arm64: Add software workaround for Falkor erratum 1041

commit 932b50c7c1c65e6f23002e075b97ee083c4a9e71 upstream.

The ARM architecture defines the memory locations that are permitted
to be accessed as the result of a speculative instruction fetch from
an exception level for which all stages of translation are disabled.
Specifically, the core is permitted to speculatively fetch from the
4KB region containing the current program counter 4K and next 4K.

When translation is changed from enabled to disabled for the running
exception level (SCTLR_ELn[M] changed from a value of 1 to 0), the
Falkor core may errantly speculatively access memory locations outside
of the 4KB region permitted by the architecture. The errant memory
access may lead to one of the following unexpected behaviors.

1) A System Error Interrupt (SEI) being raised by the Falkor core due
   to the errant memory access attempting to access a region of memory
   that is protected by a slave-side memory protection unit.
2) Unpredictable device behavior due to a speculative read from device
   memory. This behavior may only occur if the instruction cache is
   disabled prior to or coincident with translation being changed from
   enabled to disabled.

The conditions leading to this erratum will not occur when either of the
following occur:
 1) A higher exception level disables translation of a lower exception level
   (e.g. EL2 changing SCTLR_EL1[M] from a value of 1 to 0).
 2) An exception level disabling its stage-1 translation if its stage-2
    translation is enabled (e.g. EL1 changing SCTLR_EL1[M] from a value of 1
    to 0 when HCR_EL2[VM] has a value of 1).

To avoid the errant behavior, software must execute an ISB immediately
prior to executing the MSR that will change SCTLR_ELn[M] from 1 to 0.

Signed-off-by: Shanker Donthineni <shankerd@codeaurora.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>
Cc: Timur Tabi <timur@codeaurora.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/Documentation/arm64/silicon-errata.txt b/Documentation/arm64/silicon-errata.txt
index 66e8ce14d23d03ab654c0c14699bd7845ad91aa9..704770c0edf2e3a8c938eba5f24d66d4550bbec6 100644 (file)
--- a/Documentation/arm64/silicon-errata.txt
+++ b/Documentation/arm64/silicon-errata.txt
@@ -74,3 +74,4 @@ stable kernels.
 | Qualcomm Tech. | Falkor v1       | E1003           | QCOM_FALKOR_ERRATUM_1003    |
 | Qualcomm Tech. | Falkor v1       | E1009           | QCOM_FALKOR_ERRATUM_1009    |
 | Qualcomm Tech. | QDF2400 ITS     | E0065           | QCOM_QDF2400_ERRATUM_0065   |
+| Qualcomm Tech. | Falkor v{1,2}   | E1041           | QCOM_FALKOR_ERRATUM_1041    |

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 0df64a6a56d4985b9c9da0ea3b9092adddb71194..8f73eaccf50a8aeeeacc2db8bcb40507b41f5f78 100644 (file)
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -539,6 +539,16 @@ config QCOM_QDF2400_ERRATUM_0065
 
          If unsure, say Y.
 
+config QCOM_FALKOR_ERRATUM_E1041
+       bool "Falkor E1041: Speculative instruction fetches might cause errant memory access"
+       default y
+       help
+         Falkor CPU may speculatively fetch instructions from an improper
+         memory location when MMU translation is changed from SCTLR_ELn[M]=1
+         to SCTLR_ELn[M]=0. Prefix an ISB instruction to fix the problem.
+
+         If unsure, say Y.
+
 endmenu
 
 

diff --git a/arch/arm64/include/asm/assembler.h b/arch/arm64/include/asm/assembler.h
index d58a6253c6abc4e8ff04b1d96082d71150006de9..7896728f3b220a2b6ead8494c6e6b398dd66dca2 100644 (file)
--- a/arch/arm64/include/asm/assembler.h
+++ b/arch/arm64/include/asm/assembler.h
@@ -499,4 +499,14 @@ alternative_else_nop_endif
 #endif
        .endm
 
+/**
+ * Errata workaround prior to disable MMU. Insert an ISB immediately prior
+ * to executing the MSR that will change SCTLR_ELn[M] from a value of 1 to 0.
+ */
+       .macro pre_disable_mmu_workaround
+#ifdef CONFIG_QCOM_FALKOR_ERRATUM_E1041
+       isb
+#endif
+       .endm
+
 #endif /* __ASM_ASSEMBLER_H */

diff --git a/arch/arm64/kernel/cpu-reset.S b/arch/arm64/kernel/cpu-reset.S
index 65f42d2574142d4b37bebf49ed1fc3cdccbb56ae..2a752cb2a0f35a82f2a60e744d160af9b5f6c6a1 100644 (file)
--- a/arch/arm64/kernel/cpu-reset.S
+++ b/arch/arm64/kernel/cpu-reset.S
@@ -37,6 +37,7 @@ ENTRY(__cpu_soft_restart)
        mrs     x12, sctlr_el1
        ldr     x13, =SCTLR_ELx_FLAGS
        bic     x12, x12, x13
+       pre_disable_mmu_workaround
        msr     sctlr_el1, x12
        isb
 

diff --git a/arch/arm64/kernel/efi-entry.S b/arch/arm64/kernel/efi-entry.S
index 4e6ad355bd058e6a4ab73a0f94832a7b1fe719a6..6b9736c3fb5630ab31c17b662b5c5cfe2b7d0832 100644 (file)
--- a/arch/arm64/kernel/efi-entry.S
+++ b/arch/arm64/kernel/efi-entry.S
@@ -96,6 +96,7 @@ ENTRY(entry)
        mrs     x0, sctlr_el2
        bic     x0, x0, #1 << 0 // clear SCTLR.M
        bic     x0, x0, #1 << 2 // clear SCTLR.C
+       pre_disable_mmu_workaround
        msr     sctlr_el2, x0
        isb
        b       2f
@@ -103,6 +104,7 @@ ENTRY(entry)
        mrs     x0, sctlr_el1
        bic     x0, x0, #1 << 0 // clear SCTLR.M
        bic     x0, x0, #1 << 2 // clear SCTLR.C
+       pre_disable_mmu_workaround
        msr     sctlr_el1, x0
        isb
 2:

diff --git a/arch/arm64/kernel/head.S b/arch/arm64/kernel/head.S
index 0b243ecaf7ac87faa81fed0a09db996757d71f4e..6657ae4f3c7a39cf141827359d67f72f1baecd51 100644 (file)
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -732,6 +732,7 @@ __primary_switch:
         * to take into account by discarding the current kernel mapping and
         * creating a new one.
         */
+       pre_disable_mmu_workaround
        msr     sctlr_el1, x20                  // disable the MMU
        isb
        bl      __create_page_tables            // recreate kernel mapping

diff --git a/arch/arm64/kernel/relocate_kernel.S b/arch/arm64/kernel/relocate_kernel.S
index ce704a4aeadd438bf637472bb7037b89fba15087..f407e422a7200b86072349cc70e1e6d5e7e1753b 100644 (file)
--- a/arch/arm64/kernel/relocate_kernel.S
+++ b/arch/arm64/kernel/relocate_kernel.S
@@ -45,6 +45,7 @@ ENTRY(arm64_relocate_new_kernel)
        mrs     x0, sctlr_el2
        ldr     x1, =SCTLR_ELx_FLAGS
        bic     x0, x0, x1
+       pre_disable_mmu_workaround
        msr     sctlr_el2, x0
        isb
 1:

diff --git a/arch/arm64/kvm/hyp-init.S b/arch/arm64/kvm/hyp-init.S
index 3f9615582377661a88fab8be6a12365d625d830a..870828c364c508f825eacc1c49c17886dc9c8cb2 100644 (file)
--- a/arch/arm64/kvm/hyp-init.S
+++ b/arch/arm64/kvm/hyp-init.S
@@ -151,6 +151,7 @@ reset:
        mrs     x5, sctlr_el2
        ldr     x6, =SCTLR_ELx_FLAGS
        bic     x5, x5, x6              // Clear SCTL_M and etc
+       pre_disable_mmu_workaround
        msr     sctlr_el2, x5
        isb