Author: jkim
Date: Wed Feb 15 21:32:05 2012
New Revision: 231781
URL: http://svn.freebsd.org/changeset/base/231781
Log:
Some BIOSes are known for corrupting low 64KB between suspend and resume.
Mask off the first 16 pages unless we appear to be running in a VM. This
address may be overridden by 'hw.physmem.start' tunable from loader.
Note Linux used to have a BIOS quirk table for this issue but it seems they
made it default recently.
Modified:
head/sys/amd64/amd64/machdep.c
Modified: head/sys/amd64/amd64/machdep.c
==============================================================================
--- head/sys/amd64/amd64/machdep.c Wed Feb 15 21:20:58 2012
(r231780)
+++ head/sys/amd64/amd64/machdep.c Wed Feb 15 21:32:05 2012
(r231781)
@@ -1381,7 +1381,7 @@ getmemsize(caddr_t kmdp, u_int64_t first
{
int i, physmap_idx, pa_indx, da_indx;
vm_paddr_t pa, physmap[PHYSMAP_SIZE];
- u_long physmem_tunable, memtest;
+ u_long physmem_start, physmem_tunable, memtest;
pt_entry_t *pte;
struct bios_smap *smapbase, *smap, *smapend;
u_int32_t smapsize;
@@ -1469,8 +1469,19 @@ getmemsize(caddr_t kmdp, u_int64_t first
/*
* Size up each available chunk of physical memory.
+ *
+ * XXX Some BIOSes corrupt low 64KB between suspend and resume.
+ * By default, mask off the first 16 pages unless we appear to be
+ * running in a VM.
*/
- physmap[0] = PAGE_SIZE; /* mask off page 0 */
+ physmem_start = (vm_guest > VM_GUEST_NO ? 1 : 16) << PAGE_SHIFT;
+ TUNABLE_ULONG_FETCH("hw.physmem.start", &physmem_start);
+ if (physmem_start < PAGE_SIZE)
+ physmap[0] = PAGE_SIZE;
+ else if (physmem_start >= physmap[1])
+ physmap[0] = round_page(physmap[1] - PAGE_SIZE);
+ else
+ physmap[0] = round_page(physmem_start);
pa_indx = 0;
da_indx = 1;
phys_avail[pa_indx++] = physmap[0];
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