linux-kernel - Re: [PATCH v10 2/5] arm64: KVM: export the capability to set guest SError syndrome

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Date:   Thu, 15 Mar 2018 20:39:55 +0000
From:   James Morse <james.morse@....com>
To:     Dongjiu Geng <gengdongjiu@...wei.com>
CC:     rkrcmar@...hat.com, corbet@....net, christoffer.dall@...aro.org,
        marc.zyngier@....com, linux@...linux.org.uk,
        catalin.marinas@....com, rjw@...ysocki.net, bp@...en8.de,
        lenb@...nel.org, kvm@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        kvmarm@...ts.cs.columbia.edu, linux-acpi@...r.kernel.org,
        devel@...ica.org, huangshaoyu@...wei.com
Subject: Re: [PATCH v10 2/5] arm64: KVM: export the capability to set guest
 SError syndrome

Hi Dongjiu Geng,

On 03/03/18 16:09, Dongjiu Geng wrote:
> Before user space injects a SError, it needs to know whether it can
> specify the guest Exception Syndrome, so KVM should tell user space
> whether it has such capability.

> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
> index fc3ae95..8a3d708 100644
> --- a/Documentation/virtual/kvm/api.txt
> +++ b/Documentation/virtual/kvm/api.txt
> @@ -4415,3 +4415,14 @@ Parameters: none
>  This capability indicates if the flic device will be able to get/set the
>  AIS states for migration via the KVM_DEV_FLIC_AISM_ALL attribute and allows
>  to discover this without having to create a flic device.
> +
> +8.14 KVM_CAP_ARM_SET_SERROR_ESR
> +
> +Architectures: arm, arm64
> +
> +This capability indicates that userspace can specify syndrome value reported to
> +guest OS when guest takes a virtual SError interrupt exception.

"when userspace triggers a virtual SError"... how?


> +If KVM has this capability, userspace can only specify the ISS field for the ESR
> +syndrome, can not specify the EC field which is not under control by KVM.

Where do I put the ESR?
If you re-order this after the patch that adds the API, you can describe how
this can be used.


Thanks,

James



> +If this virtual SError is taken to EL1 using AArch64, this value will be reported
> +into ISS filed of ESR_EL1.
> diff --git a/arch/arm64/kvm/reset.c b/arch/arm64/kvm/reset.c
> index 3256b92..38c8a64 100644
> --- a/arch/arm64/kvm/reset.c
> +++ b/arch/arm64/kvm/reset.c
> @@ -77,6 +77,9 @@ int kvm_arch_dev_ioctl_check_extension(struct kvm *kvm, long ext)
>  	case KVM_CAP_ARM_PMU_V3:
>  		r = kvm_arm_support_pmu_v3();
>  		break;
> +	case KVM_CAP_ARM_INJECT_SERROR_ESR:
> +		r = cpus_have_const_cap(ARM64_HAS_RAS_EXTN);
> +		break;
>  	case KVM_CAP_SET_GUEST_DEBUG:
>  	case KVM_CAP_VCPU_ATTRIBUTES:
>  		r = 1;
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index 8fb90a0..3587b33 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -934,6 +934,7 @@ struct kvm_ppc_resize_hpt {
>  #define KVM_CAP_S390_AIS_MIGRATION 150
>  #define KVM_CAP_PPC_GET_CPU_CHAR 151
>  #define KVM_CAP_S390_BPB 152
> +#define KVM_CAP_ARM_INJECT_SERROR_ESR 153
>  
>  #ifdef KVM_CAP_IRQ_ROUTING
>  
>