[PATCH RFC 2/2] mm/x86/pat: Do proper PAT bit shift for large mappings

Peter Xu
2024-05-23T22:38:00Z

For large mappings, the pgtable PAT is set on bit 12 (_PAGE_PAT_LARGE)
rather than bit 9 (_PAGE_PAT), while bit 9 is used as PAE hint. Do proper
shifting when inject large pfn pgtable mappings to make cache mode alright.

Cc: Alex Williamson <alex.williamson@redhat.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Kirill A. Shutemov <kirill@shutemov.name>
Cc: x86@kernel.org
Signed-off-by: Peter Xu <peterx@redhat.com>
---
mm/huge_memory.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 317de2afd371..c4a2356b1a54 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1135,7 +1135,7 @@ static void insert_pfn_pmd(struct vm_area_struct *vma, unsigned long addr,
goto out_unlock;
}

- entry = pmd_mkhuge(pfn_t_pmd(pfn, prot));
+ entry = pmd_mkhuge(pfn_t_pmd(pfn, pgprot_4k_2_large(prot)));
if (pfn_t_devmap(pfn))
entry = pmd_mkdevmap(entry);
if (write) {
@@ -1233,7 +1233,7 @@ static void insert_pfn_pud(struct vm_area_struct *vma, unsigned long addr,
goto out_unlock;
}

- entry = pud_mkhuge(pfn_t_pud(pfn, prot));
+ entry = pud_mkhuge(pfn_t_pud(pfn, pgprot_4k_2_large(prot)));
if (pfn_t_devmap(pfn))
entry = pud_mkdevmap(entry);
if (write) {
--
2.45.0