From: Ashish Kalra <ashish.kalra@xxxxxxx> Add checks in interrupt exit code paths in case of returns to user mode to check if currently executing the #HV handler then don't follow the irqentry_exit_to_user_mode path as that can potentially cause the #HV handler to be preempted and rescheduled on another CPU. Rescheduled #HV handler on another cpu will cause interrupts to be handled on a different cpu than the injected one, causing invalid EOIs and missed/lost guest interrupts and corresponding hangs and/or per-cpu IRQs handled on non-intended cpu. Signed-off-by: Ashish Kalra <ashish.kalra@xxxxxxx> --- arch/x86/include/asm/idtentry.h | 66 +++++++++++++++++++++++++++++++++ arch/x86/kernel/sev.c | 30 +++++++++++++++ 2 files changed, 96 insertions(+) diff --git a/arch/x86/include/asm/idtentry.h b/arch/x86/include/asm/idtentry.h index 652fea10d377..45b47132be7c 100644 --- a/arch/x86/include/asm/idtentry.h +++ b/arch/x86/include/asm/idtentry.h @@ -13,6 +13,10 @@ #include <asm/irq_stack.h> +#ifdef CONFIG_AMD_MEM_ENCRYPT +noinstr void irqentry_exit_hv_cond(struct pt_regs *regs, irqentry_state_t state); +#endif + /** * DECLARE_IDTENTRY - Declare functions for simple IDT entry points * No error code pushed by hardware @@ -176,6 +180,7 @@ __visible noinstr void func(struct pt_regs *regs, unsigned long error_code) #define DECLARE_IDTENTRY_IRQ(vector, func) \ DECLARE_IDTENTRY_ERRORCODE(vector, func) +#ifndef CONFIG_AMD_MEM_ENCRYPT /** * DEFINE_IDTENTRY_IRQ - Emit code for device interrupt IDT entry points * @func: Function name of the entry point @@ -205,6 +210,26 @@ __visible noinstr void func(struct pt_regs *regs, \ } \ \ static noinline void __##func(struct pt_regs *regs, u32 vector) +#else + +#define DEFINE_IDTENTRY_IRQ(func) \ +static void __##func(struct pt_regs *regs, u32 vector); \ + \ +__visible noinstr void func(struct pt_regs *regs, \ + unsigned long error_code) \ +{ \ + irqentry_state_t state = irqentry_enter(regs); \ + u32 vector = (u32)(u8)error_code; \ + \ + instrumentation_begin(); \ + kvm_set_cpu_l1tf_flush_l1d(); \ + run_irq_on_irqstack_cond(__##func, regs, vector); \ + instrumentation_end(); \ + irqentry_exit_hv_cond(regs, state); \ +} \ + \ +static noinline void __##func(struct pt_regs *regs, u32 vector) +#endif /** * DECLARE_IDTENTRY_SYSVEC - Declare functions for system vector entry points @@ -221,6 +246,7 @@ static noinline void __##func(struct pt_regs *regs, u32 vector) #define DECLARE_IDTENTRY_SYSVEC(vector, func) \ DECLARE_IDTENTRY(vector, func) +#ifndef CONFIG_AMD_MEM_ENCRYPT /** * DEFINE_IDTENTRY_SYSVEC - Emit code for system vector IDT entry points * @func: Function name of the entry point @@ -245,6 +271,26 @@ __visible noinstr void func(struct pt_regs *regs) \ } \ \ static noinline void __##func(struct pt_regs *regs) +#else + +#define DEFINE_IDTENTRY_SYSVEC(func) \ +static void __##func(struct pt_regs *regs); \ + \ +__visible noinstr void func(struct pt_regs *regs) \ +{ \ + irqentry_state_t state = irqentry_enter(regs); \ + \ + instrumentation_begin(); \ + kvm_set_cpu_l1tf_flush_l1d(); \ + run_sysvec_on_irqstack_cond(__##func, regs); \ + instrumentation_end(); \ + irqentry_exit_hv_cond(regs, state); \ +} \ + \ +static noinline void __##func(struct pt_regs *regs) +#endif + +#ifndef CONFIG_AMD_MEM_ENCRYPT /** * DEFINE_IDTENTRY_SYSVEC_SIMPLE - Emit code for simple system vector IDT @@ -274,6 +320,26 @@ __visible noinstr void func(struct pt_regs *regs) \ } \ \ static __always_inline void __##func(struct pt_regs *regs) +#else + +#define DEFINE_IDTENTRY_SYSVEC_SIMPLE(func) \ +static __always_inline void __##func(struct pt_regs *regs); \ + \ +__visible noinstr void func(struct pt_regs *regs) \ +{ \ + irqentry_state_t state = irqentry_enter(regs); \ + \ + instrumentation_begin(); \ + __irq_enter_raw(); \ + kvm_set_cpu_l1tf_flush_l1d(); \ + __##func(regs); \ + __irq_exit_raw(); \ + instrumentation_end(); \ + irqentry_exit_hv_cond(regs, state); \ +} \ + \ +static __always_inline void __##func(struct pt_regs *regs) +#endif /** * DECLARE_IDTENTRY_XENCB - Declare functions for XEN HV callback entry point diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c index b1a98c2a52f8..23f15e95838b 100644 --- a/arch/x86/kernel/sev.c +++ b/arch/x86/kernel/sev.c @@ -147,6 +147,10 @@ struct sev_hv_doorbell_page { struct sev_snp_runtime_data { struct sev_hv_doorbell_page hv_doorbell_page; + /* + * Indication that we are currently handling #HV events. + */ + bool hv_handling_events; }; static DEFINE_PER_CPU(struct sev_snp_runtime_data*, snp_runtime_data); @@ -200,6 +204,8 @@ static void do_exc_hv(struct pt_regs *regs) union hv_pending_events pending_events; u8 vector; + this_cpu_read(snp_runtime_data)->hv_handling_events = true; + while (sev_hv_pending()) { pending_events.events = xchg( &sev_snp_current_doorbell_page()->pending_events.events, @@ -234,6 +240,8 @@ static void do_exc_hv(struct pt_regs *regs) common_interrupt(regs, pending_events.vector); } } + + this_cpu_read(snp_runtime_data)->hv_handling_events = false; } static __always_inline bool on_vc_stack(struct pt_regs *regs) @@ -2529,3 +2537,25 @@ static int __init snp_init_platform_device(void) return 0; } device_initcall(snp_init_platform_device); + +noinstr void irqentry_exit_hv_cond(struct pt_regs *regs, irqentry_state_t state) +{ + /* + * Check whether this returns to user mode, if so and if + * we are currently executing the #HV handler then we don't + * want to follow the irqentry_exit_to_user_mode path as + * that can potentially cause the #HV handler to be + * preempted and rescheduled on another CPU. Rescheduled #HV + * handler on another cpu will cause interrupts to be handled + * on a different cpu than the injected one, causing + * invalid EOIs and missed/lost guest interrupts and + * corresponding hangs and/or per-cpu IRQs handled on + * non-intended cpu. + */ + if (user_mode(regs) && + this_cpu_read(snp_runtime_data)->hv_handling_events) + return; + + /* follow normal interrupt return/exit path */ + irqentry_exit(regs, state); +} -- 2.25.1