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0d124e9605
Problem: ======= On arm64, block and section mapping is supported to build page tables. However, currently it enforces to take base page mapping for the whole linear mapping if CONFIG_ZONE_DMA or CONFIG_ZONE_DMA32 is enabled and crashkernel kernel parameter is set. This will cause longer time of the linear mapping process during bootup and severe performance degradation during running time. Root cause: ========== On arm64, crashkernel reservation relies on knowing the upper limit of low memory zone because it needs to reserve memory in the zone so that devices' DMA addressing in kdump kernel can be satisfied. However, the upper limit of low memory on arm64 is variant. And the upper limit can only be decided late till bootmem_init() is called [1]. And we need to map the crashkernel region with base page granularity when doing linear mapping, because kdump needs to protect the crashkernel region via set_memory_valid(,0) after kdump kernel loading. However, arm64 doesn't support well on splitting the built block or section mapping due to some cpu reststriction [2]. And unfortunately, the linear mapping is done before bootmem_init(). To resolve the above conflict on arm64, the compromise is enforcing to take base page mapping for the entire linear mapping if crashkernel is set, and CONFIG_ZONE_DMA or CONFIG_ZONE_DMA32 is enabed. Hence performance is sacrificed. Solution: ========= Comparing with the base page mapping for the whole linear region, it's better to take off the protection on crashkernel memory region for the time being because the anticipated stamping on crashkernel memory region could only happen in a chance in one million, while the base page mapping for the whole linear region is mitigating arm64 systems with crashkernel set always. [1] https://lore.kernel.org/all/YrIIJkhKWSuAqkCx@arm.com/T/#u [2] https://lore.kernel.org/linux-arm-kernel/20190911182546.17094-1-nsaenzjulienne@suse.de/T/ Signed-off-by: Baoquan He <bhe@redhat.com> Acked-by: Catalin Marinas <catalin.marinas@arm.com> Acked-by: Mike Rapoport (IBM) <rppt@kernel.org> Reviewed-by: Zhen Lei <thunder.leizhen@huawei.com> Link: https://lore.kernel.org/r/20230407011507.17572-2-bhe@redhat.com Signed-off-by: Will Deacon <will@kernel.org>
135 lines
3.4 KiB
C
135 lines
3.4 KiB
C
/* SPDX-License-Identifier: GPL-2.0-only */
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/*
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* kexec for arm64
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*
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* Copyright (C) Linaro.
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* Copyright (C) Huawei Futurewei Technologies.
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*/
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#ifndef _ARM64_KEXEC_H
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#define _ARM64_KEXEC_H
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/* Maximum physical address we can use pages from */
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#define KEXEC_SOURCE_MEMORY_LIMIT (-1UL)
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/* Maximum address we can reach in physical address mode */
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#define KEXEC_DESTINATION_MEMORY_LIMIT (-1UL)
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/* Maximum address we can use for the control code buffer */
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#define KEXEC_CONTROL_MEMORY_LIMIT (-1UL)
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#define KEXEC_CONTROL_PAGE_SIZE 4096
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#define KEXEC_ARCH KEXEC_ARCH_AARCH64
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#ifndef __ASSEMBLY__
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/**
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* crash_setup_regs() - save registers for the panic kernel
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*
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* @newregs: registers are saved here
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* @oldregs: registers to be saved (may be %NULL)
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*/
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static inline void crash_setup_regs(struct pt_regs *newregs,
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struct pt_regs *oldregs)
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{
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if (oldregs) {
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memcpy(newregs, oldregs, sizeof(*newregs));
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} else {
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u64 tmp1, tmp2;
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__asm__ __volatile__ (
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"stp x0, x1, [%2, #16 * 0]\n"
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"stp x2, x3, [%2, #16 * 1]\n"
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"stp x4, x5, [%2, #16 * 2]\n"
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"stp x6, x7, [%2, #16 * 3]\n"
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"stp x8, x9, [%2, #16 * 4]\n"
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"stp x10, x11, [%2, #16 * 5]\n"
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"stp x12, x13, [%2, #16 * 6]\n"
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"stp x14, x15, [%2, #16 * 7]\n"
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"stp x16, x17, [%2, #16 * 8]\n"
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"stp x18, x19, [%2, #16 * 9]\n"
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"stp x20, x21, [%2, #16 * 10]\n"
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"stp x22, x23, [%2, #16 * 11]\n"
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"stp x24, x25, [%2, #16 * 12]\n"
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"stp x26, x27, [%2, #16 * 13]\n"
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"stp x28, x29, [%2, #16 * 14]\n"
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"mov %0, sp\n"
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"stp x30, %0, [%2, #16 * 15]\n"
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"/* faked current PSTATE */\n"
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"mrs %0, CurrentEL\n"
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"mrs %1, SPSEL\n"
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"orr %0, %0, %1\n"
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"mrs %1, DAIF\n"
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"orr %0, %0, %1\n"
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"mrs %1, NZCV\n"
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"orr %0, %0, %1\n"
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/* pc */
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"adr %1, 1f\n"
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"1:\n"
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"stp %1, %0, [%2, #16 * 16]\n"
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: "=&r" (tmp1), "=&r" (tmp2)
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: "r" (newregs)
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: "memory"
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);
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}
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}
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#if defined(CONFIG_KEXEC_CORE) && defined(CONFIG_HIBERNATION)
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extern bool crash_is_nosave(unsigned long pfn);
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extern void crash_prepare_suspend(void);
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extern void crash_post_resume(void);
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void crash_free_reserved_phys_range(unsigned long begin, unsigned long end);
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#define crash_free_reserved_phys_range crash_free_reserved_phys_range
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#else
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static inline bool crash_is_nosave(unsigned long pfn) {return false; }
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static inline void crash_prepare_suspend(void) {}
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static inline void crash_post_resume(void) {}
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#endif
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struct kimage;
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#if defined(CONFIG_KEXEC_CORE)
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void cpu_soft_restart(unsigned long el2_switch, unsigned long entry,
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unsigned long arg0, unsigned long arg1,
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unsigned long arg2);
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int machine_kexec_post_load(struct kimage *image);
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#define machine_kexec_post_load machine_kexec_post_load
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#endif
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#define ARCH_HAS_KIMAGE_ARCH
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struct kimage_arch {
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void *dtb;
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phys_addr_t dtb_mem;
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phys_addr_t kern_reloc;
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phys_addr_t el2_vectors;
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phys_addr_t ttbr0;
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phys_addr_t ttbr1;
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phys_addr_t zero_page;
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unsigned long phys_offset;
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unsigned long t0sz;
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};
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#ifdef CONFIG_KEXEC_FILE
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extern const struct kexec_file_ops kexec_image_ops;
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int arch_kimage_file_post_load_cleanup(struct kimage *image);
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#define arch_kimage_file_post_load_cleanup arch_kimage_file_post_load_cleanup
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extern int load_other_segments(struct kimage *image,
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unsigned long kernel_load_addr, unsigned long kernel_size,
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char *initrd, unsigned long initrd_len,
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char *cmdline);
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#endif
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#endif /* __ASSEMBLY__ */
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#endif
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