From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:37688 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1725948AbgFIPBJ (ORCPT ); Tue, 9 Jun 2020 11:01:09 -0400 Subject: Re: [kvm-unit-tests PATCH v8 09/12] s390x: Library resources for CSS tests References: <1591603981-16879-1-git-send-email-pmorel@linux.ibm.com> <1591603981-16879-10-git-send-email-pmorel@linux.ibm.com> From: Pierre Morel Message-ID: <17e5ccdd-f2b2-00bd-4ee2-c0a0b78a669a@linux.ibm.com> Date: Tue, 9 Jun 2020 17:01:01 +0200 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-s390-owner@vger.kernel.org List-ID: To: Thomas Huth , kvm@vger.kernel.org Cc: linux-s390@vger.kernel.org, frankja@linux.ibm.com, david@redhat.com, cohuck@redhat.com On 2020-06-09 09:09, Thomas Huth wrote: > On 08/06/2020 10.12, Pierre Morel wrote: >> Provide some definitions and library routines that can be used by ...snip... >> +static inline int ssch(unsigned long schid, struct orb *addr) >> +{ >> + register long long reg1 asm("1") = schid; >> + int cc; >> + >> + asm volatile( >> + " ssch 0(%2)\n" >> + " ipm %0\n" >> + " srl %0,28\n" >> + : "=d" (cc) >> + : "d" (reg1), "a" (addr), "m" (*addr) > > Hmm... What's the "m" (*addr) here good for? %3 is not used in the > assembly code? addr is %2 "m" (*addr) means memory pointed by addr is read > >> + : "cc", "memory"); > > Why "memory" ? Can this instruction also change the orb? The orb not but this instruction modifies memory as follow: orb -> ccw -> data The CCW can be a READ or a WRITE instruction and the data my be anywhere in memory (<2G) A compiler memory barrier is need to avoid write instructions started before the SSCH instruction to occur after for a write and memory read made after the instruction to be executed before for a read. > >> + return cc; >> +} >> + >> +static inline int stsch(unsigned long schid, struct schib *addr) >> +{ >> + register unsigned long reg1 asm ("1") = schid; >> + int cc; >> + >> + asm volatile( >> + " stsch 0(%3)\n" >> + " ipm %0\n" >> + " srl %0,28" >> + : "=d" (cc), "=m" (*addr) >> + : "d" (reg1), "a" (addr) >> + : "cc"); > > I'm surprised that this does not use "memory" in the clobber list ... I > guess that's what the "=m" (*addr) is good for? Yes the "=m" (*addr) is there to specify that the SCHIB pointed to by addr will be modified. > >> + return cc; >> +} >> + >> +static inline int msch(unsigned long schid, struct schib *addr) >> +{ >> + register unsigned long reg1 asm ("1") = schid; >> + int cc; >> + >> + asm volatile( >> + " msch 0(%3)\n" >> + " ipm %0\n" >> + " srl %0,28" >> + : "=d" (cc), "=m" (*addr) >> + : "d" (reg1), "a" (addr) > > I'm not an expert with these IO instructions, but this looks wrong to me > ... Is MSCH reading or writing the SCHIB data? MSCH is reading the SCHIB data in memory. > ...snip... >> +/* Debug functions */ >> +char *dump_pmcw_flags(uint16_t f); >> +char *dump_scsw_flags(uint32_t f); >> + >> +void dump_scsw(struct scsw *); >> +void dump_irb(struct irb *irbp); >> +void dump_schib(struct schib *sch); >> +struct ccw1 *dump_ccw(struct ccw1 *cp); >> +void dump_irb(struct irb *irbp); >> +void dump_pmcw(struct pmcw *p); >> +void dump_orb(struct orb *op); > > In the patch description, you said that DEBUG_CSS needs to be defined > for these - but now DEBUG_CSS is not used in this header... does the > patch description need to be changed? Yes, thanks, will do. I removed it because it seems not useful to me. > >> +int css_enumerate(void); >> +#define MAX_ENABLE_RETRIES 5 >> +int css_enable(int schid); >> + >> +#endif >> diff --git a/lib/s390x/css_dump.c b/lib/s390x/css_dump.c >> new file mode 100644 >> index 0000000..0c2b64e >> --- /dev/null >> +++ b/lib/s390x/css_dump.c >> @@ -0,0 +1,153 @@ >> +/* >> + * Channel subsystem structures dumping >> + * >> + * Copyright (c) 2020 IBM Corp. >> + * >> + * Authors: >> + * Pierre Morel >> + * >> + * This code is free software; you can redistribute it and/or modify it >> + * under the terms of the GNU General Public License version 2. > > In the header you used "or any later version" - here it's version 2 > only. Maybe you want to standardize one one of the two flavors? Yes, I will choose the shortest one, v2 only, as it seems to be the most used in kvm-unit-test. Thanks for the review. Regards, Pierre -- Pierre Morel IBM Lab Boeblingen