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- Use a GB page for identity mapping only when memory of this size is

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requested so that mapping of reserved regions is prevented which would
   otherwise lead to system crashes on UV machines
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Merge tag 'x86_urgent_for_v6.8_rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull x86 fix from Borislav Petkov:

 - Use a GB page for identity mapping only when memory of this size is
   requested so that mapping of reserved regions is prevented which
   would otherwise lead to system crashes on UV machines

* tag 'x86_urgent_for_v6.8_rc5' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/mm/ident_map: Use gbpages only where full GB page should be mapped.
This commit is contained in:
Linus Torvalds 2024-02-18 09:22:48 -08:00
commit ddac3d8b8a
1 changed files with 18 additions and 5 deletions
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23
arch/x86/mm/ident_map.c
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@ -26,18 +26,31 @@ static int ident_pud_init(struct x86_mapping_info *info, pud_t *pud_page,
for (; addr < end; addr = next) {
pud_t *pud = pud_page + pud_index(addr);
pmd_t *pmd;
bool use_gbpage;
next = (addr & PUD_MASK) + PUD_SIZE;
if (next > end)
next = end;
if (info->direct_gbpages) {
/* if this is already a gbpage, this portion is already mapped */
if (pud_large(*pud))
continue;
/* Is using a gbpage allowed? */
use_gbpage = info->direct_gbpages;
/* Don't use gbpage if it maps more than the requested region. */
/* at the begining: */
use_gbpage &= ((addr & ~PUD_MASK) == 0);
/* ... or at the end: */
use_gbpage &= ((next & ~PUD_MASK) == 0);
/* Never overwrite existing mappings */
use_gbpage &= !pud_present(*pud);
if (use_gbpage) {
pud_t pudval;
if (pud_present(*pud))
continue;
addr &= PUD_MASK;
pudval = __pud((addr - info->offset) | info->page_flag);
set_pud(pud, pudval);
continue;