[patch V4 part 1 27/36] arm64: Prepare arch_nmi_enter() for recursion

Thomas Gleixner
2020-05-05T14:23:08Z

From: Frederic Weisbecker <frederic@kernel.org>

Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
---
arch/arm64/include/asm/hardirq.h | 78 +++++++++++++++++++++++++++++----------
1 file changed, 59 insertions(+), 19 deletions(-)

--- a/arch/arm64/include/asm/hardirq.h
+++ b/arch/arm64/include/asm/hardirq.h
@@ -32,30 +32,70 @@ u64 smp_irq_stat_cpu(unsigned int cpu);

struct nmi_ctx {
u64 hcr;
+ unsigned int cnt;
};

DECLARE_PER_CPU(struct nmi_ctx, nmi_contexts);

-#define arch_nmi_enter() \
- do { \
- if (is_kernel_in_hyp_mode()) { \
- struct nmi_ctx *nmi_ctx = this_cpu_ptr(&nmi_contexts); \
- nmi_ctx->hcr = read_sysreg(hcr_el2); \
- if (!(nmi_ctx->hcr & HCR_TGE)) { \
- write_sysreg(nmi_ctx->hcr | HCR_TGE, hcr_el2); \
- isb(); \
- } \
- } \
- } while (0)
+#define arch_nmi_enter() \
+do { \
+ struct nmi_ctx *___ctx; \
+ u64 ___hcr; \
+ \
+ if (!is_kernel_in_hyp_mode()) \
+ break; \
+ \
+ ___ctx = this_cpu_ptr(&nmi_contexts); \
+ if (___ctx->cnt) { \
+ ___ctx->cnt++; \
+ break; \
+ } \
+ \
+ ___hcr = read_sysreg(hcr_el2); \
+ if (!(___hcr & HCR_TGE)) { \
+ write_sysreg(___hcr | HCR_TGE, hcr_el2); \
+ isb(); \
+ } \
+ /* \
+ * Make sure the sysreg write is performed before ___ctx->cnt \
+ * is set to 1. NMIs that see cnt == 1 will rely on us. \
+ */ \
+ barrier(); \
+ ___ctx->cnt = 1; \
+ /* \
+ * Make sure ___ctx->cnt is set before we save ___hcr. We \
+ * don't want ___ctx->hcr to be overwritten. \
+ */ \
+ barrier(); \
+ ___ctx->hcr = ___hcr; \
+} while (0)

-#define arch_nmi_exit() \
- do { \
- if (is_kernel_in_hyp_mode()) { \
- struct nmi_ctx *nmi_ctx = this_cpu_ptr(&nmi_contexts); \
- if (!(nmi_ctx->hcr & HCR_TGE)) \
- write_sysreg(nmi_ctx->hcr, hcr_el2); \
- } \
- } while (0)
+#define arch_nmi_exit() \
+do { \
+ struct nmi_ctx *___ctx; \
+ u64 ___hcr; \
+ \
+ if (!is_kernel_in_hyp_mode()) \
+ break; \
+ \
+ ___ctx = this_cpu_ptr(&nmi_contexts); \
+ ___hcr = ___ctx->hcr; \
+ /* \
+ * Make sure we read ___ctx->hcr before we release \
+ * ___ctx->cnt as it makes ___ctx->hcr updatable again. \
+ */ \
+ barrier(); \
+ ___ctx->cnt--; \
+ /* \
+ * Make sure ___ctx->cnt release is visible before we \
+ * restore the sysreg. Otherwise a new NMI occurring \
+ * right after write_sysreg() can be fooled and think \
+ * we secured things for it. \
+ */ \
+ barrier(); \
+ if (!___ctx->cnt && !(___hcr & HCR_TGE)) \
+ write_sysreg(___hcr, hcr_el2); \
+} while (0)

static inline void ack_bad_irq(unsigned int irq)
{