[RFC PATCH v2 2/6] kvm: arm64: Add support for get_cur_cpufreq service

From: David Dai
Date: Thu Mar 30 2023 - 21:44:49 EST

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This service allows guests to query the host for frequency of the CPU
that the vCPU is currently running on.

Co-developed-by: Saravana Kannan <saravanak@xxxxxxxxxx>
Signed-off-by: Saravana Kannan <saravanak@xxxxxxxxxx>
Signed-off-by: David Dai <davidai@xxxxxxxxxx>
---
Documentation/virt/kvm/api.rst | 8 +++++++
.../virt/kvm/arm/get_cur_cpufreq.rst | 21 +++++++++++++++++++
Documentation/virt/kvm/arm/index.rst | 1 +
arch/arm64/include/uapi/asm/kvm.h | 1 +
arch/arm64/kvm/arm.c | 1 +
arch/arm64/kvm/hypercalls.c | 18 ++++++++++++++++
include/linux/arm-smccc.h | 7 +++++++
include/uapi/linux/kvm.h | 1 +
tools/arch/arm64/include/uapi/asm/kvm.h | 1 +
9 files changed, 59 insertions(+)
create mode 100644 Documentation/virt/kvm/arm/get_cur_cpufreq.rst

diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 62de0768d6aa..b0ff0ad700bf 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -8380,6 +8380,14 @@ structure.
When getting the Modified Change Topology Report value, the attr->addr
must point to a byte where the value will be stored or retrieved from.

+8.40 KVM_CAP_GET_CUR_CPUFREQ
+------------------------
+
+:Architectures: arm64
+
+This capability indicates that KVM supports getting the
+frequency of the current CPU that the vCPU thread is running on.
+
9. Known KVM API problems
=========================

diff --git a/Documentation/virt/kvm/arm/get_cur_cpufreq.rst b/Documentation/virt/kvm/arm/get_cur_cpufreq.rst
new file mode 100644
index 000000000000..06e0ed5b3868
--- /dev/null
+++ b/Documentation/virt/kvm/arm/get_cur_cpufreq.rst
@@ -0,0 +1,21 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+get_cur_cpufreq support for arm/arm64
+=============================
+
+Get_cur_cpufreq support is used to get current frequency(in KHz) of the
+current CPU that the vCPU thread is running on.
+
+* ARM_SMCCC_VENDOR_HYP_KVM_GET_CUR_CPUFREQ_FUNC_ID: 0x86000040
+
+This hypercall uses the SMC32/HVC32 calling convention:
+
+ARM_SMCCC_VENDOR_HYP_KVM_GET_CUR_CPUFREQ_FUNC_ID
+ ============== ======== =====================================
+ Function ID: (uint32) 0x86000040
+ Return Values: (int32) NOT_SUPPORTED(-1) on error, or
+ (uint32) Frequency in KHz of current CPU that the
+ vCPU thread is running on.
+ Endianness: Must be the same endianness
+ as the host.
+ ============== ======== =====================================
diff --git a/Documentation/virt/kvm/arm/index.rst b/Documentation/virt/kvm/arm/index.rst
index e84848432158..47afc5c1f24a 100644
--- a/Documentation/virt/kvm/arm/index.rst
+++ b/Documentation/virt/kvm/arm/index.rst
@@ -11,3 +11,4 @@ ARM
hypercalls
pvtime
ptp_kvm
+ get_cur_cpufreq
diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h
index f8129c624b07..ed8b63e91bdc 100644
--- a/arch/arm64/include/uapi/asm/kvm.h
+++ b/arch/arm64/include/uapi/asm/kvm.h
@@ -367,6 +367,7 @@ enum {
enum {
KVM_REG_ARM_VENDOR_HYP_BIT_FUNC_FEAT = 0,
KVM_REG_ARM_VENDOR_HYP_BIT_PTP = 1,
+ KVM_REG_ARM_VENDOR_HYP_BIT_GET_CUR_CPUFREQ = 2,
#ifdef __KERNEL__
KVM_REG_ARM_VENDOR_HYP_BMAP_BIT_COUNT,
#endif
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 3bd732eaf087..f960b136c611 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -220,6 +220,7 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext)
case KVM_CAP_VCPU_ATTRIBUTES:
case KVM_CAP_PTP_KVM:
case KVM_CAP_ARM_SYSTEM_SUSPEND:
+ case KVM_CAP_GET_CUR_CPUFREQ:
r = 1;
break;
case KVM_CAP_SET_GUEST_DEBUG2:
diff --git a/arch/arm64/kvm/hypercalls.c b/arch/arm64/kvm/hypercalls.c
index 5da884e11337..b3f4b90c024b 100644
--- a/arch/arm64/kvm/hypercalls.c
+++ b/arch/arm64/kvm/hypercalls.c
@@ -3,6 +3,9 @@

#include <linux/arm-smccc.h>
#include <linux/kvm_host.h>
+#include <linux/cpufreq.h>
+#include <linux/sched.h>
+#include <uapi/linux/sched/types.h>

#include <asm/kvm_emulate.h>

@@ -16,6 +19,15 @@
#define KVM_ARM_SMCCC_VENDOR_HYP_FEATURES \
GENMASK(KVM_REG_ARM_VENDOR_HYP_BMAP_BIT_COUNT - 1, 0)

+static void kvm_sched_get_cur_cpufreq(struct kvm_vcpu *vcpu, u64 *val)
+{
+ unsigned long ret_freq;
+
+ ret_freq = cpufreq_get(task_cpu(current));
+
+ val[0] = ret_freq;
+}
+
static void kvm_ptp_get_time(struct kvm_vcpu *vcpu, u64 *val)
{
struct system_time_snapshot systime_snapshot;
@@ -116,6 +128,9 @@ static bool kvm_hvc_call_allowed(struct kvm_vcpu *vcpu, u32 func_id)
case ARM_SMCCC_VENDOR_HYP_KVM_PTP_FUNC_ID:
return test_bit(KVM_REG_ARM_VENDOR_HYP_BIT_PTP,
&smccc_feat->vendor_hyp_bmap);
+ case ARM_SMCCC_VENDOR_HYP_KVM_GET_CUR_CPUFREQ_FUNC_ID:
+ return test_bit(KVM_REG_ARM_VENDOR_HYP_BIT_GET_CUR_CPUFREQ,
+ &smccc_feat->vendor_hyp_bmap);
default:
return kvm_hvc_call_default_allowed(func_id);
}
@@ -213,6 +228,9 @@ int kvm_hvc_call_handler(struct kvm_vcpu *vcpu)
case ARM_SMCCC_VENDOR_HYP_KVM_PTP_FUNC_ID:
kvm_ptp_get_time(vcpu, val);
break;
+ case ARM_SMCCC_VENDOR_HYP_KVM_GET_CUR_CPUFREQ_FUNC_ID:
+ kvm_sched_get_cur_cpufreq(vcpu, val);
+ break;
case ARM_SMCCC_TRNG_VERSION:
case ARM_SMCCC_TRNG_FEATURES:
case ARM_SMCCC_TRNG_GET_UUID:
diff --git a/include/linux/arm-smccc.h b/include/linux/arm-smccc.h
index 220c8c60e021..e15f1bdcf3f1 100644
--- a/include/linux/arm-smccc.h
+++ b/include/linux/arm-smccc.h
@@ -112,6 +112,7 @@
/* KVM "vendor specific" services */
#define ARM_SMCCC_KVM_FUNC_FEATURES 0
#define ARM_SMCCC_KVM_FUNC_PTP 1
+#define ARM_SMCCC_KVM_FUNC_GET_CUR_CPUFREQ 64
#define ARM_SMCCC_KVM_FUNC_FEATURES_2 127
#define ARM_SMCCC_KVM_NUM_FUNCS 128

@@ -138,6 +139,12 @@
#define KVM_PTP_VIRT_COUNTER 0
#define KVM_PTP_PHYS_COUNTER 1

+#define ARM_SMCCC_VENDOR_HYP_KVM_GET_CUR_CPUFREQ_FUNC_ID \
+ ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, \
+ ARM_SMCCC_SMC_32, \
+ ARM_SMCCC_OWNER_VENDOR_HYP, \
+ ARM_SMCCC_KVM_FUNC_GET_CUR_CPUFREQ)
+
/* Paravirtualised time calls (defined by ARM DEN0057A) */
#define ARM_SMCCC_HV_PV_TIME_FEATURES \
ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, \
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index d77aef872a0a..0a1a260243bf 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1184,6 +1184,7 @@ struct kvm_ppc_resize_hpt {
#define KVM_CAP_S390_PROTECTED_ASYNC_DISABLE 224
#define KVM_CAP_DIRTY_LOG_RING_WITH_BITMAP 225
#define KVM_CAP_PMU_EVENT_MASKED_EVENTS 226
+#define KVM_CAP_GET_CUR_CPUFREQ 512

#ifdef KVM_CAP_IRQ_ROUTING

diff --git a/tools/arch/arm64/include/uapi/asm/kvm.h b/tools/arch/arm64/include/uapi/asm/kvm.h
index f8129c624b07..ed8b63e91bdc 100644
--- a/tools/arch/arm64/include/uapi/asm/kvm.h
+++ b/tools/arch/arm64/include/uapi/asm/kvm.h
@@ -367,6 +367,7 @@ enum {
enum {
KVM_REG_ARM_VENDOR_HYP_BIT_FUNC_FEAT = 0,
KVM_REG_ARM_VENDOR_HYP_BIT_PTP = 1,
+ KVM_REG_ARM_VENDOR_HYP_BIT_GET_CUR_CPUFREQ = 2,
#ifdef __KERNEL__
KVM_REG_ARM_VENDOR_HYP_BMAP_BIT_COUNT,
#endif
--
2.40.0.348.gf938b09366-goog

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