From d9a688add3d412c840e31060847a6a297b552316 Mon Sep 17 00:00:00 2001 From: Jan Beulich Date: Tue, 7 Sep 2021 14:05:12 +0200 Subject: 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: Jan Beulich Reviewed-by: Christoph Hellwig Link: https://lore.kernel.org/r/dc054cb0-bec4-4db0-fc06-c9fc957b6e66@suse.com Signed-off-by: Juergen Gross --- drivers/xen/swiotlb-xen.c | 19 +++++++++---------- 1 file changed, 9 insertions(+), 10 deletions(-) (limited to 'drivers/xen') diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c index dbb18dc956f3..08fc694f05b7 100644 --- a/drivers/xen/swiotlb-xen.c +++ b/drivers/xen/swiotlb-xen.c @@ -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 @@ retry: 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 @@ retry: 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; -- cgit v1.2.3