From: Daniel Lezcano <daniel.lezcano@linaro.org> To: Marc Zyngier <marc.zyngier@arm.com> Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Mark Rutland <mark.rutland@arm.com>, Catalin Marinas <catalin.marinas@arm.com>, Will Deacon <will.deacon@arm.com>, Scott Wood <oss@buserror.net>, Hanjun Guo <hanjun.guo@linaro.org>, Ding Tianhong <dingtianhong@huawei.com>, dann frazier <dann.frazier@canonical.com> Subject: Re: [PATCH v2 06/18] arm64: arch_timer: Add infrastructure for multiple erratum detection methods Date: Tue, 28 Mar 2017 16:36:33 +0200 [thread overview] Message-ID: <20170328143633.GC2123@mai> (raw) In-Reply-To: <ec5e673c-6d02-fc88-9913-b0f9261da05e@arm.com> On Tue, Mar 28, 2017 at 03:07:52PM +0100, Marc Zyngier wrote: [ ... ] > >>> -bool arch_timer_check_global_cap_erratum(const struct arch_timer_erratum_workaround *wa, > >>> - const void *arg) > >>> +bool arch_timer_check_cap_erratum(const struct arch_timer_erratum_workaround *wa, > >>> + const void *arg) > >>> { > >>> - return cpus_have_cap((uintptr_t)wa->id); > >>> + return cpus_have_cap((uintptr_t)wa->id) | this_cpu_has_cap((uintptr_t)wa->id); > >> > >> Not quite. Here, you're making all capability-based errata to be be > >> global (if a single CPU in the system has a capability, then by > >> transitivity cpus_have_cap returns true). If that's a big-little system, > >> you end-up applying the workaround to all CPUs, including those unaffected. > >> > >> I'd rather drop cpus_have_cap altogether and rely on individual CPU > >> matching (since we don't have a need for a global capability erratum > >> handling yet). > > > > Ok, thanks. > > Quick update. I've just implemented this, and found out that getting rid > of local/global has an unfortunate effect: > > Since we only probe the global errata (using ACPI for example) on the > boot CPU path, we lose propagation of the erratum across the secondary > CPUs. One way of solving this is to convert the secondary boot path to > be aware of DT vs ACPI vs detection method of the month. Which isn't > easy, since by the time we boot secondary CPUs, we don't have the > pointers to the various ACPI tables anymore. Also, assuming we were > careful and saved the pointers, the tables may have been unmapped. Fun. My proposal was supposed to prevent that. The detecion is done in the subsystems, ACPI detects ACPI errata, DT detects DT errata and CPU detects CPU errata. The drivers get the errata and enable the workaround. The id association <-> errata self contains errata types (void *, char *, int). So everything can be done in a CPU basis without local / global dance. > Given that, I'm reintroducing the global/local flag for good. It's not > pretty, but it doesn't require reinventing new ways of dealing with CPUs > booting late. -- <http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs Follow Linaro: <http://www.facebook.com/pages/Linaro> Facebook | <http://twitter.com/#!/linaroorg> Twitter | <http://www.linaro.org/linaro-blog/> Blog
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From: daniel.lezcano@linaro.org (Daniel Lezcano) To: linux-arm-kernel@lists.infradead.org Subject: [PATCH v2 06/18] arm64: arch_timer: Add infrastructure for multiple erratum detection methods Date: Tue, 28 Mar 2017 16:36:33 +0200 [thread overview] Message-ID: <20170328143633.GC2123@mai> (raw) In-Reply-To: <ec5e673c-6d02-fc88-9913-b0f9261da05e@arm.com> On Tue, Mar 28, 2017 at 03:07:52PM +0100, Marc Zyngier wrote: [ ... ] > >>> -bool arch_timer_check_global_cap_erratum(const struct arch_timer_erratum_workaround *wa, > >>> - const void *arg) > >>> +bool arch_timer_check_cap_erratum(const struct arch_timer_erratum_workaround *wa, > >>> + const void *arg) > >>> { > >>> - return cpus_have_cap((uintptr_t)wa->id); > >>> + return cpus_have_cap((uintptr_t)wa->id) | this_cpu_has_cap((uintptr_t)wa->id); > >> > >> Not quite. Here, you're making all capability-based errata to be be > >> global (if a single CPU in the system has a capability, then by > >> transitivity cpus_have_cap returns true). If that's a big-little system, > >> you end-up applying the workaround to all CPUs, including those unaffected. > >> > >> I'd rather drop cpus_have_cap altogether and rely on individual CPU > >> matching (since we don't have a need for a global capability erratum > >> handling yet). > > > > Ok, thanks. > > Quick update. I've just implemented this, and found out that getting rid > of local/global has an unfortunate effect: > > Since we only probe the global errata (using ACPI for example) on the > boot CPU path, we lose propagation of the erratum across the secondary > CPUs. One way of solving this is to convert the secondary boot path to > be aware of DT vs ACPI vs detection method of the month. Which isn't > easy, since by the time we boot secondary CPUs, we don't have the > pointers to the various ACPI tables anymore. Also, assuming we were > careful and saved the pointers, the tables may have been unmapped. Fun. My proposal was supposed to prevent that. The detecion is done in the subsystems, ACPI detects ACPI errata, DT detects DT errata and CPU detects CPU errata. The drivers get the errata and enable the workaround. The id association <-> errata self contains errata types (void *, char *, int). So everything can be done in a CPU basis without local / global dance. > Given that, I'm reintroducing the global/local flag for good. It's not > pretty, but it doesn't require reinventing new ways of dealing with CPUs > booting late. -- <http://www.linaro.org/> Linaro.org ? Open source software for ARM SoCs Follow Linaro: <http://www.facebook.com/pages/Linaro> Facebook | <http://twitter.com/#!/linaroorg> Twitter | <http://www.linaro.org/linaro-blog/> Blog
next prev parent reply other threads:[~2017-03-28 14:44 UTC|newest] Thread overview: 88+ messages / expand[flat|nested] mbox.gz Atom feed top 2017-03-20 17:48 [PATCH v2 00/18] clocksource/arch_timer: Errata workaround infrastructure rework Marc Zyngier 2017-03-20 17:48 ` Marc Zyngier 2017-03-20 17:48 ` [PATCH v2 01/18] arm64: Allow checking of a CPU-local erratum Marc Zyngier 2017-03-20 17:48 ` Marc Zyngier 2017-03-22 9:22 ` Daniel Lezcano 2017-03-22 9:22 ` Daniel Lezcano 2017-03-20 17:48 ` [PATCH v2 02/18] arm64: Add CNTVCT_EL0 trap handler Marc Zyngier 2017-03-20 17:48 ` Marc Zyngier 2017-03-20 17:48 ` [PATCH v2 03/18] arm64: Define Cortex-A73 MIDR Marc Zyngier 2017-03-20 17:48 ` Marc Zyngier 2017-03-20 17:48 ` [PATCH v2 04/18] arm64: cpu_errata: Allow an erratum to be match for all revisions of a core Marc Zyngier 2017-03-20 17:48 ` Marc Zyngier 2017-03-22 14:57 ` Daniel Lezcano 2017-03-22 14:57 ` Daniel Lezcano 2017-03-20 17:48 ` [PATCH v2 05/18] arm64: cpu_errata: Add capability to advertise Cortex-A73 erratum 858921 Marc Zyngier 2017-03-20 17:48 ` Marc Zyngier 2017-03-22 15:01 ` Daniel Lezcano 2017-03-22 15:01 ` Daniel Lezcano 2017-03-20 17:48 ` [PATCH v2 06/18] arm64: arch_timer: Add infrastructure for multiple erratum detection methods Marc Zyngier 2017-03-20 17:48 ` Marc Zyngier 2017-03-22 15:41 ` Daniel Lezcano 2017-03-22 15:41 ` Daniel Lezcano 2017-03-22 15:53 ` Marc Zyngier 2017-03-22 15:53 ` Marc Zyngier 2017-03-22 15:59 ` Marc Zyngier 2017-03-22 15:59 ` Marc Zyngier 2017-03-22 16:52 ` Daniel Lezcano 2017-03-22 16:52 ` Daniel Lezcano 2017-03-23 17:30 ` Daniel Lezcano 2017-03-23 17:30 ` Daniel Lezcano 2017-03-24 13:51 ` Marc Zyngier 2017-03-24 13:51 ` Marc Zyngier 2017-03-27 7:56 ` Daniel Lezcano 2017-03-27 7:56 ` Daniel Lezcano 2017-03-28 13:07 ` Marc Zyngier 2017-03-28 13:07 ` Marc Zyngier 2017-03-28 13:34 ` Daniel Lezcano 2017-03-28 13:34 ` Daniel Lezcano 2017-03-28 14:07 ` Marc Zyngier 2017-03-28 14:07 ` Marc Zyngier 2017-03-28 14:36 ` Daniel Lezcano [this message] 2017-03-28 14:36 ` Daniel Lezcano 2017-03-28 14:48 ` Marc Zyngier 2017-03-28 14:48 ` Marc Zyngier 2017-03-28 14:55 ` Daniel Lezcano 2017-03-28 14:55 ` Daniel Lezcano 2017-03-28 15:38 ` Marc Zyngier 2017-03-28 15:38 ` Marc Zyngier 2017-03-29 14:27 ` Daniel Lezcano 2017-03-29 14:27 ` Daniel Lezcano 2017-03-29 14:56 ` Marc Zyngier 2017-03-29 14:56 ` Marc Zyngier 2017-03-29 15:12 ` Daniel Lezcano 2017-03-29 15:12 ` Daniel Lezcano 2017-03-24 17:48 ` dann frazier 2017-03-24 17:48 ` dann frazier 2017-03-24 18:00 ` Marc Zyngier 2017-03-24 18:00 ` Marc Zyngier 2017-03-30 9:28 ` Daniel Lezcano 2017-03-30 9:28 ` Daniel Lezcano 2017-03-20 17:48 ` [PATCH v2 07/18] arm64: arch_timer: Add erratum handler for globally defined capability Marc Zyngier 2017-03-20 17:48 ` Marc Zyngier 2017-03-20 17:48 ` [PATCH v2 08/18] arm64: arch_timer: Add erratum handler for CPU-specific capability Marc Zyngier 2017-03-20 17:48 ` Marc Zyngier 2017-03-20 17:48 ` [PATCH v2 09/18] arm64: arch_timer: Move arch_timer_reg_read/write around Marc Zyngier 2017-03-20 17:48 ` Marc Zyngier 2017-03-22 15:47 ` Daniel Lezcano 2017-03-22 15:47 ` Daniel Lezcano 2017-03-20 17:48 ` [PATCH v2 10/18] arm64: arch_timer: Get rid of erratum_workaround_set_sne Marc Zyngier 2017-03-20 17:48 ` Marc Zyngier 2017-03-20 17:48 ` [PATCH v2 11/18] arm64: arch_timer: Rework the set_next_event workarounds Marc Zyngier 2017-03-20 17:48 ` Marc Zyngier 2017-03-20 17:48 ` [PATCH v2 12/18] arm64: arch_timer: Make workaround methods optional Marc Zyngier 2017-03-20 17:48 ` Marc Zyngier 2017-03-20 17:48 ` [PATCH v2 13/18] arm64: arch_timer: Allows a CPU-specific erratum to only affect a subset of CPUs Marc Zyngier 2017-03-20 17:48 ` Marc Zyngier 2017-03-20 17:48 ` [PATCH v2 14/18] arm64: arch_timer: Move clocksource_counter and co around Marc Zyngier 2017-03-20 17:48 ` Marc Zyngier 2017-03-20 17:48 ` [PATCH v2 15/18] arm64: arch_timer: Enable CNTVCT_EL0 trap if workaround is enabled Marc Zyngier 2017-03-20 17:48 ` Marc Zyngier 2017-03-20 17:48 ` [PATCH v2 16/18] arm64: arch_timer: Workaround for Cortex-A73 erratum 858921 Marc Zyngier 2017-03-20 17:48 ` Marc Zyngier 2017-03-20 17:48 ` [PATCH v2 17/18] arm64: arch_timer: Allow erratum matching with ACPI OEM information Marc Zyngier 2017-03-20 17:48 ` Marc Zyngier 2017-03-20 17:48 ` [PATCH v2 18/18] arm64: arch_timer: Add HISILICON_ERRATUM_161010101 ACPI matching data Marc Zyngier 2017-03-20 17:48 ` Marc Zyngier 2017-03-22 13:56 ` [PATCH v2 00/18] clocksource/arch_timer: Errata workaround infrastructure rework Ding Tianhong 2017-03-22 13:56 ` Ding Tianhong
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