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Some BIOSes are known for corrupting low 64KB between suspend and resume.

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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.
This commit is contained in:
Jung-uk Kim 2012-02-15 21:32:05 +00:00
parent c693bd2ff6
commit ceb9fa549f
1 changed files with 13 additions and 2 deletions
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15
sys/amd64/amd64/machdep.c
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@ -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];