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: Tue, 8 Jan 2019 09:06:59 +0100 Message-ID: <9a114fdc-0924-9730-7ca4-c483ed2c4eb7@linux.ibm.com> References: <20181219191756.57973-1-mimu@linux.ibm.com> <20181219191756.57973-12-mimu@linux.ibm.com> <20190107003244.219e873e@oc2783563651> Reply-To: mimu@linux.ibm.com Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20190107003244.219e873e@oc2783563651> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-Archive: List-Post: To: Halil Pasic Cc: KVM Mailing List , 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 , Pierre Morel List-ID: On 07.01.19 00:32, Halil Pasic wrote: > On Wed, 19 Dec 2018 20:17:52 +0100 > 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); > ^^ > > Shouldn't this rather be: > } while (cmpxchg(&gisa->u64.word[0], word, _word) != word); Yes, the comparison needs to be done against the old value of the memory region. > > Regards, > Halil >> + >> + return 0; >> }