Hi,
On Thu, Feb 24, 2022 at 04:51:03PM +0000, Sebastian Ene 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 | 1 +
> arm/aarch64/include/kvm/kvm-cpu-arch.h | 1 +
> arm/aarch64/pvtime.c | 94 ++++++++++++++++++++++++++
> arm/include/arm-common/kvm-arch.h | 6 +-
> include/kvm/kvm-config.h | 1 +
> 6 files changed, 103 insertions(+), 1 deletion(-)
> 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..326fb20 100644
> --- a/arm/aarch64/arm-cpu.c
> +++ b/arm/aarch64/arm-cpu.c
> @@ -22,6 +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;
> + kvm_cpu__setup_pvtime(vcpu);
> return 0;
> }
>
> diff --git a/arm/aarch64/include/kvm/kvm-cpu-arch.h b/arm/aarch64/include/kvm/kvm-cpu-arch.h
> index 8dfb82e..b57d6e6 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);
> +void 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..8251f6a
> --- /dev/null
> +++ b/arm/aarch64/pvtime.c
> @@ -0,0 +1,94 @@
> +#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;
> +};
> +
> +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,
> + MAP_ANON_NORESERVE, -1, 0);
> + if (mem == MAP_FAILED)
> + return -ENOMEM;
Hm... man 2 mmap lists a few dozen error codes, why use -ENOMEM here instead of
-errno? This just makes debugging harder.
> +
> + ret = kvm__register_dev_mem(kvm, ARM_PVTIME_MMIO_BASE,
> + ARM_PVTIME_MMIO_SIZE, mem);
> + 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;
> +}
> +
> +void kvm_cpu__setup_pvtime(struct kvm_cpu *vcpu)
> +{
> + int ret;
> + u64 pvtime_guest_addr = ARM_PVTIME_MMIO_BASE + vcpu->cpu_id *
That's trange, cpu_id is not initialized here because target->init() is called
before setting up the cpu_id. The following patch in the series, "aarch64:
Populate the vCPU struct before target->init()" should come before this one.
> + 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
> + };
> +
> + BUG_ON(!vcpu);
> + BUG_ON(!vcpu->kvm);
> +
> + kvm_cfg = &vcpu->kvm->cfg;
> + if (kvm_cfg && kvm_cfg->no_pvtime)
If you move the next patch in the series before this one, all the above checks
will not be needed and should be removed.
In general, each patch in a series should be able to build properly and run a VM
without errors. This is to help users when bisecting [1]. If I build kvmtool
from this patch and I try to run a VM I get the error:
Error: BUG at arm/aarch64/pvtime.c:65
[1] https://github.com/torvalds/linux/blob/master/Documentation/process/submitting-patches.rst#separate-your-changes
> + return;
> +
> + if (!pvtime_data.is_supported)
> + return;
> +
> + ret = ioctl(vcpu->vcpu_fd, KVM_HAS_DEVICE_ATTR, &pvtime_attr);
> + if (ret)
> + goto out_err;
You should check that pvtime is supported by checking the KVM_CAP_STEAL_TIME on
the VM fd, as that's how capabilities are advertised by KVM.
> +
> + if (!pvtime_data.usr_mem) {
> + ret = pvtime__alloc_region(vcpu->kvm);
pvtime__alloc_region() can fail pretty catastrophically, is it ok to ignore it
and go on? I would have expected kvm_cpu__setup_pvtime() to return an error
which is then propagated to target->init().
> + if (ret)
> + goto out_err;
> + }
> +
> + pvtime_attr.addr = (u64)&pvtime_guest_addr;
> + ret = ioctl(vcpu->vcpu_fd, KVM_SET_DEVICE_ATTR, &pvtime_attr);
> + if (!ret)
> + return;
> +
> + pvtime__teardown_region(vcpu->kvm);
> +out_err:
> + pvtime_data.is_supported = false;
> +}
> +
> +dev_exit(pvtime__teardown_region);
It is customary to put the dev_exit() exactly after the function it refers to.
> 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
This looks good.
Thanks,
Alex
> +
> #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
> --
> 2.35.1.473.g83b2b277ed-goog
>
> _______________________________________________
> kvmarm mailing list
> kvmarm@xxxxxxxxxxxxxxxxxxxxx
> https://lists.cs.columbia.edu/mailman/listinfo/kvmarm
