From: Mohamed Mediouni <mohamed.mediouni@caramail.com>
To: Alexander Graf <graf@amazon.com>
Cc: Mark Rutland <mark.rutland@arm.com>,
Catalin Marinas <catalin.marinas@arm.com>,
Hector Martin <marcan@marcan.st>,
linux-kernel@vger.kernel.org, Marc Zyngier <maz@kernel.org>,
Will Deacon <will@kernel.org>,
linux-arm-kernel@lists.infradead.org,
Stan Skowronek <stan@corellium.com>
Subject: Re: [RFC PATCH 3/7] arm64: mm: use nGnRnE instead of nGnRE on Apple processors
Date: Wed, 20 Jan 2021 19:06:48 +0100 [thread overview]
Message-ID: <17579DC5-13AF-48E1-9B72-91B14AB485FA@caramail.com> (raw)
In-Reply-To: <ce5692a9-e716-514a-f196-b0645bb03eb8@amazon.com>
> On 20 Jan 2021, at 17:47, Alexander Graf <graf@amazon.com> wrote:
>
> On 20.01.21 14:27, Mohamed Mediouni wrote:
>> Use nGnRnE instead of nGnRE on Apple SoCs to workaround a serious hardware quirk.
>> On Apple processors, writes using the nGnRE device memory type get dropped in flight,
>> getting to nowhere.
>> Signed-off-by: Stan Skowronek <stan@corellium.com>
>> Signed-off-by: Mohamed Mediouni <mohamed.mediouni@caramail.com>
>> ---
>> arch/arm64/mm/proc.S | 26 ++++++++++++++++++++++++++
>> 1 file changed, 26 insertions(+)
>> diff --git a/arch/arm64/mm/proc.S b/arch/arm64/mm/proc.S
>> index 1f7ee8c8b7b8..06436916f137 100644
>> --- a/arch/arm64/mm/proc.S
>> +++ b/arch/arm64/mm/proc.S
>> @@ -51,6 +51,25 @@
>> #define TCR_KASAN_HW_FLAGS 0
>> #endif
>> +#ifdef CONFIG_ARCH_APPLE
>
> Is there any particular reason for this #ifdef?
>
>
> Alex
>
Not a particular reason, as we explicitly check for the implementer ID. However,
without CONFIG_ARCH_APPLE, other parts of the support for Apple CPUs
will not be available anyway.
>> +
>> +/*
>> + * Apple cores appear to black-hole writes done with nGnRE.
>> + * We settled on a work-around that uses MAIR vs changing every single user of
>> + * nGnRE across the arm64 code.
>> + */
>> +
>> +#define MAIR_EL1_SET_APPLE \
>> + (MAIR_ATTRIDX(MAIR_ATTR_DEVICE_nGnRnE, MT_DEVICE_nGnRnE) | \
>> + MAIR_ATTRIDX(MAIR_ATTR_DEVICE_nGnRnE, MT_DEVICE_nGnRE) | \
>> + MAIR_ATTRIDX(MAIR_ATTR_DEVICE_GRE, MT_DEVICE_GRE) | \
>> + MAIR_ATTRIDX(MAIR_ATTR_NORMAL_NC, MT_NORMAL_NC) | \
>> + MAIR_ATTRIDX(MAIR_ATTR_NORMAL, MT_NORMAL) | \
>> + MAIR_ATTRIDX(MAIR_ATTR_NORMAL_WT, MT_NORMAL_WT) | \
>> + MAIR_ATTRIDX(MAIR_ATTR_NORMAL, MT_NORMAL_TAGGED))
>> +
>> +#endif
>> +
>> /*
>> * Default MAIR_EL1. MT_NORMAL_TAGGED is initially mapped as Normal memory and
>> * changed during __cpu_setup to Normal Tagged if the system supports MTE.
>> @@ -432,6 +451,13 @@ SYM_FUNC_START(__cpu_setup)
>> * Memory region attributes
>> */
>> mov_q x5, MAIR_EL1_SET
>> +#ifdef CONFIG_ARCH_APPLE
>> + mrs x0, MIDR_EL1
>> + lsr w0, w0, #24
>> + mov_q x1, MAIR_EL1_SET_APPLE
>> + cmp x0, #0x61 // 0x61 = Implementer: Apple
>> + csel x5, x1, x5, eq
>> +#endif
>> #ifdef CONFIG_ARM64_MTE
>> mte_tcr .req x20
>> --
>> 2.29.2
>
>
>
>
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next prev parent reply other threads:[~2021-01-20 18:09 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-01-20 13:27 [RFC PATCH 0/7] Linux on Apple Silicon Mohamed Mediouni
2021-01-20 13:27 ` [RFC PATCH 1/7] arm64: kernel: FIQ support Mohamed Mediouni
2021-01-20 13:27 ` [RFC PATCH 2/7] arm64: kernel: Add a WFI hook Mohamed Mediouni
2021-01-20 16:46 ` Alexander Graf
[not found] ` <94C20F55-D3B8-4349-B26F-9EA8AAEBF639@caramail.com>
2021-01-21 12:33 ` Hector Martin 'marcan'
2021-01-21 10:52 ` Arnd Bergmann
2021-01-21 11:01 ` Mohamed Mediouni
2021-01-21 11:36 ` Arnd Bergmann
2021-01-20 13:27 ` [RFC PATCH 3/7] arm64: mm: use nGnRnE instead of nGnRE on Apple processors Mohamed Mediouni
2021-01-20 16:47 ` Alexander Graf
2021-01-20 18:06 ` Mohamed Mediouni [this message]
2021-01-20 18:10 ` Alexander Graf
2021-01-21 11:27 ` Will Deacon
2021-01-21 11:38 ` Arnd Bergmann
2021-01-21 11:44 ` Marc Zyngier
2021-01-21 12:47 ` Will Deacon
2021-01-21 15:12 ` Mohamed Mediouni
2021-01-21 16:25 ` Marc Zyngier
2021-01-21 17:55 ` Will Deacon
2021-01-21 18:15 ` Marc Zyngier
2021-01-21 18:22 ` Mohamed Mediouni
2021-01-21 18:22 ` Will Deacon
2021-01-20 13:27 ` [RFC PATCH 4/7] irqchip/apple-aic: Add support for Apple AIC Mohamed Mediouni
2021-01-20 17:11 ` Alexander Graf
2021-01-20 18:04 ` Mohamed Mediouni
2021-01-20 20:16 ` Andrew Lunn
2021-01-20 21:18 ` Stan Skowronek
2021-01-21 9:48 ` Linus Walleij
2021-01-21 10:37 ` Arnd Bergmann
2021-01-21 15:29 ` Hector Martin 'marcan'
2021-01-21 17:09 ` Rob Herring
2021-01-21 17:45 ` Rob Herring
2021-01-21 16:44 ` Rob Herring
2021-01-21 16:53 ` Hector Martin 'marcan'
2021-01-20 13:27 ` [RFC PATCH 5/7] arm64/Kconfig: Add Apple Silicon SoC platform Mohamed Mediouni
2021-01-20 13:27 ` [RFC PATCH 6/7] arm64: kernel: Apple CPU start driver Mohamed Mediouni
2021-01-21 11:14 ` Arnd Bergmann
2021-01-20 13:27 ` [RFC PATCH 7/7] irqchip/apple-aic: add SMP support to the Apple AIC driver Mohamed Mediouni
2021-01-21 12:44 ` Arnd Bergmann
2021-01-21 12:50 ` Mohamed Mediouni
2021-01-21 13:00 ` Arnd Bergmann
2021-01-21 13:01 ` Hector Martin 'marcan'
2021-01-21 13:22 ` Marc Zyngier
2021-01-21 13:32 ` Mark Rutland
2021-01-21 14:05 ` Marc Zyngier
2021-01-21 13:34 ` Mohamed Mediouni
2021-01-21 14:10 ` Marc Zyngier
2021-01-21 15:09 ` Arnd Bergmann
2021-01-21 15:18 ` Mohamed Mediouni
2021-01-21 16:40 ` Rob Herring
2021-01-21 16:43 ` Mohamed Mediouni
2021-01-21 17:37 ` Rob Herring
2021-01-21 18:08 ` Mohamed Mediouni
2021-01-21 18:57 ` Rob Herring
2021-02-02 19:15 ` Linus Walleij
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