[patch 4/5] kvm: x86: add host poll control msrs

Marcelo Tosatti
2019-07-01T18:57:34Z

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 | 23 +++++++++++++++++++++++
6 files changed, 39 insertions(+), 1 deletion(-)

Index: linux-2.6-newcpuidle.git/Documentation/virtual/kvm/msr.txt
===================================================================
--- linux-2.6-newcpuidle.git.orig/Documentation/virtual/kvm/msr.txt
+++ linux-2.6-newcpuidle.git/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 halt poll
+ logic.
+ KVM guests can disable host halt polling when performing
+ polling themselves.
+
Index: linux-2.6-newcpuidle.git/arch/x86/include/asm/kvm_host.h
===================================================================
--- linux-2.6-newcpuidle.git.orig/arch/x86/include/asm/kvm_host.h
+++ linux-2.6-newcpuidle.git/arch/x86/include/asm/kvm_host.h
@@ -752,6 +752,8 @@ 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
Index: linux-2.6-newcpuidle.git/arch/x86/include/uapi/asm/kvm_para.h
===================================================================
--- linux-2.6-newcpuidle.git.orig/arch/x86/include/uapi/asm/kvm_para.h
+++ linux-2.6-newcpuidle.git/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;
Index: linux-2.6-newcpuidle.git/arch/x86/kvm/Kconfig
===================================================================
--- linux-2.6-newcpuidle.git.orig/arch/x86/kvm/Kconfig
+++ linux-2.6-newcpuidle.git/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
Index: linux-2.6-newcpuidle.git/arch/x86/kvm/cpuid.c
===================================================================
--- linux-2.6-newcpuidle.git.orig/arch/x86/kvm/cpuid.c
+++ linux-2.6-newcpuidle.git/arch/x86/kvm/cpuid.c
@@ -640,7 +640,8 @@ static inline int __do_cpuid_ent(struct
(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-newcpuidle.git/arch/x86/kvm/x86.c
===================================================================
--- linux-2.6-newcpuidle.git.orig/arch/x86/kvm/x86.c
+++ linux-2.6-newcpuidle.git/arch/x86/kvm/x86.c
@@ -1174,6 +1174,7 @@ static u32 emulated_msrs[] = {
MSR_IA32_POWER_CTL,

MSR_K7_HWCR,
+ MSR_KVM_POLL_CONTROL,
};

static unsigned num_emulated_msrs;
@@ -2625,6 +2626,14 @@ int kvm_set_msr_common(struct kvm_vcpu *
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:
@@ -2874,6 +2883,9 @@ int kvm_get_msr_common(struct kvm_vcpu *
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 @@ void kvm_arch_vcpu_postcreate(struct kvm
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 +9964,13 @@ 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);