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Subject[PATCH v3 3/3] xen/swiotlb: remember having called xen_create_contiguous_region()
Date
Instead of always calling xen_destroy_contiguous_region() in case the
memory is DMA-able for the used device, do so only in case it has been
made DMA-able via xen_create_contiguous_region() before.

This will avoid a lot of xen_destroy_contiguous_region() calls for
64-bit capable devices.

As the memory in question is owned by swiotlb-xen the PG_owner_priv_1
flag of the first allocated page can be used for remembering.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
V2: add PG_xen_remapped alias for PG_owner_priv_1 (Boris Ostrovsky)
only clear page flag in case of sane conditions (Jan Beulich)
V3: use TestClearPageXenRemapped() (Jan Beulich)
---
drivers/xen/swiotlb-xen.c | 4 +++-
include/linux/page-flags.h | 4 ++++
2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
index 37ddcfcfbb21..ceb681cf64bb 100644
--- a/drivers/xen/swiotlb-xen.c
+++ b/drivers/xen/swiotlb-xen.c
@@ -322,6 +322,7 @@ xen_swiotlb_alloc_coherent(struct device *hwdev, size_t size,
xen_free_coherent_pages(hwdev, size, ret, (dma_addr_t)phys, attrs);
return NULL;
}
+ SetPageXenRemapped(virt_to_page(ret));
}
memset(ret, 0, size);
return ret;
@@ -346,7 +347,8 @@ xen_swiotlb_free_coherent(struct device *hwdev, size_t size, void *vaddr,
size = 1UL << (order + XEN_PAGE_SHIFT);

if (!WARN_ON((dev_addr + size - 1 > dma_mask) ||
- range_straddles_page_boundary(phys, size)))
+ range_straddles_page_boundary(phys, size)) &&
+ TestClearPageXenRemapped(virt_to_page(vaddr)))
xen_destroy_contiguous_region(phys, order);

xen_free_coherent_pages(hwdev, size, vaddr, (dma_addr_t)phys, attrs);
diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h
index 9f8712a4b1a5..fc503a47e7db 100644
--- a/include/linux/page-flags.h
+++ b/include/linux/page-flags.h
@@ -152,6 +152,8 @@ enum pageflags {
PG_savepinned = PG_dirty,
/* Has a grant mapping of another (foreign) domain's page. */
PG_foreign = PG_owner_priv_1,
+ /* Remapped by swiotlb-xen. */
+ PG_xen_remapped = PG_owner_priv_1,

/* SLOB */
PG_slob_free = PG_private,
@@ -329,6 +331,8 @@ PAGEFLAG(Pinned, pinned, PF_NO_COMPOUND)
TESTSCFLAG(Pinned, pinned, PF_NO_COMPOUND)
PAGEFLAG(SavePinned, savepinned, PF_NO_COMPOUND);
PAGEFLAG(Foreign, foreign, PF_NO_COMPOUND);
+PAGEFLAG(XenRemapped, xen_remapped, PF_NO_COMPOUND)
+ TESTCLEARFLAG(XenRemapped, xen_remapped, PF_NO_COMPOUND)

PAGEFLAG(Reserved, reserved, PF_NO_COMPOUND)
__CLEARPAGEFLAG(Reserved, reserved, PF_NO_COMPOUND)
--
2.16.4
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