On 22 Apr 2022, at 6:04 am, Christoph Hellwig <hch@xxxxxx> wrote:
On Thu, Apr 21, 2022 at 03:01:32PM -0700, Stefano Stabellini wrote:
swiotlb-xen: handle DMA_ATTR_NO_KERNEL_MAPPING
If DMA_ATTR_NO_KERNEL_MAPPING is set then the returned vaddr is a struct
*page instead of the virtual mapping of the buffer.
In xen_swiotlb_alloc_coherent, do not call virt_to_page, instead use the
returned pointer directly. Also do not memset the buffer or struct page
to zero.
In xen_swiotlb_free_coherent, check DMA_ATTR_NO_KERNEL_MAPPING and set
the page pointer appropriately.
Something like that should work, but it makes swiotlb-xen poke even
more into the opaque dma-direct internals. I'd rather do something
like the patch below that uses the dma_direct allocator directly for
arm, and simplifies the xen-swiotlb allocator now that it just needs
to cater to the x86 case:
diff --git a/arch/arm/include/asm/xen/page-coherent.h
b/arch/arm/include/asm/xen/page-coherent.h
deleted file mode 100644
index 27e984977402b..0000000000000
--- a/arch/arm/include/asm/xen/page-coherent.h
+++ /dev/null
@@ -1,2 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-#include <xen/arm/page-coherent.h>
diff --git a/arch/arm/xen/mm.c b/arch/arm/xen/mm.c
index a7e54a087b802..6e603e5fdebb1 100644
--- a/arch/arm/xen/mm.c
+++ b/arch/arm/xen/mm.c
@@ -118,23 +118,6 @@ bool xen_arch_need_swiotlb(struct device *dev,
!dev_is_dma_coherent(dev));
}
-int xen_create_contiguous_region(phys_addr_t pstart, unsigned int order,
- unsigned int address_bits,
- dma_addr_t *dma_handle)
-{
- if (!xen_initial_domain())
- return -EINVAL;
-
- /* we assume that dom0 is mapped 1:1 for now */
- *dma_handle = pstart;
- return 0;
-}
-
-void xen_destroy_contiguous_region(phys_addr_t pstart, unsigned int order)
-{
- return;
-}
-
static int __init xen_mm_init(void)
{
struct gnttab_cache_flush cflush;
diff --git a/arch/arm64/include/asm/xen/page-coherent.h
b/arch/arm64/include/asm/xen/page-coherent.h
deleted file mode 100644
index 27e984977402b..0000000000000
--- a/arch/arm64/include/asm/xen/page-coherent.h
+++ /dev/null
@@ -1,2 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-#include <xen/arm/page-coherent.h>
diff --git a/arch/x86/include/asm/xen/page-coherent.h
b/arch/x86/include/asm/xen/page-coherent.h
deleted file mode 100644
index 63cd41b2e17ac..0000000000000
--- a/arch/x86/include/asm/xen/page-coherent.h
+++ /dev/null
@@ -1,24 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-#ifndef _ASM_X86_XEN_PAGE_COHERENT_H
-#define _ASM_X86_XEN_PAGE_COHERENT_H
-
-#include <asm/page.h>
-#include <linux/dma-mapping.h>
-
-static inline void *xen_alloc_coherent_pages(struct device *hwdev, size_t size,
- dma_addr_t *dma_handle, gfp_t flags,
- unsigned long attrs)
-{
- void *vstart = (void*)__get_free_pages(flags, get_order(size));
- *dma_handle = virt_to_phys(vstart);
- return vstart;
-}
-
-static inline void xen_free_coherent_pages(struct device *hwdev, size_t size,
- void *cpu_addr, dma_addr_t dma_handle,
- unsigned long attrs)
-{
- free_pages((unsigned long) cpu_addr, get_order(size));
-}
-
-#endif /* _ASM_X86_XEN_PAGE_COHERENT_H */
diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
index 47aebd98f52f5..557edb9c54879 100644
--- a/drivers/xen/swiotlb-xen.c
+++ b/drivers/xen/swiotlb-xen.c
@@ -36,7 +36,6 @@
#include <xen/hvc-console.h>
#include <asm/dma-mapping.h>
-#include <asm/xen/page-coherent.h>
#include <trace/events/swiotlb.h>
#define MAX_DMA_BITS 32
@@ -104,6 +103,7 @@ static int is_xen_swiotlb_buffer(struct device *dev,
dma_addr_t dma_addr)
return 0;
}
+#ifdef CONFIG_X86
static int xen_swiotlb_fixup(void *buf, unsigned long nslabs)
{
int rc;
@@ -129,6 +129,12 @@ static int xen_swiotlb_fixup(void *buf, unsigned long
nslabs)
} while (i < nslabs);
return 0;
}
+#else
+static int xen_swiotlb_fixup(void *buf, unsigned long nslabs)
+{
+ return 0;
+}
+#endif
enum xen_swiotlb_err {
XEN_SWIOTLB_UNKNOWN = 0,
@@ -256,97 +262,60 @@ void __init xen_swiotlb_init_early(void)
panic("Cannot allocate SWIOTLB buffer");
swiotlb_set_max_segment(PAGE_SIZE);
}
-#endif /* CONFIG_X86 */
static void *
-xen_swiotlb_alloc_coherent(struct device *hwdev, size_t size,
- dma_addr_t *dma_handle, gfp_t flags,
- unsigned long attrs)
+xen_swiotlb_alloc_coherent(struct device *dev, size_t size,
+ dma_addr_t *dma_handle, gfp_t flags, unsigned long attrs)
{
- void *ret;
+ u64 dma_mask = dev->coherent_dma_mask;
int order = get_order(size);
- u64 dma_mask = DMA_BIT_MASK(32);
phys_addr_t phys;
- dma_addr_t dev_addr;
-
- /*
- * Ignore region specifiers - the kernel's ideas of
- * pseudo-phys memory layout has nothing to do with the
- * machine physical layout. We can't allocate highmem
- * because we can't return a pointer to it.
- */
- flags &= ~(__GFP_DMA | __GFP_HIGHMEM);
+ void *ret;
- /* Convert the size to actually allocated. */
+ /* Align the allocation to the Xen page size */
size = 1UL << (order + XEN_PAGE_SHIFT);
- /* On ARM this function returns an ioremap'ped virtual address for
- * which virt_to_phys doesn't return the corresponding physical
- * address. In fact on ARM virt_to_phys only works for kernel direct
- * mapped RAM memory. Also see comment below.
- */
- ret = xen_alloc_coherent_pages(hwdev, size, dma_handle, flags, attrs);
-
+ ret = (void *)__get_free_pages(flags, get_order(size));
if (!ret)
return ret;
-
- if (hwdev && hwdev->coherent_dma_mask)
- dma_mask = hwdev->coherent_dma_mask;
-
- /* At this point dma_handle is the dma address, next we are
- * going to set it to the machine address.
- * Do not use virt_to_phys(ret) because on ARM it doesn't correspond
- * to *dma_handle. */
- phys = dma_to_phys(hwdev, *dma_handle);
- dev_addr = xen_phys_to_dma(hwdev, phys);
- if (((dev_addr + size - 1 <= dma_mask)) &&
- !range_straddles_page_boundary(phys, size))
- *dma_handle = dev_addr;
- else {
- if (xen_create_contiguous_region(phys, order,
- fls64(dma_mask), dma_handle)
!= 0) {
- xen_free_coherent_pages(hwdev, size, ret,
(dma_addr_t)phys, attrs);
- return NULL;
- }
- *dma_handle = phys_to_dma(hwdev, *dma_handle);
+ phys = virt_to_phys(ret);
+
+ *dma_handle = xen_phys_to_dma(dev, phys);
+ if (*dma_handle + size - 1 > dma_mask ||
+ range_straddles_page_boundary(phys, size)) {
+ if (xen_create_contiguous_region(phys, order, fls64(dma_mask),
+ dma_handle) != 0)
+ goto out_free_pages;
SetPageXenRemapped(virt_to_page(ret));
}
+
memset(ret, 0, size);
return ret;
+
+out_free_pages:
+ free_pages((unsigned long)ret, get_order(size));
+ return NULL;
}
static void
-xen_swiotlb_free_coherent(struct device *hwdev, size_t size, void *vaddr,
- dma_addr_t dev_addr, unsigned long attrs)
+xen_swiotlb_free_coherent(struct device *dev, size_t size, void *vaddr,
+ dma_addr_t dma_handle, unsigned long attrs)
{
+ phys_addr_t phys = virt_to_phys(vaddr);
int order = get_order(size);
- phys_addr_t phys;
- u64 dma_mask = DMA_BIT_MASK(32);
- struct page *page;
-
- if (hwdev && hwdev->coherent_dma_mask)
- dma_mask = hwdev->coherent_dma_mask;
-
- /* do not use virt_to_phys because on ARM it doesn't return you the
- * physical address */
- phys = xen_dma_to_phys(hwdev, dev_addr);
/* Convert the size to actually allocated. */
size = 1UL << (order + XEN_PAGE_SHIFT);
- if (is_vmalloc_addr(vaddr))
- page = vmalloc_to_page(vaddr);
- else
- page = virt_to_page(vaddr);
+ if (WARN_ON_ONCE(dma_handle + size - 1 > dev->coherent_dma_mask) ||
+ WARN_ON_ONCE(range_straddles_page_boundary(phys, size)))
+ return;
- if (!WARN_ON((dev_addr + size - 1 > dma_mask) ||
- range_straddles_page_boundary(phys, size)) &&
- TestClearPageXenRemapped(page))
+ if (TestClearPageXenRemapped(virt_to_page(vaddr)))
xen_destroy_contiguous_region(phys, order);
-
- xen_free_coherent_pages(hwdev, size, vaddr, phys_to_dma(hwdev, phys),
- attrs);
+ free_pages((unsigned long)vaddr, get_order(size));
}
+#endif /* CONFIG_X86 */
/*
* Map a single buffer of the indicated size for DMA in streaming mode. The
@@ -549,8 +518,13 @@ xen_swiotlb_dma_supported(struct device *hwdev, u64 mask)
}
const struct dma_map_ops xen_swiotlb_dma_ops = {
+#ifdef CONFIG_X86
.alloc = xen_swiotlb_alloc_coherent,
.free = xen_swiotlb_free_coherent,
+#else
+ .alloc = dma_direct_alloc,
+ .free = dma_direct_free,
+#endif
.sync_single_for_cpu = xen_swiotlb_sync_single_for_cpu,
.sync_single_for_device = xen_swiotlb_sync_single_for_device,
.sync_sg_for_cpu = xen_swiotlb_sync_sg_for_cpu,
diff --git a/include/xen/arm/page-coherent.h b/include/xen/arm/page-coherent.h
deleted file mode 100644
index b9cc11e887ed5..0000000000000
--- a/include/xen/arm/page-coherent.h
+++ /dev/null
@@ -1,20 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-#ifndef _XEN_ARM_PAGE_COHERENT_H
-#define _XEN_ARM_PAGE_COHERENT_H
-
-#include <linux/dma-mapping.h>
-#include <asm/page.h>
-
-static inline void *xen_alloc_coherent_pages(struct device *hwdev, size_t size,
- dma_addr_t *dma_handle, gfp_t flags, unsigned long attrs)
-{
- return dma_direct_alloc(hwdev, size, dma_handle, flags, attrs);
-}
-
-static inline void xen_free_coherent_pages(struct device *hwdev, size_t size,
- void *cpu_addr, dma_addr_t dma_handle, unsigned long attrs)
-{
- dma_direct_free(hwdev, size, cpu_addr, dma_handle, attrs);
-}
-
-#endif /* _XEN_ARM_PAGE_COHERENT_H */
