linux-kernel - [RFC PATCH 5/9] psci: Add hypercall service for ptp

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Date:   Mon, 10 Feb 2020 16:49:02 +0800
From:   Jianyong Wu <jianyong.wu@....com>
To:     netdev@...r.kernel.org, yangbo.lu@....com, john.stultz@...aro.org,
        tglx@...utronix.de, pbonzini@...hat.com,
        sean.j.christopherson@...el.com, maz@...nel.org,
        richardcochran@...il.com, Mark.Rutland@....com, will@...nel.org,
        suzuki.poulose@....com, steven.price@....com
Cc:     linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        kvmarm@...ts.cs.columbia.edu, kvm@...r.kernel.org,
        Steve.Capper@....com, Kaly.Xin@....com, justin.he@....com,
        jianyong.wu@....com, nd@....com
Subject: [RFC PATCH 5/9] psci: Add hypercall service for ptp_kvm.

ptp_kvm modules will get this service through smccc call.
The service offers real time and counter cycle of host for guest.
Also let caller determine which cycle of virtual counter or physical counter
to return.

Signed-off-by: Jianyong Wu <jianyong.wu@....com>
---
 include/linux/arm-smccc.h | 21 +++++++++++++++++++
 virt/kvm/arm/hypercalls.c | 44 ++++++++++++++++++++++++++++++++++++++-
 2 files changed, 64 insertions(+), 1 deletion(-)

diff --git a/include/linux/arm-smccc.h b/include/linux/arm-smccc.h
index 59494df0f55b..747b7595d0c6 100644
--- a/include/linux/arm-smccc.h
+++ b/include/linux/arm-smccc.h
@@ -77,6 +77,27 @@
 			   ARM_SMCCC_SMC_32,				\
 			   0, 0x7fff)
 
+/* PTP KVM call requests clock time from guest OS to host */
+#define ARM_SMCCC_HYP_KVM_PTP_FUNC_ID				\
+	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL,			\
+			   ARM_SMCCC_SMC_32,			\
+			   ARM_SMCCC_OWNER_STANDARD_HYP,	\
+			   0)
+
+/* request for virtual counter from ptp_kvm guest */
+#define ARM_SMCCC_HYP_KVM_PTP_VIRT				\
+	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL,			\
+			   ARM_SMCCC_SMC_32,			\
+			   ARM_SMCCC_OWNER_STANDARD_HYP,	\
+			   1)
+
+/* request for physical counter from ptp_kvm guest */
+#define ARM_SMCCC_HYP_KVM_PTP_PHY				\
+	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL,			\
+			   ARM_SMCCC_SMC_32,			\
+			   ARM_SMCCC_OWNER_STANDARD_HYP,	\
+			   2)
+
 #ifndef __ASSEMBLY__
 
 #include <linux/linkage.h>
diff --git a/virt/kvm/arm/hypercalls.c b/virt/kvm/arm/hypercalls.c
index 550dfa3e53cd..a5309c28d4dc 100644
--- a/virt/kvm/arm/hypercalls.c
+++ b/virt/kvm/arm/hypercalls.c
@@ -3,6 +3,7 @@
 
 #include <linux/arm-smccc.h>
 #include <linux/kvm_host.h>
+#include <linux/clocksource_ids.h>
 
 #include <asm/kvm_emulate.h>
 
@@ -11,8 +12,11 @@
 
 int kvm_hvc_call_handler(struct kvm_vcpu *vcpu)
 {
-	u32 func_id = smccc_get_function(vcpu);
+	struct system_time_snapshot systime_snapshot;
+	long arg[4];
+	u64 cycles;
 	long val = SMCCC_RET_NOT_SUPPORTED;
+	u32 func_id = smccc_get_function(vcpu);
 	u32 feature;
 	gpa_t gpa;
 
@@ -62,6 +66,44 @@ int kvm_hvc_call_handler(struct kvm_vcpu *vcpu)
 		if (gpa != GPA_INVALID)
 			val = gpa;
 		break;
+	/*
+	 * This serves virtual kvm_ptp.
+	 * Four values will be passed back.
+	 * reg0 stores high 32-bit host ktime;
+	 * reg1 stores low 32-bit host ktime;
+	 * reg2 stores high 32-bit difference of host cycles and cntvoff;
+	 * reg3 stores low 32-bit difference of host cycles and cntvoff.
+	 */
+	case ARM_SMCCC_HYP_KVM_PTP_FUNC_ID:
+		/*
+		 * system time and counter value must captured in the same
+		 * time to keep consistency and precision.
+		 */
+		ktime_get_snapshot(&systime_snapshot);
+		if (systime_snapshot.cs_id != CSID_ARM_ARCH_COUNTER)
+			break;
+		arg[0] = upper_32_bits(systime_snapshot.real);
+		arg[1] = lower_32_bits(systime_snapshot.real);
+		/*
+		 * which of virtual counter or physical counter being
+		 * asked for is decided by the first argument.
+		 */
+		feature = smccc_get_arg1(vcpu);
+		switch (feature) {
+		case ARM_SMCCC_HYP_KVM_PTP_PHY:
+			cycles = systime_snapshot.cycles;
+			break;
+		case ARM_SMCCC_HYP_KVM_PTP_VIRT:
+		default:
+			cycles = systime_snapshot.cycles -
+			vcpu_vtimer(vcpu)->cntvoff;
+		}
+		arg[2] = upper_32_bits(cycles);
+		arg[3] = lower_32_bits(cycles);
+
+		smccc_set_retval(vcpu, arg[0], arg[1], arg[2], arg[3]);
+		return 1;
+
 	default:
 		return kvm_psci_call(vcpu);
 	}
-- 
2.17.1