6.4-stable review patch. If anyone has any objections, please let me know.
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From: Alexandre Ghiti alexghiti@rivosinc.com
commit a50420c79731fc5cf27ad43719c1091e842a2606 upstream.
flush_cache_vmap() must be called after new vmalloc mappings are installed in the page table in order to allow architectures to make sure the new mapping is visible.
It could lead to a panic since on some architectures (like powerpc), the page table walker could see the wrong pte value and trigger a spurious page fault that can not be resolved (see commit f1cb8f9beba8 ("powerpc/64s/radix: avoid ptesync after set_pte and ptep_set_access_flags")).
But actually the patch is aiming at riscv: the riscv specification allows the caching of invalid entries in the TLB, and since we recently removed the vmalloc page fault handling, we now need to emit a tlb shootdown whenever a new vmalloc mapping is emitted (https://lore.kernel.org/linux-riscv/20230725132246.817726-1-alexghiti@rivosi...). That's a temporary solution, there are ways to avoid that :)
Link: https://lkml.kernel.org/r/20230809164633.1556126-1-alexghiti@rivosinc.com Fixes: 3e9a9e256b1e ("mm: add a vmap_pfn function") Reported-by: Dylan Jhong dylan@andestech.com Closes: https://lore.kernel.org/linux-riscv/ZMytNY2J8iyjbPPy@atctrx.andestech.com/ Signed-off-by: Alexandre Ghiti alexghiti@rivosinc.com Reviewed-by: Christoph Hellwig hch@lst.de Reviewed-by: Palmer Dabbelt palmer@rivosinc.com Acked-by: Palmer Dabbelt palmer@rivosinc.com Reviewed-by: Dylan Jhong dylan@andestech.com Cc: stable@vger.kernel.org Signed-off-by: Andrew Morton akpm@linux-foundation.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- mm/vmalloc.c | 4 ++++ 1 file changed, 4 insertions(+)
--- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -2929,6 +2929,10 @@ void *vmap_pfn(unsigned long *pfns, unsi free_vm_area(area); return NULL; } + + flush_cache_vmap((unsigned long)area->addr, + (unsigned long)area->addr + count * PAGE_SIZE); + return area->addr; } EXPORT_SYMBOL_GPL(vmap_pfn);