linux-kernel - [RFC PATCH 05/47] mm: asi: Make __get_current_cr3

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Date:   Tue, 22 Feb 2022 21:21:41 -0800
From:   Junaid Shahid <junaids@...gle.com>
To:     linux-kernel@...r.kernel.org
Cc:     kvm@...r.kernel.org, pbonzini@...hat.com, jmattson@...gle.com,
        pjt@...gle.com, oweisse@...gle.com, alexandre.chartre@...cle.com,
        rppt@...ux.ibm.com, dave.hansen@...ux.intel.com,
        peterz@...radead.org, tglx@...utronix.de, luto@...nel.org,
        linux-mm@...ck.org
Subject: [RFC PATCH 05/47] mm: asi: Make __get_current_cr3_fast() ASI-aware

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 <junaids@...gle.com>


---
 arch/x86/include/asm/asi.h |  7 +++++++
 arch/x86/mm/tlb.c          | 20 ++++++++++++++++++--
 2 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/asi.h b/arch/x86/include/asm/asi.h
index 7702332c62e8..95557211dabd 100644
--- a/arch/x86/include/asm/asi.h
+++ b/arch/x86/include/asm/asi.h
@@ -112,6 +112,11 @@ static inline void asi_intr_exit(void)
 	}
 }
 
+static inline pgd_t *asi_pgd(struct asi *asi)
+{
+	return asi->pgd;
+}
+
 #else	/* CONFIG_ADDRESS_SPACE_ISOLATION */
 
 static inline void asi_intr_enter(void) { }
@@ -120,6 +125,8 @@ static inline void asi_intr_exit(void) { }
 
 static inline void asi_init_thread_state(struct thread_struct *thread) { }
 
+static inline pgd_t *asi_pgd(struct asi *asi) { return NULL; }
+
 #endif	/* CONFIG_ADDRESS_SPACE_ISOLATION */
 
 #endif
diff --git a/arch/x86/mm/tlb.c b/arch/x86/mm/tlb.c
index 88d9298720dc..25bee959d1d3 100644
--- a/arch/x86/mm/tlb.c
+++ b/arch/x86/mm/tlb.c
@@ -17,6 +17,7 @@
 #include <asm/cacheflush.h>
 #include <asm/apic.h>
 #include <asm/perf_event.h>
+#include <asm/asi.h>
 
 #include "mm_internal.h"
 
@@ -1073,12 +1074,27 @@ void flush_tlb_kernel_range(unsigned long start, unsigned long end)
  */
 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));
+	unsigned long cr3;
+	pgd_t *pgd;
+	u16 asid = this_cpu_read(cpu_tlbstate.loaded_mm_asid);
+	struct asi *asi = asi_get_current();
+
+	if (asi)
+		pgd = asi_pgd(asi);
+	else
+		pgd = this_cpu_read(cpu_tlbstate.loaded_mm)->pgd;
+
+	cr3 = build_cr3(pgd, asid);
 
 	/* For now, be very restrictive about when this can be called. */
 	VM_WARN_ON(in_nmi() || preemptible());
 
+	/*
+	 * CR3 is unstable if the target ASI is unrestricted
+	 * and a restricted ASI is currently loaded.
+	 */
+	VM_WARN_ON_ONCE(asi && asi_is_target_unrestricted());
+
 	VM_BUG_ON(cr3 != __read_cr3());
 	return cr3;
 }
-- 
2.35.1.473.g83b2b277ed-goog