riscv: mm: notify remote harts about mmu cache updates

commit 4bd1d80 upstream. Current implementation of update_mmu_cache function performs local TLB flush. It does not take into account ASID information. Besides, it does not take into account other harts currently running the same mm context or possible migration of the running context to other harts. Meanwhile TLB flush is not performed for every context switch if ASID support is enabled. Patch [1] proposed to add ASID support to update_mmu_cache to avoid flushing local TLB entirely. This patch takes into account other harts currently running the same mm context as well as possible migration of this context to other harts. For this purpose the approach from flush_icache_mm is reused. Remote harts currently running the same mm context are informed via SBI calls that they need to flush their local TLBs. All the other harts are marked as needing a deferred TLB flush when this mm context runs on them. [1] https://lore.kernel.org/linux-riscv/20220821013926.8968-1-tjytimi@163.com/ Signed-off-by: Sergey Matyukevich <sergey.matyukevich@syntacore.com> Fixes: 65d4b9c ("RISC-V: Implement ASID allocator") Cc: stable@vger.kernel.org Link: https://lore.kernel.org/linux-riscv/20220829205219.283543-1-geomatsi@gmail.com/#t Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
xanmod · Jan 12, 2023 · 4830750 · 4830750
1 parent 16b6d95
commit 4830750
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Showing 5 changed files with 42 additions and 18 deletions.
diff --git a/arch/riscv/include/asm/mmu.h b/arch/riscv/include/asm/mmu.h
@@ -19,6 +19,8 @@ typedef struct {
 #ifdef CONFIG_SMP
 	/* A local icache flush is needed before user execution can resume. */
 	cpumask_t icache_stale_mask;
+	/* A local tlb flush is needed before user execution can resume. */
+	cpumask_t tlb_stale_mask;
 #endif
 } mm_context_t;
 

diff --git a/arch/riscv/include/asm/pgtable.h b/arch/riscv/include/asm/pgtable.h
@@ -386,7 +386,7 @@ static inline void update_mmu_cache(struct vm_area_struct *vma,
 	 * Relying on flush_tlb_fix_spurious_fault would suffice, but
 	 * the extra traps reduce performance.  So, eagerly SFENCE.VMA.
 	 */
-	local_flush_tlb_page(address);
+	flush_tlb_page(vma, address);
 }
 
 static inline void update_mmu_cache_pmd(struct vm_area_struct *vma,

diff --git a/arch/riscv/include/asm/tlbflush.h b/arch/riscv/include/asm/tlbflush.h
@@ -22,6 +22,24 @@ static inline void local_flush_tlb_page(unsigned long addr)
 {
 	ALT_FLUSH_TLB_PAGE(__asm__ __volatile__ ("sfence.vma %0" : : "r" (addr) : "memory"));
 }
+
+static inline void local_flush_tlb_all_asid(unsigned long asid)
+{
+	__asm__ __volatile__ ("sfence.vma x0, %0"
+			:
+			: "r" (asid)
+			: "memory");
+}
+
+static inline void local_flush_tlb_page_asid(unsigned long addr,
+		unsigned long asid)
+{
+	__asm__ __volatile__ ("sfence.vma %0, %1"
+			:
+			: "r" (addr), "r" (asid)
+			: "memory");
+}
+
 #else /* CONFIG_MMU */
 #define local_flush_tlb_all()			do { } while (0)
 #define local_flush_tlb_page(addr)		do { } while (0)

diff --git a/arch/riscv/mm/context.c b/arch/riscv/mm/context.c
@@ -196,6 +196,16 @@ static void set_mm_asid(struct mm_struct *mm, unsigned int cpu)
 
 	if (need_flush_tlb)
 		local_flush_tlb_all();
+#ifdef CONFIG_SMP
+	else {
+		cpumask_t *mask = &mm->context.tlb_stale_mask;
+
+		if (cpumask_test_cpu(cpu, mask)) {
+			cpumask_clear_cpu(cpu, mask);
+			local_flush_tlb_all_asid(cntx & asid_mask);
+		}
+	}
+#endif
 }
 
 static void set_mm_noasid(struct mm_struct *mm)

diff --git a/arch/riscv/mm/tlbflush.c b/arch/riscv/mm/tlbflush.c
@@ -5,23 +5,7 @@
 #include <linux/sched.h>
 #include <asm/sbi.h>
 #include <asm/mmu_context.h>
-
-static inline void local_flush_tlb_all_asid(unsigned long asid)
-{
-	__asm__ __volatile__ ("sfence.vma x0, %0"
-			:
-			: "r" (asid)
-			: "memory");
-}
-
-static inline void local_flush_tlb_page_asid(unsigned long addr,
-		unsigned long asid)
-{
-	__asm__ __volatile__ ("sfence.vma %0, %1"
-			:
-			: "r" (addr), "r" (asid)
-			: "memory");
-}
+#include <asm/tlbflush.h>
 
 void flush_tlb_all(void)
 {
@@ -31,6 +15,7 @@ void flush_tlb_all(void)
 static void __sbi_tlb_flush_range(struct mm_struct *mm, unsigned long start,
 				  unsigned long size, unsigned long stride)
 {
+	struct cpumask *pmask = &mm->context.tlb_stale_mask;
 	struct cpumask *cmask = mm_cpumask(mm);
 	struct cpumask hmask;
 	unsigned int cpuid;
@@ -45,6 +30,15 @@ static void __sbi_tlb_flush_range(struct mm_struct *mm, unsigned long start,
 	if (static_branch_unlikely(&use_asid_allocator)) {
 		unsigned long asid = atomic_long_read(&mm->context.id);
 
+		/*
+		 * TLB will be immediately flushed on harts concurrently
+		 * executing this MM context. TLB flush on other harts
+		 * is deferred until this MM context migrates there.
+		 */
+		cpumask_setall(pmask);
+		cpumask_clear_cpu(cpuid, pmask);
+		cpumask_andnot(pmask, pmask, cmask);
+
 		if (broadcast) {
 			riscv_cpuid_to_hartid_mask(cmask, &hmask);
 			sbi_remote_sfence_vma_asid(cpumask_bits(&hmask),