki
2023-05-19 12:41 ` Christoph Hellwig
2023-05-19 12:49 ` Andrew Cooper
2023-05-19 12:58 ` Christoph Hellwig
2023-05-20 6:21 ` Christoph Hellwig [this message]
2023-05-22 7:52 ` Petr Tesařík
2023-05-22 7:54 ` Petr Tesařík
2023-05-22 8:37 ` Juergen Gross
2023-06-07 13:12 ` Christoph Hellwig
2023-06-09 15:38 ` Juergen Gross
2023-06-12 6:47 ` Christoph Hellwig
2023-06-12 8:08 ` Juergen Gross
2023-06-12 8:23 ` Christoph Hellwig
2023-05-18 13:42 ` [PATCH 3/4] drm/nouveau: stop using is_swiotlb_active Christoph Hellwig
2023-05-18 20:30 ` Lyude Paul
2023-06-07 13:11 ` Christoph Hellwig
2023-05-18 13:42 ` [PATCH 4/4] swiotlb: unexport is_swiotlb_active Christoph Hellwig
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