From mboxrd@z Thu Jan 1 00:00:00 1970 From: bdegraaf@codeaurora.org (Brent DeGraaf) Date: Mon, 19 Sep 2016 13:36:26 -0400 Subject: [RFC] arm64: Ensure proper addressing for ldnp/stnp Message-ID: <1474306586-25118-1-git-send-email-bdegraaf@codeaurora.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org According to section 6.3.8 of the ARM Programmer's Guide, non-temporal loads and stores do not verify that address dependency is met between a load of an address to a register and a subsequent non-temporal load or store using that address on the executing PE. Therefore, context switch code and subroutine calls that use non-temporally accessed addresses as parameters that might depend on a load of an address into an argument register must ensure that ordering requirements are met by introducing a barrier prior to the successive non-temporal access. Add appropriate barriers whereever this specific situation comes into play. Signed-off-by: Brent DeGraaf --- arch/arm64/kernel/entry.S | 1 + arch/arm64/lib/copy_page.S | 2 ++ 2 files changed, 3 insertions(+) diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index 441420c..982c4d3 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -679,6 +679,7 @@ ENTRY(cpu_switch_to) ldp x27, x28, [x8], #16 ldp x29, x9, [x8], #16 ldr lr, [x8] + dmb nshld // Existence of instructions with loose load-use dependencies (e.g. ldnp/stnp) make this barrier necessary mov sp, x9 and x9, x9, #~(THREAD_SIZE - 1) msr sp_el0, x9 diff --git a/arch/arm64/lib/copy_page.S b/arch/arm64/lib/copy_page.S index 4c1e700..21c6892 100644 --- a/arch/arm64/lib/copy_page.S +++ b/arch/arm64/lib/copy_page.S @@ -47,6 +47,8 @@ alternative_endif ldp x14, x15, [x1, #96] ldp x16, x17, [x1, #112] + dmb nshld // In case x0 (for stnp) is dependent on a load + mov x18, #(PAGE_SIZE - 128) add x1, x1, #128 1: -- Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm Technologies, Inc. Qualcomm Technologies, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project.