The patch titled Subject: crash: Fix riscv64 crash memory reserve dead loop has been added to the -mm mm-hotfixes-unstable branch. Its filename is crash-fix-riscv64-crash-memory-reserve-dead-loop.patch

This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches...

This patch will later appear in the mm-hotfixes-unstable 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: Jinjie Ruan ruanjinjie@huawei.com Subject: crash: Fix riscv64 crash memory reserve dead loop Date: Fri, 2 Aug 2024 17:01:05 +0800

On RISCV64 Qemu machine with 512MB memory, cmdline "crashkernel=500M,high" will cause system stall as below:

Zone ranges: DMA32 [mem 0x0000000080000000-0x000000009fffffff] Normal empty Movable zone start for each node Early memory node ranges node 0: [mem 0x0000000080000000-0x000000008005ffff] node 0: [mem 0x0000000080060000-0x000000009fffffff] Initmem setup node 0 [mem 0x0000000080000000-0x000000009fffffff] (stall here)

commit 5d99cadf1568 ("crash: fix x86_32 crash memory reserve dead loop bug") fix this on 32-bit architecture. However, the problem is not completely solved. If `CRASH_ADDR_LOW_MAX = CRASH_ADDR_HIGH_MAX` on 64-bit architecture, for example, when system memory is equal to CRASH_ADDR_LOW_MAX on RISCV64, the following infinite loop will also occur:

-> reserve_crashkernel_generic() and high is true -> alloc at [CRASH_ADDR_LOW_MAX, CRASH_ADDR_HIGH_MAX] fail -> alloc at [0, CRASH_ADDR_LOW_MAX] fail and repeatedly (because CRASH_ADDR_LOW_MAX = CRASH_ADDR_HIGH_MAX).

Before refactor in commit 9c08a2a139fe ("x86: kdump: use generic interface to simplify crashkernel reservation code"), x86 do not try to reserve crash memory at low if it fails to alloc above high 4G. However before refator in commit fdc268232dbba ("arm64: kdump: use generic interface to simplify crashkernel reservation"), arm64 try to reserve crash memory at low if it fails above high 4G. For 64-bit systems, this attempt is less beneficial than the opposite, remove it to fix this bug and align with native x86 implementation.

After this patch, it print: cannot allocate crashkernel (size:0x1f400000)

Link: https://lkml.kernel.org/r/20240802090105.3871929-1-ruanjinjie@huawei.com Fixes: 39365395046f ("riscv: kdump: use generic interface to simplify crashkernel reservation") Signed-off-by: Jinjie Ruan ruanjinjie@huawei.com Acked-by: Baoquan He bhe@redhat.com Cc: Albert Ou aou@eecs.berkeley.edu Cc: Chen Jiahao chenjiahao16@huawei.com Cc: Dave Young dyoung@redhat.com Cc: Palmer Dabbelt palmer@dabbelt.com Cc: Paul Walmsley paul.walmsley@sifive.com Cc: Vivek Goyal vgoyal@redhat.com Cc: Alexandre Ghiti alex@ghiti.fr Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org ---

kernel/crash_reserve.c | 9 --------- 1 file changed, 9 deletions(-)

--- a/kernel/crash_reserve.c~crash-fix-riscv64-crash-memory-reserve-dead-loop +++ a/kernel/crash_reserve.c @@ -416,15 +416,6 @@ retry: goto retry; }

- /* - * For crashkernel=size[KMG],high, if the first attempt was - * for high memory, fall back to low memory. - */ - if (high && search_end == CRASH_ADDR_HIGH_MAX) { - search_end = CRASH_ADDR_LOW_MAX; - search_base = 0; - goto retry; - } pr_warn("cannot allocate crashkernel (size:0x%llx)\n", crash_size); return; _

Patches currently in -mm which might be from ruanjinjie@huawei.com are

crash-fix-riscv64-crash-memory-reserve-dead-loop.patch crash-fix-x86_32-crash-memory-reserve-dead-loop-bug.patch crash-fix-x86_32-crash-memory-reserve-dead-loop.patch arm-use-generic-interface-to-simplify-crashkernel-reservation.patch crash-fix-crash-memory-reserve-exceed-system-memory-bug.patch