From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michael Mueller Subject: Re: [PATCH v5 11/15] KVM: s390: restore IAM in get_ipm() when IPM is clean Date: Mon, 7 Jan 2019 19:17:15 +0100 Message-ID: References: <20181219191756.57973-1-mimu@linux.ibm.com> <20181219191756.57973-12-mimu@linux.ibm.com> <08327d88-388e-2ffe-9bd0-b0de2e0a0ff3@linux.ibm.com> Reply-To: mimu@linux.ibm.com Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8"; format="flowed" Content-Transfer-Encoding: 8bit Return-path: In-Reply-To: <08327d88-388e-2ffe-9bd0-b0de2e0a0ff3@linux.ibm.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-Archive: List-Post: To: pmorel@linux.ibm.com, KVM Mailing List Cc: Linux-S390 Mailing List , linux-kernel@vger.kernel.org, kvm390-list@tuxmaker.boeblingen.de.ibm.com, Martin Schwidefsky , Heiko Carstens , Christian Borntraeger , Janosch Frank , David Hildenbrand , Cornelia Huck , Halil Pasic List-ID: On 03.01.19 16:06, Pierre Morel wrote: > On 19/12/2018 20:17, Michael Mueller wrote: >> The patch adds the parameter irq_flags and allows to >> restore the Interruption Alert Mask (IAM) in the GISA >> atomically while guaranteeing the IPM is clean. >> >> The function returns the IPM of the GISA. If the returned >> value is 0x00 and the IRQ_FLAG_IAM was set, the IAM has >> been restored. >> >> New irq flag: >>    IRQ_FLAG_IAM: When set, the IAM is restored if no ISC bit >>            is set in the IPM, i.e. no new airqs are >>         pending. The test and restore operations >>         are done atomically. >> >> Signed-off-by: Michael Mueller >> --- >>   arch/s390/kvm/interrupt.c | 34 +++++++++++++++++++++++++++++----- >>   1 file changed, 29 insertions(+), 5 deletions(-) >> >> diff --git a/arch/s390/kvm/interrupt.c b/arch/s390/kvm/interrupt.c >> index 1cc3ad2e6c7e..8307717e3caf 100644 >> --- a/arch/s390/kvm/interrupt.c >> +++ b/arch/s390/kvm/interrupt.c >> @@ -37,6 +37,7 @@ >>   #define IRQ_FLAG_LOCAL    0x8000 /* include local interruption >> pending mask */ >>   #define IRQ_FLAG_FLOATING 0x4000 /* include float interruption >> pending mask */ >>   #define IRQ_FLAG_GISA     0x2000 /* include GISA interruption >> pending mask */ >> +#define IRQ_FLAG_IAM      0x0080 /* when set try to restore IAM */ >>   #define IRQ_MASK_ALL      (IRQ_FLAG_LOCAL | IRQ_FLAG_FLOATING | >> IRQ_FLAG_GISA) >>   #define IRQ_MASK_NO_GISA  (IRQ_MASK_ALL & ~IRQ_FLAG_GISA) >> @@ -253,9 +254,32 @@ static inline void set_ipm_gisc(struct >> kvm_s390_gisa *gisa, u32 gisc) >>       set_bit_inv(IPM_BIT_OFFSET + gisc, (unsigned long *) gisa); >>   } >> -static inline u8 get_ipm(struct kvm_s390_gisa *gisa) >> +static inline u8 get_ipm(struct kvm_s390_gisa *gisa, u16 irq_flags) >>   { >> -    return READ_ONCE(gisa->ipm); >> +    u64 word, _word; >> +    u8 ipm; >> + >> +    if (!(irq_flags & IRQ_FLAG_IAM)) >> +        return READ_ONCE(gisa->ipm); >> + >> +    do { >> +        word = READ_ONCE(gisa->u64.word[0]); >> +        ipm = word >> 24; >> +        /* If the GISA is in the alert list, return the IPM. */ >> +        if ((u64)gisa != word >> 32) >> +            return ipm; >> +        /* If the IPM is dirty, return the IPM. */ >> +        if (ipm) >> +            return ipm; >> +        /* >> +         * Try to restore the IAM or loop, if the IPM is dirty >> +         * again or the GISA has been inserted into the alert list. >> +         */ >> +        _word = (word & ~0xffUL) | >> +            container_of(gisa, struct sie_page2, gisa)->kvm->arch.iam; >> +    } while (cmpxchg(&gisa->u64.word[0], word, _word) != _word); >> + >> +    return 0; >>   } > > Personal opinion, but this function do more than just getting the IPM, > shouldn't it be reflected in the function name? The main task of this function is to fetch the IPM. The additional functionality is expressed in the flags. A call like get_ipm_try_iam_restore(kvm, 0) would be more confusing. > >>   static inline void clear_ipm_gisc(struct kvm_s390_gisa *gisa, u32 gisc) >> @@ -277,7 +301,7 @@ static inline unsigned long pending_irqs(struct >> kvm_vcpu *vcpu, u16 irq_flags) >>       if (irq_flags & IRQ_FLAG_FLOATING) >>           pending_irqs |= vcpu->kvm->arch.float_int.pending_irqs; >>       if (irq_flags & IRQ_FLAG_GISA) >> -        pending_irqs |= get_ipm(vcpu->kvm->arch.gisa) << >> +        pending_irqs |= get_ipm(vcpu->kvm->arch.gisa, irq_flags) << >>               IRQ_PEND_IO_ISC_7; >>       return pending_irqs; >>   } >> @@ -1574,7 +1598,7 @@ static int get_top_gisa_isc(struct kvm *kvm, u64 >> isc_mask, u32 schid) >>       if (!kvm->arch.gisa) >>           goto out; >> -    active_mask = (isc_mask & get_ipm(kvm->arch.gisa) << 24) << 32; >> +    active_mask = (isc_mask & get_ipm(kvm->arch.gisa, IRQ_FLAG_IAM) >> << 24) << 32; > > why do we need to set the IAM here? Yes, it should not be required, only when a vcpu goes into wait state. > >>       while (active_mask) { >>           isc = __fls(active_mask) ^ (BITS_PER_LONG - 1); >>           if (tac_ipm_gisc(kvm->arch.gisa, isc)) >> @@ -2060,7 +2084,7 @@ static int get_all_floating_irqs(struct kvm >> *kvm, u8 __user *usrbuf, u64 len) >>       max_irqs = len / sizeof(struct kvm_s390_irq); >>       if (kvm->arch.gisa && >> -        get_ipm(kvm->arch.gisa)) { >> +        get_ipm(kvm->arch.gisa, IRQ_FLAG_IAM)) { > > and here? Yes, it should not be required, only when a vcpu goes into wait state. > >>           for (i = 0; i <= MAX_ISC; i++) { >>               if (n == max_irqs) { >>                   /* signal userspace to try again */ >> > >