From 5043694eb8270a19040fb798f6d6f1dbd86c7a3c Mon Sep 17 00:00:00 2001 From: Dave Martin Date: Fri, 23 Mar 2018 18:08:31 +0000 Subject: [PATCH] arm64/sve: Document firmware support requirements in Kconfig Use of SVE by EL2 and below requires explicit support in the firmware. There is no means to hide the presence of SVE from EL2, so a kernel configured with CONFIG_ARM64_SVE=y will typically not work correctly on SVE capable hardware unless the firmware does include the appropriate support. This is not expected to pose a problem in the wild, since platform integrators are responsible for ensuring that they ship up-to-date firmware to support their hardware. However, developers may hit the issue when using mismatched compoments. In order to draw attention to the issue and how to solve it, this patch adds some Kconfig text giving a brief explanation and details of compatible firmware versions. Signed-off-by: Dave Martin Acked-by: Catalin Marinas Signed-off-by: Will Deacon --- arch/arm64/Kconfig | 17 +++++++++++++++++ 1 file changed, 17 insertions(+) diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 0f350b80aa84..a6688fcf3dc6 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -1105,6 +1105,23 @@ config ARM64_SVE To enable use of this extension on CPUs that implement it, say Y. + Note that for architectural reasons, firmware _must_ implement SVE + support when running on SVE capable hardware. The required support + is present in: + + * version 1.5 and later of the ARM Trusted Firmware + * the AArch64 boot wrapper since commit 5e1261e08abf + ("bootwrapper: SVE: Enable SVE for EL2 and below"). + + For other firmware implementations, consult the firmware documentation + or vendor. + + If you need the kernel to boot on SVE-capable hardware with broken + firmware, you may need to say N here until you get your firmware + fixed. Otherwise, you may experience firmware panics or lockups when + booting the kernel. If unsure and you are not observing these + symptoms, you should assume that it is safe to say Y. + config ARM64_MODULE_PLTS bool select HAVE_MOD_ARCH_SPECIFIC