[PATCHv2 4/4] arm64: add host pv-vcpu-state support
Sergey Senozhatsky
senozhatsky at chromium.org
Thu Jul 8 21:37:13 PDT 2021
Add PV-vcpu-state support bits to the host. Host uses the guest
PV-state per-CPU pointers to update the VCPU state each time
it kvm_arch_vcpu_load() or kvm_arch_vcpu_put() the VCPU, so
that guest scheduler can become aware of the fact that not
all VCPUs are always available. Currently guest scheduler
on amr64 always assumes that all CPUs are available because
vcpu_is_preempted() is not implemented on arm64.
- schbench -t 3 -m 3 -p 4096
Latency percentiles (usec)
BASE
================================================
50.0th: 1 (3556427 samples)
75.0th: 13 (879210 samples)
90.0th: 15 (893311 samples)
95.0th: 18 (159594 samples)
*99.0th: 118 (224187 samples)
99.5th: 691 (28555 samples)
99.9th: 7384 (23076 samples)
min=1, max=104218
avg worker transfer: 25192.00 ops/sec 98.41MB/s
PATCHED
================================================
50.0th: 1 (3507010 samples)
75.0th: 13 (1635775 samples)
90.0th: 16 (901271 samples)
95.0th: 24 (281051 samples)
*99.0th: 114 (255581 samples)
99.5th: 382 (33051 samples)
99.9th: 6392 (26592 samples)
min=1, max=83877
avg worker transfer: 28613.39 ops/sec 111.77MB/s
- perf bench sched all
ops/sec
BASE PATCHED
================================================
33452 36485
33541 39405
33365 36858
33455 38047
33449 37866
33616 34922
33479 34388
33594 37203
33458 35363
33704 35180
Student's T-test
N Min Max Median Avg Stddev
base 10 33365 33704 33479 33511.3 100.92467
patched 10 34388 39405 36858 36571.7 1607.454
Difference at 95.0% confidence
3060.4 +/- 1070.09
9.13244% +/- 3.19321%
(Student's t, pooled s = 1138.88)
Signed-off-by: Sergey Senozhatsky <senozhatsky at chromium.org>
---
arch/arm64/include/asm/kvm_host.h | 23 +++++++++++
arch/arm64/kvm/Makefile | 3 +-
arch/arm64/kvm/arm.c | 3 ++
arch/arm64/kvm/hypercalls.c | 11 ++++++
arch/arm64/kvm/pv-vcpu-state.c | 64 +++++++++++++++++++++++++++++++
5 files changed, 103 insertions(+), 1 deletion(-)
create mode 100644 arch/arm64/kvm/pv-vcpu-state.c
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 41911585ae0c..e782f4d0c916 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -381,6 +381,12 @@ struct kvm_vcpu_arch {
u64 last_steal;
gpa_t base;
} steal;
+
+ /* PV state of the VCPU */
+ struct {
+ gpa_t base;
+ struct gfn_to_hva_cache ghc;
+ } vcpu_state;
};
/* Pointer to the vcpu's SVE FFR for sve_{save,load}_state() */
@@ -695,6 +701,23 @@ static inline bool kvm_arm_is_pvtime_enabled(struct kvm_vcpu_arch *vcpu_arch)
return (vcpu_arch->steal.base != GPA_INVALID);
}
+int kvm_init_vcpu_state(struct kvm_vcpu *vcpu, gfn_t addr);
+int kvm_release_vcpu_state(struct kvm_vcpu *vcpu);
+
+static inline void kvm_arm_vcpu_state_init(struct kvm_vcpu_arch *vcpu_arch)
+{
+ vcpu_arch->vcpu_state.base = GPA_INVALID;
+ memset(&vcpu_arch->vcpu_state.ghc, 0, sizeof(struct gfn_to_hva_cache));
+}
+
+static inline bool
+kvm_arm_is_vcpu_state_enabled(struct kvm_vcpu_arch *vcpu_arch)
+{
+ return (vcpu_arch->vcpu_state.base != GPA_INVALID);
+}
+
+void kvm_update_vcpu_preempted(struct kvm_vcpu *vcpu, bool preempted);
+
void kvm_set_sei_esr(struct kvm_vcpu *vcpu, u64 syndrome);
struct kvm_vcpu *kvm_mpidr_to_vcpu(struct kvm *kvm, unsigned long mpidr);
diff --git a/arch/arm64/kvm/Makefile b/arch/arm64/kvm/Makefile
index 989bb5dad2c8..2a3ee82c6d90 100644
--- a/arch/arm64/kvm/Makefile
+++ b/arch/arm64/kvm/Makefile
@@ -12,7 +12,8 @@ obj-$(CONFIG_KVM) += hyp/
kvm-y := $(KVM)/kvm_main.o $(KVM)/coalesced_mmio.o $(KVM)/eventfd.o \
$(KVM)/vfio.o $(KVM)/irqchip.o $(KVM)/binary_stats.o \
- arm.o mmu.o mmio.o psci.o perf.o hypercalls.o pvtime.o \
+ arm.o mmu.o mmio.o psci.o perf.o hypercalls.o \
+ pvtime.o pv-vcpu-state.o \
inject_fault.o va_layout.o handle_exit.o \
guest.o debug.o reset.o sys_regs.o \
vgic-sys-reg-v3.o fpsimd.o pmu.o \
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index e9a2b8f27792..43e995c9fddb 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -332,6 +332,7 @@ int kvm_arch_vcpu_create(struct kvm_vcpu *vcpu)
kvm_arm_reset_debug_ptr(vcpu);
kvm_arm_pvtime_vcpu_init(&vcpu->arch);
+ kvm_arm_vcpu_state_init(&vcpu->arch);
vcpu->arch.hw_mmu = &vcpu->kvm->arch.mmu;
@@ -429,10 +430,12 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
if (vcpu_has_ptrauth(vcpu))
vcpu_ptrauth_disable(vcpu);
kvm_arch_vcpu_load_debug_state_flags(vcpu);
+ kvm_update_vcpu_preempted(vcpu, false);
}
void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
{
+ kvm_update_vcpu_preempted(vcpu, true);
kvm_arch_vcpu_put_debug_state_flags(vcpu);
kvm_arch_vcpu_put_fp(vcpu);
if (has_vhe())
diff --git a/arch/arm64/kvm/hypercalls.c b/arch/arm64/kvm/hypercalls.c
index 30da78f72b3b..95bcf86e0b6f 100644
--- a/arch/arm64/kvm/hypercalls.c
+++ b/arch/arm64/kvm/hypercalls.c
@@ -110,6 +110,9 @@ int kvm_hvc_call_handler(struct kvm_vcpu *vcpu)
case ARM_SMCCC_HV_PV_TIME_FEATURES:
val[0] = SMCCC_RET_SUCCESS;
break;
+ case ARM_SMCCC_HV_PV_VCPU_STATE_FEATURES:
+ val[0] = SMCCC_RET_SUCCESS;
+ break;
}
break;
case ARM_SMCCC_HV_PV_TIME_FEATURES:
@@ -139,6 +142,14 @@ int kvm_hvc_call_handler(struct kvm_vcpu *vcpu)
case ARM_SMCCC_TRNG_RND32:
case ARM_SMCCC_TRNG_RND64:
return kvm_trng_call(vcpu);
+ case ARM_SMCCC_HV_PV_VCPU_STATE_INIT:
+ if (kvm_init_vcpu_state(vcpu, smccc_get_arg1(vcpu)) == 0)
+ val[0] = SMCCC_RET_SUCCESS;
+ break;
+ case ARM_SMCCC_HV_PV_VCPU_STATE_RELEASE:
+ if (kvm_release_vcpu_state(vcpu) == 0)
+ val[0] = SMCCC_RET_SUCCESS;
+ break;
default:
return kvm_psci_call(vcpu);
}
diff --git a/arch/arm64/kvm/pv-vcpu-state.c b/arch/arm64/kvm/pv-vcpu-state.c
new file mode 100644
index 000000000000..8496bb2a5966
--- /dev/null
+++ b/arch/arm64/kvm/pv-vcpu-state.c
@@ -0,0 +1,64 @@
+// SPDX-License-Identifier: GPL-2.0-only
+
+#include <linux/arm-smccc.h>
+#include <linux/kvm_host.h>
+
+#include <asm/kvm_mmu.h>
+#include <asm/paravirt.h>
+
+#include <kvm/arm_psci.h>
+
+int kvm_init_vcpu_state(struct kvm_vcpu *vcpu, gpa_t addr)
+{
+ struct kvm *kvm = vcpu->kvm;
+ int ret;
+ u64 idx;
+
+ if (kvm_arm_is_vcpu_state_enabled(&vcpu->arch))
+ return 0;
+
+ idx = srcu_read_lock(&kvm->srcu);
+ ret = kvm_gfn_to_hva_cache_init(vcpu->kvm,
+ &vcpu->arch.vcpu_state.ghc,
+ addr,
+ sizeof(struct vcpu_state));
+ srcu_read_unlock(&kvm->srcu, idx);
+
+ if (!ret)
+ vcpu->arch.vcpu_state.base = addr;
+ return ret;
+}
+
+int kvm_release_vcpu_state(struct kvm_vcpu *vcpu)
+{
+ if (!kvm_arm_is_vcpu_state_enabled(&vcpu->arch))
+ return 0;
+
+ kvm_arm_vcpu_state_init(&vcpu->arch);
+ return 0;
+}
+
+void kvm_update_vcpu_preempted(struct kvm_vcpu *vcpu, bool preempted)
+{
+ struct kvm *kvm = vcpu->kvm;
+ u64 idx;
+
+ if (!kvm_arm_is_vcpu_state_enabled(&vcpu->arch))
+ return;
+
+ /*
+ * This function is called from atomic context, so we need to
+ * disable page faults. kvm_write_guest_cached() will call
+ * might_fault().
+ */
+ pagefault_disable();
+ /*
+ * Need to take the SRCU lock because kvm_write_guest_offset_cached()
+ * calls kvm_memslots();
+ */
+ idx = srcu_read_lock(&kvm->srcu);
+ kvm_write_guest_cached(kvm, &vcpu->arch.vcpu_state.ghc,
+ &preempted, sizeof(bool));
+ srcu_read_unlock(&kvm->srcu, idx);
+ pagefault_enable();
+}
--
2.32.0.93.g670b81a890-goog
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