arm64: erratum: Work around Falkor erratum #E1003 in trampoline code

We rely on an atomic swizzling of TTBR1 when transitioning from the entry
trampoline to the kernel proper on an exception. We can't rely on this
atomicity in the face of Falkor erratum #E1003, so on affected cores we
can issue a TLB invalidation to invalidate the walk cache prior to
jumping into the kernel. There is still the possibility of a TLB conflict
here due to conflicting walk cache entries prior to the invalidation, but
this doesn't appear to be the case on these CPUs in practice.

Reviewed-by: Mark Rutland <mark.rutland@arm.com>
Tested-by: Laura Abbott <labbott@redhat.com>
Tested-by: Shanker Donthineni <shankerd@codeaurora.org>
Signed-off-by: Will Deacon <will.deacon@arm.com>

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index a93339f5178f2eff247144eb9244c077225094bc..fdcc7b9bb15dd4e4997c9f3a1ce4054571c3b8f2 100644 (file)
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -522,20 +522,13 @@ config CAVIUM_ERRATUM_30115
 config QCOM_FALKOR_ERRATUM_1003
        bool "Falkor E1003: Incorrect translation due to ASID change"
        default y
-       select ARM64_PAN if ARM64_SW_TTBR0_PAN
        help
          On Falkor v1, an incorrect ASID may be cached in the TLB when ASID
-         and BADDR are changed together in TTBRx_EL1. The workaround for this
-         issue is to use a reserved ASID in cpu_do_switch_mm() before
-         switching to the new ASID. Saying Y here selects ARM64_PAN if
-         ARM64_SW_TTBR0_PAN is selected. This is done because implementing and
-         maintaining the E1003 workaround in the software PAN emulation code
-         would be an unnecessary complication. The affected Falkor v1 CPU
-         implements ARMv8.1 hardware PAN support and using hardware PAN
-         support versus software PAN emulation is mutually exclusive at
-         runtime.
-
-         If unsure, say Y.
+         and BADDR are changed together in TTBRx_EL1. Since we keep the ASID
+         in TTBR1_EL1, this situation only occurs in the entry trampoline and
+         then only for entries in the walk cache, since the leaf translation
+         is unchanged. Work around the erratum by invalidating the walk cache
+         entries for the trampoline before entering the kernel proper.
 
 config QCOM_FALKOR_ERRATUM_1009
        bool "Falkor E1009: Prematurely complete a DSB after a TLBI"

diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index 39e3873b8d5affeeca9e3f4307a5403502ae4182..ce56592b5f7038a3140c2467a9e2e2bd7a713c21 100644 (file)
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S
@@ -989,6 +989,18 @@ __ni_sys_trace:
        sub     \tmp, \tmp, #(SWAPPER_DIR_SIZE + RESERVED_TTBR0_SIZE)
        bic     \tmp, \tmp, #USER_ASID_FLAG
        msr     ttbr1_el1, \tmp
+#ifdef CONFIG_QCOM_FALKOR_ERRATUM_1003
+alternative_if ARM64_WORKAROUND_QCOM_FALKOR_E1003
+       /* ASID already in \tmp[63:48] */
+       movk    \tmp, #:abs_g2_nc:(TRAMP_VALIAS >> 12)
+       movk    \tmp, #:abs_g1_nc:(TRAMP_VALIAS >> 12)
+       /* 2MB boundary containing the vectors, so we nobble the walk cache */
+       movk    \tmp, #:abs_g0_nc:((TRAMP_VALIAS & ~(SZ_2M - 1)) >> 12)
+       isb
+       tlbi    vae1, \tmp
+       dsb     nsh
+alternative_else_nop_endif
+#endif /* CONFIG_QCOM_FALKOR_ERRATUM_1003 */
        .endm
 
        .macro tramp_unmap_kernel, tmp