To Jinjie, if you make generic changes that affect other architectures, please either cc the individual lists/maintainers or at least cross-post to linux-arch. I don't follow lkml, there's just too much traffic there. On Fri, Aug 02, 2024 at 06:11:01PM +0800, Baoquan He wrote: > On 08/02/24 at 05:01pm, Jinjie Ruan wrote: > > 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: > > Interesting, I didn't expect risc-v defining them like these. > > #define CRASH_ADDR_LOW_MAX dma32_phys_limit > #define CRASH_ADDR_HIGH_MAX memblock_end_of_DRAM() arm64 defines the high limit as PHYS_MASK+1, it doesn't need to be dynamic and x86 does something similar (SZ_64T). Not sure why the generic code and riscv define it like this. > > -> 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. > > And I don't like the idea crashkernel=,high failure will fallback to > attempt in low area, so this looks good to me. Well, I kind of liked this behaviour. One can specify ,high as a preference rather than forcing a range. The arm64 land has different platforms with some constrained memory layouts. Such fallback works well as a default command line option shipped with distros without having to guess the SoC memory layout. Something like below should fix the issue as well (untested): diff --git a/kernel/crash_reserve.c b/kernel/crash_reserve.c index d3b4cd12bdd1..ae92d6745ef4 100644 --- a/kernel/crash_reserve.c +++ b/kernel/crash_reserve.c @@ -420,7 +420,8 @@ void __init reserve_crashkernel_generic(char *cmdline, * 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) { + if (high && search_end == CRASH_ADDR_HIGH_MAX && + CRASH_ADDR_LOW_MAX < CRASH_ADDR_HIGH_MAX) { search_end = CRASH_ADDR_LOW_MAX; search_base = 0; goto retry; -- Catalin _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec