Mailing List Archive

# HG changeset patch
# User kaf24@firebug.cl.cam.ac.uk
# Node ID fad187cad5bd39eedc8fef9a9ecf4a656cb4eb17
# Parent fd7c4221fc561c8f450c3fd02a2007d4d36004af
Always initialise a swiotlb for domain0. Make it a small
aperture (2MB) for small systems (< 2GB).

Signed-off-by: Keir Fraser <keir@xensource.com>

diff -r fd7c4221fc56 -r fad187cad5bd linux-2.6-xen-sparse/arch/xen/i386/kernel/swiotlb.c
--- a/linux-2.6-xen-sparse/arch/xen/i386/kernel/swiotlb.c Sat Dec 3 16:59:37 2005
+++ b/linux-2.6-xen-sparse/arch/xen/i386/kernel/swiotlb.c Sat Dec 3 18:09:19 2005
@@ -43,7 +43,7 @@
*/
#define IO_TLB_SHIFT 11

-int swiotlb_force;
+static int swiotlb_force;
static char *iotlb_virt_start;
static unsigned long iotlb_nslabs;

@@ -101,10 +101,13 @@
++str;
/*
* NB. 'force' enables the swiotlb, but doesn't force its use for
- * every DMA like it does on native Linux.
+ * every DMA like it does on native Linux. 'off' forcibly disables
+ * use of the swiotlb.
*/
if (!strcmp(str, "force"))
swiotlb_force = 1;
+ else if (!strcmp(str, "off"))
+ swiotlb_force = -1;
return 1;
}
__setup("swiotlb=", setup_io_tlb_npages);
@@ -179,23 +182,21 @@
swiotlb_init(void)
{
long ram_end;
-
- /* The user can forcibly enable swiotlb. */
- if (swiotlb_force)
+ size_t defsz = 64 * (1 << 20); /* 64MB default size */
+
+ if (swiotlb_force == 1) {
swiotlb = 1;
-
- /*
- * Otherwise, enable for domain 0 if the machine has 'lots of memory',
- * which we take to mean more than 2GB.
- */
- if (xen_start_info->flags & SIF_INITDOMAIN) {
+ } else if ((swiotlb_force != -1) &&
+ (xen_start_info->flags & SIF_INITDOMAIN)) {
+ /* Domain 0 always has a swiotlb. */
ram_end = HYPERVISOR_memory_op(XENMEM_maximum_ram_page, NULL);
- if (ram_end > 0x7ffff)
- swiotlb = 1;
+ if (ram_end <= 0x7ffff)
+ defsz = 2 * (1 << 20); /* 2MB on <2GB on systems. */
+ swiotlb = 1;
}

if (swiotlb)
- swiotlb_init_with_default_size(64 * (1<<20));
+ swiotlb_init_with_default_size(defsz);
else
printk(KERN_INFO "Software IO TLB disabled\n");
}

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