aarch64: Add stolen time support

This patch adds support for stolen time by sharing a memory region
with the guest which will be used by the hypervisor to store the stolen
time information. Reserve a 64kb MMIO memory region after the RTC peripheral
to be used by pvtime. The exact format of the structure stored by the
hypervisor is described in the ARM DEN0057A document.

Reviewed-by: Alexandru Elisei <alexandru.elisei@arm.com>
Tested-by: Alexandru Elisei <alexandru.elisei@arm.com>
Signed-off-by: Sebastian Ene <sebastianene@google.com>
Link: https://lore.kernel.org/r/20220313161949.3565171-3-sebastianene@google.com
Signed-off-by: Will Deacon <will@kernel.org>

8 files changed, 114 insertions, 2 deletions

diff --git a/Makefile b/Makefile
index f2511475..e9121dc3 100644
--- a/Makefile
+++ b/Makefile
@@ -182,6 +182,7 @@ ifeq ($(ARCH), arm64)
 	OBJS		+= arm/aarch64/arm-cpu.o
 	OBJS		+= arm/aarch64/kvm-cpu.o
 	OBJS		+= arm/aarch64/kvm.o
+	OBJS		+= arm/aarch64/pvtime.o
 	ARCH_INCLUDE	:= $(HDRS_ARM_COMMON)
 	ARCH_INCLUDE	+= -Iarm/aarch64/include
 
diff --git a/arm/aarch32/include/kvm/kvm-cpu-arch.h b/arm/aarch32/include/kvm/kvm-cpu-arch.h
index 780e0e2f..6fe02068 100644
--- a/arm/aarch32/include/kvm/kvm-cpu-arch.h
+++ b/arm/aarch32/include/kvm/kvm-cpu-arch.h
@@ -20,4 +20,9 @@ static inline int kvm_cpu__configure_features(struct kvm_cpu *vcpu)
 	return 0;
 }
 
+static inline int kvm_cpu__teardown_pvtime(struct kvm *kvm)
+{
+	return 0;
+}
+
 #endif /* KVM__KVM_CPU_ARCH_H */
diff --git a/arm/aarch64/arm-cpu.c b/arm/aarch64/arm-cpu.c
index d7572b77..7e4a3c17 100644
--- a/arm/aarch64/arm-cpu.c
+++ b/arm/aarch64/arm-cpu.c
@@ -22,7 +22,7 @@ static void generate_fdt_nodes(void *fdt, struct kvm *kvm)
 static int arm_cpu__vcpu_init(struct kvm_cpu *vcpu)
 {
 	vcpu->generate_fdt_nodes = generate_fdt_nodes;
-	return 0;
+	return kvm_cpu__setup_pvtime(vcpu);
 }
 
 static struct kvm_arm_target target_generic_v8 = {
diff --git a/arm/aarch64/include/kvm/kvm-cpu-arch.h b/arm/aarch64/include/kvm/kvm-cpu-arch.h
index 8dfb82ec..35996dc0 100644
--- a/arm/aarch64/include/kvm/kvm-cpu-arch.h
+++ b/arm/aarch64/include/kvm/kvm-cpu-arch.h
@@ -19,5 +19,7 @@
 
 void kvm_cpu__select_features(struct kvm *kvm, struct kvm_vcpu_init *init);
 int kvm_cpu__configure_features(struct kvm_cpu *vcpu);
+int kvm_cpu__setup_pvtime(struct kvm_cpu *vcpu);
+int kvm_cpu__teardown_pvtime(struct kvm *kvm);
 
 #endif /* KVM__KVM_CPU_ARCH_H */
diff --git a/arm/aarch64/pvtime.c b/arm/aarch64/pvtime.c
new file mode 100644
index 00000000..2f5774e9
--- /dev/null
+++ b/arm/aarch64/pvtime.c
@@ -0,0 +1,98 @@
+#include "kvm/kvm.h"
+#include "kvm/kvm-cpu.h"
+#include "kvm/util.h"
+
+#include <linux/byteorder.h>
+#include <linux/types.h>
+
+#define ARM_PVTIME_STRUCT_SIZE		(64)
+
+static void *usr_mem;
+
+static int pvtime__alloc_region(struct kvm *kvm)
+{
+	char *mem;
+	int ret = 0;
+
+	mem = mmap(NULL, ARM_PVTIME_BASE, PROT_RW,
+		   MAP_ANON_NORESERVE, -1, 0);
+	if (mem == MAP_FAILED)
+		return -errno;
+
+	ret = kvm__register_ram(kvm, ARM_PVTIME_BASE,
+				ARM_PVTIME_BASE, mem);
+	if (ret) {
+		munmap(mem, ARM_PVTIME_BASE);
+		return ret;
+	}
+
+	usr_mem = mem;
+	return ret;
+}
+
+static int pvtime__teardown_region(struct kvm *kvm)
+{
+	if (usr_mem == NULL)
+		return 0;
+
+	kvm__destroy_mem(kvm, ARM_PVTIME_BASE,
+			 ARM_PVTIME_BASE, usr_mem);
+	munmap(usr_mem, ARM_PVTIME_BASE);
+	usr_mem = NULL;
+	return 0;
+}
+
+int kvm_cpu__setup_pvtime(struct kvm_cpu *vcpu)
+{
+	int ret;
+	bool has_stolen_time;
+	u64 pvtime_guest_addr = ARM_PVTIME_BASE + vcpu->cpu_id *
+		ARM_PVTIME_STRUCT_SIZE;
+	struct kvm_config *kvm_cfg = NULL;
+	struct kvm_device_attr pvtime_attr = (struct kvm_device_attr) {
+		.group	= KVM_ARM_VCPU_PVTIME_CTRL,
+		.attr	= KVM_ARM_VCPU_PVTIME_IPA
+	};
+
+	kvm_cfg = &vcpu->kvm->cfg;
+	if (kvm_cfg->no_pvtime)
+		return 0;
+
+	has_stolen_time = kvm__supports_extension(vcpu->kvm,
+						  KVM_CAP_STEAL_TIME);
+	if (!has_stolen_time) {
+		kvm_cfg->no_pvtime = true;
+		return 0;
+	}
+
+	ret = ioctl(vcpu->vcpu_fd, KVM_HAS_DEVICE_ATTR, &pvtime_attr);
+	if (ret) {
+		ret = -errno;
+		perror("KVM_HAS_DEVICE_ATTR failed\n");
+		goto out_err;
+	}
+
+	if (!usr_mem) {
+		ret = pvtime__alloc_region(vcpu->kvm);
+		if (ret) {
+			perror("Failed allocating pvtime region\n");
+			goto out_err;
+		}
+	}
+
+	pvtime_attr.addr = (u64)&pvtime_guest_addr;
+	ret = ioctl(vcpu->vcpu_fd, KVM_SET_DEVICE_ATTR, &pvtime_attr);
+	if (!ret)
+		return 0;
+
+	ret = -errno;
+	perror("KVM_SET_DEVICE_ATTR failed\n");
+	pvtime__teardown_region(vcpu->kvm);
+out_err:
+	return ret;
+}
+
+int kvm_cpu__teardown_pvtime(struct kvm *kvm)
+{
+	return pvtime__teardown_region(kvm);
+}
diff --git a/arm/include/arm-common/kvm-arch.h b/arm/include/arm-common/kvm-arch.h
index c645ac00..43b1f77d 100644
--- a/arm/include/arm-common/kvm-arch.h
+++ b/arm/include/arm-common/kvm-arch.h
@@ -15,7 +15,8 @@
  * |  PCI  |////| plat  |       |        |     |         |
  * |  I/O  |////| MMIO: | Flash | virtio | GIC |   PCI   |  DRAM
  * | space |////| UART, |       |  MMIO  |     |  (AXI)  |
- * |       |////| RTC   |       |        |     |         |
+ * |       |////| RTC,  |       |        |     |         |
+ * |       |////| PVTIME|       |        |     |         |
  * +-------+----+-------+-------+--------+-----+---------+---......
  */
 
@@ -34,6 +35,9 @@
 #define ARM_RTC_MMIO_BASE	(ARM_UART_MMIO_BASE + ARM_UART_MMIO_SIZE)
 #define ARM_RTC_MMIO_SIZE	0x10000
 
+#define ARM_PVTIME_BASE		(ARM_RTC_MMIO_BASE + ARM_RTC_MMIO_SIZE)
+#define ARM_PVTIME_SIZE		SZ_64K
+
 #define KVM_FLASH_MMIO_BASE	(ARM_MMIO_AREA + 0x1000000)
 #define KVM_FLASH_MAX_SIZE	0x1000000
 
diff --git a/arm/kvm-cpu.c b/arm/kvm-cpu.c
index 84ac1e9e..00660d6e 100644
--- a/arm/kvm-cpu.c
+++ b/arm/kvm-cpu.c
@@ -144,6 +144,7 @@ void kvm_cpu__arch_nmi(struct kvm_cpu *cpu)
 
 void kvm_cpu__delete(struct kvm_cpu *vcpu)
 {
+	kvm_cpu__teardown_pvtime(vcpu->kvm);
 	free(vcpu);
 }
 
diff --git a/include/kvm/kvm-config.h b/include/kvm/kvm-config.h
index 6a5720c4..48adf274 100644
--- a/include/kvm/kvm-config.h
+++ b/include/kvm/kvm-config.h
@@ -62,6 +62,7 @@ struct kvm_config {
 	bool no_dhcp;
 	bool ioport_debug;
 	bool mmio_debug;
+	bool no_pvtime;
 };
 
 #endif