Re: [RFC PATCH 2/5] Add basic MTE support to KVM guest

[Haibo Xu <haibo.xu@linaro.org>]

++ more migration experts!

On Mon, 8 Feb 2021 at 11:20, Haibo Xu <haibo.xu@linaro.org> wrote:
>
> Enable the virt machine feature "mte" to work with
> KVM guest. This feature is still hiden from the user
> in this patch, and will be available in a later patch.
>
> Signed-off-by: Haibo Xu <haibo.xu@linaro.org>
> ---
>  hw/arm/virt.c      | 22 +++++++++++-----------
>  target/arm/cpu.c   |  2 +-
>  target/arm/kvm.c   |  9 +++++++++
>  target/arm/kvm64.c |  7 +++++++
>  4 files changed, 28 insertions(+), 12 deletions(-)
>
> diff --git a/hw/arm/virt.c b/hw/arm/virt.c
> index 399da73454..623d5e9397 100644
> --- a/hw/arm/virt.c
> +++ b/hw/arm/virt.c
> @@ -1974,18 +1974,18 @@ static void machvirt_init(MachineState *machine)
>          }
>
>          if (vms->mte) {
> +            /*
> +             * The property exists only if MemTag is supported.
> +             * If it is, we must allocate the ram to back that up.
> +             */
> +            if (!object_property_find(cpuobj, "tag-memory")) {
> +                error_report("MTE requested, but not supported "
> +                             "by the guest CPU");
> +                exit(1);
> +            }
> +
>              /* Create the memory region only once, but link to all cpus. */
> -            if (!tag_sysmem) {
> -                /*
> -                 * The property exists only if MemTag is supported.
> -                 * If it is, we must allocate the ram to back that up.
> -                 */
> -                if (!object_property_find(cpuobj, "tag-memory")) {
> -                    error_report("MTE requested, but not supported "
> -                                 "by the guest CPU");
> -                    exit(1);
> -                }
> -
> +            if (!tag_sysmem && !kvm_enabled()) {
>                  tag_sysmem = g_new(MemoryRegion, 1);
>                  memory_region_init(tag_sysmem, OBJECT(machine),
>                                     "tag-memory", UINT64_MAX / 32);
> diff --git a/target/arm/cpu.c b/target/arm/cpu.c
> index 40142ac141..50f3223944 100644
> --- a/target/arm/cpu.c
> +++ b/target/arm/cpu.c
> @@ -1831,7 +1831,7 @@ static void arm_cpu_realizefn(DeviceState *dev, Error **errp)
>                                 cpu->secure_memory);
>      }
>
> -    if (cpu->tag_memory != NULL) {
> +    if (cpu->tag_memory != NULL && !kvm_enabled()) {
>          cpu_address_space_init(cs, ARMASIdx_TagNS, "cpu-tag-memory",
>                                 cpu->tag_memory);
>          if (has_secure) {
> diff --git a/target/arm/kvm.c b/target/arm/kvm.c
> index ffe186de8d..33630b2b70 100644
> --- a/target/arm/kvm.c
> +++ b/target/arm/kvm.c
> @@ -32,6 +32,7 @@
>  #include "hw/boards.h"
>  #include "hw/irq.h"
>  #include "qemu/log.h"
> +#include "hw/arm/virt.h"
>
>  const KVMCapabilityInfo kvm_arch_required_capabilities[] = {
>      KVM_CAP_LAST_INFO
> @@ -272,6 +273,14 @@ int kvm_arch_init(MachineState *ms, KVMState *s)
>          }
>      }
>
> +    if (kvm_check_extension(s, KVM_CAP_ARM_MTE) &&
> +        object_dynamic_cast(OBJECT(ms), TYPE_VIRT_MACHINE) &&
> +        VIRT_MACHINE(ms)->mte) {
> +            if (kvm_vm_enable_cap(s, KVM_CAP_ARM_MTE, 0)) {
> +                error_report("Failed to enable KVM_CAP_ARM_MTE cap");
> +            }
> +    }
> +
>      return ret;
>  }
>
> diff --git a/target/arm/kvm64.c b/target/arm/kvm64.c
> index 3c37fc4fb6..23f34034db 100644
> --- a/target/arm/kvm64.c
> +++ b/target/arm/kvm64.c
> @@ -500,6 +500,7 @@ bool kvm_arm_get_host_cpu_features(ARMHostCPUFeatures *ahcf)
>       */
>      int fdarray[3];
>      bool sve_supported;
> +    bool mte_supported;
>      uint64_t features = 0;
>      uint64_t t;
>      int err;
> @@ -646,6 +647,7 @@ bool kvm_arm_get_host_cpu_features(ARMHostCPUFeatures *ahcf)
>      }
>
>      sve_supported = ioctl(fdarray[0], KVM_CHECK_EXTENSION, KVM_CAP_ARM_SVE) > 0;
> +    mte_supported = ioctl(fdarray[0], KVM_CHECK_EXTENSION, KVM_CAP_ARM_MTE) > 0;
>
>      kvm_arm_destroy_scratch_host_vcpu(fdarray);
>
> @@ -659,6 +661,11 @@ bool kvm_arm_get_host_cpu_features(ARMHostCPUFeatures *ahcf)
>          t = FIELD_DP64(t, ID_AA64PFR0, SVE, 1);
>          ahcf->isar.id_aa64pfr0 = t;
>      }
> +    if (mte_supported) {
> +        t = ahcf->isar.id_aa64pfr1;
> +        t = FIELD_DP64(t, ID_AA64PFR1, MTE, 2);
> +        ahcf->isar.id_aa64pfr1 = t;
> +    }
>
>      /*
>       * We can assume any KVM supporting CPU is at least a v8
> --
> 2.17.1
>