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, 148 insertions, 0 deletions

diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
index 5c0ab6bfd44a..5377e4c2eba2 100644
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -11,6 +11,7 @@
 #include <asm/cpu.h>
 #include <asm/cputype.h>
 #include <asm/cpufeature.h>
+#include <asm/fpsimd.h>
 #include <asm/kvm_asm.h>
 #include <asm/smp_plat.h>
 
@@ -575,6 +576,23 @@ static const struct midr_range erratum_spec_ssbs_list[] = {
 };
 #endif
 
+#ifdef CONFIG_ARM64_ERRATUM_4193714
+static bool has_sme_dvmsync_erratum(const struct arm64_cpu_capabilities *entry,
+				    int scope)
+{
+	if (!id_aa64pfr1_sme(read_sanitised_ftr_reg(SYS_ID_AA64PFR1_EL1)))
+		return false;
+
+	return is_affected_midr_range(entry, scope);
+}
+
+static void cpu_enable_sme_dvmsync(const struct arm64_cpu_capabilities *__unused)
+{
+	if (this_cpu_has_cap(ARM64_WORKAROUND_4193714))
+		sme_enable_dvmsync();
+}
+#endif
+
 #ifdef CONFIG_AMPERE_ERRATUM_AC03_CPU_38
 static const struct midr_range erratum_ac03_cpu_38_list[] = {
 	MIDR_ALL_VERSIONS(MIDR_AMPERE1),
@@ -901,6 +919,18 @@ const struct arm64_cpu_capabilities arm64_errata[] = {
 		.matches = need_arm_si_l1_workaround_4311569,
 	},
 #endif
+#ifdef CONFIG_ARM64_ERRATUM_4193714
+	{
+		.desc = "C1-Pro SME DVMSync early acknowledgement",
+		.capability = ARM64_WORKAROUND_4193714,
+		.type = ARM64_CPUCAP_LOCAL_CPU_ERRATUM,
+		.matches = has_sme_dvmsync_erratum,
+		.cpu_enable = cpu_enable_sme_dvmsync,
+		/* C1-Pro r0p0 - r1p2 (the latter only when REVIDR_EL1[0]==0) */
+		.midr_range = MIDR_RANGE(MIDR_C1_PRO, 0, 0, 1, 2),
+		MIDR_FIXED(MIDR_CPU_VAR_REV(1, 2), BIT(0)),
+	},
+#endif
 #ifdef CONFIG_ARM64_WORKAROUND_SPECULATIVE_UNPRIV_LOAD
 	{
 		.desc = "ARM errata 2966298, 3117295",
diff --git a/arch/arm64/kernel/entry-common.c b/arch/arm64/kernel/entry-common.c
index 3625797e9ee8..fb1e374af622 100644
--- a/arch/arm64/kernel/entry-common.c
+++ b/arch/arm64/kernel/entry-common.c
@@ -21,6 +21,7 @@
 #include <asm/daifflags.h>
 #include <asm/esr.h>
 #include <asm/exception.h>
+#include <asm/fpsimd.h>
 #include <asm/irq_regs.h>
 #include <asm/kprobes.h>
 #include <asm/mmu.h>
@@ -67,6 +68,7 @@ static __always_inline void arm64_enter_from_user_mode(struct pt_regs *regs)
 {
 	enter_from_user_mode(regs);
 	mte_disable_tco_entry(current);
+	sme_enter_from_user_mode();
 }
 
 /*
@@ -80,6 +82,7 @@ static __always_inline void arm64_exit_to_user_mode(struct pt_regs *regs)
 	local_irq_disable();
 	exit_to_user_mode_prepare_legacy(regs);
 	local_daif_mask();
+	sme_exit_to_user_mode();
 	mte_check_tfsr_exit();
 	exit_to_user_mode();
 }
diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c
index 9de1d8a604cb..60a45d600b46 100644
--- a/arch/arm64/kernel/fpsimd.c
+++ b/arch/arm64/kernel/fpsimd.c
@@ -15,6 +15,7 @@
 #include <linux/compiler.h>
 #include <linux/cpu.h>
 #include <linux/cpu_pm.h>
+#include <linux/cpumask.h>
 #include <linux/ctype.h>
 #include <linux/kernel.h>
 #include <linux/linkage.h>
@@ -28,6 +29,7 @@
 #include <linux/sched/task_stack.h>
 #include <linux/signal.h>
 #include <linux/slab.h>
+#include <linux/smp.h>
 #include <linux/stddef.h>
 #include <linux/sysctl.h>
 #include <linux/swab.h>
@@ -1358,6 +1360,83 @@ void do_sve_acc(unsigned long esr, struct pt_regs *regs)
 	put_cpu_fpsimd_context();
 }
 
+#ifdef CONFIG_ARM64_ERRATUM_4193714
+
+/*
+ * SME/CME erratum handling.
+ */
+static cpumask_t sme_dvmsync_cpus;
+
+/*
+ * These helpers are only called from non-preemptible contexts, so
+ * smp_processor_id() is safe here.
+ */
+void sme_set_active(void)
+{
+	unsigned int cpu = smp_processor_id();
+
+	if (!cpumask_test_cpu(cpu, &sme_dvmsync_cpus))
+		return;
+
+	cpumask_set_cpu(cpu, mm_cpumask(current->mm));
+
+	/*
+	 * A subsequent (post ERET) SME access may use a stale address
+	 * translation. On C1-Pro, a TLBI+DSB on a different CPU will wait for
+	 * the completion of cpumask_set_cpu() above as it appears in program
+	 * order before the SME access. The post-TLBI+DSB read of mm_cpumask()
+	 * will lead to the IPI being issued.
+	 *
+	 * https://lore.kernel.org/r/ablEXwhfKyJW1i7l@J2N7QTR9R3
+	 */
+}
+
+void sme_clear_active(void)
+{
+	unsigned int cpu = smp_processor_id();
+
+	if (!cpumask_test_cpu(cpu, &sme_dvmsync_cpus))
+		return;
+
+	/*
+	 * With SCTLR_EL1.IESB enabled, the SME memory transactions are
+	 * completed on entering EL1.
+	 */
+	cpumask_clear_cpu(cpu, mm_cpumask(current->mm));
+}
+
+static void sme_dvmsync_ipi(void *unused)
+{
+	/*
+	 * With SCTLR_EL1.IESB on, taking an exception is sufficient to ensure
+	 * the completion of the SME memory accesses, so no need for an
+	 * explicit DSB.
+	 */
+}
+
+void sme_do_dvmsync(const struct cpumask *mask)
+{
+	/*
+	 * This is called from the TLB maintenance functions after the DSB ISH
+	 * to send the hardware DVMSync message. If this CPU sees the mask as
+	 * empty, the remote CPU executing sme_set_active() would have seen
+	 * the DVMSync and no IPI required.
+	 */
+	if (cpumask_empty(mask))
+		return;
+
+	preempt_disable();
+	smp_call_function_many(mask, sme_dvmsync_ipi, NULL, true);
+	preempt_enable();
+}
+
+void sme_enable_dvmsync(void)
+{
+	cpumask_set_cpu(smp_processor_id(), &sme_dvmsync_cpus);
+}
+
+#endif /* CONFIG_ARM64_ERRATUM_4193714 */
+
 /*
  * Trapped SME access
  *
diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
index 489554931231..4c328b7c79ba 100644
--- a/arch/arm64/kernel/process.c
+++ b/arch/arm64/kernel/process.c
@@ -26,6 +26,7 @@
 #include <linux/reboot.h>
 #include <linux/interrupt.h>
 #include <linux/init.h>
+#include <linux/cpumask.h>
 #include <linux/cpu.h>
 #include <linux/elfcore.h>
 #include <linux/pm.h>
@@ -339,8 +340,41 @@ void flush_thread(void)
 	flush_gcs();
 }
 
+#ifdef CONFIG_ARM64_ERRATUM_4193714
+
+static void arch_dup_tlbbatch_mask(struct task_struct *dst)
+{
+	/*
+	 * Clear the inherited cpumask with memset() to cover both cases where
+	 * cpumask_var_t is a pointer or an array. It will be allocated lazily
+	 * in sme_dvmsync_add_pending() if CPUMASK_OFFSTACK=y.
+	 */
+	if (alternative_has_cap_unlikely(ARM64_WORKAROUND_4193714))
+		memset(&dst->tlb_ubc.arch.cpumask, 0,
+		       sizeof(dst->tlb_ubc.arch.cpumask));
+}
+
+static void arch_release_tlbbatch_mask(struct task_struct *tsk)
+{
+	if (alternative_has_cap_unlikely(ARM64_WORKAROUND_4193714))
+		free_cpumask_var(tsk->tlb_ubc.arch.cpumask);
+}
+
+#else
+
+static void arch_dup_tlbbatch_mask(struct task_struct *dst)
+{
+}
+
+static void arch_release_tlbbatch_mask(struct task_struct *tsk)
+{
+}
+
+#endif /* CONFIG_ARM64_ERRATUM_4193714 */
+
 void arch_release_task_struct(struct task_struct *tsk)
 {
+	arch_release_tlbbatch_mask(tsk);
 	fpsimd_release_task(tsk);
 }
 
@@ -356,6 +390,8 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src)
 
 	*dst = *src;
 
+	arch_dup_tlbbatch_mask(dst);
+
 	/*
 	 * Drop stale reference to src's sve_state and convert dst to
 	 * non-streaming FPSIMD mode.