6.6-stable review patch. If anyone has any objections, please let me know.
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From: Aditya Gupta adityag@linux.ibm.com
[ Upstream commit 36e826b568e412f61d68fedc02a67b4d8b7583cc ]
Since below commit, address mapping for vmemmap has changed for Radix MMU, where address mapping is stored in kernel page table itself, instead of earlier used 'vmemmap_list'.
commit 368a0590d954 ("powerpc/book3s64/vmemmap: switch radix to use a different vmemmap handling function")
Hence with upstream kernel, in case of Radix MMU, makedumpfile fails to do address translation for vmemmap addresses, as it depended on vmemmap_list, which can now be empty.
While fixing the address translation in makedumpfile, it was identified that currently makedumpfile cannot distinguish between Hash MMU and Radix MMU, unless VMLINUX is passed with -x flag to makedumpfile. And hence fails to assign offsets and shifts correctly (such as in L4 to PGDIR offset calculation in makedumpfile).
For getting the MMU, makedumpfile uses `cur_cpu_spec.mmu_features`.
Add `cur_cpu_spec` symbol and offset of `mmu_features` in the `cpu_spec` struct, to VMCOREINFO, so that makedumpfile can assign the offsets correctly, without needing a VMLINUX.
Also, even along with `cur_cpu_spec->mmu_features` makedumpfile has to depend on the 'MMU_FTR_TYPE_RADIX' flag in mmu_features, implying kernel developers need to be cautious of changes to 'MMU_FTR_*' defines.
A more stable approach was suggested in the below thread by contributors: https://lore.kernel.org/linuxppc-dev/20230920105706.853626-1-adityag@linux.i...
The suggestion was to add whether 'RADIX_MMU' is enabled in vmcoreinfo
This patch also implements the suggestion, by adding 'RADIX_MMU' in vmcoreinfo, which makedumpfile can use to get whether the crashed system had RADIX MMU (in which case 'NUMBER(RADIX_MMU)=1') or not (in which case 'NUMBER(RADIX_MMU)=0')
Fixes: 368a0590d954 ("powerpc/book3s64/vmemmap: switch radix to use a different vmemmap handling function") Reported-by: Sachin Sant sachinp@linux.ibm.com Signed-off-by: Aditya Gupta adityag@linux.ibm.com Signed-off-by: Michael Ellerman mpe@ellerman.id.au Link: https://msgid.link/20231023072612.50874-1-adityag@linux.ibm.com Signed-off-by: Sasha Levin sashal@kernel.org --- arch/powerpc/kexec/core.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/arch/powerpc/kexec/core.c b/arch/powerpc/kexec/core.c index de64c79629912..005269ac3244c 100644 --- a/arch/powerpc/kexec/core.c +++ b/arch/powerpc/kexec/core.c @@ -74,6 +74,9 @@ void arch_crash_save_vmcoreinfo(void) VMCOREINFO_STRUCT_SIZE(mmu_psize_def); VMCOREINFO_OFFSET(mmu_psize_def, shift); #endif + VMCOREINFO_SYMBOL(cur_cpu_spec); + VMCOREINFO_OFFSET(cpu_spec, mmu_features); + vmcoreinfo_append_str("NUMBER(RADIX_MMU)=%d\n", early_radix_enabled()); vmcoreinfo_append_str("KERNELOFFSET=%lx\n", kaslr_offset()); }