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SubjectRe: [PATCH v11 4/6] target-arm: kvm64: detect guest RAS EXTENSION feature
On 18 August 2017 at 15:23, Dongjiu Geng <gengdongjiu@huawei.com> wrote:
> check if kvm supports guest RAS EXTENSION. if so, set
> corresponding feature bit for vcpu.
>
> Signed-off-by: Dongjiu Geng <gengdongjiu@huawei.com>
> ---
> linux-headers/linux/kvm.h | 1 +
> target/arm/cpu.h | 3 +++
> target/arm/kvm64.c | 8 ++++++++
> 3 files changed, 12 insertions(+)
>
> diff --git a/linux-headers/linux/kvm.h b/linux-headers/linux/kvm.h
> index 7971a4f..2aa176e 100644
> --- a/linux-headers/linux/kvm.h
> +++ b/linux-headers/linux/kvm.h
> @@ -929,6 +929,7 @@ struct kvm_ppc_resize_hpt {
> #define KVM_CAP_PPC_SMT_POSSIBLE 147
> #define KVM_CAP_HYPERV_SYNIC2 148
> #define KVM_CAP_HYPERV_VP_INDEX 149
> +#define KVM_CAP_ARM_RAS_EXTENSION 150
>
> #ifdef KVM_CAP_IRQ_ROUTING
>

Hi. Changes to linux-headers need to be done as a patch of their
own created using scripts/update-linux-headers.sh run against a
mainline kernel tree (and with a commit message that quotes the
kernel commit hash used). This ensures that we have a consistent
set of headers that don't diverge from the kernel copy.

> diff --git a/target/arm/cpu.h b/target/arm/cpu.h
> index b39d64a..6b0961b 100644
> --- a/target/arm/cpu.h
> +++ b/target/arm/cpu.h
> @@ -611,6 +611,8 @@ struct ARMCPU {
>
> /* CPU has memory protection unit */
> bool has_mpu;
> + /* CPU has ras extension unit */
> + bool has_ras_extension;
> /* PMSAv7 MPU number of supported regions */
> uint32_t pmsav7_dregion;
>
> @@ -1229,6 +1231,7 @@ enum arm_features {
> ARM_FEATURE_THUMB_DSP, /* DSP insns supported in the Thumb encodings */
> ARM_FEATURE_PMU, /* has PMU support */
> ARM_FEATURE_VBAR, /* has cp15 VBAR */
> + ARM_FEATURE_RAS_EXTENSION, /*has RAS extension support */

Missing space after '/*' ?

> };
>
> static inline int arm_feature(CPUARMState *env, int feature)
> diff --git a/target/arm/kvm64.c b/target/arm/kvm64.c
> index a16abc8..0781367 100644
> --- a/target/arm/kvm64.c
> +++ b/target/arm/kvm64.c
> @@ -518,6 +518,14 @@ int kvm_arch_init_vcpu(CPUState *cs)
> unset_feature(&env->features, ARM_FEATURE_PMU);
> }
>
> + if (kvm_check_extension(cs->kvm_state, KVM_CAP_ARM_RAS_EXTENSION)) {
> + cpu->has_ras_extension = true;
> + set_feature(&env->features, ARM_FEATURE_RAS_EXTENSION);
> + } else {
> + cpu->has_ras_extension = false;
> + unset_feature(&env->features, ARM_FEATURE_RAS_EXTENSION);
> + }
> +

Shouldn't we need to also tell the kernel that we actually want
it to expose RAS to the guest? Compare the PMU code in this
function, where we set a kvm_init_features bit to do this.
(This suggests that your ABI for the kernel part of this feature
may not be correct?)

You should also not be calling set_feature() here -- if the
CPU features bit doesn't say "this CPU should have the RAS
extensions" we shouldn't create a CPU with them. Instead
you should set it in kvm_arm_get_host_cpu_features() (again,
compare the PMU code).

thanks
-- PMM

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