Hi Sebastian,
On Wed, 02 Mar 2022 14:07:35 +0000,
Sebastian Ene <sebastianene@xxxxxxxxxx> wrote:
>
> 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.
>
> Signed-off-by: Sebastian Ene <sebastianene@xxxxxxxxxx>
> ---
> Makefile | 1 +
> arm/aarch64/arm-cpu.c | 2 +-
> arm/aarch64/include/kvm/kvm-cpu-arch.h | 1 +
> arm/aarch64/pvtime.c | 103 +++++++++++++++++++++++++
> arm/include/arm-common/kvm-arch.h | 6 +-
> include/kvm/kvm-config.h | 1 +
> 6 files changed, 112 insertions(+), 2 deletions(-)
> create mode 100644 arm/aarch64/pvtime.c
>
> diff --git a/Makefile b/Makefile
> index f251147..e9121dc 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/aarch64/arm-cpu.c b/arm/aarch64/arm-cpu.c
> index d7572b7..7e4a3c1 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 8dfb82e..2b2c1ff 100644
> --- a/arm/aarch64/include/kvm/kvm-cpu-arch.h
> +++ b/arm/aarch64/include/kvm/kvm-cpu-arch.h
> @@ -19,5 +19,6 @@
>
> 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);
>
> #endif /* KVM__KVM_CPU_ARCH_H */
> diff --git a/arm/aarch64/pvtime.c b/arm/aarch64/pvtime.c
> new file mode 100644
> index 0000000..fdde683
> --- /dev/null
> +++ b/arm/aarch64/pvtime.c
> @@ -0,0 +1,103 @@
> +#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)
> +
> +struct pvtime_data_priv {
> + bool is_supported;
> + char *usr_mem;
Consider using void * for pointers that do not have any particular
semantics associated to them.
> +};
> +
> +static struct pvtime_data_priv pvtime_data = {
> + .is_supported = true,
> + .usr_mem = NULL
> +};
> +
> +static int pvtime__alloc_region(struct kvm *kvm)
> +{
> + char *mem;
> + int ret = 0;
> +
> + mem = mmap(NULL, ARM_PVTIME_MMIO_SIZE, PROT_RW,
I sort of object to the 'MMIO' part of the name. The spec is quite
clear that this should be normal memory. That's purely cosmetic, but
still a bit confusing.
> + MAP_ANON_NORESERVE, -1, 0);
> + if (mem == MAP_FAILED)
> + return -errno;
> +
> + ret = kvm__register_dev_mem(kvm, ARM_PVTIME_MMIO_BASE,
> + ARM_PVTIME_MMIO_SIZE, mem);
This, on the other side, is wrong. Since the pvtime pages are memory,
mapping them with device attributes will do the wrong thing (the
hypervisor will write to a cacheable mapping, and the guest will
bypass the cache due to the S2 override that you provide here).
kvm__register_ram() is more likely to lead to the behaviour you'd
expect.
> + if (ret) {
> + munmap(mem, ARM_PVTIME_MMIO_SIZE);
> + return ret;
> + }
> +
> + pvtime_data.usr_mem = mem;
> + return ret;
> +}
> +
> +static int pvtime__teardown_region(struct kvm *kvm)
> +{
> + if (pvtime_data.usr_mem == NULL)
> + return 0;
> +
> + kvm__destroy_mem(kvm, ARM_PVTIME_MMIO_BASE,
> + ARM_PVTIME_MMIO_SIZE, pvtime_data.usr_mem);
> + munmap(pvtime_data.usr_mem, ARM_PVTIME_MMIO_SIZE);
> + pvtime_data.usr_mem = NULL;
> + return 0;
> +}
> +
> +dev_exit(pvtime__teardown_region);
> +
> +int kvm_cpu__setup_pvtime(struct kvm_cpu *vcpu)
> +{
> + int ret;
> + bool has_stolen_time;
> + u64 pvtime_guest_addr = ARM_PVTIME_MMIO_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,
> + .addr = KVM_ARM_VCPU_PVTIME_IPA
> + };
> +
> + kvm_cfg = &vcpu->kvm->cfg;
> + if (kvm_cfg->no_pvtime)
> + return 0;
> +
> + if (!pvtime_data.is_supported)
> + return -ENOTSUP;
It is a bit odd to have this hard failure if running on a system that
doesn't have pvtime. It forces the user to alter their command-line,
which is a bit annoying. I'd rather have a soft-fail here.
> +
> + has_stolen_time = kvm__supports_extension(vcpu->kvm,
> + KVM_CAP_STEAL_TIME);
> + if (!has_stolen_time)
> + return 0;
> +
> + ret = ioctl(vcpu->vcpu_fd, KVM_HAS_DEVICE_ATTR, &pvtime_attr);
> + if (ret) {
> + perror("KVM_HAS_DEVICE_ATTR failed\n");
> + goto out_err;
> + }
> +
> + if (!pvtime_data.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;
> +
> + perror("KVM_SET_DEVICE_ATTR failed\n");
> + pvtime__teardown_region(vcpu->kvm);
> +out_err:
> + pvtime_data.is_supported = false;
> + return ret;
> +}
> diff --git a/arm/include/arm-common/kvm-arch.h b/arm/include/arm-common/kvm-arch.h
> index c645ac0..3f82663 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_MMIO_BASE (ARM_RTC_MMIO_BASE + ARM_RTC_MMIO_SIZE)
> +#define ARM_PVTIME_MMIO_SIZE SZ_64K
> +
> #define KVM_FLASH_MMIO_BASE (ARM_MMIO_AREA + 0x1000000)
> #define KVM_FLASH_MAX_SIZE 0x1000000
>
> diff --git a/include/kvm/kvm-config.h b/include/kvm/kvm-config.h
> index 6a5720c..48adf27 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
Thanks,
M.
--
Without deviation from the norm, progress is not possible.
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