linux-kernel - [PATCH RFC 04/11] x86/mm/asi: Sync physmap into ASI_GLOBAL

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Message-ID: <20250313-asi-page-alloc-v1-4-04972e046cea@google.com>
Date: Thu, 13 Mar 2025 18:11:23 +0000
From: Brendan Jackman <jackmanb@...gle.com>
To: Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, 
	Dave Hansen <dave.hansen@...ux.intel.com>, x86@...nel.org, 
	Andrew Morton <akpm@...ux-foundation.org>, David Rientjes <rientjes@...gle.com>, 
	Vlastimil Babka <vbabka@...e.cz>, David Hildenbrand <david@...hat.com>
Cc: linux-kernel@...r.kernel.org, linux-mm@...ck.org, 
	Mike Rapoport <rppt@...nel.org>, Junaid Shahid <junaids@...gle.com>, Reiji Watanabe <reijiw@...gle.com>, 
	Patrick Bellasi <derkling@...gle.com>, Brendan Jackman <jackmanb@...gle.com>, 
	Yosry Ahmed <yosry.ahmed@...ux.dev>
Subject: [PATCH RFC 04/11] x86/mm/asi: Sync physmap into ASI_GLOBAL_NONSENSITIVE

Mirror the physmap into the ASI pagetables, but with a maximum
granularity that's guaranteed to allow changing pageblock sensitivity
without having to allocate pagetables.

Signed-off-by: Brendan Jackman <jackmanb@...gle.com>
---
 arch/x86/mm/init_64.c | 30 ++++++++++++++++++++++++++++--
 1 file changed, 28 insertions(+), 2 deletions(-)

diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 8f75274fddd96b8285aff48493ebad93e30daebe..4ca6bb419b9643b0e72cb5b6da6d905f2b2be84b 100644
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -7,6 +7,7 @@
  *  Copyright (C) 2002,2003 Andi Kleen <ak@...e.de>
  */
 
+#include <linux/asi.h>
 #include <linux/signal.h>
 #include <linux/sched.h>
 #include <linux/kernel.h>
@@ -736,7 +737,8 @@ phys_pgd_init(pgd_t *pgd_page, unsigned long paddr_start, unsigned long paddr_en
 {
 	unsigned long vaddr, vaddr_start, vaddr_end, vaddr_next, paddr_last;
 
-	*pgd_changed = false;
+	if (pgd_changed)
+		*pgd_changed = false;
 
 	paddr_last = paddr_end;
 	vaddr = (unsigned long)__va(paddr_start);
@@ -770,9 +772,13 @@ phys_pgd_init(pgd_t *pgd_page, unsigned long paddr_start, unsigned long paddr_en
 					  (pud_t *) p4d, init);
 
 		spin_unlock(&init_mm.page_table_lock);
-		*pgd_changed = true;
+		if (pgd_changed)
+			*pgd_changed = true;
 	}
 
+	if (pgd_changed)
+		sync_global_pgds(vaddr_start, vaddr_end - 1);
+
 	return paddr_last;
 }
 
@@ -784,9 +790,29 @@ __kernel_physical_mapping_init(unsigned long paddr_start,
 {
 	bool pgd_changed;
 	unsigned long paddr_last;
+	pgd_t *pgd_asi = asi_pgd(ASI_GLOBAL_NONSENSITIVE);
 
 	paddr_last = phys_pgd_init(init_mm.pgd, paddr_start, paddr_end, page_size_mask,
 				   prot, init, &pgd_changed);
+
+	/*
+	 * Set up ASI's global-nonsensitive physmap. This needs to mapped at max
+	 * 2M size so that regions can be mapped and unmapped at pageblock
+	 * granularity without requiring allocations.
+	 */
+	if (pgd_asi) {
+		/*
+		 * Since most memory is expected to end up sensitive, start with
+		 * everything unmapped in this pagetable. The page allocator
+		 * assumes that's the case.
+		 */
+		pgprot_t prot_np = __pgprot(pgprot_val(prot) & ~_PAGE_PRESENT);
+
+		VM_BUG_ON((PAGE_SHIFT + pageblock_order) < page_level_shift(PG_LEVEL_2M));
+		phys_pgd_init(pgd_asi, paddr_start, paddr_end, 1 << PG_LEVEL_2M,
+			      prot_np, init, NULL);
+	}
+
 	if (pgd_changed)
 		sync_global_pgds((unsigned long)__va(paddr_start),
 				 (unsigned long)__va(paddr_end) - 1);

-- 
2.49.0.rc1.451.g8f38331e32-goog