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Peter Anvin" , , , , , Kefeng Wang , Xie XiuQi , Guohanjun References: <20220420030418.3189040-1-tongtiangen@huawei.com> <20220420030418.3189040-8-tongtiangen@huawei.com> From: Tong Tiangen In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.179.234] X-ClientProxiedBy: dggems705-chm.china.huawei.com (10.3.19.182) To kwepemm600017.china.huawei.com (7.193.23.234) X-CFilter-Loop: Reflected X-Spam-Status: No, score=-4.9 required=5.0 tests=BAYES_00,NICE_REPLY_A, RCVD_IN_DNSWL_MED,SPF_HELO_NONE,SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 在 2022/5/13 23:44, Mark Rutland 写道: > On Wed, Apr 20, 2022 at 03:04:18AM +0000, Tong Tiangen wrote: >> In the cow(copy on write) processing, the data of the user process is >> copied, when hardware memory error is encountered during copy, only the >> relevant processes are affected, so killing the user process and isolate >> the user page with hardware memory errors is a more reasonable choice than >> kernel panic. > > There are plenty of other places we'll access user pages via a kernel > alias (e.g. when performing IO), so why is this special? > > To be clear, I am not entirely averse to this, but it seems like this is > being done because it's easy to do rather than necessarily being all > that useful, and I'm not keen on having to duplicate a bunch of logic > for this. Yeah, There are lots of cases, COW is selected because it is more general. In addition, this provides the machine check safe capability of page copy(copy_highpage_mc), valuable cases can be based on this step by step[1]. [1]https://lore.kernel.org/all/20220429000947.2172219-1-jiaqiyan@google.com/T/ Thanks, Tong. > >> Add new helper copy_page_mc() which provide a page copy implementation with >> machine check safe. At present, only used in cow. In future, we can expand >> more scenes. As long as the consequences of page copy failure are not >> fatal(eg: only affect user process), we can use this helper. >> >> The copy_page_mc() in copy_page_mc.S is largely borrows from copy_page() >> in copy_page.S and the main difference is copy_page_mc() add extable entry >> to every load/store insn to support machine check safe. largely to keep the >> patch simple. If needed those optimizations can be folded in. >> >> Add new extable type EX_TYPE_COPY_PAGE_MC which used in copy_page_mc(). >> >> This type only be processed in fixup_exception_mc(), The reason is that >> copy_page_mc() is consistent with copy_page() except machine check safe is >> considered, and copy_page() do not need to consider exception fixup. >> >> Signed-off-by: Tong Tiangen >> --- >> arch/arm64/include/asm/asm-extable.h | 5 ++ >> arch/arm64/include/asm/page.h | 10 ++++ >> arch/arm64/lib/Makefile | 2 + >> arch/arm64/lib/copy_page_mc.S | 86 ++++++++++++++++++++++++++++ >> arch/arm64/mm/copypage.c | 36 ++++++++++-- >> arch/arm64/mm/extable.c | 2 + >> include/linux/highmem.h | 8 +++ >> mm/memory.c | 2 +- >> 8 files changed, 144 insertions(+), 7 deletions(-) >> create mode 100644 arch/arm64/lib/copy_page_mc.S >> >> diff --git a/arch/arm64/include/asm/asm-extable.h b/arch/arm64/include/asm/asm-extable.h >> index 80410899a9ad..74c056ddae15 100644 >> --- a/arch/arm64/include/asm/asm-extable.h >> +++ b/arch/arm64/include/asm/asm-extable.h >> @@ -14,6 +14,7 @@ >> /* _MC indicates that can fixup from machine check errors */ >> #define EX_TYPE_UACCESS_MC 5 >> #define EX_TYPE_UACCESS_MC_ERR_ZERO 6 >> +#define EX_TYPE_COPY_PAGE_MC 7 >> >> #ifdef __ASSEMBLY__ >> >> @@ -42,6 +43,10 @@ >> __ASM_EXTABLE_RAW(\insn, \fixup, EX_TYPE_UACCESS_MC, 0) >> .endm >> >> + .macro _asm_extable_copy_page_mc, insn, fixup >> + __ASM_EXTABLE_RAW(\insn, \fixup, EX_TYPE_COPY_PAGE_MC, 0) >> + .endm >> + >> /* >> * Create an exception table entry for `insn` if `fixup` is provided. Otherwise >> * do nothing. >> diff --git a/arch/arm64/include/asm/page.h b/arch/arm64/include/asm/page.h >> index 993a27ea6f54..832571a7dddb 100644 >> --- a/arch/arm64/include/asm/page.h >> +++ b/arch/arm64/include/asm/page.h >> @@ -29,6 +29,16 @@ void copy_user_highpage(struct page *to, struct page *from, >> void copy_highpage(struct page *to, struct page *from); >> #define __HAVE_ARCH_COPY_HIGHPAGE >> >> +#ifdef CONFIG_ARCH_HAS_COPY_MC >> +extern void copy_page_mc(void *to, const void *from); >> +void copy_highpage_mc(struct page *to, struct page *from); >> +#define __HAVE_ARCH_COPY_HIGHPAGE_MC >> + >> +void copy_user_highpage_mc(struct page *to, struct page *from, >> + unsigned long vaddr, struct vm_area_struct *vma); >> +#define __HAVE_ARCH_COPY_USER_HIGHPAGE_MC >> +#endif >> + >> struct page *alloc_zeroed_user_highpage_movable(struct vm_area_struct *vma, >> unsigned long vaddr); >> #define __HAVE_ARCH_ALLOC_ZEROED_USER_HIGHPAGE_MOVABLE >> diff --git a/arch/arm64/lib/Makefile b/arch/arm64/lib/Makefile >> index 29490be2546b..0d9f292ef68a 100644 >> --- a/arch/arm64/lib/Makefile >> +++ b/arch/arm64/lib/Makefile >> @@ -15,6 +15,8 @@ endif >> >> lib-$(CONFIG_ARCH_HAS_UACCESS_FLUSHCACHE) += uaccess_flushcache.o >> >> +lib-$(CONFIG_ARCH_HAS_COPY_MC) += copy_page_mc.o >> + >> obj-$(CONFIG_CRC32) += crc32.o >> >> obj-$(CONFIG_FUNCTION_ERROR_INJECTION) += error-inject.o >> diff --git a/arch/arm64/lib/copy_page_mc.S b/arch/arm64/lib/copy_page_mc.S >> new file mode 100644 >> index 000000000000..655161363dcf >> --- /dev/null >> +++ b/arch/arm64/lib/copy_page_mc.S >> @@ -0,0 +1,86 @@ >> +/* SPDX-License-Identifier: GPL-2.0-only */ >> +/* >> + * Copyright (C) 2012 ARM Ltd. >> + */ >> + >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> +#include >> + >> +#define CPY_MC(l, x...) \ >> +9999: x; \ >> + _asm_extable_copy_page_mc 9999b, l >> + >> +/* >> + * Copy a page from src to dest (both are page aligned) with machine check >> + * >> + * Parameters: >> + * x0 - dest >> + * x1 - src >> + */ >> +SYM_FUNC_START(__pi_copy_page_mc) >> +alternative_if ARM64_HAS_NO_HW_PREFETCH >> + // Prefetch three cache lines ahead. >> + prfm pldl1strm, [x1, #128] >> + prfm pldl1strm, [x1, #256] >> + prfm pldl1strm, [x1, #384] >> +alternative_else_nop_endif >> + >> +CPY_MC(9998f, ldp x2, x3, [x1]) >> +CPY_MC(9998f, ldp x4, x5, [x1, #16]) >> +CPY_MC(9998f, ldp x6, x7, [x1, #32]) >> +CPY_MC(9998f, ldp x8, x9, [x1, #48]) >> +CPY_MC(9998f, ldp x10, x11, [x1, #64]) >> +CPY_MC(9998f, ldp x12, x13, [x1, #80]) >> +CPY_MC(9998f, ldp x14, x15, [x1, #96]) >> +CPY_MC(9998f, ldp x16, x17, [x1, #112]) >> + >> + add x0, x0, #256 >> + add x1, x1, #128 >> +1: >> + tst x0, #(PAGE_SIZE - 1) >> + >> +alternative_if ARM64_HAS_NO_HW_PREFETCH >> + prfm pldl1strm, [x1, #384] >> +alternative_else_nop_endif >> + >> +CPY_MC(9998f, stnp x2, x3, [x0, #-256]) >> +CPY_MC(9998f, ldp x2, x3, [x1]) >> +CPY_MC(9998f, stnp x4, x5, [x0, #16 - 256]) >> +CPY_MC(9998f, ldp x4, x5, [x1, #16]) >> +CPY_MC(9998f, stnp x6, x7, [x0, #32 - 256]) >> +CPY_MC(9998f, ldp x6, x7, [x1, #32]) >> +CPY_MC(9998f, stnp x8, x9, [x0, #48 - 256]) >> +CPY_MC(9998f, ldp x8, x9, [x1, #48]) >> +CPY_MC(9998f, stnp x10, x11, [x0, #64 - 256]) >> +CPY_MC(9998f, ldp x10, x11, [x1, #64]) >> +CPY_MC(9998f, stnp x12, x13, [x0, #80 - 256]) >> +CPY_MC(9998f, ldp x12, x13, [x1, #80]) >> +CPY_MC(9998f, stnp x14, x15, [x0, #96 - 256]) >> +CPY_MC(9998f, ldp x14, x15, [x1, #96]) >> +CPY_MC(9998f, stnp x16, x17, [x0, #112 - 256]) >> +CPY_MC(9998f, ldp x16, x17, [x1, #112]) >> + >> + add x0, x0, #128 >> + add x1, x1, #128 >> + >> + b.ne 1b >> + >> +CPY_MC(9998f, stnp x2, x3, [x0, #-256]) >> +CPY_MC(9998f, stnp x4, x5, [x0, #16 - 256]) >> +CPY_MC(9998f, stnp x6, x7, [x0, #32 - 256]) >> +CPY_MC(9998f, stnp x8, x9, [x0, #48 - 256]) >> +CPY_MC(9998f, stnp x10, x11, [x0, #64 - 256]) >> +CPY_MC(9998f, stnp x12, x13, [x0, #80 - 256]) >> +CPY_MC(9998f, stnp x14, x15, [x0, #96 - 256]) >> +CPY_MC(9998f, stnp x16, x17, [x0, #112 - 256]) >> + >> +9998: ret >> + >> +SYM_FUNC_END(__pi_copy_page_mc) >> +SYM_FUNC_ALIAS(copy_page_mc, __pi_copy_page_mc) >> +EXPORT_SYMBOL(copy_page_mc) >> diff --git a/arch/arm64/mm/copypage.c b/arch/arm64/mm/copypage.c >> index 0dea80bf6de4..0f28edfcb234 100644 >> --- a/arch/arm64/mm/copypage.c >> +++ b/arch/arm64/mm/copypage.c >> @@ -14,13 +14,8 @@ >> #include >> #include >> >> -void copy_highpage(struct page *to, struct page *from) >> +static void do_mte(struct page *to, struct page *from, void *kto, void *kfrom) >> { >> - void *kto = page_address(to); >> - void *kfrom = page_address(from); >> - >> - copy_page(kto, kfrom); >> - >> if (system_supports_mte() && test_bit(PG_mte_tagged, &from->flags)) { >> set_bit(PG_mte_tagged, &to->flags); >> page_kasan_tag_reset(to); >> @@ -35,6 +30,15 @@ void copy_highpage(struct page *to, struct page *from) >> mte_copy_page_tags(kto, kfrom); >> } >> } >> + >> +void copy_highpage(struct page *to, struct page *from) >> +{ >> + void *kto = page_address(to); >> + void *kfrom = page_address(from); >> + >> + copy_page(kto, kfrom); >> + do_mte(to, from, kto, kfrom); >> +} >> EXPORT_SYMBOL(copy_highpage); >> >> void copy_user_highpage(struct page *to, struct page *from, >> @@ -44,3 +48,23 @@ void copy_user_highpage(struct page *to, struct page *from, >> flush_dcache_page(to); >> } >> EXPORT_SYMBOL_GPL(copy_user_highpage); >> + >> +#ifdef CONFIG_ARCH_HAS_COPY_MC >> +void copy_highpage_mc(struct page *to, struct page *from) >> +{ >> + void *kto = page_address(to); >> + void *kfrom = page_address(from); >> + >> + copy_page_mc(kto, kfrom); >> + do_mte(to, from, kto, kfrom); >> +} >> +EXPORT_SYMBOL(copy_highpage_mc); > > IIUC the do_mte() portion won't handle mermoy errors, so this isn't > actually going to recover safely. > > Thanks, > Mark. OK, Missing that, do_mte needs to be handled. Thanks, Tong. > >> + >> +void copy_user_highpage_mc(struct page *to, struct page *from, >> + unsigned long vaddr, struct vm_area_struct *vma) >> +{ >> + copy_highpage_mc(to, from); >> + flush_dcache_page(to); >> +} >> +EXPORT_SYMBOL_GPL(copy_user_highpage_mc); >> +#endif >> diff --git a/arch/arm64/mm/extable.c b/arch/arm64/mm/extable.c >> index 1023ccdb2f89..4c882d36dd64 100644 >> --- a/arch/arm64/mm/extable.c >> +++ b/arch/arm64/mm/extable.c >> @@ -110,6 +110,8 @@ bool fixup_exception_mc(struct pt_regs *regs) >> return ex_handler_uaccess_type(ex, regs, FIXUP_TYPE_MC); >> case EX_TYPE_UACCESS_MC_ERR_ZERO: >> return ex_handler_uaccess_err_zero(ex, regs); >> + case EX_TYPE_COPY_PAGE_MC: >> + return ex_handler_fixup(ex, regs); >> >> } >> >> diff --git a/include/linux/highmem.h b/include/linux/highmem.h >> index 39bb9b47fa9c..a9dbf331b038 100644 >> --- a/include/linux/highmem.h >> +++ b/include/linux/highmem.h >> @@ -283,6 +283,10 @@ static inline void copy_user_highpage(struct page *to, struct page *from, >> >> #endif >> >> +#ifndef __HAVE_ARCH_COPY_USER_HIGHPAGE_MC >> +#define copy_user_highpage_mc copy_user_highpage >> +#endif >> + >> #ifndef __HAVE_ARCH_COPY_HIGHPAGE >> >> static inline void copy_highpage(struct page *to, struct page *from) >> @@ -298,6 +302,10 @@ static inline void copy_highpage(struct page *to, struct page *from) >> >> #endif >> >> +#ifndef __HAVE_ARCH_COPY_HIGHPAGE_MC >> +#define cop_highpage_mc copy_highpage >> +#endif >> + >> static inline void memcpy_page(struct page *dst_page, size_t dst_off, >> struct page *src_page, size_t src_off, >> size_t len) >> diff --git a/mm/memory.c b/mm/memory.c >> index 76e3af9639d9..d5f62234152d 100644 >> --- a/mm/memory.c >> +++ b/mm/memory.c >> @@ -2767,7 +2767,7 @@ static inline bool cow_user_page(struct page *dst, struct page *src, >> unsigned long addr = vmf->address; >> >> if (likely(src)) { >> - copy_user_highpage(dst, src, addr, vma); >> + copy_user_highpage_mc(dst, src, addr, vma); >> return true; >> } >> >> -- >> 2.25.1 >> > .