| Message ID | 20200525144125.143875-9-vkuznets@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | KVM: x86: Interrupt-based mechanism for async_pf 'page present' notifications | expand |
On Mon, May 25, 2020 at 04:41:23PM +0200, Vitaly Kuznetsov wrote: > KVM now supports using interrupt for 'page ready' APF event delivery and > legacy mechanism was deprecated. Switch KVM guests to the new one. Hi Vitaly, I see we have all this code in guest which tries to take care of cases where PAGE_READY can be delivered before PAGE_NOT_PRESENT. In this new schedume of things, can it still happen. We are using an exception to deliver PAGE_NOT_PRESENT while using interrupt to deliver PAGE_READY. If re-ordeing is not possible, then it will be good to get rid of that extra complexity in guest. Thanks Vivek > > Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com> > --- > arch/x86/entry/entry_32.S | 5 ++++ > arch/x86/entry/entry_64.S | 5 ++++ > arch/x86/include/asm/hardirq.h | 3 ++ > arch/x86/include/asm/irq_vectors.h | 6 +++- > arch/x86/include/asm/kvm_para.h | 6 ++++ > arch/x86/kernel/irq.c | 9 ++++++ > arch/x86/kernel/kvm.c | 45 ++++++++++++++++++++++-------- > 7 files changed, 66 insertions(+), 13 deletions(-) > > diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S > index b67bae7091d7..d574dadcb2a1 100644 > --- a/arch/x86/entry/entry_32.S > +++ b/arch/x86/entry/entry_32.S > @@ -1475,6 +1475,11 @@ BUILD_INTERRUPT3(hv_stimer0_callback_vector, HYPERV_STIMER0_VECTOR, > > #endif /* CONFIG_HYPERV */ > > +#ifdef CONFIG_KVM_GUEST > +BUILD_INTERRUPT3(kvm_async_pf_vector, KVM_ASYNC_PF_VECTOR, > + kvm_async_pf_intr) > +#endif > + > SYM_CODE_START(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 3063aa9090f9..138f5c5aca2e 100644 > --- a/arch/x86/entry/entry_64.S > +++ b/arch/x86/entry/entry_64.S > @@ -1190,6 +1190,11 @@ apicinterrupt3 HYPERVISOR_CALLBACK_VECTOR \ > acrn_hv_callback_vector acrn_hv_vector_handler > #endif > > +#ifdef CONFIG_KVM_GUEST > +apicinterrupt3 KVM_ASYNC_PF_VECTOR \ > + kvm_async_pf_vector kvm_async_pf_intr > +#endif > + > idtentry debug do_debug has_error_code=0 paranoid=1 shift_ist=IST_INDEX_DB ist_offset=DB_STACK_OFFSET > 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 07533795b8d2..be0fbb15ad7f 100644 > --- a/arch/x86/include/asm/hardirq.h > +++ b/arch/x86/include/asm/hardirq.h > @@ -44,6 +44,9 @@ typedef struct { > unsigned int irq_hv_reenlightenment_count; > unsigned int hyperv_stimer0_count; > #endif > +#ifdef CONFIG_KVM_GUEST > + unsigned int kvm_async_pf_pageready_count; > +#endif > } ____cacheline_aligned irq_cpustat_t; > > DECLARE_PER_CPU_SHARED_ALIGNED(irq_cpustat_t, irq_stat); > diff --git a/arch/x86/include/asm/irq_vectors.h b/arch/x86/include/asm/irq_vectors.h > index 889f8b1b5b7f..8879a9ecd908 100644 > --- a/arch/x86/include/asm/irq_vectors.h > +++ b/arch/x86/include/asm/irq_vectors.h > @@ -104,7 +104,11 @@ > #define HYPERV_STIMER0_VECTOR 0xed > #endif > > -#define LOCAL_TIMER_VECTOR 0xec > +#ifdef CONFIG_KVM_GUEST > +#define KVM_ASYNC_PF_VECTOR 0xec > +#endif > + > +#define LOCAL_TIMER_VECTOR 0xeb > > #define NR_VECTORS 256 > > diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h > index 2a3102fee189..a075cd8fa5c7 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); > @@ -93,6 +94,11 @@ void kvm_async_pf_task_wake(u32 token); > u32 kvm_read_and_reset_apf_flags(void); > extern void kvm_disable_steal_time(void); > void do_async_page_fault(struct pt_regs *regs, unsigned long error_code, unsigned long address); > +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); > diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c > index c7965ff429c5..a4c2f25ad74d 100644 > --- a/arch/x86/kernel/irq.c > +++ b/arch/x86/kernel/irq.c > @@ -159,6 +159,15 @@ int arch_show_interrupts(struct seq_file *p, int prec) > irq_stats(j)->hyperv_stimer0_count); > seq_puts(p, " Hyper-V stimer0 interrupts\n"); > } > +#endif > +#ifdef CONFIG_KVM_GUEST > + if (test_bit(KVM_ASYNC_PF_VECTOR, system_vectors)) { > + seq_printf(p, "%*s: ", prec, "APF"); > + for_each_online_cpu(j) > + seq_printf(p, "%10u ", > + irq_stats(j)->kvm_async_pf_pageready_count); > + seq_puts(p, " KVM async PF page ready interrupts\n"); > + } > #endif > seq_printf(p, "%*s: %10u\n", prec, "ERR", atomic_read(&irq_err_count)); > #if defined(CONFIG_X86_IO_APIC) > diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c > index 340df5dab30d..79730eaef1e1 100644 > --- a/arch/x86/kernel/kvm.c > +++ b/arch/x86/kernel/kvm.c > @@ -245,23 +245,39 @@ NOKPROBE_SYMBOL(kvm_read_and_reset_apf_flags); > dotraplinkage void > do_async_page_fault(struct pt_regs *regs, unsigned long error_code, unsigned long address) > { > - switch (kvm_read_and_reset_apf_flags()) { > - default: > + u32 flags = kvm_read_and_reset_apf_flags(); > + > + if (!flags) { > + /* This is a normal page fault */ > do_page_fault(regs, error_code, address); > - break; > - case KVM_PV_REASON_PAGE_NOT_PRESENT: > + return; > + } else if (flags & KVM_PV_REASON_PAGE_NOT_PRESENT) { > /* page is swapped out by the host. */ > kvm_async_pf_task_wait((u32)address, !user_mode(regs)); > - break; > - case KVM_PV_REASON_PAGE_READY: > - rcu_irq_enter(); > - kvm_async_pf_task_wake((u32)address); > - rcu_irq_exit(); > - break; > + } else { > + WARN_ONCE(1, "Unexpected async PF flags: %x\n", flags); > } > } > 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(kvm_async_pf_pageready_count); > + > + if (__this_cpu_read(apf_reason.enabled)) { > + token = __this_cpu_read(apf_reason.token); > + kvm_async_pf_task_wake(token); > + __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"; > @@ -305,17 +321,19 @@ static notrace void kvm_guest_apic_eoi_write(u32 reg, u32 val) > > static void kvm_guest_cpu_init(void) > { > - if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF) && kvmapf) { > + if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF_INT) && kvmapf) { > u64 pa = slow_virt_to_phys(this_cpu_ptr(&apf_reason)); > > #ifdef CONFIG_PREEMPTION > pa |= KVM_ASYNC_PF_SEND_ALWAYS; > #endif > - pa |= KVM_ASYNC_PF_ENABLED; > + pa |= KVM_ASYNC_PF_ENABLED | KVM_ASYNC_PF_DELIVERY_AS_INT; > > if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF_VMEXIT)) > pa |= KVM_ASYNC_PF_DELIVERY_AS_PF_VMEXIT; > > + wrmsrl(MSR_KVM_ASYNC_PF_INT, KVM_ASYNC_PF_VECTOR); > + > 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", > @@ -649,6 +667,9 @@ static void __init kvm_guest_init(void) > if (kvm_para_has_feature(KVM_FEATURE_PV_EOI)) > apic_set_eoi_write(kvm_guest_apic_eoi_write); > > + if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF_INT)) > + alloc_intr_gate(KVM_ASYNC_PF_VECTOR, kvm_async_pf_vector); > + > #ifdef CONFIG_SMP > smp_ops.smp_prepare_cpus = kvm_smp_prepare_cpus; > smp_ops.smp_prepare_boot_cpu = kvm_smp_prepare_boot_cpu; > -- > 2.25.4 >
On 10/06/20 22:51, Vivek Goyal wrote: >> KVM now supports using interrupt for 'page ready' APF event delivery and >> legacy mechanism was deprecated. Switch KVM guests to the new one. > Hi Vitaly, > > I see we have all this code in guest which tries to take care of > cases where PAGE_READY can be delivered before PAGE_NOT_PRESENT. In > this new schedume of things, can it still happen. We are using > an exception to deliver PAGE_NOT_PRESENT while using interrupt to > deliver PAGE_READY. > > If re-ordeing is not possible, then it will be good to get rid of > that extra complexity in guest. It is perhaps less likely but still possible, because the interrupt might be delivered to another CPU and race against the exception. Paolo
diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S index b67bae7091d7..d574dadcb2a1 100644 --- a/arch/x86/entry/entry_32.S +++ b/arch/x86/entry/entry_32.S @@ -1475,6 +1475,11 @@ BUILD_INTERRUPT3(hv_stimer0_callback_vector, HYPERV_STIMER0_VECTOR, #endif /* CONFIG_HYPERV */ +#ifdef CONFIG_KVM_GUEST +BUILD_INTERRUPT3(kvm_async_pf_vector, KVM_ASYNC_PF_VECTOR, + kvm_async_pf_intr) +#endif + SYM_CODE_START(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 3063aa9090f9..138f5c5aca2e 100644 --- a/arch/x86/entry/entry_64.S +++ b/arch/x86/entry/entry_64.S @@ -1190,6 +1190,11 @@ apicinterrupt3 HYPERVISOR_CALLBACK_VECTOR \ acrn_hv_callback_vector acrn_hv_vector_handler #endif +#ifdef CONFIG_KVM_GUEST +apicinterrupt3 KVM_ASYNC_PF_VECTOR \ + kvm_async_pf_vector kvm_async_pf_intr +#endif + idtentry debug do_debug has_error_code=0 paranoid=1 shift_ist=IST_INDEX_DB ist_offset=DB_STACK_OFFSET 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 07533795b8d2..be0fbb15ad7f 100644 --- a/arch/x86/include/asm/hardirq.h +++ b/arch/x86/include/asm/hardirq.h @@ -44,6 +44,9 @@ typedef struct { unsigned int irq_hv_reenlightenment_count; unsigned int hyperv_stimer0_count; #endif +#ifdef CONFIG_KVM_GUEST + unsigned int kvm_async_pf_pageready_count; +#endif } ____cacheline_aligned irq_cpustat_t; DECLARE_PER_CPU_SHARED_ALIGNED(irq_cpustat_t, irq_stat); diff --git a/arch/x86/include/asm/irq_vectors.h b/arch/x86/include/asm/irq_vectors.h index 889f8b1b5b7f..8879a9ecd908 100644 --- a/arch/x86/include/asm/irq_vectors.h +++ b/arch/x86/include/asm/irq_vectors.h @@ -104,7 +104,11 @@ #define HYPERV_STIMER0_VECTOR 0xed #endif -#define LOCAL_TIMER_VECTOR 0xec +#ifdef CONFIG_KVM_GUEST +#define KVM_ASYNC_PF_VECTOR 0xec +#endif + +#define LOCAL_TIMER_VECTOR 0xeb #define NR_VECTORS 256 diff --git a/arch/x86/include/asm/kvm_para.h b/arch/x86/include/asm/kvm_para.h index 2a3102fee189..a075cd8fa5c7 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); @@ -93,6 +94,11 @@ void kvm_async_pf_task_wake(u32 token); u32 kvm_read_and_reset_apf_flags(void); extern void kvm_disable_steal_time(void); void do_async_page_fault(struct pt_regs *regs, unsigned long error_code, unsigned long address); +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); diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c index c7965ff429c5..a4c2f25ad74d 100644 --- a/arch/x86/kernel/irq.c +++ b/arch/x86/kernel/irq.c @@ -159,6 +159,15 @@ int arch_show_interrupts(struct seq_file *p, int prec) irq_stats(j)->hyperv_stimer0_count); seq_puts(p, " Hyper-V stimer0 interrupts\n"); } +#endif +#ifdef CONFIG_KVM_GUEST + if (test_bit(KVM_ASYNC_PF_VECTOR, system_vectors)) { + seq_printf(p, "%*s: ", prec, "APF"); + for_each_online_cpu(j) + seq_printf(p, "%10u ", + irq_stats(j)->kvm_async_pf_pageready_count); + seq_puts(p, " KVM async PF page ready interrupts\n"); + } #endif seq_printf(p, "%*s: %10u\n", prec, "ERR", atomic_read(&irq_err_count)); #if defined(CONFIG_X86_IO_APIC) diff --git a/arch/x86/kernel/kvm.c b/arch/x86/kernel/kvm.c index 340df5dab30d..79730eaef1e1 100644 --- a/arch/x86/kernel/kvm.c +++ b/arch/x86/kernel/kvm.c @@ -245,23 +245,39 @@ NOKPROBE_SYMBOL(kvm_read_and_reset_apf_flags); dotraplinkage void do_async_page_fault(struct pt_regs *regs, unsigned long error_code, unsigned long address) { - switch (kvm_read_and_reset_apf_flags()) { - default: + u32 flags = kvm_read_and_reset_apf_flags(); + + if (!flags) { + /* This is a normal page fault */ do_page_fault(regs, error_code, address); - break; - case KVM_PV_REASON_PAGE_NOT_PRESENT: + return; + } else if (flags & KVM_PV_REASON_PAGE_NOT_PRESENT) { /* page is swapped out by the host. */ kvm_async_pf_task_wait((u32)address, !user_mode(regs)); - break; - case KVM_PV_REASON_PAGE_READY: - rcu_irq_enter(); - kvm_async_pf_task_wake((u32)address); - rcu_irq_exit(); - break; + } else { + WARN_ONCE(1, "Unexpected async PF flags: %x\n", flags); } } 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(kvm_async_pf_pageready_count); + + if (__this_cpu_read(apf_reason.enabled)) { + token = __this_cpu_read(apf_reason.token); + kvm_async_pf_task_wake(token); + __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"; @@ -305,17 +321,19 @@ static notrace void kvm_guest_apic_eoi_write(u32 reg, u32 val) static void kvm_guest_cpu_init(void) { - if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF) && kvmapf) { + if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF_INT) && kvmapf) { u64 pa = slow_virt_to_phys(this_cpu_ptr(&apf_reason)); #ifdef CONFIG_PREEMPTION pa |= KVM_ASYNC_PF_SEND_ALWAYS; #endif - pa |= KVM_ASYNC_PF_ENABLED; + pa |= KVM_ASYNC_PF_ENABLED | KVM_ASYNC_PF_DELIVERY_AS_INT; if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF_VMEXIT)) pa |= KVM_ASYNC_PF_DELIVERY_AS_PF_VMEXIT; + wrmsrl(MSR_KVM_ASYNC_PF_INT, KVM_ASYNC_PF_VECTOR); + 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", @@ -649,6 +667,9 @@ static void __init kvm_guest_init(void) if (kvm_para_has_feature(KVM_FEATURE_PV_EOI)) apic_set_eoi_write(kvm_guest_apic_eoi_write); + if (kvm_para_has_feature(KVM_FEATURE_ASYNC_PF_INT)) + alloc_intr_gate(KVM_ASYNC_PF_VECTOR, kvm_async_pf_vector); + #ifdef CONFIG_SMP smp_ops.smp_prepare_cpus = kvm_smp_prepare_cpus; smp_ops.smp_prepare_boot_cpu = kvm_smp_prepare_boot_cpu;
KVM now supports using interrupt for 'page ready' APF event delivery and legacy mechanism was deprecated. Switch KVM guests to the new one. Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com> --- arch/x86/entry/entry_32.S | 5 ++++ arch/x86/entry/entry_64.S | 5 ++++ arch/x86/include/asm/hardirq.h | 3 ++ arch/x86/include/asm/irq_vectors.h | 6 +++- arch/x86/include/asm/kvm_para.h | 6 ++++ arch/x86/kernel/irq.c | 9 ++++++ arch/x86/kernel/kvm.c | 45 ++++++++++++++++++++++-------- 7 files changed, 66 insertions(+), 13 deletions(-)