On Thu, Jul 20, 2023 at 04:23:32PM -0700, Easwar Hariharan wrote:

From: Suzuki K Poulose <suzuki.poulose@arm.com>

commit fa82d0b4b833790ac4572377fb777dcea24a9d69 upstream

Arm Neoverse-N2 (#2067961) and Cortex-A710 (#2054223) suffers
from errata, where a TSB (trace synchronization barrier)
fails to flush the trace data completely, when executed from
a trace prohibited region. In Linux we always execute it
after we have moved the PE to trace prohibited region. So,
we can apply the workaround every time a TSB is executed.

The work around is to issue two TSB consecutively.

NOTE: This errata is defined as LOCAL_CPU_ERRATUM, implying
that a late CPU could be blocked from booting if it is the
first CPU that requires the workaround. This is because we
do not allow setting a cpu_hwcaps after the SMP boot. The
other alternative is to use "this_cpu_has_cap()" instead
of the faster system wide check, which may be a bit of an
overhead, given we may have to do this in nvhe KVM host
before a guest entry.

Cc: Will Deacon <will@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Mike Leach <redacted>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Anshuman Khandual <redacted>
Cc: Marc Zyngier <maz@kernel.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Reviewed-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Reviewed-by: Anshuman Khandual <redacted>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20211019163153.3692640-4-suzuki.poulose@arm.com (local)
Signed-off-by: Will Deacon <will@kernel.org>
---
 Documentation/arm64/silicon-errata.rst |  4 ++++
 arch/arm64/Kconfig                     | 33 ++++++++++++++++++++++++++
 arch/arm64/include/asm/barrier.h       | 16 ++++++++++++-
 arch/arm64/kernel/cpu_errata.c         | 19 +++++++++++++++
 arch/arm64/tools/cpucaps               |  1 +
 5 files changed, 72 insertions(+), 1 deletion(-)

As you forwarded this patch on to me, you forgot to sign-off on it :(

I've taken patch 1/4 of this series, but not the rest.  Please redo
them, and send the needed backports for 6.1.y and 6.4.y as a separate
series (obviously I can't apply patches in a series to trees that
already have them.)

thanks,

greg k-h

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel