Re: [PATCH v9 01/26] arm64: Fix HCR.TGE status for NMI contexts

Hi Julien,

On 21/01/2019 15:33, Julien Thierry wrote:

When using VHE, the host needs to clear HCR_EL2.TGE bit in order to interract with guest TLBs, switching from EL2&0 translation regime

(interact)

to EL1&0.

However, some non-maskable asynchronous event could happen while TGE is cleared like SDEI. Because of this address translation operations relying on EL2&0 translation regime could fail (tlb invalidation, userspace access, ...).

Fix this by properly setting HCR_EL2.TGE when entering NMI context and clear it if necessary when returning to the interrupted context.

Yes please. This would not have been fun to debug!

Reviewed-by: James Morse james.morse@arm.com

I was looking for why we need core code to do this, instead of updating the arch's call sites. Your 'irqdesc: Add domain handlers for NMIs' patch (pointed to from the cover letter) is the reason: core-code calls nmi_enter()/nmi_exit() itself.

Thanks,

James

diff --git a/arch/arm64/include/asm/hardirq.h b/arch/arm64/include/asm/hardirq.h index 1473fc2..94b7481 100644 --- a/arch/arm64/include/asm/hardirq.h +++ b/arch/arm64/include/asm/hardirq.h @@ -19,6 +19,7 @@ #include <linux/cache.h> #include <linux/threads.h> #include <asm/irq.h> +#include <asm/kvm_arm.h>

percpu.h? sysreg.h? barrier.h?

@@ -37,6 +38,33 @@ #define __ARCH_IRQ_EXIT_IRQS_DISABLED 1 +struct nmi_ctx {

• u64 hcr;

+};

+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_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)

static inline void ack_bad_irq(unsigned int irq) { extern unsigned long irq_err_count;

diff --git a/include/linux/hardirq.h b/include/linux/hardirq.h index 0fbbcdf..da0af63 100644 --- a/include/linux/hardirq.h +++ b/include/linux/hardirq.h @@ -60,8 +60,14 @@ static inline void rcu_nmi_exit(void) */ extern void irq_exit(void); +#ifndef arch_nmi_enter +#define arch_nmi_enter() do { } while (0) +#define arch_nmi_exit() do { } while (0) +#endif

#define nmi_enter() \ do { \

• arch_nmi_enter();				\
  

  printk_nmi_enter(); \ lockdep_off(); \ ftrace_nmi_enter(); \

@@ -80,6 +86,7 @@ static inline void rcu_nmi_exit(void) ftrace_nmi_exit(); \ lockdep_on(); \ printk_nmi_exit(); \

• arch_nmi_exit();				\
  

  } while (0)

#endif /* LINUX_HARDIRQ_H */