From: "Rafael J. Wysocki" <rafael@kernel.org> To: Dan Williams <dan.j.williams@intel.com> Cc: "Rafael J. Wysocki" <rafael@kernel.org>, Rafael Wysocki <rafael.j.wysocki@intel.com>, Stable <stable@vger.kernel.org>, Len Brown <lenb@kernel.org>, Borislav Petkov <bp@alien8.de>, James Morse <james.morse@arm.com>, Erik Kaneda <erik.kaneda@intel.com>, Myron Stowe <myron.stowe@redhat.com>, "Rafael J. Wysocki" <rjw@rjwysocki.net>, Andy Shevchenko <andriy.shevchenko@linux.intel.com>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, ACPI Devel Maling List <linux-acpi@vger.kernel.org>, "linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org> Subject: Re: [PATCH v2] ACPI: Drop rcu usage for MMIO mappings Date: Fri, 5 Jun 2020 19:02:24 +0200 [thread overview] Message-ID: <CAJZ5v0iAwDpFYgOa+1=7_wdt4jHVftzS-o=xTJzJSVjceqhzwQ@mail.gmail.com> (raw) In-Reply-To: <CAPcyv4iECAzRjAUJ1hymOzZRjBYQ_baFrSz=2ah=2pfehn9S_g@mail.gmail.com> On Fri, Jun 5, 2020 at 6:39 PM Dan Williams <dan.j.williams@intel.com> wrote: > > On Fri, Jun 5, 2020 at 9:22 AM Rafael J. Wysocki <rafael@kernel.org> wrote: > [..] > > > The fix we are looking at now is to pre-map operation regions in a > > > similar manner as the way APEI resources are pre-mapped. The > > > pre-mapping would arrange for synchronize_rcu_expedited() to be elided > > > on each dynamic mapping attempt. The other piece is to arrange for > > > operation-regions to be mapped at their full size at once rather than > > > a page at a time. > > > > However, if the RCU usage in ACPI OSL can be replaced with an rwlock, > > some of the ACPICA changes above may not be necessary anymore (even > > though some of them may still be worth making). > > I don't think you can replace the RCU usage in ACPI OSL and still > maintain NMI lookups in a dynamic list. I'm not sure what NMI lookups have to do with the issue at hand. If acpi_os_{read|write}_memory() is used from NMI, that is a bug already in there which is unrelated to the performance problem with opregions. > However, there are 3 solutions I see: > > - Prevent acpi_os_map_cleanup() from triggering at high frequency by > pre-mapping and never unmapping operation-regions resources (internal > discussion in progress) Yes, that can be done, if necessary. > - Prevent walks of the 'acpi_ioremaps' list (acpi_map_lookup_virt()) > from NMI context by re-writing the physical addresses in the APEI > tables with pre-mapped virtual address, i.e. remove rcu_read_lock() > and list_for_each_entry_rcu() from NMI context. That sounds a bit convoluted to me. > - Split operation-region resources into a separate mapping mechanism > than APEI resources so that typical locking can be used for the > sleepable resources and let the NMI accessible resources be managed > separately. > > That last one is one we have not discussed internally, but it occurred > to me when you mentioned replacing RCU. So NMI cannot use acpi_os_{read|write}_memory() safely which you have pointed out for a few times. But even if NMI resources are managed separately, the others will still not be sleepable (at least not all of them). Cheers! _______________________________________________ Linux-nvdimm mailing list -- linux-nvdimm@lists.01.org To unsubscribe send an email to linux-nvdimm-leave@lists.01.org
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From: "Rafael J. Wysocki" <rafael@kernel.org> To: Dan Williams <dan.j.williams@intel.com> Cc: "Rafael J. Wysocki" <rafael@kernel.org>, Rafael Wysocki <rafael.j.wysocki@intel.com>, Stable <stable@vger.kernel.org>, Len Brown <lenb@kernel.org>, Borislav Petkov <bp@alien8.de>, Ira Weiny <ira.weiny@intel.com>, James Morse <james.morse@arm.com>, Erik Kaneda <erik.kaneda@intel.com>, Myron Stowe <myron.stowe@redhat.com>, "Rafael J. Wysocki" <rjw@rjwysocki.net>, Andy Shevchenko <andriy.shevchenko@linux.intel.com>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, ACPI Devel Maling List <linux-acpi@vger.kernel.org>, "linux-nvdimm@lists.01.org" <linux-nvdimm@lists.01.org> Subject: Re: [PATCH v2] ACPI: Drop rcu usage for MMIO mappings Date: Fri, 5 Jun 2020 19:02:24 +0200 [thread overview] Message-ID: <CAJZ5v0iAwDpFYgOa+1=7_wdt4jHVftzS-o=xTJzJSVjceqhzwQ@mail.gmail.com> (raw) In-Reply-To: <CAPcyv4iECAzRjAUJ1hymOzZRjBYQ_baFrSz=2ah=2pfehn9S_g@mail.gmail.com> On Fri, Jun 5, 2020 at 6:39 PM Dan Williams <dan.j.williams@intel.com> wrote: > > On Fri, Jun 5, 2020 at 9:22 AM Rafael J. Wysocki <rafael@kernel.org> wrote: > [..] > > > The fix we are looking at now is to pre-map operation regions in a > > > similar manner as the way APEI resources are pre-mapped. The > > > pre-mapping would arrange for synchronize_rcu_expedited() to be elided > > > on each dynamic mapping attempt. The other piece is to arrange for > > > operation-regions to be mapped at their full size at once rather than > > > a page at a time. > > > > However, if the RCU usage in ACPI OSL can be replaced with an rwlock, > > some of the ACPICA changes above may not be necessary anymore (even > > though some of them may still be worth making). > > I don't think you can replace the RCU usage in ACPI OSL and still > maintain NMI lookups in a dynamic list. I'm not sure what NMI lookups have to do with the issue at hand. If acpi_os_{read|write}_memory() is used from NMI, that is a bug already in there which is unrelated to the performance problem with opregions. > However, there are 3 solutions I see: > > - Prevent acpi_os_map_cleanup() from triggering at high frequency by > pre-mapping and never unmapping operation-regions resources (internal > discussion in progress) Yes, that can be done, if necessary. > - Prevent walks of the 'acpi_ioremaps' list (acpi_map_lookup_virt()) > from NMI context by re-writing the physical addresses in the APEI > tables with pre-mapped virtual address, i.e. remove rcu_read_lock() > and list_for_each_entry_rcu() from NMI context. That sounds a bit convoluted to me. > - Split operation-region resources into a separate mapping mechanism > than APEI resources so that typical locking can be used for the > sleepable resources and let the NMI accessible resources be managed > separately. > > That last one is one we have not discussed internally, but it occurred > to me when you mentioned replacing RCU. So NMI cannot use acpi_os_{read|write}_memory() safely which you have pointed out for a few times. But even if NMI resources are managed separately, the others will still not be sleepable (at least not all of them). Cheers!
next prev parent reply other threads:[~2020-06-05 17:02 UTC|newest] Thread overview: 108+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-05-07 23:39 [PATCH v2] ACPI: Drop rcu usage for MMIO mappings Dan Williams 2020-05-07 23:39 ` Dan Williams 2020-05-09 12:30 ` Sasha Levin 2020-05-13 8:52 ` [ACPI] 5a91d41f89: BUG:sleeping_function_called_from_invalid_context_at_kernel/locking/mutex.c kernel test robot 2020-05-13 8:52 ` kernel test robot 2020-05-13 8:52 ` kernel test robot 2020-06-05 13:32 ` [PATCH v2] ACPI: Drop rcu usage for MMIO mappings Rafael J. Wysocki 2020-06-05 13:32 ` Rafael J. Wysocki 2020-06-05 16:18 ` Dan Williams 2020-06-05 16:18 ` Dan Williams 2020-06-05 16:21 ` Rafael J. Wysocki 2020-06-05 16:21 ` Rafael J. Wysocki 2020-06-05 16:39 ` Dan Williams 2020-06-05 16:39 ` Dan Williams 2020-06-05 17:02 ` Rafael J. Wysocki [this message] 2020-06-05 17:02 ` Rafael J. Wysocki 2020-06-05 14:06 ` [RFT][PATCH] ACPI: OSL: Use rwlock instead of RCU for memory management Rafael J. Wysocki 2020-06-05 14:06 ` Rafael J. Wysocki 2020-06-05 17:08 ` Dan Williams 2020-06-05 17:08 ` Dan Williams 2020-06-06 6:56 ` Rafael J. Wysocki 2020-06-06 6:56 ` Rafael J. Wysocki 2020-06-08 15:33 ` Rafael J. Wysocki 2020-06-08 15:33 ` Rafael J. Wysocki 2020-06-08 16:29 ` Rafael J. Wysocki 2020-06-08 16:29 ` Rafael J. Wysocki 2020-06-05 19:40 ` Andy Shevchenko 2020-06-05 19:40 ` Andy Shevchenko 2020-06-06 6:48 ` Rafael J. Wysocki 2020-06-06 6:48 ` Rafael J. Wysocki 2020-06-10 12:17 ` [RFT][PATCH 0/3] ACPI: ACPICA / OSL: Avoid unmapping ACPI memory inside of the AML interpreter Rafael J. Wysocki 2020-06-10 12:17 ` Rafael J. Wysocki 2020-06-10 12:20 ` [RFT][PATCH 1/3] ACPICA: Defer unmapping of memory used in memory opregions Rafael J. Wysocki 2020-06-10 12:20 ` Rafael J. Wysocki 2020-06-10 12:21 ` [RFT][PATCH 2/3] ACPICA: Remove unused memory mappings on interpreter exit Rafael J. Wysocki 2020-06-10 12:21 ` Rafael J. Wysocki 2020-06-12 0:12 ` Kaneda, Erik 2020-06-12 0:12 ` Kaneda, Erik 2020-06-12 12:05 ` Rafael J. Wysocki 2020-06-12 12:05 ` Rafael J. Wysocki 2020-06-13 19:28 ` Rafael J. Wysocki 2020-06-13 19:28 ` Rafael J. Wysocki 2020-06-15 19:06 ` Dan Williams 2020-06-15 19:06 ` Dan Williams 2020-06-10 12:22 ` [RFT][PATCH 3/3] ACPI: OSL: Define ACPI_OS_MAP_MEMORY_FAST_PATH() Rafael J. Wysocki 2020-06-10 12:22 ` Rafael J. Wysocki 2020-06-13 19:19 ` [RFT][PATCH 0/3] ACPI: ACPICA / OSL: Avoid unmapping ACPI memory inside of the AML interpreter Rafael J. Wysocki 2020-06-13 19:19 ` Rafael J. Wysocki 2020-06-22 13:50 ` [RFT][PATCH v2 0/4] " Rafael J. Wysocki 2020-06-22 13:50 ` Rafael J. Wysocki 2020-06-22 13:52 ` [RFT][PATCH v2 1/4] ACPICA: Defer unmapping of opregion memory if supported by OS Rafael J. Wysocki 2020-06-22 13:52 ` Rafael J. Wysocki 2020-06-22 13:53 ` [RFT][PATCH v2 2/4] ACPI: OSL: Add support for deferred unmapping of ACPI memory Rafael J. Wysocki 2020-06-22 13:53 ` Rafael J. Wysocki 2020-06-22 14:56 ` Andy Shevchenko 2020-06-22 14:56 ` Andy Shevchenko 2020-06-22 15:27 ` Rafael J. Wysocki 2020-06-22 15:27 ` Rafael J. Wysocki 2020-06-22 15:46 ` Andy Shevchenko 2020-06-22 15:46 ` Andy Shevchenko 2020-06-22 14:01 ` [RFT][PATCH v2 3/4] ACPICA: Preserve memory opregion mappings if supported by OS Rafael J. Wysocki 2020-06-22 14:01 ` Rafael J. Wysocki 2020-06-26 22:53 ` Kaneda, Erik 2020-06-26 22:53 ` Kaneda, Erik 2020-06-29 13:02 ` Rafael J. Wysocki 2020-06-29 13:02 ` Rafael J. Wysocki 2020-06-22 14:02 ` [RFT][PATCH v2 4/4] ACPI: OSL: Implement acpi_os_map_memory_fast_path() Rafael J. Wysocki 2020-06-22 14:02 ` Rafael J. Wysocki 2020-06-26 17:28 ` [RFT][PATCH v3 0/4] ACPI: ACPICA / OSL: Avoid unmapping ACPI memory inside of the AML interpreter Rafael J. Wysocki 2020-06-26 17:28 ` Rafael J. Wysocki 2020-06-26 17:31 ` [RFT][PATCH v3 1/4] ACPICA: Take deferred unmapping of memory into account Rafael J. Wysocki 2020-06-26 17:31 ` Rafael J. Wysocki 2020-06-26 17:31 ` [RFT][PATCH v3 2/4] ACPI: OSL: Implement deferred unmapping of ACPI memory Rafael J. Wysocki 2020-06-26 17:31 ` Rafael J. Wysocki 2020-06-27 11:32 ` kernel test robot 2020-06-26 17:32 ` [RFT][PATCH v3 3/4] ACPICA: Preserve memory opregion mappings if supported by OS Rafael J. Wysocki 2020-06-26 17:32 ` Rafael J. Wysocki 2020-06-26 17:33 ` [RFT][PATCH v3 4/4] ACPI: OSL: Implement acpi_os_map_memory_fast_path() Rafael J. Wysocki 2020-06-26 17:33 ` Rafael J. Wysocki 2020-06-26 18:41 ` [RFT][PATCH v3 0/4] ACPI: ACPICA / OSL: Avoid unmapping ACPI memory inside of the AML interpreter Dan Williams 2020-06-26 18:41 ` Dan Williams 2020-06-28 17:09 ` Rafael J. Wysocki 2020-06-28 17:09 ` Rafael J. Wysocki 2020-06-29 20:46 ` Dan Williams 2020-06-29 20:46 ` Dan Williams 2020-06-30 11:04 ` Rafael J. Wysocki 2020-06-30 11:04 ` Rafael J. Wysocki 2020-06-29 16:31 ` [PATCH v4 0/2] " Rafael J. Wysocki 2020-06-29 16:31 ` Rafael J. Wysocki 2020-06-29 16:33 ` [PATCH v4 1/2] ACPI: OSL: Implement deferred unmapping of ACPI memory Rafael J. Wysocki 2020-06-29 16:33 ` Rafael J. Wysocki 2020-06-29 16:33 ` [PATCH v4 2/2] ACPICA: Preserve memory opregion mappings Rafael J. Wysocki 2020-06-29 16:33 ` Rafael J. Wysocki 2020-06-29 20:57 ` Al Stone 2020-06-29 20:57 ` Al Stone 2020-06-30 11:44 ` Rafael J. Wysocki 2020-06-30 11:44 ` Rafael J. Wysocki 2020-06-30 15:31 ` Al Stone 2020-06-30 15:31 ` Al Stone 2020-06-30 15:52 ` Rafael J. Wysocki 2020-06-30 15:52 ` Rafael J. Wysocki 2020-06-30 19:57 ` Al Stone 2020-06-30 19:57 ` Al Stone 2020-07-16 19:22 ` Verma, Vishal L 2020-07-16 19:22 ` Verma, Vishal L 2020-07-19 19:14 ` Rafael J. Wysocki 2020-07-19 19:14 ` Rafael J. Wysocki 2020-05-11 17:51 [PATCH v2] ACPI: Drop rcu usage for MMIO mappings kbuild test robot
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