linux-kernel - Re: [PATCH 1/3] s390: uv: UV feature check utility

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Message-ID: <20230727164212.0c6cc310@p-imbrenda>
Date:   Thu, 27 Jul 2023 16:42:12 +0200
From:   Claudio Imbrenda <imbrenda@...ux.ibm.com>
To:     Steffen Eiden <seiden@...ux.ibm.com>
Cc:     linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org,
        kvm@...r.kernel.org, Janosch Frank <frankja@...ux.ibm.com>,
        David Hildenbrand <david@...hat.com>,
        Michael Mueller <mimu@...ux.vnet.ibm.com>,
        Marc Hartmayer <mhartmay@...ux.ibm.com>
Subject: Re: [PATCH 1/3] s390: uv: UV feature check utility

On Thu, 27 Jul 2023 14:20:51 +0200
Steffen Eiden <seiden@...ux.ibm.com> wrote:

> Introduces a function to check the existence of an UV feature.
> Refactor feature bit checks to use the new function.
> 
> Signed-off-by: Steffen Eiden <seiden@...ux.ibm.com>

Reviewed-by: Claudio Imbrenda <imbrenda@...ux.ibm.com>

> ---
>  arch/s390/include/asm/uv.h | 5 +++++
>  arch/s390/kernel/uv.c      | 2 +-
>  arch/s390/kvm/kvm-s390.c   | 2 +-
>  arch/s390/mm/fault.c       | 2 +-
>  4 files changed, 8 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/s390/include/asm/uv.h b/arch/s390/include/asm/uv.h
> index d6bb2f4f78d1..338845402324 100644
> --- a/arch/s390/include/asm/uv.h
> +++ b/arch/s390/include/asm/uv.h
> @@ -397,6 +397,11 @@ struct uv_info {
>  
>  extern struct uv_info uv_info;
>  
> +static inline bool uv_has_feature(u8 feature_bit)
> +{
> +	return test_bit_inv(feature_bit, &uv_info.uv_feature_indications);
> +}
> +
>  #ifdef CONFIG_PROTECTED_VIRTUALIZATION_GUEST
>  extern int prot_virt_guest;
>  
> diff --git a/arch/s390/kernel/uv.c b/arch/s390/kernel/uv.c
> index d8b25cda5471..c82a667d2113 100644
> --- a/arch/s390/kernel/uv.c
> +++ b/arch/s390/kernel/uv.c
> @@ -249,7 +249,7 @@ static bool should_export_before_import(struct uv_cb_header *uvcb, struct mm_str
>  	 * shared page from a different protected VM will automatically also
>  	 * transfer its ownership.
>  	 */
> -	if (test_bit_inv(BIT_UV_FEAT_MISC, &uv_info.uv_feature_indications))
> +	if (uv_has_feature(BIT_UV_FEAT_MISC))
>  		return false;
>  	if (uvcb->cmd == UVC_CMD_UNPIN_PAGE_SHARED)
>  		return false;
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index 17b81659cdb2..339e3190f6dc 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -2402,7 +2402,7 @@ static int kvm_s390_cpus_to_pv(struct kvm *kvm, u16 *rc, u16 *rrc)
>  	struct kvm_vcpu *vcpu;
>  
>  	/* Disable the GISA if the ultravisor does not support AIV. */
> -	if (!test_bit_inv(BIT_UV_FEAT_AIV, &uv_info.uv_feature_indications))
> +	if (!uv_has_feature(BIT_UV_FEAT_AIV))
>  		kvm_s390_gisa_disable(kvm);
>  
>  	kvm_for_each_vcpu(i, vcpu, kvm) {
> diff --git a/arch/s390/mm/fault.c b/arch/s390/mm/fault.c
> index b65144c392b0..b8ef42fac2c4 100644
> --- a/arch/s390/mm/fault.c
> +++ b/arch/s390/mm/fault.c
> @@ -824,7 +824,7 @@ void do_secure_storage_access(struct pt_regs *regs)
>  	 * reliable without the misc UV feature so we need to check
>  	 * for that as well.
>  	 */
> -	if (test_bit_inv(BIT_UV_FEAT_MISC, &uv_info.uv_feature_indications) &&
> +	if (uv_has_feature(BIT_UV_FEAT_MISC) &&
>  	    !test_bit_inv(61, &regs->int_parm_long)) {
>  		/*
>  		 * When this happens, userspace did something that it