From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 87D8313C9A3 for ; Fri, 11 Apr 2025 23:06:34 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744412794; cv=none; b=tnd7E4kAK6Brty2oI91UygWHLVyC+4NqRwliHVIG15h3+bsV6pWIyaZd66fBGLk2rPzaGSQ/7SggREFrA0TYD+oHs4ndSGnVzd5pLeBH9JExdpbiR/alz76PPCS/w61KnCFN6WUh0GNvq822FOK2uBSZo8pPQaBC25gv4dMnkqc= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1744412794; c=relaxed/simple; bh=j0ha1nMAWlyhM9UGKSye/gcE4NoK8BYAn7onlHQcGJo=; h=Date:To:From:Subject:Message-Id; b=MrBsQe93Ladoi1j7q2xviChxXmEYoIt1zSJFHyTAQp1dA7a97IP4LVkDmp+z5Bv2bQWeQgGwnK23f2sO0rEvPXm8RFVUvlSuXlRKA9i1Daa/pyZplr5EYH7/YKU+li99ZiUpBc3WuRpFKrCRPPrJ7OXrcThD71lkrDVPLByNOhg= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=HvRXZ4PL; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="HvRXZ4PL" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 335DFC4CEE2; Fri, 11 Apr 2025 23:06:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1744412794; bh=j0ha1nMAWlyhM9UGKSye/gcE4NoK8BYAn7onlHQcGJo=; h=Date:To:From:Subject:From; b=HvRXZ4PLtf+qKDWKFk0AIh3Xb5czG2obcp7B7PznOHnm7kzFaaGNGPA29HF3K9ohR eZzoMhd7TUcsPZXqqjA+dqGmI8n38YvbznJy/IYiuSpWsbzhmoGFDyapaWzIzTM1ft 7SQugeq4JpYUhJ9w8AUgoLZVkBbdzOlJwcdP+FB4= Date: Fri, 11 Apr 2025 16:06:33 -0700 To: mm-commits@vger.kernel.org,will@kernel.org,thomas.lendacky@amd.com,tglx@linutronix.de,skinsburskii@linux.microsoft.com,saravanak@google.com,rppt@kernel.org,rostedt@goodmis.org,robh@kernel.org,ptyadav@amazon.de,peterz@infradead.org,pbonzini@redhat.com,pasha.tatashin@soleen.com,mingo@redhat.com,mark.rutland@arm.com,luto@kernel.org,krzk@kernel.org,jgowans@amazon.com,jgg@nvidia.com,hpa@zytor.com,ebiederm@xmission.com,dwmw2@infradead.org,corbet@lwn.net,changyuanl@google.com,catalin.marinas@arm.com,bp@alien8.de,benh@kernel.crashing.org,ashish.kalra@amd.com,arnd@arndb.de,anthony.yznaga@oracle.com,graf@amazon.com,akpm@linux-foundation.org From: Andrew Morton Subject: + memblock-add-support-for-scratch-memory.patch added to mm-new branch Message-Id: <20250411230634.335DFC4CEE2@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: memblock: add support for scratch memory has been added to the -mm mm-new branch. Its filename is memblock-add-support-for-scratch-memory.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/memblock-add-support-for-scratch-memory.patch This patch will later appear in the mm-new branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: Alexander Graf Subject: memblock: add support for scratch memory Date: Thu, 10 Apr 2025 22:37:33 -0700 With KHO (Kexec HandOver), we need a way to ensure that the new kernel does not allocate memory on top of any memory regions that the previous kernel was handing over. But to know where those are, we need to include them in the memblock.reserved array which may not be big enough to hold all ranges that need to be persisted across kexec. To resize the array, we need to allocate memory. That brings us into a catch 22 situation. The solution to that is limit memblock allocations to the scratch regions: safe regions to operate in the case when there is memory that should remain intact across kexec. KHO provides several "scratch regions" as part of its metadata. These scratch regions are contiguous memory blocks that known not to contain any memory that should be persisted across kexec. These regions should be large enough to accommodate all memblock allocations done by the kexeced kernel. We introduce a new memblock_set_scratch_only() function that allows KHO to indicate that any memblock allocation must happen from the scratch regions. Later, we may want to perform another KHO kexec. For that, we reuse the same scratch regions. To ensure that no eventually handed over data gets allocated inside a scratch region, we flip the semantics of the scratch region with memblock_clear_scratch_only(): After that call, no allocations may happen from scratch memblock regions. We will lift that restriction in the next patch. Link: https://lkml.kernel.org/r/20250411053745.1817356-3-changyuanl@google.com Signed-off-by: Alexander Graf Co-developed-by: Mike Rapoport (Microsoft) Signed-off-by: Mike Rapoport (Microsoft) Signed-off-by: Changyuan Lyu Cc: Andy Lutomirski Cc: Anthony Yznaga Cc: Arnd Bergmann Cc: Ashish Kalra Cc: Ben Herrenschmidt Cc: Borislav Betkov Cc: Catalin Marinas Cc: David Woodhouse Cc: Eric Biederman Cc: "H. Peter Anvin" Cc: Ingo Molnar Cc: James Gowans Cc: Jason Gunthorpe Cc: Jonathan Corbet Cc: Krzysztof Kozlowski Cc: Mark Rutland Cc: Paolo Bonzini Cc: Pasha Tatashin Cc: Peter Zijlstra Cc: Pratyush Yadav Cc: Rob Herring Cc: Saravana Kannan Cc: Stanislav Kinsburskii Cc: Steven Rostedt Cc: Thomas Gleinxer Cc: Thomas Lendacky Cc: Will Deacon Signed-off-by: Andrew Morton --- include/linux/memblock.h | 20 ++++++++++++ mm/Kconfig | 4 ++ mm/memblock.c | 61 +++++++++++++++++++++++++++++++++++++ 3 files changed, 85 insertions(+) --- a/include/linux/memblock.h~memblock-add-support-for-scratch-memory +++ a/include/linux/memblock.h @@ -45,6 +45,11 @@ extern unsigned long long max_possible_p * @MEMBLOCK_RSRV_KERN: memory region that is reserved for kernel use, * either explictitly with memblock_reserve_kern() or via memblock * allocation APIs. All memblock allocations set this flag. + * @MEMBLOCK_KHO_SCRATCH: memory region that kexec can pass to the next + * kernel in handover mode. During early boot, we do not know about all + * memory reservations yet, so we get scratch memory from the previous + * kernel that we know is good to use. It is the only memory that + * allocations may happen from in this phase. */ enum memblock_flags { MEMBLOCK_NONE = 0x0, /* No special request */ @@ -54,6 +59,7 @@ enum memblock_flags { MEMBLOCK_DRIVER_MANAGED = 0x8, /* always detected via a driver */ MEMBLOCK_RSRV_NOINIT = 0x10, /* don't initialize struct pages */ MEMBLOCK_RSRV_KERN = 0x20, /* memory reserved for kernel use */ + MEMBLOCK_KHO_SCRATCH = 0x40, /* scratch memory for kexec handover */ }; /** @@ -148,6 +154,8 @@ int memblock_mark_mirror(phys_addr_t bas int memblock_mark_nomap(phys_addr_t base, phys_addr_t size); int memblock_clear_nomap(phys_addr_t base, phys_addr_t size); int memblock_reserved_mark_noinit(phys_addr_t base, phys_addr_t size); +int memblock_mark_kho_scratch(phys_addr_t base, phys_addr_t size); +int memblock_clear_kho_scratch(phys_addr_t base, phys_addr_t size); void memblock_free(void *ptr, size_t size); void reset_all_zones_managed_pages(void); @@ -291,6 +299,11 @@ static inline bool memblock_is_driver_ma return m->flags & MEMBLOCK_DRIVER_MANAGED; } +static inline bool memblock_is_kho_scratch(struct memblock_region *m) +{ + return m->flags & MEMBLOCK_KHO_SCRATCH; +} + int memblock_search_pfn_nid(unsigned long pfn, unsigned long *start_pfn, unsigned long *end_pfn); void __next_mem_pfn_range(int *idx, int nid, unsigned long *out_start_pfn, @@ -619,5 +632,12 @@ static inline void early_memtest(phys_ad static inline void memtest_report_meminfo(struct seq_file *m) { } #endif +#ifdef CONFIG_MEMBLOCK_KHO_SCRATCH +void memblock_set_kho_scratch_only(void); +void memblock_clear_kho_scratch_only(void); +#else +static inline void memblock_set_kho_scratch_only(void) { } +static inline void memblock_clear_kho_scratch_only(void) { } +#endif #endif /* _LINUX_MEMBLOCK_H */ --- a/mm/Kconfig~memblock-add-support-for-scratch-memory +++ a/mm/Kconfig @@ -469,6 +469,10 @@ config HAVE_GUP_FAST depends on MMU bool +# Enable memblock support for scratch memory which is needed for kexec handover +config MEMBLOCK_KHO_SCRATCH + bool + # Don't discard allocated memory used to track "memory" and "reserved" memblocks # after early boot, so it can still be used to test for validity of memory. # Also, memblocks are updated with memory hot(un)plug. --- a/mm/memblock.c~memblock-add-support-for-scratch-memory +++ a/mm/memblock.c @@ -107,6 +107,13 @@ unsigned long min_low_pfn; unsigned long max_pfn; unsigned long long max_possible_pfn; +#ifdef CONFIG_MEMBLOCK_KHO_SCRATCH +/* When set to true, only allocate from MEMBLOCK_KHO_SCRATCH ranges */ +static bool kho_scratch_only; +#else +#define kho_scratch_only false +#endif + static struct memblock_region memblock_memory_init_regions[INIT_MEMBLOCK_MEMORY_REGIONS] __initdata_memblock; static struct memblock_region memblock_reserved_init_regions[INIT_MEMBLOCK_RESERVED_REGIONS] __initdata_memblock; #ifdef CONFIG_HAVE_MEMBLOCK_PHYS_MAP @@ -166,6 +173,10 @@ bool __init_memblock memblock_has_mirror static enum memblock_flags __init_memblock choose_memblock_flags(void) { + /* skip non-scratch memory for kho early boot allocations */ + if (kho_scratch_only) + return MEMBLOCK_KHO_SCRATCH; + return system_has_some_mirror ? MEMBLOCK_MIRROR : MEMBLOCK_NONE; } @@ -925,6 +936,18 @@ int __init_memblock memblock_physmem_add } #endif +#ifdef CONFIG_MEMBLOCK_KHO_SCRATCH +__init_memblock void memblock_set_kho_scratch_only(void) +{ + kho_scratch_only = true; +} + +__init_memblock void memblock_clear_kho_scratch_only(void) +{ + kho_scratch_only = false; +} +#endif + /** * memblock_setclr_flag - set or clear flag for a memory region * @type: memblock type to set/clear flag for @@ -1050,6 +1073,36 @@ int __init_memblock memblock_reserved_ma MEMBLOCK_RSRV_NOINIT); } +/** + * memblock_mark_kho_scratch - Mark a memory region as MEMBLOCK_KHO_SCRATCH. + * @base: the base phys addr of the region + * @size: the size of the region + * + * Only memory regions marked with %MEMBLOCK_KHO_SCRATCH will be considered + * for allocations during early boot with kexec handover. + * + * Return: 0 on success, -errno on failure. + */ +int __init_memblock memblock_mark_kho_scratch(phys_addr_t base, phys_addr_t size) +{ + return memblock_setclr_flag(&memblock.memory, base, size, 1, + MEMBLOCK_KHO_SCRATCH); +} + +/** + * memblock_clear_kho_scratch - Clear MEMBLOCK_KHO_SCRATCH flag for a + * specified region. + * @base: the base phys addr of the region + * @size: the size of the region + * + * Return: 0 on success, -errno on failure. + */ +int __init_memblock memblock_clear_kho_scratch(phys_addr_t base, phys_addr_t size) +{ + return memblock_setclr_flag(&memblock.memory, base, size, 0, + MEMBLOCK_KHO_SCRATCH); +} + static bool should_skip_region(struct memblock_type *type, struct memblock_region *m, int nid, int flags) @@ -1081,6 +1134,13 @@ static bool should_skip_region(struct me if (!(flags & MEMBLOCK_DRIVER_MANAGED) && memblock_is_driver_managed(m)) return true; + /* + * In early alloc during kexec handover, we can only consider + * MEMBLOCK_KHO_SCRATCH regions for the allocations + */ + if ((flags & MEMBLOCK_KHO_SCRATCH) && !memblock_is_kho_scratch(m)) + return true; + return false; } @@ -2465,6 +2525,7 @@ static const char * const flagname[] = { [ilog2(MEMBLOCK_DRIVER_MANAGED)] = "DRV_MNG", [ilog2(MEMBLOCK_RSRV_NOINIT)] = "RSV_NIT", [ilog2(MEMBLOCK_RSRV_KERN)] = "RSV_KERN", + [ilog2(MEMBLOCK_KHO_SCRATCH)] = "KHO_SCRATCH", }; static int memblock_debug_show(struct seq_file *m, void *private) _ Patches currently in -mm which might be from graf@amazon.com are memblock-add-support-for-scratch-memory.patch kexec-add-kexec-handover-kho-generation-helpers.patch kexec-add-kho-parsing-support.patch kexec-add-kho-support-to-kexec-file-loads.patch kexec-add-config-option-for-kho.patch arm64-add-kho-support.patch x86-add-kho-support.patch memblock-add-kho-support-for-reserve_mem.patch documentation-add-documentation-for-kho.patch