Re: [PATCH v5 33/33] KVM: PPC: Book3S HV: Add NO_HASH flag to GET_SMMU_INFO ioctl result

From: David Gibson <david@gibson.dropbear.id.au>
To: Paul Mackerras <paulus@ozlabs.org>
Cc: linuxppc-dev@ozlabs.org, kvm-ppc@vger.kernel.org, kvm@vger.kernel.org
Subject: Re: [PATCH v5 33/33] KVM: PPC: Book3S HV: Add NO_HASH flag to GET_SMMU_INFO ioctl result
Date: Tue, 9 Oct 2018 10:34:51 +1100	[thread overview]
Message-ID: <20181008233451.GD7004@umbus.fritz.box> (raw)
In-Reply-To: <1538976679-1363-34-git-send-email-paulus@ozlabs.org>

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On Mon, Oct 08, 2018 at 04:31:19PM +1100, Paul Mackerras wrote:
> This adds a KVM_PPC_NO_HASH flag to the flags field of the
> kvm_ppc_smmu_info struct, and arranges for it to be set when
> running as a nested hypervisor, as an unambiguous indication
> to userspace that HPT guests are not supported.  Reporting the
> KVM_CAP_PPC_MMU_HASH_V3 capability as false could be taken as
> indicating only that the new HPT features in ISA V3.0 are not
> supported, leaving it ambiguous whether pre-V3.0 HPT features
> are supported.
> 
> Signed-off-by: Paul Mackerras <paulus@ozlabs.org>

Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

> ---
>  Documentation/virtual/kvm/api.txt | 4 ++++
>  arch/powerpc/kvm/book3s_hv.c      | 4 ++++
>  include/uapi/linux/kvm.h          | 1 +
>  3 files changed, 9 insertions(+)
> 
> diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
> index fde48b6..df98b63 100644
> --- a/Documentation/virtual/kvm/api.txt
> +++ b/Documentation/virtual/kvm/api.txt
> @@ -2270,6 +2270,10 @@ The supported flags are:
>          The emulated MMU supports 1T segments in addition to the
>          standard 256M ones.
>  
> +    - KVM_PPC_NO_HASH
> +	This flag indicates that HPT guests are not supported by KVM,
> +	thus all guests must use radix MMU mode.
> +
>  The "slb_size" field indicates how many SLB entries are supported
>  
>  The "sps" array contains 8 entries indicating the supported base
> diff --git a/arch/powerpc/kvm/book3s_hv.c b/arch/powerpc/kvm/book3s_hv.c
> index fa61647..f565403 100644
> --- a/arch/powerpc/kvm/book3s_hv.c
> +++ b/arch/powerpc/kvm/book3s_hv.c
> @@ -4245,6 +4245,10 @@ static int kvm_vm_ioctl_get_smmu_info_hv(struct kvm *kvm,
>  	kvmppc_add_seg_page_size(&sps, 16, SLB_VSID_L | SLB_VSID_LP_01);
>  	kvmppc_add_seg_page_size(&sps, 24, SLB_VSID_L);
>  
> +	/* If running as a nested hypervisor, we don't support HPT guests */
> +	if (kvmhv_on_pseries())
> +		info->flags |= KVM_PPC_NO_HASH;
> +
>  	return 0;
>  }
>  
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index d9cec6b..7f2ff3a 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -719,6 +719,7 @@ struct kvm_ppc_one_seg_page_size {
>  
>  #define KVM_PPC_PAGE_SIZES_REAL		0x00000001
>  #define KVM_PPC_1T_SEGMENTS		0x00000002
> +#define KVM_PPC_NO_HASH			0x00000004
>  
>  struct kvm_ppc_smmu_info {
>  	__u64 flags;

-- 
David Gibson			| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you.  NOT _the_ _other_
				| _way_ _around_!
http://www.ozlabs.org/~dgibson

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