From 754a2b7a092d3cf81767f1b5a6ab61531792e45f Mon Sep 17 00:00:00 2001 From: Achin Gupta Date: Wed, 25 Jun 2014 19:26:22 +0100 Subject: [PATCH] Remove coherent stack usage from the cold boot path This patch reworks the cold boot path across the BL1, BL2, BL3-1 and BL3-2 boot loader stages to not use stacks allocated in coherent memory for early platform setup and enabling the MMU. Stacks allocated in normal memory are used instead. Attributes for stack memory change from nGnRnE when the MMU is disabled to Normal WBWA Inner-shareable when the MMU and data cache are enabled. It is possible for the CPU to read stale stack memory after the MMU is enabled from another CPUs cache. Hence, it is unsafe to turn on the MMU and data cache while using normal stacks when multiple CPUs are a part of the same coherency domain. It is safe to do so in the cold boot path as only the primary cpu executes it. The secondary cpus are in a quiescent state. This patch does not remove the allocation of coherent stack memory. That is done in a subsequent patch. Change-Id: I12c80b7c7ab23506d425c5b3a8a7de693498f830 --- bl1/aarch64/bl1_entrypoint.S | 22 ++++++++-------------- bl2/aarch64/bl2_entrypoint.S | 17 ++++++----------- bl31/aarch64/bl31_entrypoint.S | 17 ++++++----------- bl32/tsp/aarch64/tsp_entrypoint.S | 17 ++++++----------- 4 files changed, 26 insertions(+), 47 deletions(-) diff --git a/bl1/aarch64/bl1_entrypoint.S b/bl1/aarch64/bl1_entrypoint.S index 50cfae65c..ac6d91331 100644 --- a/bl1/aarch64/bl1_entrypoint.S +++ b/bl1/aarch64/bl1_entrypoint.S @@ -130,14 +130,16 @@ func bl1_entrypoint ldr x2, =__DATA_SIZE__ bl memcpy16 - /* --------------------------------------------- - * Give ourselves a small coherent stack to - * ease the pain of initializing the MMU and - * CCI in assembler - * --------------------------------------------- + /* -------------------------------------------- + * Allocate a stack whose memory will be marked + * as Normal-IS-WBWA when the MMU is enabled. + * There is no risk of reading stale stack + * memory after enabling the MMU as only the + * primary cpu is running at the moment. + * -------------------------------------------- */ mrs x0, mpidr_el1 - bl platform_set_coherent_stack + bl platform_set_stack /* --------------------------------------------- * Architectural init. can be generic e.g. @@ -150,14 +152,6 @@ func bl1_entrypoint bl bl1_early_platform_setup bl bl1_plat_arch_setup - /* --------------------------------------------- - * Give ourselves a stack allocated in Normal - * -IS-WBWA memory - * --------------------------------------------- - */ - mrs x0, mpidr_el1 - bl platform_set_stack - /* -------------------------------------------------- * Initialize platform and jump to our c-entry point * for this type of reset. Panic if it returns diff --git a/bl2/aarch64/bl2_entrypoint.S b/bl2/aarch64/bl2_entrypoint.S index 09eadff2e..c615baf60 100644 --- a/bl2/aarch64/bl2_entrypoint.S +++ b/bl2/aarch64/bl2_entrypoint.S @@ -96,12 +96,15 @@ func bl2_entrypoint bl zeromem16 /* -------------------------------------------- - * Give ourselves a small coherent stack to - * ease the pain of initializing the MMU + * Allocate a stack whose memory will be marked + * as Normal-IS-WBWA when the MMU is enabled. + * There is no risk of reading stale stack + * memory after enabling the MMU as only the + * primary cpu is running at the moment. * -------------------------------------------- */ mrs x0, mpidr_el1 - bl platform_set_coherent_stack + bl platform_set_stack /* --------------------------------------------- * Perform early platform setup & platform @@ -112,14 +115,6 @@ func bl2_entrypoint bl bl2_early_platform_setup bl bl2_plat_arch_setup - /* --------------------------------------------- - * Give ourselves a stack allocated in Normal - * -IS-WBWA memory - * --------------------------------------------- - */ - mrs x0, mpidr_el1 - bl platform_set_stack - /* --------------------------------------------- * Jump to main function. * --------------------------------------------- diff --git a/bl31/aarch64/bl31_entrypoint.S b/bl31/aarch64/bl31_entrypoint.S index 6e48e3138..102398377 100644 --- a/bl31/aarch64/bl31_entrypoint.S +++ b/bl31/aarch64/bl31_entrypoint.S @@ -152,12 +152,15 @@ func bl31_entrypoint msr spsel, #0 /* -------------------------------------------- - * Give ourselves a small coherent stack to - * ease the pain of initializing the MMU + * Allocate a stack whose memory will be marked + * as Normal-IS-WBWA when the MMU is enabled. + * There is no risk of reading stale stack + * memory after enabling the MMU as only the + * primary cpu is running at the moment. * -------------------------------------------- */ mrs x0, mpidr_el1 - bl platform_set_coherent_stack + bl platform_set_stack /* --------------------------------------------- * Perform platform specific early arch. setup @@ -174,14 +177,6 @@ func bl31_entrypoint bl bl31_early_platform_setup bl bl31_plat_arch_setup - /* --------------------------------------------- - * Give ourselves a stack allocated in Normal - * -IS-WBWA memory - * --------------------------------------------- - */ - mrs x0, mpidr_el1 - bl platform_set_stack - /* --------------------------------------------- * Jump to main function. * --------------------------------------------- diff --git a/bl32/tsp/aarch64/tsp_entrypoint.S b/bl32/tsp/aarch64/tsp_entrypoint.S index 479ca59b3..c5ec9e34a 100644 --- a/bl32/tsp/aarch64/tsp_entrypoint.S +++ b/bl32/tsp/aarch64/tsp_entrypoint.S @@ -111,12 +111,15 @@ func tsp_entrypoint bl zeromem16 /* -------------------------------------------- - * Give ourselves a small coherent stack to - * ease the pain of initializing the MMU + * Allocate a stack whose memory will be marked + * as Normal-IS-WBWA when the MMU is enabled. + * There is no risk of reading stale stack + * memory after enabling the MMU as only the + * primary cpu is running at the moment. * -------------------------------------------- */ mrs x0, mpidr_el1 - bl platform_set_coherent_stack + bl platform_set_stack /* --------------------------------------------- * Perform early platform setup & platform @@ -126,14 +129,6 @@ func tsp_entrypoint bl bl32_early_platform_setup bl bl32_plat_arch_setup - /* --------------------------------------------- - * Give ourselves a stack allocated in Normal - * -IS-WBWA memory - * --------------------------------------------- - */ - mrs x0, mpidr_el1 - bl platform_set_stack - /* --------------------------------------------- * Jump to main function. * ---------------------------------------------