Commit d9a688ad authored by Jan Beulich's avatar Jan Beulich Committed by Juergen Gross
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swiotlb-xen: maintain slab count properly 



Generic swiotlb code makes sure to keep the slab count a multiple of the
number of slabs per segment. Yet even without checking whether any such
assumption is made elsewhere, it is easy to see that xen_swiotlb_fixup()
might alter unrelated memory when calling xen_create_contiguous_region()
for the last segment, when that's not a full one - the function acts on
full order-N regions, not individual pages.

Align the slab count suitably when halving it for a retry. Add a build
time check and a runtime one. Replace the no longer useful local
variable "slabs" by an "order" one calculated just once, outside of the
loop. Re-use "order" for calculating "dma_bits", and change the type of
the latter as well as the one of "i" while touching this anyway.

Signed-off-by: default avatarJan Beulich <jbeulich@suse.com>
Reviewed-by: default avatarChristoph Hellwig <hch@lst.de>

Link: https://lore.kernel.org/r/dc054cb0-bec4-4db0-fc06-c9fc957b6e66@suse.com


Signed-off-by: default avatarJuergen Gross <jgross@suse.com>
parent 4c092c59

drivers/xen/swiotlb-xen.c

+9 −10
Original line number Diff line number Diff line
@@ -106,27 +106,26 @@ static int is_xen_swiotlb_buffer(struct device *dev, dma_addr_t dma_addr) 


static int xen_swiotlb_fixup(void *buf, unsigned long nslabs)

{

	int i, rc;

	int dma_bits;

	int rc;

	unsigned int order = get_order(IO_TLB_SEGSIZE << IO_TLB_SHIFT);

	unsigned int i, dma_bits = order + PAGE_SHIFT;

	dma_addr_t dma_handle;

	phys_addr_t p = virt_to_phys(buf);



	dma_bits = get_order(IO_TLB_SEGSIZE << IO_TLB_SHIFT) + PAGE_SHIFT;

	BUILD_BUG_ON(IO_TLB_SEGSIZE & (IO_TLB_SEGSIZE - 1));

	BUG_ON(nslabs % IO_TLB_SEGSIZE);



	i = 0;

	do {

		int slabs = min(nslabs - i, (unsigned long)IO_TLB_SEGSIZE);



		do {

			rc = xen_create_contiguous_region(

				p + (i << IO_TLB_SHIFT),

				get_order(slabs << IO_TLB_SHIFT),

				p + (i << IO_TLB_SHIFT), order,

				dma_bits, &dma_handle);

		} while (rc && dma_bits++ < MAX_DMA_BITS);

		if (rc)

			return rc;



		i += slabs;

		i += IO_TLB_SEGSIZE;

	} while (i < nslabs);

	return 0;

}
@@ -210,7 +209,7 @@ int __ref xen_swiotlb_init(void) 
error:

	if (repeat--) {

		/* Min is 2MB */

		nslabs = max(1024UL, (nslabs >> 1));

		nslabs = max(1024UL, ALIGN(nslabs >> 1, IO_TLB_SEGSIZE));

		bytes = nslabs << IO_TLB_SHIFT;

		pr_info("Lowering to %luMB\n", bytes >> 20);

		goto retry;
@@ -245,7 +244,7 @@ void __init xen_swiotlb_init_early(void) 
		memblock_free(__pa(start), PAGE_ALIGN(bytes));

		if (repeat--) {

			/* Min is 2MB */

			nslabs = max(1024UL, (nslabs >> 1));

			nslabs = max(1024UL, ALIGN(nslabs >> 1, IO_TLB_SEGSIZE));

			bytes = nslabs << IO_TLB_SHIFT;

			pr_info("Lowering to %luMB\n", bytes >> 20);

			goto retry;