[09/26] mm: asi: Make __get_current_cr3_fast() ASI-aware

Commit Message

Brendan Jackman July 12, 2024, 5 p.m. UTC

From: Junaid Shahid <[e-mail]>

When ASI is active, __get_current_cr3_fast() adjusts the returned CR3
value accordingly to reflect the actual ASI CR3.

Signed-off-by: Junaid Shahid <[e-mail]>
Signed-off-by: Brendan Jackman <[e-mail]>
---
 arch/x86/mm/tlb.c | 27 +++++++++++++++++++++++----
 1 file changed, 23 insertions(+), 4 deletions(-)

Patch

diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index 34d61b56d33f..02f73a71d4ea 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -18,6 +18,7 @@ 
 #include <asm/cache.h>
 #include <asm/cacheflush.h>
 #include <asm/apic.h>
+#include <asm/asi.h>
 #include <asm/perf_event.h>
 
 #include "mm_internal.h"
@@ -1125,14 +1126,32 @@  void flush_tlb_kernel_range(unsigned long start, unsigned long end)
  */
 inline_or_noinstr unsigned long __get_current_cr3_fast(void)
 {
-	unsigned long cr3 =
-		build_cr3(this_cpu_read(cpu_tlbstate.loaded_mm)->pgd,
-			  this_cpu_read(cpu_tlbstate.loaded_mm_asid),
-			  tlbstate_lam_cr3_mask());
+	unsigned long cr3;
+	pgd_t *pgd;
+	u16 asid = this_cpu_read(cpu_tlbstate.loaded_mm_asid);
+	struct asi *asi = asi_get_current();
+	u16 pcid;
+
+	if (asi) {
+		pgd = asi_pgd(asi);
+		pcid = asi_pcid(asi, asid);
+	} else {
+		pgd = this_cpu_read(cpu_tlbstate.loaded_mm)->pgd;
+		pcid = kern_pcid(asid);
+	}
+
+	cr3 = build_cr3_pcid(pgd, pcid, tlbstate_lam_cr3_mask(), false);
 
 	/* For now, be very restrictive about when this can be called. */
 	VM_WARN_ON(in_nmi() || preemptible());
 
+	/*
+	 * Outside of the ASI critical section, an ASI-restricted CR3 is
+	 * unstable because an interrupt (including an inner interrupt, if we're
+	 * already in one) could cause a persistent asi_exit.
+	 */
+	VM_WARN_ON_ONCE(asi && (asi_is_relaxed() || asi_intr_nest_depth()));
+
 	VM_BUG_ON(cr3 != __read_cr3());
 	return cr3;
 }