From 12dd4a0848c460f5c133099d0c585319a434e58e Mon Sep 17 00:00:00 2001 From: Nathan Lynch Date: Fri, 10 Feb 2023 12:41:54 -0600 Subject: [PATCH] powerpc/rtas: ensure 4KB alignment for rtas_data_buf [ Upstream commit 836b5b9fcc8e09cea7e8a59a070349a00e818308 ] Some RTAS functions that have work area parameters impose alignment requirements on the work area passed to them by the OS. Examples include: - ibm,configure-connector - ibm,update-nodes - ibm,update-properties 4KB is the greatest alignment required by PAPR for such buffers. rtas_data_buf used to have a __page_aligned attribute in the arch/ppc64 days, but that was changed to __cacheline_aligned for unknown reasons by commit 033ef338b6e0 ("powerpc: Merge rtas.c into arch/powerpc/kernel"). That works out to 128-byte alignment on ppc64, which isn't right. This was found by inspection and I'm not aware of any real problems caused by this. Either current RTAS implementations don't enforce the alignment constraints, or rtas_data_buf is always being placed at a 4KB boundary by accident (or both, perhaps). Use __aligned(SZ_4K) to ensure the rtas_data_buf has alignment appropriate for all users. Signed-off-by: Nathan Lynch Fixes: 033ef338b6e0 ("powerpc: Merge rtas.c into arch/powerpc/kernel") Signed-off-by: Michael Ellerman Link: https://lore.kernel.org/r/20230125-b4-powerpc-rtas-queue-v3-6-26929c8cce78@linux.ibm.com Signed-off-by: Sasha Levin --- arch/powerpc/kernel/rtas.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c index 4da9baa0fbe8c..d01a0ad57e38e 100644 --- a/arch/powerpc/kernel/rtas.c +++ b/arch/powerpc/kernel/rtas.c @@ -70,7 +70,7 @@ EXPORT_SYMBOL(rtas); DEFINE_SPINLOCK(rtas_data_buf_lock); EXPORT_SYMBOL_GPL(rtas_data_buf_lock); -char rtas_data_buf[RTAS_DATA_BUF_SIZE] __cacheline_aligned; +char rtas_data_buf[RTAS_DATA_BUF_SIZE] __aligned(SZ_4K); EXPORT_SYMBOL_GPL(rtas_data_buf); unsigned long rtas_rmo_buf; -- 2.47.3