Messages in this thread | | | Subject | Re: [RFC PATCH 3/7] arm64: mm: use nGnRnE instead of nGnRE on Apple processors | From | Alexander Graf <> | Date | Wed, 20 Jan 2021 17:47:33 +0100 |
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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
> + > +/* > + * 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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