From: Paul Mackerras <paulus@ozlabs.org>
To: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Cc: ego@linux.vnet.ibm.com, Michael Neuling <mikey@neuling.org>,
maddy@linux.vnet.ibm.com, kvm@vger.kernel.org,
kvm-ppc@vger.kernel.org, svaidyan@in.ibm.com, acme@kernel.org,
jolsa@kernel.org, linuxppc-dev@lists.ozlabs.org
Subject: Re: [v3 02/15] KVM: PPC: Book3S HV: Cleanup updates for kvm vcpu MMCR
Date: Wed, 22 Jul 2020 14:54:48 +1000 [thread overview]
Message-ID: <20200722045448.GC3878639@thinks.paulus.ozlabs.org> (raw)
In-Reply-To: <B83C440A-1AC4-4737-8AB1-EB9A6B8A474B@linux.vnet.ibm.com>
On Wed, Jul 22, 2020 at 07:39:26AM +0530, Athira Rajeev wrote:
>
>
> > On 21-Jul-2020, at 9:24 AM, Paul Mackerras <paulus@ozlabs.org> wrote:
> >
> > On Fri, Jul 17, 2020 at 10:38:14AM -0400, Athira Rajeev wrote:
> >> Currently `kvm_vcpu_arch` stores all Monitor Mode Control registers
> >> in a flat array in order: mmcr0, mmcr1, mmcra, mmcr2, mmcrs
> >> Split this to give mmcra and mmcrs its own entries in vcpu and
> >> use a flat array for mmcr0 to mmcr2. This patch implements this
> >> cleanup to make code easier to read.
> >
> > Changing the way KVM stores these values internally is fine, but
> > changing the user ABI is not. This part:
> >
> >> diff --git a/arch/powerpc/include/uapi/asm/kvm.h b/arch/powerpc/include/uapi/asm/kvm.h
> >> index 264e266..e55d847 100644
> >> --- a/arch/powerpc/include/uapi/asm/kvm.h
> >> +++ b/arch/powerpc/include/uapi/asm/kvm.h
> >> @@ -510,8 +510,8 @@ struct kvm_ppc_cpu_char {
> >>
> >> #define KVM_REG_PPC_MMCR0 (KVM_REG_PPC | KVM_REG_SIZE_U64 | 0x10)
> >> #define KVM_REG_PPC_MMCR1 (KVM_REG_PPC | KVM_REG_SIZE_U64 | 0x11)
> >> -#define KVM_REG_PPC_MMCRA (KVM_REG_PPC | KVM_REG_SIZE_U64 | 0x12)
> >> -#define KVM_REG_PPC_MMCR2 (KVM_REG_PPC | KVM_REG_SIZE_U64 | 0x13)
> >> +#define KVM_REG_PPC_MMCR2 (KVM_REG_PPC | KVM_REG_SIZE_U64 | 0x12)
> >> +#define KVM_REG_PPC_MMCRA (KVM_REG_PPC | KVM_REG_SIZE_U64 | 0x13)
> >
> > means that existing userspace programs that used to work would now be
> > broken. That is not acceptable (breaking the user ABI is only ever
> > acceptable with a very compelling reason). So NAK to this part of the
> > patch.
>
> Hi Paul
>
> Thanks for checking the patch. I understood your point on user ABI breakage that this particular change can cause.
> I will retain original KVM_REG_PPC_MMCRA and KVM_REG_PPC_MMCR2 order in `kvm.h`
> And with that, additionally I will need below change ( on top of current patch ) for my clean up updates for kvm cpu MMCR to work,
> Because now mmcra and mmcrs will have its own entries in vcpu and is not part of the mmcr[] array
> Please suggest if this looks good
Yes, that looks fine.
By the way, is the new MMCRS register here at all related to the MMCRS
that there used to be on POWER8, but which wasn't present (as far as I
know) on POWER9?
Paul.
next prev parent reply other threads:[~2020-07-22 5:07 UTC|newest]
Thread overview: 51+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-17 14:38 [v3 00/15] powerpc/perf: Add support for power10 PMU Hardware Athira Rajeev
2020-07-17 14:38 ` [v3 01/15] powerpc/perf: Update cpu_hw_event to use `struct` for storing MMCR registers Athira Rajeev
2020-07-21 3:42 ` Jordan Niethe
2020-07-22 2:15 ` Athira Rajeev
2020-07-17 14:38 ` [v3 02/15] KVM: PPC: Book3S HV: Cleanup updates for kvm vcpu MMCR Athira Rajeev
2020-07-21 3:54 ` Paul Mackerras
2020-07-22 2:09 ` Athira Rajeev
2020-07-22 4:37 ` Michael Ellerman
2020-07-22 5:49 ` Athira Rajeev
2020-07-22 4:54 ` Paul Mackerras [this message]
2020-07-22 6:03 ` Madhavan Srinivasan
2020-07-22 4:38 ` Michael Ellerman
2020-07-17 14:38 ` [v3 03/15] powerpc/perf: Update Power PMU cache_events to u64 type Athira Rajeev
2020-07-17 14:38 ` [v3 04/15] powerpc/perf: Add support for ISA3.1 PMU SPRs Athira Rajeev
2020-07-22 4:18 ` Jordan Niethe
2020-07-22 8:07 ` Athira Rajeev
2020-07-22 10:52 ` Jordan Niethe
2020-07-22 12:03 ` Michael Ellerman
2020-07-17 14:38 ` [v3 05/15] KVM: PPC: Book3S HV: Save/restore new PMU registers Athira Rajeev
2020-07-17 14:38 ` [v3 06/15] powerpc/xmon: Add PowerISA v3.1 PMU SPRs Athira Rajeev
2020-07-17 14:38 ` [v3 07/15] powerpc/perf: Add power10_feat to dt_cpu_ftrs Athira Rajeev
2020-07-22 4:41 ` Jordan Niethe
2020-07-22 7:55 ` Athira Rajeev
2020-07-22 10:39 ` Michael Ellerman
2020-07-22 10:49 ` Jordan Niethe
2020-07-22 12:28 ` Athira Rajeev
2020-07-17 14:38 ` [v3 08/15] powerpc/perf: power10 Performance Monitoring support Athira Rajeev
2020-07-17 14:38 ` [v3 09/15] powerpc/perf: Ignore the BHRB kernel address filtering for P10 Athira Rajeev
2020-07-17 14:38 ` [v3 10/15] powerpc/perf: Add Power10 BHRB filter support for PERF_SAMPLE_BRANCH_IND_CALL/COND Athira Rajeev
2020-07-17 14:38 ` [v3 11/15] powerpc/perf: BHRB control to disable BHRB logic when not used Athira Rajeev
2020-07-20 10:05 ` Gautham R Shenoy
2020-07-23 1:26 ` Jordan Niethe
2020-07-23 1:28 ` Jordan Niethe
2020-07-17 14:38 ` [v3 12/15] powerpc/perf: Add support for outputting extended regs in perf intr_regs Athira Rajeev
2020-07-19 11:17 ` kernel test robot
2020-07-20 8:09 ` Athira Rajeev
2020-07-21 6:02 ` kajoljain
2020-07-23 5:44 ` kajoljain
2020-07-23 14:56 ` Arnaldo Carvalho de Melo
2020-07-24 8:25 ` Athira Rajeev
2020-07-24 12:26 ` Ravi Bangoria
2020-07-24 18:13 ` Athira Rajeev
2020-07-17 14:38 ` [v3 13/15] tools/perf: Add perf tools support for extended register capability in powerpc Athira Rajeev
2020-07-21 6:03 ` kajoljain
2020-07-24 11:02 ` Ravi Bangoria
2020-07-24 18:02 ` Athira Rajeev
2020-07-17 14:38 ` [v3 14/15] powerpc/perf: Add extended regs support for power10 platform Athira Rajeev
2020-07-21 6:03 ` kajoljain
2020-07-17 14:38 ` [v3 15/15] tools/perf: Add perf tools support for extended regs in power10 Athira Rajeev
2020-07-21 6:04 ` kajoljain
2020-07-24 13:24 ` [v3 00/15] powerpc/perf: Add support for power10 PMU Hardware Michael Ellerman
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