arm64: errata: Work around early CME DVMSync acknowledgement

C1-Pro acknowledges DVMSync messages before completing the SME/CME
memory accesses. Work around this by issuing an IPI to the affected CPUs
if they are running in EL0 with SME enabled.

Note that we avoid the local DSB in the IPI handler as the kernel runs
with SCTLR_EL1.IESB=1. This is sufficient to complete SME memory
accesses at EL0 on taking an exception to EL1. On the return to user
path, no barrier is necessary either. See the comment in
sme_set_active() and the more detailed explanation in the link below.

To avoid a potential IPI flood from malicious applications (e.g.
madvise(MADV_PAGEOUT) in a tight loop), track where a process is active
via mm_cpumask() and only interrupt those CPUs.

Link: https://lore.kernel.org/r/ablEXwhfKyJW1i7l@J2N7QTR9R3
Cc: Will Deacon <will@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Mark Brown <broonie@kernel.org>
Reviewed-by: Will Deacon <will@kernel.org>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

4 files changed, 101 insertions, 4 deletions

diff --git a/arch/arm64/include/asm/cpucaps.h b/arch/arm64/include/asm/cpucaps.h
index 177c691914f8..0b1b78a4c03e 100644
--- a/arch/arm64/include/asm/cpucaps.h
+++ b/arch/arm64/include/asm/cpucaps.h
@@ -64,6 +64,8 @@ cpucap_is_possible(const unsigned int cap)
 		return IS_ENABLED(CONFIG_ARM64_WORKAROUND_REPEAT_TLBI);
 	case ARM64_WORKAROUND_SPECULATIVE_SSBS:
 		return IS_ENABLED(CONFIG_ARM64_ERRATUM_3194386);
+	case ARM64_WORKAROUND_4193714:
+		return IS_ENABLED(CONFIG_ARM64_ERRATUM_4193714);
 	case ARM64_MPAM:
 		/*
 		 * KVM MPAM support doesn't rely on the host kernel supporting MPAM.
diff --git a/arch/arm64/include/asm/fpsimd.h b/arch/arm64/include/asm/fpsimd.h
index 1d2e33559bd5..d9d00b45ab11 100644
--- a/arch/arm64/include/asm/fpsimd.h
+++ b/arch/arm64/include/asm/fpsimd.h
@@ -428,6 +428,24 @@ static inline size_t sme_state_size(struct task_struct const *task)
 	return __sme_state_size(task_get_sme_vl(task));
 }
 
+void sme_enable_dvmsync(void);
+void sme_set_active(void);
+void sme_clear_active(void);
+
+static inline void sme_enter_from_user_mode(void)
+{
+	if (alternative_has_cap_unlikely(ARM64_WORKAROUND_4193714) &&
+	    test_thread_flag(TIF_SME))
+		sme_clear_active();
+}
+
+static inline void sme_exit_to_user_mode(void)
+{
+	if (alternative_has_cap_unlikely(ARM64_WORKAROUND_4193714) &&
+	    test_thread_flag(TIF_SME))
+		sme_set_active();
+}
+
 #else
 
 static inline void sme_user_disable(void) { BUILD_BUG(); }
@@ -456,6 +474,9 @@ static inline size_t sme_state_size(struct task_struct const *task)
 	return 0;
 }
 
+static inline void sme_enter_from_user_mode(void) { }
+static inline void sme_exit_to_user_mode(void) { }
+
 #endif /* ! CONFIG_ARM64_SME */
 
 /* For use by EFI runtime services calls only */
diff --git a/arch/arm64/include/asm/tlbbatch.h b/arch/arm64/include/asm/tlbbatch.h
index fedb0b87b8db..6297631532e5 100644
--- a/arch/arm64/include/asm/tlbbatch.h
+++ b/arch/arm64/include/asm/tlbbatch.h
@@ -2,11 +2,17 @@
 #ifndef _ARCH_ARM64_TLBBATCH_H
 #define _ARCH_ARM64_TLBBATCH_H
 
+#include <linux/cpumask.h>
+
 struct arch_tlbflush_unmap_batch {
+#ifdef CONFIG_ARM64_ERRATUM_4193714
 	/*
-	 * For arm64, HW can do tlb shootdown, so we don't
-	 * need to record cpumask for sending IPI
+	 * Track CPUs that need SME DVMSync on completion of this batch.
+	 * Otherwise, the arm64 HW can do tlb shootdown, so we don't need to
+	 * record cpumask for sending IPI
 	 */
+	cpumask_var_t cpumask;
+#endif
 };
 
 #endif /* _ARCH_ARM64_TLBBATCH_H */
diff --git a/arch/arm64/include/asm/tlbflush.h b/arch/arm64/include/asm/tlbflush.h
index 262791191935..4aae42b83049 100644
--- a/arch/arm64/include/asm/tlbflush.h
+++ b/arch/arm64/include/asm/tlbflush.h
@@ -80,6 +80,71 @@ static inline unsigned long get_trans_granule(void)
 	}
 }
 
+#ifdef CONFIG_ARM64_ERRATUM_4193714
+
+void sme_do_dvmsync(const struct cpumask *mask);
+
+static inline void sme_dvmsync(struct mm_struct *mm)
+{
+	if (!alternative_has_cap_unlikely(ARM64_WORKAROUND_4193714))
+		return;
+
+	sme_do_dvmsync(mm_cpumask(mm));
+}
+
+static inline void sme_dvmsync_add_pending(struct arch_tlbflush_unmap_batch *batch,
+					   struct mm_struct *mm)
+{
+	if (!alternative_has_cap_unlikely(ARM64_WORKAROUND_4193714))
+		return;
+
+	/*
+	 * Order the mm_cpumask() read after the hardware DVMSync.
+	 */
+	dsb(ish);
+	if (cpumask_empty(mm_cpumask(mm)))
+		return;
+
+	/*
+	 * Allocate the batch cpumask on first use. Fall back to an immediate
+	 * IPI for this mm in case of failure.
+	 */
+	if (!cpumask_available(batch->cpumask) &&
+	    !zalloc_cpumask_var(&batch->cpumask, GFP_ATOMIC)) {
+		sme_do_dvmsync(mm_cpumask(mm));
+		return;
+	}
+
+	cpumask_or(batch->cpumask, batch->cpumask, mm_cpumask(mm));
+}
+
+static inline void sme_dvmsync_batch(struct arch_tlbflush_unmap_batch *batch)
+{
+	if (!alternative_has_cap_unlikely(ARM64_WORKAROUND_4193714))
+		return;
+
+	if (!cpumask_available(batch->cpumask))
+		return;
+
+	sme_do_dvmsync(batch->cpumask);
+	cpumask_clear(batch->cpumask);
+}
+
+#else
+
+static inline void sme_dvmsync(struct mm_struct *mm)
+{
+}
+static inline void sme_dvmsync_add_pending(struct arch_tlbflush_unmap_batch *batch,
+					   struct mm_struct *mm)
+{
+}
+static inline void sme_dvmsync_batch(struct arch_tlbflush_unmap_batch *batch)
+{
+}
+
+#endif /* CONFIG_ARM64_ERRATUM_4193714 */
+
 /*
  * Level-based TLBI operations.
  *
@@ -189,12 +254,14 @@ static inline void __tlbi_sync_s1ish(struct mm_struct *mm)
 {
 	dsb(ish);
 	__repeat_tlbi_sync(vale1is, 0);
+	sme_dvmsync(mm);
 }
 
-static inline void __tlbi_sync_s1ish_batch(void)
+static inline void __tlbi_sync_s1ish_batch(struct arch_tlbflush_unmap_batch *batch)
 {
 	dsb(ish);
 	__repeat_tlbi_sync(vale1is, 0);
+	sme_dvmsync_batch(batch);
 }
 
 static inline void __tlbi_sync_s1ish_kernel(void)
@@ -397,7 +464,7 @@ static inline bool arch_tlbbatch_should_defer(struct mm_struct *mm)
  */
 static inline void arch_tlbbatch_flush(struct arch_tlbflush_unmap_batch *batch)
 {
-	__tlbi_sync_s1ish_batch();
+	__tlbi_sync_s1ish_batch(batch);
 }
 
 /*
@@ -602,6 +669,7 @@ static inline void arch_tlbbatch_add_pending(struct arch_tlbflush_unmap_batch *b
 		struct mm_struct *mm, unsigned long start, unsigned long end)
 {
 	__flush_tlb_range_nosync(mm, start, end, PAGE_SIZE, true, 3);
+	sme_dvmsync_add_pending(batch, mm);
 }
 
 static inline bool __pte_flags_need_flush(ptdesc_t oldval, ptdesc_t newval)