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Commit f4b2f07b authored by Konrad Rzeszutek Wilk's avatar Konrad Rzeszutek Wilk
Browse files

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: default avatarKonrad Rzeszutek Wilk <konrad.wilk@oracle.com>
parent 917e3e65

drivers/xen/swiotlb-xen.c

+25 −10
Original line number Diff line number Diff line
@@ -38,6 +38,7 @@ 
#include <xen/swiotlb-xen.h>

#include <xen/page.h>

#include <xen/xen-ops.h>

#include <xen/hvc-console.h>

/*

 * 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 *