[PATCH kvmtool v7 3/6] arm64: Add counter offset control

[Andre Przywara <andre.przywara@arm.com>]

From: Marc Zyngier <maz@kernel.org>

KVM allows the offsetting of the global counter in order to help with
migration of a VM. This offset applies cumulatively with the offsets
provided by the architecture.

Although kvmtool doesn't provide a way to migrate a VM, controlling
this offset is useful to test the timer subsystem.

Add the command line option --counter-offset to allow setting this value
when creating a VM.

Signed-off-by: Marc Zyngier <maz@kernel.org>
Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Sascha Bischoff <sascha.bischoff@arm.com>
---
 arm64/include/kvm/kvm-config-arch.h |  3 +++
 arm64/kvm.c                         | 17 +++++++++++++++++
 2 files changed, 20 insertions(+)

diff --git a/arm64/include/kvm/kvm-config-arch.h b/arm64/include/kvm/kvm-config-arch.h
index a1dac28e..44c43367 100644
--- a/arm64/include/kvm/kvm-config-arch.h
+++ b/arm64/include/kvm/kvm-config-arch.h
@@ -14,6 +14,7 @@ struct kvm_config_arch {
 	u64		kaslr_seed;
 	enum irqchip_type irqchip;
 	u64		fw_addr;
+	u64		counter_offset;
 	unsigned int	sve_max_vq;
 	bool		no_pvtime;
 };
@@ -59,6 +60,8 @@ int sve_vl_parser(const struct option *opt, const char *arg, int unset);
 		     irqchip_parser, NULL),					\
 	OPT_U64('\0', "firmware-address", &(cfg)->fw_addr,			\
 		"Address where firmware should be loaded"),			\
+	OPT_U64('\0', "counter-offset", &(cfg)->counter_offset,			\
+		"Specify the counter offset, defaulting to 0"),			\
 	OPT_BOOLEAN('\0', "nested", &(cfg)->nested_virt,			\
 		    "Start VCPUs in EL2 (for nested virt)"),
 
diff --git a/arm64/kvm.c b/arm64/kvm.c
index 23b4dab1..6e971dd7 100644
--- a/arm64/kvm.c
+++ b/arm64/kvm.c
@@ -119,6 +119,22 @@ static void kvm__arch_enable_mte(struct kvm *kvm)
 	pr_debug("MTE capability enabled");
 }
 
+static void kvm__arch_set_counter_offset(struct kvm *kvm)
+{
+	struct kvm_arm_counter_offset offset = {
+		.counter_offset = kvm->cfg.arch.counter_offset,
+	};
+
+	if (!kvm->cfg.arch.counter_offset)
+		return;
+
+	if (!kvm__supports_extension(kvm, KVM_CAP_COUNTER_OFFSET))
+		die("No support for global counter offset");
+
+	if (ioctl(kvm->vm_fd, KVM_ARM_SET_COUNTER_OFFSET, &offset))
+		die_perror("KVM_ARM_SET_COUNTER_OFFSET");
+}
+
 void kvm__arch_init(struct kvm *kvm)
 {
 	/* Create the virtual GIC. */
@@ -126,6 +142,7 @@ void kvm__arch_init(struct kvm *kvm)
 		die("Failed to create virtual GIC");
 
 	kvm__arch_enable_mte(kvm);
+	kvm__arch_set_counter_offset(kvm);
 }
 
 static u64 kvm__arch_get_payload_region_size(struct kvm *kvm)
-- 
2.43.0