linux-kernel - Re: [PATCH] KVM: s390: Fix KVM_S390_GET_CMMA

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Message-Id: <09c0760e-729d-548a-c3c4-b3afd9e67225@de.ibm.com>
Date:   Mon, 10 Jul 2017 20:43:12 +0200
From:   Christian Borntraeger <borntraeger@...ibm.com>
To:     Gleb Fotengauer-Malinovskiy <glebfm@...linux.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Radim Krčmář <rkrcmar@...hat.com>,
        Claudio Imbrenda <imbrenda@...ux.vnet.ibm.com>
Cc:     "Dmitry V. Levin" <ldv@...linux.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] KVM: s390: Fix KVM_S390_GET_CMMA_BITS ioctl definition

On 07/10/2017 04:44 PM, Gleb Fotengauer-Malinovskiy wrote:
> This ioctl actually writes to parameter too.

Maybe rephrase that to:
The kernel does not only read struct kvm_s390_cmma_log for KVM_S390_GET_CMMA_BITS,
it also writes back a return value making this _IOWR instead of _IOW.


> Fixes: 4036e387 ("KVM: s390: ioctls to get and set guest storage attributes")
> Signed-off-by: Gleb Fotengauer-Malinovskiy <glebfm@...linux.org>
Acked-by: Christian Borntraeger <borntraeger@...ibm.com>


Out of curiosity, how did you notice that? 

> ---
>  include/uapi/linux/kvm.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
> index c0b6dfe..ebd604c 100644
> --- a/include/uapi/linux/kvm.h
> +++ b/include/uapi/linux/kvm.h
> @@ -1351,7 +1351,7 @@ struct kvm_s390_ucas_mapping {
>  /* Available with KVM_CAP_X86_SMM */
>  #define KVM_SMI                   _IO(KVMIO,   0xb7)
>  /* Available with KVM_CAP_S390_CMMA_MIGRATION */
> -#define KVM_S390_GET_CMMA_BITS      _IOW(KVMIO, 0xb8, struct kvm_s390_cmma_log)
> +#define KVM_S390_GET_CMMA_BITS      _IOWR(KVMIO, 0xb8, struct kvm_s390_cmma_log)
>  #define KVM_S390_SET_CMMA_BITS      _IOW(KVMIO, 0xb9, struct kvm_s390_cmma_log)
> 
>  #define KVM_DEV_ASSIGN_ENABLE_IOMMU	(1 << 0)
>