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

From: Vitaly Kuznetsov <vkuznets@redhat.com>
To: kvm@vger.kernel.org, x86@kernel.org
Cc: Paolo Bonzini <pbonzini@redhat.com>,
	Andy Lutomirski <luto@kernel.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	Borislav Petkov <bp@alien8.de>, "H. Peter Anvin" <hpa@zytor.com>,
	Wanpeng Li <wanpengli@tencent.com>,
	Sean Christopherson <sean.j.christopherson@intel.com>,
	Jim Mattson <jmattson@google.com>,
	Vivek Goyal <vgoyal@redhat.com>, Gavin Shan <gshan@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	linux-kernel@vger.kernel.org
Subject: [PATCH 7/8] KVM: x86: Switch KVM guest to using interrupts for page ready APF delivery
Date: Mon, 11 May 2020 18:47:51 +0200	[thread overview]
Message-ID: <20200511164752.2158645-8-vkuznets@redhat.com> (raw)
In-Reply-To: <20200511164752.2158645-1-vkuznets@redhat.com>

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

