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

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Date: Thu, 23 May 2024 18:37:45 -0400
From: Peter Xu <peterx@...hat.com>
To: linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Cc: Thomas Gleixner <tglx@...utronix.de>,
	Jason Gunthorpe <jgg@...dia.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	Dave Hansen <dave.hansen@...ux.intel.com>,
	Andy Lutomirski <luto@...nel.org>,
	Matthew Wilcox <willy@...radead.org>,
	peterx@...hat.com,
	Dan Williams <dan.j.williams@...el.com>,
	"Kirill A . Shutemov" <kirill@...temov.name>,
	Mike Rapoport <rppt@...nel.org>,
	Ingo Molnar <mingo@...hat.com>,
	Michal Hocko <mhocko@...e.com>,
	Alex Williamson <alex.williamson@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Suren Baghdasaryan <surenb@...gle.com>,
	Borislav Petkov <bp@...en8.de>,
	x86@...nel.org
Subject: [PATCH RFC 2/2] mm/x86/pat: Do proper PAT bit shift for large mappings

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@...hat.com>
Cc: Jason Gunthorpe <jgg@...dia.com>
Cc: Al Viro <viro@...iv.linux.org.uk>
Cc: Dave Hansen <dave.hansen@...ux.intel.com>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Kirill A. Shutemov <kirill@...temov.name>
Cc: x86@...nel.org
Signed-off-by: Peter Xu <peterx@...hat.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