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Date: Thu, 12 May 2022 13:32:51 +0200
From: Janosch Frank <frankja@...ux.ibm.com>
To: Pierre Morel <pmorel@...ux.ibm.com>, kvm@...r.kernel.org
Cc: linux-s390@...r.kernel.org, linux-kernel@...r.kernel.org,
borntraeger@...ibm.com, cohuck@...hat.com, david@...hat.com,
thuth@...hat.com, imbrenda@...ux.ibm.com, hca@...ux.ibm.com,
gor@...ux.ibm.com, wintera@...ux.ibm.com, seiden@...ux.ibm.com,
nrb@...ux.ibm.com
Subject: Re: [PATCH v9 1/3] s390x: KVM: ipte lock for SCA access should be
contained in KVM
On 5/6/22 11:24, Pierre Morel wrote:
> The former check to chose between SIIF or not SIIF can be done
> using the sclp.has_siif instead of accessing per vCPU structures
Maybe replace this paragraph with:
We can check if SIIF is enabled by testing the sclp_info struct instead
of testing the sie control block eca variable. sclp.has_ssif is the only
requirement to set ECA_SII anyway so we can go straight to the source
for that.
Reviewed-by: Janosch Frank <frankja@...ux.ibm.com>
>
> When accessing the SCA, ipte lock and ipte_unlock do not need
> to access any vcpu structures but only the KVM structure.
>
> Let's simplify the ipte handling.
>
> Signed-off-by: Pierre Morel <pmorel@...ux.ibm.com>
> ---
> arch/s390/kvm/gaccess.c | 96 ++++++++++++++++++++---------------------
> arch/s390/kvm/gaccess.h | 6 +--
> arch/s390/kvm/priv.c | 6 +--
> 3 files changed, 54 insertions(+), 54 deletions(-)
>
> diff --git a/arch/s390/kvm/gaccess.c b/arch/s390/kvm/gaccess.c
> index d53a183c2005..0e1f6dd31882 100644
> --- a/arch/s390/kvm/gaccess.c
> +++ b/arch/s390/kvm/gaccess.c
> @@ -262,77 +262,77 @@ struct aste {
> /* .. more fields there */
> };
>
> -int ipte_lock_held(struct kvm_vcpu *vcpu)
> +int ipte_lock_held(struct kvm *kvm)
> {
> - if (vcpu->arch.sie_block->eca & ECA_SII) {
> + if (sclp.has_siif) {
> int rc;
>
> - read_lock(&vcpu->kvm->arch.sca_lock);
> - rc = kvm_s390_get_ipte_control(vcpu->kvm)->kh != 0;
> - read_unlock(&vcpu->kvm->arch.sca_lock);
> + read_lock(&kvm->arch.sca_lock);
> + rc = kvm_s390_get_ipte_control(kvm)->kh != 0;
> + read_unlock(&kvm->arch.sca_lock);
> return rc;
> }
> - return vcpu->kvm->arch.ipte_lock_count != 0;
> + return kvm->arch.ipte_lock_count != 0;
> }
>
> -static void ipte_lock_simple(struct kvm_vcpu *vcpu)
> +static void ipte_lock_simple(struct kvm *kvm)
> {
> union ipte_control old, new, *ic;
>
> - mutex_lock(&vcpu->kvm->arch.ipte_mutex);
> - vcpu->kvm->arch.ipte_lock_count++;
> - if (vcpu->kvm->arch.ipte_lock_count > 1)
> + mutex_lock(&kvm->arch.ipte_mutex);
> + kvm->arch.ipte_lock_count++;
> + if (kvm->arch.ipte_lock_count > 1)
> goto out;
> retry:
> - read_lock(&vcpu->kvm->arch.sca_lock);
> - ic = kvm_s390_get_ipte_control(vcpu->kvm);
> + read_lock(&kvm->arch.sca_lock);
> + ic = kvm_s390_get_ipte_control(kvm);
> do {
> old = READ_ONCE(*ic);
> if (old.k) {
> - read_unlock(&vcpu->kvm->arch.sca_lock);
> + read_unlock(&kvm->arch.sca_lock);
> cond_resched();
> goto retry;
> }
> new = old;
> new.k = 1;
> } while (cmpxchg(&ic->val, old.val, new.val) != old.val);
> - read_unlock(&vcpu->kvm->arch.sca_lock);
> + read_unlock(&kvm->arch.sca_lock);
> out:
> - mutex_unlock(&vcpu->kvm->arch.ipte_mutex);
> + mutex_unlock(&kvm->arch.ipte_mutex);
> }
>
> -static void ipte_unlock_simple(struct kvm_vcpu *vcpu)
> +static void ipte_unlock_simple(struct kvm *kvm)
> {
> union ipte_control old, new, *ic;
>
> - mutex_lock(&vcpu->kvm->arch.ipte_mutex);
> - vcpu->kvm->arch.ipte_lock_count--;
> - if (vcpu->kvm->arch.ipte_lock_count)
> + mutex_lock(&kvm->arch.ipte_mutex);
> + kvm->arch.ipte_lock_count--;
> + if (kvm->arch.ipte_lock_count)
> goto out;
> - read_lock(&vcpu->kvm->arch.sca_lock);
> - ic = kvm_s390_get_ipte_control(vcpu->kvm);
> + read_lock(&kvm->arch.sca_lock);
> + ic = kvm_s390_get_ipte_control(kvm);
> do {
> old = READ_ONCE(*ic);
> new = old;
> new.k = 0;
> } while (cmpxchg(&ic->val, old.val, new.val) != old.val);
> - read_unlock(&vcpu->kvm->arch.sca_lock);
> - wake_up(&vcpu->kvm->arch.ipte_wq);
> + read_unlock(&kvm->arch.sca_lock);
> + wake_up(&kvm->arch.ipte_wq);
> out:
> - mutex_unlock(&vcpu->kvm->arch.ipte_mutex);
> + mutex_unlock(&kvm->arch.ipte_mutex);
> }
>
> -static void ipte_lock_siif(struct kvm_vcpu *vcpu)
> +static void ipte_lock_siif(struct kvm *kvm)
> {
> union ipte_control old, new, *ic;
>
> retry:
> - read_lock(&vcpu->kvm->arch.sca_lock);
> - ic = kvm_s390_get_ipte_control(vcpu->kvm);
> + read_lock(&kvm->arch.sca_lock);
> + ic = kvm_s390_get_ipte_control(kvm);
> do {
> old = READ_ONCE(*ic);
> if (old.kg) {
> - read_unlock(&vcpu->kvm->arch.sca_lock);
> + read_unlock(&kvm->arch.sca_lock);
> cond_resched();
> goto retry;
> }
> @@ -340,15 +340,15 @@ static void ipte_lock_siif(struct kvm_vcpu *vcpu)
> new.k = 1;
> new.kh++;
> } while (cmpxchg(&ic->val, old.val, new.val) != old.val);
> - read_unlock(&vcpu->kvm->arch.sca_lock);
> + read_unlock(&kvm->arch.sca_lock);
> }
>
> -static void ipte_unlock_siif(struct kvm_vcpu *vcpu)
> +static void ipte_unlock_siif(struct kvm *kvm)
> {
> union ipte_control old, new, *ic;
>
> - read_lock(&vcpu->kvm->arch.sca_lock);
> - ic = kvm_s390_get_ipte_control(vcpu->kvm);
> + read_lock(&kvm->arch.sca_lock);
> + ic = kvm_s390_get_ipte_control(kvm);
> do {
> old = READ_ONCE(*ic);
> new = old;
> @@ -356,25 +356,25 @@ static void ipte_unlock_siif(struct kvm_vcpu *vcpu)
> if (!new.kh)
> new.k = 0;
> } while (cmpxchg(&ic->val, old.val, new.val) != old.val);
> - read_unlock(&vcpu->kvm->arch.sca_lock);
> + read_unlock(&kvm->arch.sca_lock);
> if (!new.kh)
> - wake_up(&vcpu->kvm->arch.ipte_wq);
> + wake_up(&kvm->arch.ipte_wq);
> }
>
> -void ipte_lock(struct kvm_vcpu *vcpu)
> +void ipte_lock(struct kvm *kvm)
> {
> - if (vcpu->arch.sie_block->eca & ECA_SII)
> - ipte_lock_siif(vcpu);
> + if (sclp.has_siif)
> + ipte_lock_siif(kvm);
> else
> - ipte_lock_simple(vcpu);
> + ipte_lock_simple(kvm);
> }
>
> -void ipte_unlock(struct kvm_vcpu *vcpu)
> +void ipte_unlock(struct kvm *kvm)
> {
> - if (vcpu->arch.sie_block->eca & ECA_SII)
> - ipte_unlock_siif(vcpu);
> + if (sclp.has_siif)
> + ipte_unlock_siif(kvm);
> else
> - ipte_unlock_simple(vcpu);
> + ipte_unlock_simple(kvm);
> }
>
> static int ar_translation(struct kvm_vcpu *vcpu, union asce *asce, u8 ar,
> @@ -1075,7 +1075,7 @@ int access_guest_with_key(struct kvm_vcpu *vcpu, unsigned long ga, u8 ar,
> try_storage_prot_override = storage_prot_override_applicable(vcpu);
> need_ipte_lock = psw_bits(*psw).dat && !asce.r;
> if (need_ipte_lock)
> - ipte_lock(vcpu);
> + ipte_lock(vcpu->kvm);
> /*
> * Since we do the access further down ultimately via a move instruction
> * that does key checking and returns an error in case of a protection
> @@ -1113,7 +1113,7 @@ int access_guest_with_key(struct kvm_vcpu *vcpu, unsigned long ga, u8 ar,
> rc = trans_exc(vcpu, rc, ga, ar, mode, prot);
> out_unlock:
> if (need_ipte_lock)
> - ipte_unlock(vcpu);
> + ipte_unlock(vcpu->kvm);
> if (nr_pages > ARRAY_SIZE(gpa_array))
> vfree(gpas);
> return rc;
> @@ -1185,10 +1185,10 @@ int check_gva_range(struct kvm_vcpu *vcpu, unsigned long gva, u8 ar,
> rc = get_vcpu_asce(vcpu, &asce, gva, ar, mode);
> if (rc)
> return rc;
> - ipte_lock(vcpu);
> + ipte_lock(vcpu->kvm);
> rc = guest_range_to_gpas(vcpu, gva, ar, NULL, length, asce, mode,
> access_key);
> - ipte_unlock(vcpu);
> + ipte_unlock(vcpu->kvm);
>
> return rc;
> }
> @@ -1451,7 +1451,7 @@ int kvm_s390_shadow_fault(struct kvm_vcpu *vcpu, struct gmap *sg,
> * tables/pointers we read stay valid - unshadowing is however
> * always possible - only guest_table_lock protects us.
> */
> - ipte_lock(vcpu);
> + ipte_lock(vcpu->kvm);
>
> rc = gmap_shadow_pgt_lookup(sg, saddr, &pgt, &dat_protection, &fake);
> if (rc)
> @@ -1485,7 +1485,7 @@ int kvm_s390_shadow_fault(struct kvm_vcpu *vcpu, struct gmap *sg,
> pte.p |= dat_protection;
> if (!rc)
> rc = gmap_shadow_page(sg, saddr, __pte(pte.val));
> - ipte_unlock(vcpu);
> + ipte_unlock(vcpu->kvm);
> mmap_read_unlock(sg->mm);
> return rc;
> }
> diff --git a/arch/s390/kvm/gaccess.h b/arch/s390/kvm/gaccess.h
> index 1124ff282012..9408d6cc8e2c 100644
> --- a/arch/s390/kvm/gaccess.h
> +++ b/arch/s390/kvm/gaccess.h
> @@ -440,9 +440,9 @@ int read_guest_real(struct kvm_vcpu *vcpu, unsigned long gra, void *data,
> return access_guest_real(vcpu, gra, data, len, 0);
> }
>
> -void ipte_lock(struct kvm_vcpu *vcpu);
> -void ipte_unlock(struct kvm_vcpu *vcpu);
> -int ipte_lock_held(struct kvm_vcpu *vcpu);
> +void ipte_lock(struct kvm *kvm);
> +void ipte_unlock(struct kvm *kvm);
> +int ipte_lock_held(struct kvm *kvm);
> int kvm_s390_check_low_addr_prot_real(struct kvm_vcpu *vcpu, unsigned long gra);
>
> /* MVPG PEI indication bits */
> diff --git a/arch/s390/kvm/priv.c b/arch/s390/kvm/priv.c
> index 5beb7a4a11b3..0e8603acc105 100644
> --- a/arch/s390/kvm/priv.c
> +++ b/arch/s390/kvm/priv.c
> @@ -443,7 +443,7 @@ static int handle_ipte_interlock(struct kvm_vcpu *vcpu)
> vcpu->stat.instruction_ipte_interlock++;
> if (psw_bits(vcpu->arch.sie_block->gpsw).pstate)
> return kvm_s390_inject_program_int(vcpu, PGM_PRIVILEGED_OP);
> - wait_event(vcpu->kvm->arch.ipte_wq, !ipte_lock_held(vcpu));
> + wait_event(vcpu->kvm->arch.ipte_wq, !ipte_lock_held(vcpu->kvm));
> kvm_s390_retry_instr(vcpu);
> VCPU_EVENT(vcpu, 4, "%s", "retrying ipte interlock operation");
> return 0;
> @@ -1472,7 +1472,7 @@ static int handle_tprot(struct kvm_vcpu *vcpu)
> access_key = (operand2 & 0xf0) >> 4;
>
> if (vcpu->arch.sie_block->gpsw.mask & PSW_MASK_DAT)
> - ipte_lock(vcpu);
> + ipte_lock(vcpu->kvm);
>
> ret = guest_translate_address_with_key(vcpu, address, ar, &gpa,
> GACC_STORE, access_key);
> @@ -1509,7 +1509,7 @@ static int handle_tprot(struct kvm_vcpu *vcpu)
> }
>
> if (vcpu->arch.sie_block->gpsw.mask & PSW_MASK_DAT)
> - ipte_unlock(vcpu);
> + ipte_unlock(vcpu->kvm);
> return ret;
> }
>
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