linux-kernel - Re: [PATCH 5/7] KVM: s390: Replace KVM_REQ_MMU

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Date:   Thu, 9 Dec 2021 11:52:30 +0100
From:   Janosch Frank <frankja@...ux.ibm.com>
To:     Sean Christopherson <seanjc@...gle.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Christian Borntraeger <borntraeger@...ux.ibm.com>
Cc:     David Hildenbrand <david@...hat.com>,
        Claudio Imbrenda <imbrenda@...ux.ibm.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Joerg Roedel <joro@...tes.org>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, Maxim Levitsky <mlevitsk@...hat.com>,
        Ben Gardon <bgardon@...gle.com>,
        Lai Jiangshan <jiangshanlai@...il.com>
Subject: Re: [PATCH 5/7] KVM: s390: Replace KVM_REQ_MMU_RELOAD usage with arch
 specific request

On 12/9/21 07:05, Sean Christopherson wrote:
> Add an arch request, KVM_REQ_REFRESH_GUEST_PREFIX, to deal with guest
> prefix changes instead of piggybacking KVM_REQ_MMU_RELOAD.  This will
> allow for the removal of the generic KVM_REQ_MMU_RELOAD, which isn't
> actually used by generic KVM.

Yes, that does sound nicer.

> 
> No functional change intended.

Reviewed-by: Janosch Frank <frankja@...ux.ibm.com>

> 
> Signed-off-by: Sean Christopherson <seanjc@...gle.com>
> ---
>   arch/s390/include/asm/kvm_host.h | 2 ++
>   arch/s390/kvm/kvm-s390.c         | 8 ++++----
>   arch/s390/kvm/kvm-s390.h         | 2 +-
>   3 files changed, 7 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/s390/include/asm/kvm_host.h b/arch/s390/include/asm/kvm_host.h
> index a22c9266ea05..766028d54a3e 100644
> --- a/arch/s390/include/asm/kvm_host.h
> +++ b/arch/s390/include/asm/kvm_host.h
> @@ -45,6 +45,8 @@
>   #define KVM_REQ_START_MIGRATION KVM_ARCH_REQ(3)
>   #define KVM_REQ_STOP_MIGRATION  KVM_ARCH_REQ(4)
>   #define KVM_REQ_VSIE_RESTART	KVM_ARCH_REQ(5)
> +#define KVM_REQ_REFRESH_GUEST_PREFIX	\
> +	KVM_ARCH_REQ_FLAGS(6, KVM_REQUEST_WAIT | KVM_REQUEST_NO_WAKEUP)
>   
>   #define SIGP_CTRL_C		0x80
>   #define SIGP_CTRL_SCN_MASK	0x3f
> diff --git a/arch/s390/kvm/kvm-s390.c b/arch/s390/kvm/kvm-s390.c
> index dd099d352753..e161df69520c 100644
> --- a/arch/s390/kvm/kvm-s390.c
> +++ b/arch/s390/kvm/kvm-s390.c
> @@ -3394,7 +3394,7 @@ static void kvm_gmap_notifier(struct gmap *gmap, unsigned long start,
>   		if (prefix <= end && start <= prefix + 2*PAGE_SIZE - 1) {
>   			VCPU_EVENT(vcpu, 2, "gmap notifier for %lx-%lx",
>   				   start, end);
> -			kvm_s390_sync_request(KVM_REQ_MMU_RELOAD, vcpu);
> +			kvm_s390_sync_request(KVM_REQ_REFRESH_GUEST_PREFIX, vcpu);
>   		}
>   	}
>   }
> @@ -3796,19 +3796,19 @@ static int kvm_s390_handle_requests(struct kvm_vcpu *vcpu)
>   	if (!kvm_request_pending(vcpu))
>   		return 0;
>   	/*
> -	 * We use MMU_RELOAD just to re-arm the ipte notifier for the
> +	 * If the guest prefix changed, re-arm the ipte notifier for the
>   	 * guest prefix page. gmap_mprotect_notify will wait on the ptl lock.
>   	 * This ensures that the ipte instruction for this request has
>   	 * already finished. We might race against a second unmapper that
>   	 * wants to set the blocking bit. Lets just retry the request loop.
>   	 */
> -	if (kvm_check_request(KVM_REQ_MMU_RELOAD, vcpu)) {
> +	if (kvm_check_request(KVM_REQ_REFRESH_GUEST_PREFIX, vcpu)) {
>   		int rc;
>   		rc = gmap_mprotect_notify(vcpu->arch.gmap,
>   					  kvm_s390_get_prefix(vcpu),
>   					  PAGE_SIZE * 2, PROT_WRITE);
>   		if (rc) {
> -			kvm_make_request(KVM_REQ_MMU_RELOAD, vcpu);
> +			kvm_make_request(KVM_REQ_REFRESH_GUEST_PREFIX, vcpu);
>   			return rc;
>   		}
>   		goto retry;
> diff --git a/arch/s390/kvm/kvm-s390.h b/arch/s390/kvm/kvm-s390.h
> index 60f0effcce99..219f92ffd556 100644
> --- a/arch/s390/kvm/kvm-s390.h
> +++ b/arch/s390/kvm/kvm-s390.h
> @@ -105,7 +105,7 @@ static inline void kvm_s390_set_prefix(struct kvm_vcpu *vcpu, u32 prefix)
>   		   prefix);
>   	vcpu->arch.sie_block->prefix = prefix >> GUEST_PREFIX_SHIFT;
>   	kvm_make_request(KVM_REQ_TLB_FLUSH, vcpu);
> -	kvm_make_request(KVM_REQ_MMU_RELOAD, vcpu);
> +	kvm_make_request(KVM_REQ_REFRESH_GUEST_PREFIX, vcpu);
>   }
>   
>   static inline u64 kvm_s390_get_base_disp_s(struct kvm_vcpu *vcpu, u8 *ar)
>