From: Paul Mackerras <paulus@ozlabs.org>
To: Athira Rajeev <atrajeev@linux.vnet.ibm.com>
Cc: ego@linux.vnet.ibm.com, 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: Tue, 21 Jul 2020 13:54:20 +1000 [thread overview]
Message-ID: <20200721035420.GA3819606@thinks.paulus.ozlabs.org> (raw)
In-Reply-To: <1594996707-3727-3-git-send-email-atrajeev@linux.vnet.ibm.com>
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.
Regards,
Paul.
next prev parent reply other threads:[~2020-07-21 4:56 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 [this message]
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
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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