linux-kernel - [PATCH v3 03/29] KVM: arm64: pkvm: Add pkvm_time

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Message-ID: <20250728175316.3706196-4-smostafa@google.com>
Date: Mon, 28 Jul 2025 17:52:50 +0000
From: Mostafa Saleh <smostafa@...gle.com>
To: linux-kernel@...r.kernel.org, kvmarm@...ts.linux.dev, 
	linux-arm-kernel@...ts.infradead.org, iommu@...ts.linux.dev
Cc: maz@...nel.org, oliver.upton@...ux.dev, joey.gouly@....com, 
	suzuki.poulose@....com, yuzenghui@...wei.com, catalin.marinas@....com, 
	will@...nel.org, robin.murphy@....com, jean-philippe@...aro.org, 
	qperret@...gle.com, tabba@...gle.com, jgg@...pe.ca, mark.rutland@....com, 
	praan@...gle.com, Mostafa Saleh <smostafa@...gle.com>
Subject: [PATCH v3 03/29] KVM: arm64: pkvm: Add pkvm_time_get()

Add a function to return time in us.

This can be used from IOMMU drivers while waiting for conditions as
for SMMUv3 TLB invalidation waiting for sync.

Signed-off-by: Mostafa Saleh <smostafa@...gle.com>
Signed-off-by: Jean-Philippe Brucker <jean-philippe@...aro.org>
---
 arch/arm64/kvm/hyp/include/nvhe/pkvm.h |  2 ++
 arch/arm64/kvm/hyp/nvhe/setup.c        |  4 ++++
 arch/arm64/kvm/hyp/nvhe/timer-sr.c     | 33 ++++++++++++++++++++++++++
 3 files changed, 39 insertions(+)

diff --git a/arch/arm64/kvm/hyp/include/nvhe/pkvm.h b/arch/arm64/kvm/hyp/include/nvhe/pkvm.h
index ce31d3b73603..6c19691720cd 100644
--- a/arch/arm64/kvm/hyp/include/nvhe/pkvm.h
+++ b/arch/arm64/kvm/hyp/include/nvhe/pkvm.h
@@ -87,4 +87,6 @@ bool kvm_handle_pvm_restricted(struct kvm_vcpu *vcpu, u64 *exit_code);
 void kvm_init_pvm_id_regs(struct kvm_vcpu *vcpu);
 int kvm_check_pvm_sysreg_table(void);
 
+int pkvm_timer_init(void);
+u64 pkvm_time_get(void);
 #endif /* __ARM64_KVM_NVHE_PKVM_H__ */
diff --git a/arch/arm64/kvm/hyp/nvhe/setup.c b/arch/arm64/kvm/hyp/nvhe/setup.c
index a48d3f5a5afb..ee6435473204 100644
--- a/arch/arm64/kvm/hyp/nvhe/setup.c
+++ b/arch/arm64/kvm/hyp/nvhe/setup.c
@@ -304,6 +304,10 @@ void __noreturn __pkvm_init_finalise(void)
 	};
 	pkvm_pgtable.mm_ops = &pkvm_pgtable_mm_ops;
 
+	ret = pkvm_timer_init();
+	if (ret)
+		goto out;
+
 	ret = fix_host_ownership();
 	if (ret)
 		goto out;
diff --git a/arch/arm64/kvm/hyp/nvhe/timer-sr.c b/arch/arm64/kvm/hyp/nvhe/timer-sr.c
index ff176f4ce7de..e166cd5a56b8 100644
--- a/arch/arm64/kvm/hyp/nvhe/timer-sr.c
+++ b/arch/arm64/kvm/hyp/nvhe/timer-sr.c
@@ -11,6 +11,10 @@
 #include <asm/kvm_hyp.h>
 #include <asm/kvm_mmu.h>
 
+#include <nvhe/pkvm.h>
+
+static u32 timer_freq;
+
 void __kvm_timer_set_cntvoff(u64 cntvoff)
 {
 	write_sysreg(cntvoff, cntvoff_el2);
@@ -68,3 +72,32 @@ void __timer_enable_traps(struct kvm_vcpu *vcpu)
 
 	sysreg_clear_set(cnthctl_el2, clr, set);
 }
+
+static u64 pkvm_ticks_get(void)
+{
+	return __arch_counter_get_cntvct();
+}
+
+#define SEC_TO_US 1000000
+
+int pkvm_timer_init(void)
+{
+	timer_freq = read_sysreg(cntfrq_el0);
+	/*
+	 * TODO: The highest privileged level is supposed to initialize this
+	 * register. But on some systems (which?), this information is only
+	 * contained in the device-tree, so we'll need to find it out some other
+	 * way.
+	 */
+	if (!timer_freq || timer_freq < SEC_TO_US)
+		return -ENODEV;
+	return 0;
+}
+
+#define pkvm_time_ticks_to_us(ticks) ((u64)(ticks) * SEC_TO_US / timer_freq)
+
+/* Return time in us. */
+u64 pkvm_time_get(void)
+{
+	return pkvm_time_ticks_to_us(pkvm_ticks_get());
+}
-- 
2.50.1.552.g942d659e1b-goog