[PATCH 6/8] KVM: x86: announce KVM_FEATURE_ASYNC_PF_INT

[Vitaly Kuznetsov]

Introduce new capability to indicate that KVM supports interrupt based
delivery of type 2 APF events (page ready notifications). This includes
support for both MSR_KVM_ASYNC_PF_INT and MSR_KVM_ASYNC_PF_ACK.

Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
---
 Documentation/virt/kvm/cpuid.rst     | 6 ++++++
 Documentation/virt/kvm/msr.rst       | 9 ++++++---
 arch/x86/include/uapi/asm/kvm_para.h | 1 +
 arch/x86/kvm/cpuid.c                 | 3 ++-
 arch/x86/kvm/x86.c                   | 1 +
 include/uapi/linux/kvm.h             | 1 +
 6 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/Documentation/virt/kvm/cpuid.rst b/Documentation/virt/kvm/cpuid.rst
index 01b081f6e7ea..98cbd257ac33 100644
--- a/Documentation/virt/kvm/cpuid.rst
+++ b/Documentation/virt/kvm/cpuid.rst
@@ -86,6 +86,12 @@ KVM_FEATURE_PV_SCHED_YIELD        13          guest checks this feature bit
                                               before using paravirtualized
                                               sched yield.
 
+KVM_FEATURE_ASYNC_PF_INT          14          guest checks this feature bit
+                                              before using the second async
+                                              pf control msr 0x4b564d06 and
+                                              async pf acknowledgment msr
+                                              0x4b564d07.
+
 KVM_FEATURE_CLOCSOURCE_STABLE_BIT 24          host will warn if no guest-side
                                               per-cpu warps are expeced in
                                               kvmclock
diff --git a/Documentation/virt/kvm/msr.rst b/Documentation/virt/kvm/msr.rst
index 3c7afbcd243f..0e1ec0412714 100644
--- a/Documentation/virt/kvm/msr.rst
+++ b/Documentation/virt/kvm/msr.rst
@@ -209,7 +209,8 @@ data:
 	cpl == 0. Bit 2 is 1 if asynchronous page faults are delivered to L1 as
 	#PF vmexits.  Bit 2 can be set only if KVM_FEATURE_ASYNC_PF_VMEXIT is
 	present in CPUID. Bit 3 enables interrupt based delivery of type 2
-	(page present) events.
+	(page present) events. Bit 3 can be set only if KVM_FEATURE_ASYNC_PF_INT
+	is present in CPUID.
 
 	First 4 byte of 64 byte memory location ('reason') will be written to
 	by the hypervisor at the time APF type 1 (page not present) injection.
@@ -352,7 +353,8 @@ data:
 
 	Interrupt vector for asynchnonous page ready notifications delivery.
 	The vector has to be set up before asynchronous page fault mechanism
-	is enabled in MSR_KVM_ASYNC_PF_EN.
+	is enabled in MSR_KVM_ASYNC_PF_EN.  The MSR is only available if
+	KVM_FEATURE_ASYNC_PF_INT is present in CPUID.
 
 MSR_KVM_ASYNC_PF_ACK:
 	0x4b564d07
@@ -363,4 +365,5 @@ data:
 	When the guest is done processing type 2 APF event and 'pageready_token'
 	field in 'struct kvm_vcpu_pv_apf_data' is cleared it is supposed to
 	write '1' to bit 0 of the MSR, this caused the host to re-scan its queue
-	and check if there are more notifications pending.
+	and check if there are more notifications pending. The MSR is only
+	available if KVM_FEATURE_ASYNC_PF_INT is present in CPUID.
diff --git a/arch/x86/include/uapi/asm/kvm_para.h b/arch/x86/include/uapi/asm/kvm_para.h
index 941fdf4569a4..921a55de5004 100644
--- a/arch/x86/include/uapi/asm/kvm_para.h
+++ b/arch/x86/include/uapi/asm/kvm_para.h
@@ -31,6 +31,7 @@
 #define KVM_FEATURE_PV_SEND_IPI	11
 #define KVM_FEATURE_POLL_CONTROL	12
 #define KVM_FEATURE_PV_SCHED_YIELD	13
+#define KVM_FEATURE_ASYNC_PF_INT	14
 
 #define KVM_HINTS_REALTIME      0
 
diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 901cd1fdecd9..790fe4988001 100644
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -712,7 +712,8 @@ static inline int __do_cpuid_func(struct kvm_cpuid_array *array, u32 function)
 			     (1 << KVM_FEATURE_ASYNC_PF_VMEXIT) |
 			     (1 << KVM_FEATURE_PV_SEND_IPI) |
 			     (1 << KVM_FEATURE_POLL_CONTROL) |
-			     (1 << KVM_FEATURE_PV_SCHED_YIELD);
+			     (1 << KVM_FEATURE_PV_SCHED_YIELD) |
+			     (1 << KVM_FEATURE_ASYNC_PF_INT);
 
 		if (sched_info_on())
 			entry->eax |= (1 << KVM_FEATURE_STEAL_TIME);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index d21adc23a99f..ad826d922368 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -3412,6 +3412,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
 	case KVM_CAP_X86_ROBUST_SINGLESTEP:
 	case KVM_CAP_XSAVE:
 	case KVM_CAP_ASYNC_PF:
+	case KVM_CAP_ASYNC_PF_INT:
 	case KVM_CAP_GET_TSC_KHZ:
 	case KVM_CAP_KVMCLOCK_CTRL:
 	case KVM_CAP_READONLY_MEM:
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 428c7dde6b4b..15012f78a691 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1017,6 +1017,7 @@ struct kvm_ppc_resize_hpt {
 #define KVM_CAP_S390_VCPU_RESETS 179
 #define KVM_CAP_S390_PROTECTED 180
 #define KVM_CAP_PPC_SECURE_GUEST 181
+#define KVM_CAP_ASYNC_PF_INT 182
 
 #ifdef KVM_CAP_IRQ_ROUTING
 
-- 
2.25.4