arm64: Add software workaround for Falkor erratum 1041

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>
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>

diff --git a/Documentation/arm64/silicon-errata.txt b/Documentation/arm64/silicon-errata.txt
index b9d93e9..c1d520d 100644 (file)
--- a/Documentation/arm64/silicon-errata.txt
+++ b/Documentation/arm64/silicon-errata.txt
@@ -75,3 +75,4 @@ stable kernels.
 | Qualcomm Tech. | Kryo/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 1d51c8e..b488076 100644 (file)
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -550,7 +550,6 @@ config QCOM_QDF2400_ERRATUM_0065
 
          If unsure, say Y.
 
-
 config SOCIONEXT_SYNQUACER_PREITS
        bool "Socionext Synquacer: Workaround for GICv3 pre-ITS"
        default y
@@ -569,6 +568,17 @@ config HISILICON_ERRATUM_161600802
          a 128kB offset to be applied to the target address in this commands.
 
          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 794fe81..3873dd7 100644 (file)
--- a/arch/arm64/include/asm/assembler.h
+++ b/arch/arm64/include/asm/assembler.h
@@ -523,4 +523,14 @@ alternative_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 65f42d2..2a752cb 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 4e6ad35..6b9736c 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 c3b241b..ba3ab04 100644 (file)
--- a/arch/arm64/kernel/head.S
+++ b/arch/arm64/kernel/head.S
@@ -849,6 +849,7 @@ __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 ce704a4..f407e42 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 8a00de1..e086c6e 100644 (file)
--- a/arch/arm64/kvm/hyp-init.S
+++ b/arch/arm64/kvm/hyp-init.S
@@ -153,6 +153,7 @@ 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