kvm: x86: add host poll control msrs

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>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/Documentation/virtual/kvm/msr.txt b/Documentation/virtual/kvm/msr.txt
index f3f0d57ced8e1827fe8e8e6dc49808b18c9253fb..df1f4338b3caf3e466e783fec42b767cef1ad72c 100644 (file)
--- a/Documentation/virtual/kvm/msr.txt
+++ b/Documentation/virtual/kvm/msr.txt
@@ -273,3 +273,12 @@ MSR_KVM_EOI_EN: 0x4b564d04
        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-side HLT polling logic.
+
+       KVM guests can request the host not to poll on HLT, for example if
+       they are performing polling themselves.
+

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index aeadbc770eb2cea9116dd3a301f990aa05ddfc94..a86026969b19e67a3272e2af0863b4c90ac31fe6 100644 (file)
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -755,6 +755,8 @@ struct kvm_vcpu_arch {
                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

diff --git a/arch/x86/include/uapi/asm/kvm_para.h b/arch/x86/include/uapi/asm/kvm_para.h
index 19980ec1a316e8dc80a513948d5a5dff7b48fbda..21d5f0240595f51b3514e833b674cfc538161e4c 100644 (file)
--- a/arch/x86/include/uapi/asm/kvm_para.h
+++ b/arch/x86/include/uapi/asm/kvm_para.h
@@ -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;

diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
index fc042419e670b10199808251d8f7310454c283e2..840e12583b85bac9dd46d0628833e43a12f073f0 100644 (file)
--- a/arch/x86/kvm/Kconfig
+++ b/arch/x86/kvm/Kconfig
@@ -41,6 +41,7 @@ config KVM
        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

diff --git a/arch/x86/kvm/cpuid.c b/arch/x86/kvm/cpuid.c
index 9872f86fdbe9b5e08843db78434d404d1520418e..68c74e948e28a7884b2733fa11a8c7cc91506d03 100644 (file)
--- a/arch/x86/kvm/cpuid.c
+++ b/arch/x86/kvm/cpuid.c
@@ -658,7 +658,8 @@ static inline int __do_cpuid_ent(struct kvm_cpuid_entry2 *entry, u32 function,
                             (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);

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index eadd987ae350bdb892e36f0c90608f1f7523f02e..eb87d71ec14ab2c6f756a7f25aa2166ede8de107 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1177,6 +1177,7 @@ static u32 emulated_msrs[] = {
        MSR_IA32_POWER_CTL,
 
        MSR_K7_HWCR,
+       MSR_KVM_POLL_CONTROL,
 };
 
 static unsigned num_emulated_msrs;
@@ -2636,6 +2637,14 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
                        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:
@@ -2885,6 +2894,9 @@ int kvm_get_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
        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:
@@ -8861,6 +8873,10 @@ void kvm_arch_vcpu_postcreate(struct kvm_vcpu *vcpu)
        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)
@@ -9972,6 +9988,13 @@ bool kvm_vector_hashing_enabled(void)
 }
 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);