Hey Vitaly, Paolo, thank you both for the comments! For visibility, here is the complete v2 patch with the additional safety check to avoid handling page ready notifications from #PF if async-pf-int is enabled. Thanks, Riccardo Commit follows: This patch backports support for interrupt-based delivery of Async Page Fault notifications in KVM guests from commit b1d405751cd5 ("KVM: x86: Switch KVM guest to using interrupts for page ready APF delivery") [1]. Differently from the patchet upstream, this patch does not remove support for the legacy #PF-based delivery, and removes unnecessary refactoring to limit changes to KVM guest code. v2: add kvm_apf_int_enabled flag to prevent handling of PAGE_READY [1] https://lore.kernel.org/kvm/20200525144125.143875-1-vkuznets@xxxxxxxxxx/ Reviewed-by: Eugene Batalov <bataloe@xxxxxxxxxx> Reviewed-by: Greg Farrell <gffarre@xxxxxxxxxx> Signed-off-by: Riccardo Mancini <mancio@xxxxxxxxxx> --- arch/x86/entry/entry_32.S | 5 +++ arch/x86/entry/entry_64.S | 5 +++ arch/x86/include/asm/hardirq.h | 2 +- arch/x86/include/asm/kvm_para.h | 7 ++++ arch/x86/include/uapi/asm/kvm_para.h | 16 +++++++++- arch/x86/kernel/irq.c | 2 +- arch/x86/kernel/kvm.c | 48 ++++++++++++++++++++++++---- 7 files changed, 75 insertions(+), 10 deletions(-) diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S index 1fdedb2eaef3..460eb7a9981e 100644 --- a/arch/x86/entry/entry_32.S +++ b/arch/x86/entry/entry_32.S @@ -896,6 +896,11 @@ BUILD_INTERRUPT3(hyperv_callback_vector, HYPERVISOR_CALLBACK_VECTOR, #endif /* CONFIG_HYPERV */ +#ifdef CONFIG_KVM_GUEST +BUILD_INTERRUPT3(kvm_async_pf_vector, HYPERVISOR_CALLBACK_VECTOR, + kvm_async_pf_intr) +#endif + ENTRY(page_fault) ASM_CLAC pushl $do_page_fault diff --git a/arch/x86/entry/entry_64.S b/arch/x86/entry/entry_64.S index 1804ccf52d9b..545d911a2c9e 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -1113,6 +1113,11 @@ apicinterrupt3 HYPERVISOR_CALLBACK_VECTOR \ hyperv_callback_vector hyperv_vector_handler #endif /* CONFIG_HYPERV */ +#ifdef CONFIG_KVM_GUEST +apicinterrupt3 HYPERVISOR_CALLBACK_VECTOR \ + kvm_async_pf_vector kvm_async_pf_intr +#endif + idtentry debug do_debug has_error_code=0 paranoid=1 shift_ist=DEBUG_STACK idtentry int3 do_int3 has_error_code=0 create_gap=1 idtentry stack_segment do_stack_segment has_error_code=1 diff --git a/arch/x86/include/asm/hardirq.h b/arch/x86/include/asm/hardirq.h index 486c843273c4..75e51b7c9f50 100644 --- a/arch/x86/include/asm/hardirq.h +++ b/arch/x86/include/asm/hardirq.h @@ -37,7 +37,7 @@ typedef struct { #ifdef CONFIG_X86_MCE_AMD unsigned int irq_deferred_error_count; #endif -#if IS_ENABLED(CONFIG_HYPERV) || defined(CONFIG_XEN) +#if IS_ENABLED(CONFIG_HYPERV) || defined(CONFIG_XEN) || defined(CONFIG_KVM_GUEST) unsigned int irq_hv_callback_count; #endif } ____cacheline_aligned irq_cpustat_t; diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h index c373e44049b1..f4806dd3c38d 100644 --- a/arch/x86/include/asm/kvm_para.h +++ b/arch/x86/include/asm/kvm_para.h @@ -4,6 +4,7 @@ #include <asm/processor.h> #include <asm/alternative.h> +#include <linux/interrupt.h> #include <uapi/asm/kvm_para.h> extern void kvmclock_init(void); @@ -94,6 +95,12 @@ void kvm_async_pf_task_wake(u32 token); u32 kvm_read_and_reset_pf_reason(void); extern void kvm_disable_steal_time(void); +extern __visible void kvm_async_pf_vector(void); +#ifdef CONFIG_TRACING +#define trace_kvm_async_pf_vector kvm_async_pf_vector +#endif +__visible void __irq_entry kvm_async_pf_intr(struct pt_regs *regs); + #ifdef CONFIG_PARAVIRT_SPINLOCKS void __init kvm_spinlock_init(void); #else /* !CONFIG_PARAVIRT_SPINLOCKS */ diff --git a/arch/x86/include/uapi/asm/kvm_para.h b/arch/x86/include/uapi/asm/kvm_para.h index 341db0462b85..29b86e9adc9a 100644 --- a/arch/x86/include/uapi/asm/kvm_para.h +++ b/arch/x86/include/uapi/asm/kvm_para.h @@ -26,6 +26,8 @@ #define KVM_FEATURE_PV_EOI 6 #define KVM_FEATURE_PV_UNHALT 7 #define KVM_FEATURE_ASYNC_PF_VMEXIT 10 +#define KVM_FEATURE_ASYNC_PF_INT 14 +#define KVM_FEATURE_MSI_EXT_DEST_ID 15 /* The last 8 bits are used to indicate how to interpret the flags field * in pvclock structure. If no bits are set, all flags are ignored. @@ -42,6 +44,8 @@ #define MSR_KVM_ASYNC_PF_EN 0x4b564d02 #define MSR_KVM_STEAL_TIME 0x4b564d03 #define MSR_KVM_PV_EOI_EN 0x4b564d04 +#define MSR_KVM_ASYNC_PF_INT 0x4b564d06 +#define MSR_KVM_ASYNC_PF_ACK 0x4b564d07 struct kvm_steal_time { __u64 steal; @@ -70,6 +74,11 @@ struct kvm_clock_pairing { #define KVM_ASYNC_PF_ENABLED (1 << 0) #define KVM_ASYNC_PF_SEND_ALWAYS (1 << 1) #define KVM_ASYNC_PF_DELIVERY_AS_PF_VMEXIT (1 << 2) +#define KVM_ASYNC_PF_DELIVERY_AS_INT (1 << 3) + +/* MSR_KVM_ASYNC_PF_INT */ +#define KVM_ASYNC_PF_VEC_MASK GENMASK(7, 0) + /* Operations for KVM_HC_MMU_OP */ #define KVM_MMU_OP_WRITE_PTE 1 @@ -101,8 +110,13 @@ struct kvm_mmu_op_release_pt { #define KVM_PV_REASON_PAGE_READY 2 struct kvm_vcpu_pv_apf_data { + /* Used for 'page not present' events delivered via #PF */ __u32 reason; - __u8 pad[60]; + + /* Used for 'page ready' events delivered via interrupt notification */ + __u32 token; + + __u8 pad[56]; __u32 enabled; }; diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c index fbcc303fb1f9..d1def86b66bd 100644 --- a/arch/x86/kernel/irq.c +++ b/arch/x86/kernel/irq.c @@ -134,7 +134,7 @@ int arch_show_interrupts(struct seq_file *p, int prec) seq_printf(p, "%10u ", per_cpu(mce_poll_count, j)); seq_puts(p, " Machine check polls\n"); #endif -#if IS_ENABLED(CONFIG_HYPERV) || defined(CONFIG_XEN) +#if IS_ENABLED(CONFIG_HYPERV) || defined(CONFIG_XEN) || defined(CONFIG_KVM_GUEST) if (test_bit(HYPERVISOR_CALLBACK_VECTOR, used_vectors)) { seq_printf(p, "%*s: ", prec, "HYP"); for_each_online_cpu(j) diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c index 5853eb50138e..12e5fddb6da1 100644 --- a/arch/x86/kernel/kvm.c +++ b/arch/x86/kernel/kvm.c @@ -79,6 +79,8 @@ static DEFINE_PER_CPU(struct kvm_vcpu_pv_apf_data, apf_reason) __aligned(64); static DEFINE_PER_CPU(struct kvm_steal_time, steal_time) __aligned(64); static int has_steal_clock = 0; +static DEFINE_PER_CPU(u32, kvm_apf_int_enabled); + /* * No need for any "IO delay" on KVM */ @@ -267,26 +269,48 @@ dotraplinkage void do_async_page_fault(struct pt_regs *regs, unsigned long error_code) { enum ctx_state prev_state; + u32 reason = kvm_read_and_reset_pf_reason(); + u32 handle_page_ready = !__this_cpu_read(kvm_apf_int_enabled); - switch (kvm_read_and_reset_pf_reason()) { - default: + if (!reason) { + /* This is a normal page fault */ do_page_fault(regs, error_code); - break; - case KVM_PV_REASON_PAGE_NOT_PRESENT: + } else if (reason & KVM_PV_REASON_PAGE_NOT_PRESENT) { /* page is swapped out by the host. */ prev_state = exception_enter(); kvm_async_pf_task_wait((u32)read_cr2(), !user_mode(regs)); exception_exit(prev_state); - break; - case KVM_PV_REASON_PAGE_READY: + } else if (handle_page_ready && (reason & KVM_PV_REASON_PAGE_READY)) { + /* possible only if interrupt-based mechanism is disabled */ rcu_irq_enter(); kvm_async_pf_task_wake((u32)read_cr2()); rcu_irq_exit(); - break; + } else { + WARN_ONCE(1, "Unexpected async PF flags: %x\n", reason); } } NOKPROBE_SYMBOL(do_async_page_fault); +__visible void __irq_entry kvm_async_pf_intr(struct pt_regs *regs) +{ + u32 token; + + entering_ack_irq(); + + inc_irq_stat(irq_hv_callback_count); + + if (__this_cpu_read(apf_reason.enabled)) { + token = __this_cpu_read(apf_reason.token); + rcu_irq_enter(); + kvm_async_pf_task_wake(token); + rcu_irq_exit(); + __this_cpu_write(apf_reason.token, 0); + wrmsrl(MSR_KVM_ASYNC_PF_ACK, 1); + } + + exiting_irq(); +} + static void __init paravirt_ops_setup(void) { pv_info.name = "KVM"; @@ -344,6 +368,12 @@ static void kvm_guest_cpu_init(void) if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF_VMEXIT)) pa |= KVM_ASYNC_PF_DELIVERY_AS_PF_VMEXIT; + if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF_INT)) { + pa |= KVM_ASYNC_PF_DELIVERY_AS_INT; + wrmsrl(MSR_KVM_ASYNC_PF_INT, HYPERVISOR_CALLBACK_VECTOR); + __this_cpu_write(kvm_apf_int_enabled, 1); + } + wrmsrl(MSR_KVM_ASYNC_PF_EN, pa); __this_cpu_write(apf_reason.enabled, 1); printk(KERN_INFO"KVM setup async PF for cpu %d\n", @@ -371,6 +401,7 @@ static void kvm_pv_disable_apf(void) wrmsrl(MSR_KVM_ASYNC_PF_EN, 0); __this_cpu_write(apf_reason.enabled, 0); + __this_cpu_write(kvm_apf_int_enabled, 0); printk(KERN_INFO"Unregister pv shared memory for cpu %d\n", smp_processor_id()); @@ -490,6 +521,9 @@ void __init kvm_guest_init(void) if (kvmclock_vsyscall) kvm_setup_vsyscall_timeinfo(); + if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF_INT) && kvmapf) + alloc_intr_gate(HYPERVISOR_CALLBACK_VECTOR, kvm_async_pf_vector); + #ifdef CONFIG_SMP smp_ops.smp_prepare_boot_cpu = kvm_smp_prepare_boot_cpu; if (cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, "x86/kvm:online", -- 2.40.1