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Account for dmap limit when selecting the pages for the bootstrap

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pagetables.

physmap[] can be inconsistent with the physical memory limit due to
buggy bios, or to the hw.physmem tunable. Since bootstrap pagetables
are initialized by accesses through the DMAP, we must ensure that DMAP
really cover the selected pages. This is only relevant when machine
has less than 4G RAM and buggy BIOS, which is the combination on Acer
Chromebook 720.

The call to mp_bootaddress() is moved later to have Maxmem initialized.

An alternative could be to always cover 4G for DMAP, but this change
seems to be simpler.

Reported and tested by:	grembo
Reviewed by:	royger
Sponsored by:	The FreeBSD Foundation
MFC after:	1 week
Differential revision:	https://reviews.freebsd.org/D15675
This commit is contained in:
Konstantin Belousov 2018-06-07 17:04:34 +00:00
parent 1930b98d49
commit 943defc3a0
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=334799
2 changed files with 18 additions and 14 deletions
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18
sys/amd64/amd64/machdep.c
View File

@ -1247,15 +1247,6 @@ getmemsize(caddr_t kmdp, u_int64_t first)
basemem = 640;
}
/*
* Make hole for "AP -> long mode" bootstrap code. The
* mp_bootaddress vector is only available when the kernel
* is configured to support APs and APs for the system start
* in real mode mode (e.g. SMP bare metal).
*/
if (init_ops.mp_bootaddress)
init_ops.mp_bootaddress(physmap, &physmap_idx);
/*
* Maxmem isn't the "maximum memory", it's one larger than the
* highest page of the physical address space. It should be
@ -1294,6 +1285,15 @@ getmemsize(caddr_t kmdp, u_int64_t first)
(boothowto & RB_VERBOSE))
printf("Physical memory use set to %ldK\n", Maxmem * 4);
/*
* Make hole for "AP -> long mode" bootstrap code. The
* mp_bootaddress vector is only available when the kernel
* is configured to support APs and APs for the system start
* in real mode mode (e.g. SMP bare metal).
*/
if (init_ops.mp_bootaddress)
init_ops.mp_bootaddress(physmap, &physmap_idx);
/* call pmap initialization to make new kernel address space */
pmap_bootstrap(&first);

14
sys/amd64/amd64/mp_machdep.c
View File

@ -113,12 +113,16 @@ mp_bootaddress(vm_paddr_t *physmap, unsigned int *physmap_idx)
allocated = false;
for (i = *physmap_idx; i <= *physmap_idx; i -= 2) {
/*
* Find a memory region big enough below the 4GB boundary to
* store the initial page tables. Note that it needs to be
* aligned to a page boundary.
* Find a memory region big enough below the 4GB
* boundary to store the initial page tables. Region
* must be mapped by the direct map.
*
* Note that it needs to be aligned to a page
* boundary.
*/
if (physmap[i] >= GiB(4) ||
(physmap[i + 1] - round_page(physmap[i])) < (PAGE_SIZE * 3))
if (physmap[i] >= GiB(4) || physmap[i + 1] -
round_page(physmap[i]) < PAGE_SIZE * 3 ||
physmap[i + 1] > Maxmem)
continue;
allocated = true;