[PATCH 7/8] KVM: x86: Switch KVM guest to using interrupts for page ready APF delivery

Vitaly Kuznetsov
2020-05-11T16:48:55Z

KVM now supports using interrupt for type 2 APF event delivery (page ready
notifications) 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 | 42 +++++++++++++++++++++++-------
7 files changed, 65 insertions(+), 11 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 0e9504fabe52..6f127c1a6547 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 9b4df6eaa11a..fde4f21607f9 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_pf_reason(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 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 6efe0410fb72..b6453d227604 100644
--- a/arch/x86/kernel/kvm.c
+++ b/arch/x86/kernel/kvm.c
@@ -245,23 +245,40 @@ NOKPROBE_SYMBOL(kvm_read_and_reset_pf_reason);
dotraplinkage void
do_async_page_fault(struct pt_regs *regs, unsigned long error_code, unsigned long address)
{
- switch (kvm_read_and_reset_pf_reason()) {
- default:
- do_page_fault(regs, error_code, address);
- break;
+ u32 reason = kvm_read_and_reset_pf_reason();
+
+ switch (reason) {
case 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();
+ case 0:
+ do_page_fault(regs, error_code, address);
break;
+ default:
+ WARN_ONCE(1, "Unexpected async PF reason: %x\n", reason);
}
}
NOKPROBE_SYMBOL(do_async_page_fault);

+__visible void __irq_entry kvm_async_pf_intr(struct pt_regs *regs)
+{
+ u32 token, reason;
+
+ entering_ack_irq();
+
+ inc_irq_stat(kvm_async_pf_pageready_count);
+
+ if (__this_cpu_read(apf_reason.enabled)) {
+ token = __this_cpu_read(apf_reason.pageready_token);
+ kvm_async_pf_task_wake(token);
+ __this_cpu_write(apf_reason.pageready_token, 0);
+ wrmsrl(MSR_KVM_ASYNC_PF_ACK, 1);
+ }
+
+ exiting_irq();
+}
+
static void __init paravirt_ops_setup(void)
{
pv_info.name = "KVM";
@@ -305,17 +322,19 @@ 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 +668,9 @@ 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