From f4b2f07b2ed9b469ead87e06fc2fc3d12663a725 Mon Sep 17 00:00:00 2001 From: Konrad Rzeszutek Wilk Date: Fri, 22 Jul 2011 12:46:43 -0400 Subject: [PATCH] xen-swiotlb: Retry up three times to allocate Xen-SWIOTLB We can fail seting up Xen-SWIOTLB if: - The host does not have enough contiguous DMA32 memory available (can happen on a machine that has fragmented memory from starting, stopping many guests). - Not enough low memory (almost never happens). We retry allocating and exchanging the swath of contiguous memory up to three times. Each time we decrease the amount we need - the minimum being of 2MB. If we compleltly fail, we will print the reason for failure on the Xen console on top of doing it to earlyprintk=xen console. Signed-off-by: Konrad Rzeszutek Wilk --- drivers/xen/swiotlb-xen.c | 35 +++++++++++++++++++++++++---------- 1 file changed, 25 insertions(+), 10 deletions(-) diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c index 6e8c15a23201..d45cbacaf6ff 100644 --- a/drivers/xen/swiotlb-xen.c +++ b/drivers/xen/swiotlb-xen.c @@ -38,6 +38,7 @@ #include #include #include +#include /* * Used to do a quick range check in swiotlb_tbl_unmap_single and * swiotlb_tbl_sync_single_*, to see if the memory was in fact allocated by this @@ -146,8 +147,10 @@ xen_swiotlb_fixup(void *buf, size_t size, unsigned long nslabs) void __init xen_swiotlb_init(int verbose) { unsigned long bytes; - int rc; + int rc = -ENOMEM; unsigned long nr_tbl; + char *m = NULL; + unsigned int repeat = 3; nr_tbl = swioltb_nr_tbl(); if (nr_tbl) @@ -156,16 +159,17 @@ void __init xen_swiotlb_init(int verbose) xen_io_tlb_nslabs = (64 * 1024 * 1024 >> IO_TLB_SHIFT); xen_io_tlb_nslabs = ALIGN(xen_io_tlb_nslabs, IO_TLB_SEGSIZE); } - +retry: bytes = xen_io_tlb_nslabs << IO_TLB_SHIFT; /* * Get IO TLB memory from any location. */ xen_io_tlb_start = alloc_bootmem(bytes); - if (!xen_io_tlb_start) - panic("Cannot allocate SWIOTLB buffer"); - + if (!xen_io_tlb_start) { + m = "Cannot allocate Xen-SWIOTLB buffer!\n"; + goto error; + } xen_io_tlb_end = xen_io_tlb_start + bytes; /* * And replace that memory with pages under 4GB. @@ -173,17 +177,28 @@ void __init xen_swiotlb_init(int verbose) rc = xen_swiotlb_fixup(xen_io_tlb_start, bytes, xen_io_tlb_nslabs); - if (rc) + if (rc) { + free_bootmem(__pa(xen_io_tlb_start), bytes); + m = "Failed to get contiguous memory for DMA from Xen!\n"\ + "You either: don't have the permissions, do not have"\ + " enough free memory under 4GB, or the hypervisor memory"\ + "is too fragmented!"; goto error; - + } start_dma_addr = xen_virt_to_bus(xen_io_tlb_start); swiotlb_init_with_tbl(xen_io_tlb_start, xen_io_tlb_nslabs, verbose); return; error: - panic("DMA(%d): Failed to exchange pages allocated for DMA with Xen! "\ - "We either don't have the permission or you do not have enough"\ - "free memory under 4GB!\n", rc); + if (repeat--) { + xen_io_tlb_nslabs = max(1024UL, /* Min is 2MB */ + (xen_io_tlb_nslabs >> 1)); + printk(KERN_INFO "Xen-SWIOTLB: Lowering to %luMB\n", + (xen_io_tlb_nslabs << IO_TLB_SHIFT) >> 20); + goto retry; + } + xen_raw_printk("%s (rc:%d)", rc, m); + panic("%s (rc:%d)", rc, m); } void * -- 2.30.2