Re: [PATCH] arm64: Work around Falkor erratum 1009

Marc Zyngier
2016-12-08T11:35:39Z

On 08/12/16 11:20, Will Deacon wrote:
> On Wed, Dec 07, 2016 at 03:04:31PM -0500, Christopher Covington wrote:
>> From: Shanker Donthineni <shankerd@codeaurora.org>
>>
>> During a TLB invalidate sequence targeting the inner shareable
>> domain, Falkor may prematurely complete the DSB before all loads
>> and stores using the old translation are observed; instruction
>> fetches are not subject to the conditions of this erratum.
>>
>> Signed-off-by: Shanker Donthineni <shankerd@codeaurora.org>
>> Signed-off-by: Christopher Covington <cov@codeaurora.org>
>> ---
>> arch/arm64/Kconfig | 10 +++++++++
>> arch/arm64/include/asm/cpucaps.h | 3 ++-
>> arch/arm64/include/asm/tlbflush.h | 43 +++++++++++++++++++++++++++++++++++++++
>> arch/arm64/kernel/cpu_errata.c | 7 +++++++
>> arch/arm64/kvm/hyp/tlb.c | 39 ++++++++++++++++++++++++++++++-----
>> 5 files changed, 96 insertions(+), 6 deletions(-)
>>
>> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
>> index 1004a3d..125440f 100644
>> --- a/arch/arm64/Kconfig
>> +++ b/arch/arm64/Kconfig
>> @@ -485,6 +485,16 @@ config QCOM_FALKOR_ERRATUM_E1003
>>
>> If unsure, say Y.
>>
>> +config QCOM_FALKOR_ERRATUM_E1009
>> + bool "Falkor E1009: Prematurely complete a DSB after a TLBI"
>> + default y
>> + help
>> + Falkor CPU may prematurely complete a DSB following a TLBI xxIS
>> + invalidate maintenance operations. Repeat the TLBI operation one
>> + more time to fix the issue.
>> +
>> + If unsure, say Y.
>
> Call me perverse, but I like this workaround. People often tend to screw
> up TLBI and DVM sync, but the IPI-based workaround is horribly invasive
> and fragile. Simply repeating the operation tends to be enough to make
> the chance of failure small enough to be acceptable.
>
>> diff --git a/arch/arm64/include/asm/cpucaps.h b/arch/arm64/include/asm/cpucaps.h
>> index cb6a8c2..5357d7f 100644
>> --- a/arch/arm64/include/asm/cpucaps.h
>> +++ b/arch/arm64/include/asm/cpucaps.h
>> @@ -35,7 +35,8 @@
>> #define ARM64_HYP_OFFSET_LOW 14
>> #define ARM64_MISMATCHED_CACHE_LINE_SIZE 15
>> #define ARM64_WORKAROUND_QCOM_FALKOR_E1003 16
>> +#define ARM64_WORKAROUND_QCOM_FALKOR_E1009 17
>
> Could you rename this to something like ARM64_WORKAROUND_REPEAT_TLBI, so
> that it could potentially be used by others?

And add a parameter to it so that we can generate multiple TLBIs,
depending on the level of brokenness? ;-)

M.
--
Jazz is not dead. It just smells funny...