6.6-stable review patch. If anyone has any objections, please let me know.
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From: Heiko Carstens hca@linux.ibm.com
[ Upstream commit 64e2f60f355e556337fcffe80b9bcff1b22c9c42 ]
As reported by Luiz Capitulino enabling HVO on s390 leads to reproducible crashes. The problem is that kernel page tables are modified without flushing corresponding TLB entries.
Even if it looks like the empty flush_tlb_all() implementation on s390 is the problem, it is actually a different problem: on s390 it is not allowed to replace an active/valid page table entry with another valid page table entry without the detour over an invalid entry. A direct replacement may lead to random crashes and/or data corruption.
In order to invalidate an entry special instructions have to be used (e.g. ipte or idte). Alternatively there are also special instructions available which allow to replace a valid entry with a different valid entry (e.g. crdte or cspg).
Given that the HVO code currently does not provide the hooks to allow for an implementation which is compliant with the s390 architecture requirements, disable ARCH_WANT_OPTIMIZE_HUGETLB_VMEMMAP again, which is basically a revert of the original patch which enabled it.
Reported-by: Luiz Capitulino luizcap@redhat.com Closes: https://lore.kernel.org/all/20251028153930.37107-1-luizcap@redhat.com/ Fixes: 00a34d5a99c0 ("s390: select ARCH_WANT_HUGETLB_PAGE_OPTIMIZE_VMEMMAP") Cc: stable@vger.kernel.org Tested-by: Luiz Capitulino luizcap@redhat.com Reviewed-by: Gerald Schaefer gerald.schaefer@linux.ibm.com Reviewed-by: David Hildenbrand david@redhat.com [ Adjust context ] Signed-off-by: Heiko Carstens hca@linux.ibm.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- arch/s390/Kconfig | 1 - 1 file changed, 1 deletion(-)
--- a/arch/s390/Kconfig +++ b/arch/s390/Kconfig @@ -128,7 +128,6 @@ config S390 select ARCH_WANT_DEFAULT_BPF_JIT select ARCH_WANT_IPC_PARSE_VERSION select ARCH_WANT_KERNEL_PMD_MKWRITE - select ARCH_WANT_OPTIMIZE_HUGETLB_VMEMMAP select BUILDTIME_TABLE_SORT select CLONE_BACKWARDS2 select DMA_OPS if PCI