From: Mike Rapoport <rppt@kernel.org> To: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will@kernel.org>, "guanghui.fgh" <guanghuifeng@linux.alibaba.com>, Ard Biesheuvel <ardb@kernel.org>, baolin.wang@linux.alibaba.com, akpm@linux-foundation.org, david@redhat.com, jianyong.wu@arm.com, james.morse@arm.com, quic_qiancai@quicinc.com, christophe.leroy@csgroup.eu, jonathan@marek.ca, mark.rutland@arm.com, thunder.leizhen@huawei.com, anshuman.khandual@arm.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, geert+renesas@glider.be, linux-mm@kvack.org, yaohongbo@linux.alibaba.com, alikernel-developer@linux.alibaba.com Subject: Re: [PATCH v4] arm64: mm: fix linear mem mapping access performance degradation Date: Tue, 5 Jul 2022 18:57:53 +0300 [thread overview] Message-ID: <YsRfgX7FFZLxQU50@kernel.org> (raw) In-Reply-To: <YsRZ8V8mQ+HM31D6@arm.com> On Tue, Jul 05, 2022 at 04:34:09PM +0100, Catalin Marinas wrote: > On Tue, Jul 05, 2022 at 06:02:02PM +0300, Mike Rapoport wrote: > > +void __init remap_crashkernel(void) > > +{ > > +#ifdef CONFIG_KEXEC_CORE > > + phys_addr_t start, end, size; > > + phys_addr_t aligned_start, aligned_end; > > + > > + if (can_set_direct_map() || IS_ENABLED(CONFIG_KFENCE)) > > + return; > > + > > + if (!crashk_res.end) > > + return; > > + > > + start = crashk_res.start & PAGE_MASK; > > + end = PAGE_ALIGN(crashk_res.end); > > + > > + aligned_start = ALIGN_DOWN(crashk_res.start, PUD_SIZE); > > + aligned_end = ALIGN(end, PUD_SIZE); > > + > > + /* Clear PUDs containing crash kernel memory */ > > + unmap_hotplug_range(__phys_to_virt(aligned_start), > > + __phys_to_virt(aligned_end), false, NULL); > > What I don't understand is what happens if there's valid kernel data > between aligned_start and crashk_res.start (or the other end of the > range). Data shouldn't go anywhere :) There is + /* map area from PUD start to start of crash kernel with large pages */ + size = start - aligned_start; + __create_pgd_mapping(swapper_pg_dir, aligned_start, + __phys_to_virt(aligned_start), + size, PAGE_KERNEL, early_pgtable_alloc, 0); and + /* map area from end of crash kernel to PUD end with large pages */ + size = aligned_end - end; + __create_pgd_mapping(swapper_pg_dir, end, __phys_to_virt(end), + size, PAGE_KERNEL, early_pgtable_alloc, 0); after the unmap, so after we tear down a part of a linear map we immediately recreate it, just with a different page size. This all happens before SMP, so there is no concurrency at that point. > -- > Catalin -- Sincerely yours, Mike.
WARNING: multiple messages have this Message-ID (diff)
From: Mike Rapoport <rppt@kernel.org> To: Catalin Marinas <catalin.marinas@arm.com> Cc: Will Deacon <will@kernel.org>, "guanghui.fgh" <guanghuifeng@linux.alibaba.com>, Ard Biesheuvel <ardb@kernel.org>, baolin.wang@linux.alibaba.com, akpm@linux-foundation.org, david@redhat.com, jianyong.wu@arm.com, james.morse@arm.com, quic_qiancai@quicinc.com, christophe.leroy@csgroup.eu, jonathan@marek.ca, mark.rutland@arm.com, thunder.leizhen@huawei.com, anshuman.khandual@arm.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, geert+renesas@glider.be, linux-mm@kvack.org, yaohongbo@linux.alibaba.com, alikernel-developer@linux.alibaba.com Subject: Re: [PATCH v4] arm64: mm: fix linear mem mapping access performance degradation Date: Tue, 5 Jul 2022 18:57:53 +0300 [thread overview] Message-ID: <YsRfgX7FFZLxQU50@kernel.org> (raw) In-Reply-To: <YsRZ8V8mQ+HM31D6@arm.com> On Tue, Jul 05, 2022 at 04:34:09PM +0100, Catalin Marinas wrote: > On Tue, Jul 05, 2022 at 06:02:02PM +0300, Mike Rapoport wrote: > > +void __init remap_crashkernel(void) > > +{ > > +#ifdef CONFIG_KEXEC_CORE > > + phys_addr_t start, end, size; > > + phys_addr_t aligned_start, aligned_end; > > + > > + if (can_set_direct_map() || IS_ENABLED(CONFIG_KFENCE)) > > + return; > > + > > + if (!crashk_res.end) > > + return; > > + > > + start = crashk_res.start & PAGE_MASK; > > + end = PAGE_ALIGN(crashk_res.end); > > + > > + aligned_start = ALIGN_DOWN(crashk_res.start, PUD_SIZE); > > + aligned_end = ALIGN(end, PUD_SIZE); > > + > > + /* Clear PUDs containing crash kernel memory */ > > + unmap_hotplug_range(__phys_to_virt(aligned_start), > > + __phys_to_virt(aligned_end), false, NULL); > > What I don't understand is what happens if there's valid kernel data > between aligned_start and crashk_res.start (or the other end of the > range). Data shouldn't go anywhere :) There is + /* map area from PUD start to start of crash kernel with large pages */ + size = start - aligned_start; + __create_pgd_mapping(swapper_pg_dir, aligned_start, + __phys_to_virt(aligned_start), + size, PAGE_KERNEL, early_pgtable_alloc, 0); and + /* map area from end of crash kernel to PUD end with large pages */ + size = aligned_end - end; + __create_pgd_mapping(swapper_pg_dir, end, __phys_to_virt(end), + size, PAGE_KERNEL, early_pgtable_alloc, 0); after the unmap, so after we tear down a part of a linear map we immediately recreate it, just with a different page size. This all happens before SMP, so there is no concurrency at that point. > -- > Catalin -- Sincerely yours, Mike. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
next prev parent reply other threads:[~2022-07-05 15:58 UTC|newest] Thread overview: 79+ messages / expand[flat|nested] mbox.gz Atom feed top 2022-07-02 15:57 [PATCH v4] arm64: mm: fix linear mem mapping access performance degradation Guanghui Feng 2022-07-02 15:57 ` Guanghui Feng 2022-07-04 10:35 ` Will Deacon 2022-07-04 10:35 ` Will Deacon 2022-07-04 10:58 ` guanghui.fgh 2022-07-04 10:58 ` guanghui.fgh 2022-07-04 11:14 ` Will Deacon 2022-07-04 11:14 ` Will Deacon 2022-07-04 12:05 ` guanghui.fgh 2022-07-04 12:05 ` guanghui.fgh 2022-07-04 13:15 ` Will Deacon 2022-07-04 13:15 ` Will Deacon 2022-07-04 13:41 ` guanghui.fgh 2022-07-04 13:41 ` guanghui.fgh 2022-07-04 14:11 ` guanghui.fgh 2022-07-04 14:11 ` guanghui.fgh 2022-07-04 14:23 ` Will Deacon 2022-07-04 14:23 ` Will Deacon 2022-07-04 14:34 ` guanghui.fgh 2022-07-04 14:34 ` guanghui.fgh 2022-07-04 16:38 ` Will Deacon 2022-07-04 16:38 ` Will Deacon 2022-07-04 17:09 ` Ard Biesheuvel 2022-07-04 17:09 ` Ard Biesheuvel 2022-07-05 8:35 ` Baoquan He 2022-07-05 8:35 ` Baoquan He 2022-07-05 8:35 ` Baoquan He 2022-07-05 9:52 ` Will Deacon 2022-07-05 9:52 ` Will Deacon 2022-07-05 12:07 ` guanghui.fgh 2022-07-05 12:07 ` guanghui.fgh 2022-07-05 12:11 ` Will Deacon 2022-07-05 12:11 ` Will Deacon 2022-07-05 12:27 ` guanghui.fgh 2022-07-05 12:27 ` guanghui.fgh 2022-07-05 12:56 ` Mike Rapoport 2022-07-05 12:56 ` Mike Rapoport 2022-07-05 13:17 ` guanghui.fgh 2022-07-05 13:17 ` guanghui.fgh 2022-07-05 15:02 ` Mike Rapoport 2022-07-05 15:02 ` Mike Rapoport 2022-07-05 15:34 ` Catalin Marinas 2022-07-05 15:34 ` Catalin Marinas 2022-07-05 15:57 ` Mike Rapoport [this message] 2022-07-05 15:57 ` Mike Rapoport 2022-07-05 17:05 ` Catalin Marinas 2022-07-05 17:05 ` Catalin Marinas 2022-07-05 20:45 ` Mike Rapoport 2022-07-05 20:45 ` Mike Rapoport 2022-07-06 2:49 ` guanghui.fgh 2022-07-06 2:49 ` guanghui.fgh 2022-07-06 7:43 ` Catalin Marinas 2022-07-06 7:43 ` Catalin Marinas 2022-07-06 10:04 ` Catalin Marinas 2022-07-06 10:04 ` Catalin Marinas 2022-07-06 13:54 ` Mike Rapoport 2022-07-06 13:54 ` Mike Rapoport 2022-07-06 15:18 ` guanghui.fgh 2022-07-06 15:18 ` guanghui.fgh 2022-07-06 15:30 ` guanghui.fgh 2022-07-06 15:30 ` guanghui.fgh 2022-07-06 15:40 ` Catalin Marinas 2022-07-06 15:40 ` Catalin Marinas 2022-07-07 17:02 ` guanghui.fgh 2022-07-07 17:02 ` guanghui.fgh 2022-07-08 12:28 ` [PATCH RESEND " guanghui.fgh 2022-07-08 12:28 ` guanghui.fgh 2022-07-10 13:44 ` [PATCH v5] " Guanghui Feng 2022-07-10 13:44 ` Guanghui Feng 2022-07-10 14:32 ` guanghui.fgh 2022-07-10 14:32 ` guanghui.fgh 2022-07-10 15:33 ` guanghui.fgh 2022-07-10 15:33 ` guanghui.fgh 2022-07-18 13:10 ` Will Deacon 2022-07-18 13:10 ` Will Deacon 2022-07-25 6:46 ` Mike Rapoport 2022-07-25 6:46 ` Mike Rapoport 2022-07-05 2:44 ` [PATCH v4] " guanghui.fgh 2022-07-05 2:44 ` guanghui.fgh
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