From af26d5d45a0be34e79a92e2f69a2d20356a9e60f 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 dbb3d2cc0533 ("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: dbb3d2cc0533 ("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 8e61984b368d1..ee810df7d522d 100644 --- a/arch/powerpc/kernel/rtas.c +++ b/arch/powerpc/kernel/rtas.c @@ -53,7 +53,7 @@ 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; -- 2.39.5