[patch 2/3] kvm: x86: add host poll control msrs

[Marcelo Tosatti <mtosatti@redhat.com>]

[-- Attachment #1: 02-pollcontrol-host.patch --]
[-- Type: text/plain, Size: 5252 bytes --]

Add an MSRs which allows the guest to disable 
host polling (specifically the cpuidle-haltpoll, 
when performing polling in the guest, disables
host side polling).

Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

---
 Documentation/virtual/kvm/msr.txt    |    9 +++++++++
 arch/x86/include/asm/kvm_host.h      |    2 ++
 arch/x86/include/uapi/asm/kvm_para.h |    2 ++
 arch/x86/kvm/Kconfig                 |    1 +
 arch/x86/kvm/cpuid.c                 |    3 ++-
 arch/x86/kvm/x86.c                   |   22 ++++++++++++++++++++++
 6 files changed, 38 insertions(+), 1 deletion(-)

Index: linux-2.6.git/Documentation/virtual/kvm/msr.txt
===================================================================
--- linux-2.6.git.orig/Documentation/virtual/kvm/msr.txt	2019-06-11 15:54:16.500695464 -0300
+++ linux-2.6.git/Documentation/virtual/kvm/msr.txt	2019-06-11 16:04:09.917453903 -0300
@@ -273,3 +273,12 @@
 	guest must both read the least significant bit in the memory area and
 	clear it using a single CPU instruction, such as test and clear, or
 	compare and exchange.
+
+MSR_KVM_POLL_CONTROL: 0x4b564d05
+	Control host side polling.
+
+	data: Bit 0 enables (1) or disables (0) host halt poll
+	logic.
+	KVM guests can disable host halt polling when performing
+	polling themselves.
+
Index: linux-2.6.git/arch/x86/include/asm/kvm_host.h
===================================================================
--- linux-2.6.git.orig/arch/x86/include/asm/kvm_host.h	2019-06-11 15:54:16.500695464 -0300
+++ linux-2.6.git/arch/x86/include/asm/kvm_host.h	2019-06-11 16:04:09.917453903 -0300
@@ -755,6 +755,8 @@
 		struct gfn_to_hva_cache data;
 	} pv_eoi;
 
+	u64 msr_kvm_poll_control;
+
 	/*
 	 * Indicate whether the access faults on its page table in guest
 	 * which is set when fix page fault and used to detect unhandeable
Index: linux-2.6.git/arch/x86/include/uapi/asm/kvm_para.h
===================================================================
--- linux-2.6.git.orig/arch/x86/include/uapi/asm/kvm_para.h	2019-06-11 15:54:16.500695464 -0300
+++ linux-2.6.git/arch/x86/include/uapi/asm/kvm_para.h	2019-06-11 16:04:09.917453903 -0300
@@ -29,6 +29,7 @@
 #define KVM_FEATURE_PV_TLB_FLUSH	9
 #define KVM_FEATURE_ASYNC_PF_VMEXIT	10
 #define KVM_FEATURE_PV_SEND_IPI	11
+#define KVM_FEATURE_POLL_CONTROL	12
 
 #define KVM_HINTS_REALTIME      0
 
@@ -47,6 +48,7 @@
 #define MSR_KVM_ASYNC_PF_EN 0x4b564d02
 #define MSR_KVM_STEAL_TIME  0x4b564d03
 #define MSR_KVM_PV_EOI_EN      0x4b564d04
+#define MSR_KVM_POLL_CONTROL	0x4b564d05
 
 struct kvm_steal_time {
 	__u64 steal;
Index: linux-2.6.git/arch/x86/kvm/Kconfig
===================================================================
--- linux-2.6.git.orig/arch/x86/kvm/Kconfig	2019-06-11 15:54:16.500695464 -0300
+++ linux-2.6.git/arch/x86/kvm/Kconfig	2019-06-11 16:04:09.917453903 -0300
@@ -41,6 +41,7 @@
 	select PERF_EVENTS
 	select HAVE_KVM_MSI
 	select HAVE_KVM_CPU_RELAX_INTERCEPT
+	select HAVE_KVM_NO_POLL
 	select KVM_GENERIC_DIRTYLOG_READ_PROTECT
 	select KVM_VFIO
 	select SRCU
Index: linux-2.6.git/arch/x86/kvm/cpuid.c
===================================================================
--- linux-2.6.git.orig/arch/x86/kvm/cpuid.c	2019-06-11 15:54:16.500695464 -0300
+++ linux-2.6.git/arch/x86/kvm/cpuid.c	2019-06-11 16:04:09.918453923 -0300
@@ -643,7 +643,8 @@
 			     (1 << KVM_FEATURE_PV_UNHALT) |
 			     (1 << KVM_FEATURE_PV_TLB_FLUSH) |
 			     (1 << KVM_FEATURE_ASYNC_PF_VMEXIT) |
-			     (1 << KVM_FEATURE_PV_SEND_IPI);
+			     (1 << KVM_FEATURE_PV_SEND_IPI) |
+			     (1 << KVM_FEATURE_POLL_CONTROL);
 
 		if (sched_info_on())
 			entry->eax |= (1 << KVM_FEATURE_STEAL_TIME);
Index: linux-2.6.git/arch/x86/kvm/x86.c
===================================================================
--- linux-2.6.git.orig/arch/x86/kvm/x86.c	2019-06-11 15:54:16.500695464 -0300
+++ linux-2.6.git/arch/x86/kvm/x86.c	2019-06-11 16:04:48.002209329 -0300
@@ -1177,6 +1177,7 @@
 	MSR_IA32_POWER_CTL,
 
 	MSR_K7_HWCR,
+	MSR_KVM_POLL_CONTROL,
 };
 
 static unsigned num_emulated_msrs;
@@ -2628,6 +2629,14 @@
 			return 1;
 		break;
 
+	case MSR_KVM_POLL_CONTROL:
+		/* only enable bit supported */
+		if (data & (-1ULL << 1))
+			return 1;
+
+		vcpu->arch.msr_kvm_poll_control = data;
+		break;
+
 	case MSR_IA32_MCG_CTL:
 	case MSR_IA32_MCG_STATUS:
 	case MSR_IA32_MC0_CTL ... MSR_IA32_MCx_CTL(KVM_MAX_MCE_BANKS) - 1:
@@ -2877,6 +2886,9 @@
 	case MSR_KVM_PV_EOI_EN:
 		msr_info->data = vcpu->arch.pv_eoi.msr_val;
 		break;
+	case MSR_KVM_POLL_CONTROL:
+		msr_info->data = vcpu->arch.msr_kvm_poll_control;
+		break;
 	case MSR_IA32_P5_MC_ADDR:
 	case MSR_IA32_P5_MC_TYPE:
 	case MSR_IA32_MCG_CAP:
@@ -8874,6 +8886,10 @@
 	msr.host_initiated = true;
 	kvm_write_tsc(vcpu, &msr);
 	vcpu_put(vcpu);
+
+	/* poll control enabled by default */
+	vcpu->arch.msr_kvm_poll_control = 1;
+
 	mutex_unlock(&vcpu->mutex);
 
 	if (!kvmclock_periodic_sync)
@@ -9948,6 +9964,12 @@
 }
 EXPORT_SYMBOL_GPL(kvm_vector_hashing_enabled);
 
+bool kvm_arch_no_poll(struct kvm_vcpu *vcpu)
+{
+	return (vcpu->arch.msr_kvm_poll_control & 1) == 0;
+}
+EXPORT_SYMBOL_GPL(kvm_arch_no_poll);
+
 EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_exit);
 EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_fast_mmio);
 EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_inj_virq);