arm64: errata: Add detection for TRBE write to out-of-range

Arm Neoverse-N2 and Cortex-A710 cores are affected by an erratum where
the trbe, under some circumstances, might write upto 64bytes to an
address after the Limit as programmed by the TRBLIMITR_EL1.LIMIT.
This might -
  - Corrupt a page in the ring buffer, which may corrupt trace from a
    previous session, consumed by userspace.
  - Hit the guard page at the end of the vmalloc area and raise a fault.

To keep the handling simpler, we always leave the last page from the
range, which TRBE is allowed to write. This can be achieved by ensuring
that we always have more than a PAGE worth space in the range, while
calculating the LIMIT for TRBE. And then the LIMIT pointer can be
adjusted to leave the PAGE (TRBLIMITR.LIMIT -= PAGE_SIZE), out of the
TRBE range while enabling it. This makes sure that the TRBE will only
write to an area within its allowed limit (i.e, [head-head+size]) and
we do not have to handle address faults within the driver.

Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Mike Leach <mike.leach@linaro.org>
Cc: Leo Yan <leo.yan@linaro.org>
Cc: Will Deacon <will@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Reviewed-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20211019163153.3692640-5-suzuki.poulose@arm.com
Signed-off-by: Will Deacon <will@kernel.org>

diff --git a/Documentation/arm64/silicon-errata.rst b/Documentation/arm64/silicon-errata.rst
index 569a92411dcd3e0c7a1699f60acf1cd1f07baf77..5342e895fb604bfdfc0bead2e30283e5aec2075f 100644 (file)
--- a/Documentation/arm64/silicon-errata.rst
+++ b/Documentation/arm64/silicon-errata.rst
@@ -96,6 +96,8 @@ stable kernels.
 +----------------+-----------------+-----------------+-----------------------------+
 | ARM            | Cortex-A710     | #2054223        | ARM64_ERRATUM_2054223       |
 +----------------+-----------------+-----------------+-----------------------------+
+| ARM            | Cortex-A710     | #2224489        | ARM64_ERRATUM_2224489       |
++----------------+-----------------+-----------------+-----------------------------+
 | ARM            | Neoverse-N1     | #1188873,1418040| ARM64_ERRATUM_1418040       |
 +----------------+-----------------+-----------------+-----------------------------+
 | ARM            | Neoverse-N1     | #1349291        | N/A                         |
@@ -106,6 +108,8 @@ stable kernels.
 +----------------+-----------------+-----------------+-----------------------------+
 | ARM            | Neoverse-N2     | #2067961        | ARM64_ERRATUM_2067961       |
 +----------------+-----------------+-----------------+-----------------------------+
+| ARM            | Neoverse-N2     | #2253138        | ARM64_ERRATUM_2253138       |
++----------------+-----------------+-----------------+-----------------------------+
 | ARM            | MMU-500         | #841119,826419  | N/A                         |
 +----------------+-----------------+-----------------+-----------------------------+
 +----------------+-----------------+-----------------+-----------------------------+

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index ec3bb346957f484771786af28007e6c3284c684a..a500af15ebd59db3bd01c40d882d68df95f789bf 100644 (file)
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -740,6 +740,47 @@ config ARM64_ERRATUM_2067961
 
          If unsure, say Y.
 
+config ARM64_WORKAROUND_TRBE_WRITE_OUT_OF_RANGE
+       bool
+
+config ARM64_ERRATUM_2253138
+       bool "Neoverse-N2: 2253138: workaround TRBE writing to address out-of-range"
+       depends on COMPILE_TEST # Until the CoreSight TRBE driver changes are in
+       depends on CORESIGHT_TRBE
+       default y
+       select ARM64_WORKAROUND_TRBE_WRITE_OUT_OF_RANGE
+       help
+         This option adds the workaround for ARM Neoverse-N2 erratum 2253138.
+
+         Affected Neoverse-N2 cores might write to an out-of-range address, not reserved
+         for TRBE. Under some conditions, the TRBE might generate a write to the next
+         virtually addressed page following the last page of the TRBE address space
+         (i.e., the TRBLIMITR_EL1.LIMIT), instead of wrapping around to the base.
+
+         Work around this in the driver by always making sure that there is a
+         page beyond the TRBLIMITR_EL1.LIMIT, within the space allowed for the TRBE.
+
+         If unsure, say Y.
+
+config ARM64_ERRATUM_2224489
+       bool "Cortex-A710: 2224489: workaround TRBE writing to address out-of-range"
+       depends on COMPILE_TEST # Until the CoreSight TRBE driver changes are in
+       depends on CORESIGHT_TRBE
+       default y
+       select ARM64_WORKAROUND_TRBE_WRITE_OUT_OF_RANGE
+       help
+         This option adds the workaround for ARM Cortex-A710 erratum 2224489.
+
+         Affected Cortex-A710 cores might write to an out-of-range address, not reserved
+         for TRBE. Under some conditions, the TRBE might generate a write to the next
+         virtually addressed page following the last page of the TRBE address space
+         (i.e., the TRBLIMITR_EL1.LIMIT), instead of wrapping around to the base.
+
+         Work around this in the driver by always making sure that there is a
+         page beyond the TRBLIMITR_EL1.LIMIT, within the space allowed for the TRBE.
+
+         If unsure, say Y.
+
 config CAVIUM_ERRATUM_22375
        bool "Cavium erratum 22375, 24313"
        default y

diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
index aaa66c9eee242a4f73e16f551420c25796670210..9e1c1aef9ebd64ff4a83c660172e6d94d1c58cc5 100644 (file)
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -364,6 +364,18 @@ static const struct midr_range tsb_flush_fail_cpus[] = {
 };
 #endif /* CONFIG_ARM64_WORKAROUND_TSB_FLUSH_FAILURE */
 
+#ifdef CONFIG_ARM64_WORKAROUND_TRBE_WRITE_OUT_OF_RANGE
+static struct midr_range trbe_write_out_of_range_cpus[] = {
+#ifdef CONFIG_ARM64_ERRATUM_2253138
+       MIDR_ALL_VERSIONS(MIDR_NEOVERSE_N2),
+#endif
+#ifdef CONFIG_ARM64_ERRATUM_2224489
+       MIDR_ALL_VERSIONS(MIDR_CORTEX_A710),
+#endif
+       {},
+};
+#endif /* CONFIG_ARM64_WORKAROUND_TRBE_WRITE_OUT_OF_RANGE */
+
 const struct arm64_cpu_capabilities arm64_errata[] = {
 #ifdef CONFIG_ARM64_WORKAROUND_CLEAN_CACHE
        {
@@ -577,6 +589,14 @@ const struct arm64_cpu_capabilities arm64_errata[] = {
                .capability = ARM64_WORKAROUND_TSB_FLUSH_FAILURE,
                ERRATA_MIDR_RANGE_LIST(tsb_flush_fail_cpus),
        },
+#endif
+#ifdef CONFIG_ARM64_WORKAROUND_TRBE_WRITE_OUT_OF_RANGE
+       {
+               .desc = "ARM erratum 2253138 or 2224489",
+               .capability = ARM64_WORKAROUND_TRBE_WRITE_OUT_OF_RANGE,
+               .type = ARM64_CPUCAP_WEAK_LOCAL_CPU_FEATURE,
+               CAP_MIDR_RANGE_LIST(trbe_write_out_of_range_cpus),
+       },
 #endif
        {
        }

diff --git a/arch/arm64/tools/cpucaps b/arch/arm64/tools/cpucaps
index 2102e15af43db07c8044f7a77461e350ece45d37..90628638e0f994ff453e8bc1fa57a5c091b27b7f 100644 (file)
--- a/arch/arm64/tools/cpucaps
+++ b/arch/arm64/tools/cpucaps
@@ -55,6 +55,7 @@ WORKAROUND_1508412
 WORKAROUND_1542419
 WORKAROUND_TRBE_OVERWRITE_FILL_MODE
 WORKAROUND_TSB_FLUSH_FAILURE
+WORKAROUND_TRBE_WRITE_OUT_OF_RANGE
 WORKAROUND_CAVIUM_23154
 WORKAROUND_CAVIUM_27456
 WORKAROUND_CAVIUM_30115