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From: Mark Rutland <mark.rutland@arm.com>
To: Andre Przywara <andre.przywara@arm.com>
Cc: linux-arm-kernel@lists.infradead.org, Jaxson.Han@arm.com,
	robin.murphy@arm.com, vladimir.murzin@arm.com, Wei.Chen@arm.com
Subject: Re: [bootwrapper PATCH v2 06/13] aarch64: initialize SCTLR_ELx for the boot-wrapper
Date: Mon, 17 Jan 2022 13:05:54 +0000	[thread overview]
Message-ID: <20220117130554.GB87485@C02TD0UTHF1T.local> (raw)
In-Reply-To: <20220117121557.GA87485@C02TD0UTHF1T.local>

On Mon, Jan 17, 2022 at 12:15:57PM +0000, Mark Rutland wrote:
> On Fri, Jan 14, 2022 at 06:12:47PM +0000, Andre Przywara wrote:
> > On Fri, 14 Jan 2022 10:56:46 +0000
> > Mark Rutland <mark.rutland@arm.com> wrote:
> > 
> > Hi Mark,
> 
> Hi Andre,
 
> > > +
> > > +#define SCTLR_EL1_RES1		(BIT(29) | BIT(28) | BIT(23) | BIT(22) | \
> > > +				 BIT(11) | BIT(8) | BIT(7) | BIT(4))

> > > -#define SCTLR_EL1_RES1		(3 << 28 | 3 << 22 | 1 << 11)
> > >  
> > >  #ifdef KERNEL_32
> > >  /* 32-bit kernel decompressor uses CP15 barriers */
> > > #define SCTLR_EL1_KERNEL        (SCTLR_EL1_RES1 | SCTLR_EL1_CP15BEN)
> > 
> > So I wonder if this actually works? The ARMv7 version of SCTLR
> > differs in some bits from both the ARMv8 AArch32 version and more
> > importantly the AArch64 version.

> > I had troubles the other day running the
> > arm32 Linux kernel decompressor with some ARMv8 SCTLR_EL1 reset value. The
> > decompressor code does only read-modify-write of SCTLR (probably to
> > cover multiple architecture revisions), so some bits might stay wrong. In
> > particular I think having bits 28 and 29 set caused problems.
> > By looking at the ARMv7 ARM and with experimentation I came up
> > with 0x00c00878 as a safe and working value.

Having re-read all of this, I believe you're right; I'll rework the
AArch32-kernel SCTLR_EL1_KERNEL to not use the AArch64 bit definitions,
and I'll add some commentary explaining that we're writing to the AArch32
format.

> > Shall we have a separate reset value for 32bit?

Assuming you meant to alter the SCTLR_ELx_KERNEL definition, yes.

The idea of splitting the SCTLR_ELx_RESET and SCTLR_ELx_KERNEL
definitions was that the former would be whatever the boot-wrapper
needed to run at ELx, and the latter was whatever we must initialize for
the kernel to run at ELx, so I don't want to put the AArch32 kernel bits
into SCTLR_EL1_RESET.

My only remaining concern is exactly what we must initialize. If there's
any documentation we can refer to, that'd be great, otherwise I'll dig
through your prior suggestion.

Thanks,
Mark.

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  reply	other threads:[~2022-01-17 13:07 UTC|newest]

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-01-14 10:56 [bootwrapper PATCH v2 00/13] Cleanups and improvements Mark Rutland
2022-01-14 10:56 ` [bootwrapper PATCH v2 01/13] Document entry requirements Mark Rutland
2022-01-14 10:56 ` [bootwrapper PATCH v2 02/13] Add bit-field macros Mark Rutland
2022-01-17 12:11   ` Steven Price
2022-01-17 13:28     ` Mark Rutland
2022-01-14 10:56 ` [bootwrapper PATCH v2 03/13] aarch64: add system register accessors Mark Rutland
2022-01-14 15:32   ` Andre Przywara
2022-01-14 10:56 ` [bootwrapper PATCH v2 04/13] aarch32: add coprocessor accessors Mark Rutland
2022-01-14 10:56 ` [bootwrapper PATCH v2 05/13] aarch64: add mov_64 macro Mark Rutland
2022-01-14 15:50   ` Andre Przywara
2022-01-14 10:56 ` [bootwrapper PATCH v2 06/13] aarch64: initialize SCTLR_ELx for the boot-wrapper Mark Rutland
2022-01-14 18:12   ` Andre Przywara
2022-01-17 12:15     ` Mark Rutland
2022-01-17 13:05       ` Mark Rutland [this message]
2022-01-18 12:37         ` Andre Przywara
2022-01-25 13:32           ` Mark Rutland
2022-01-19 12:42       ` Mark Rutland
2022-01-14 10:56 ` [bootwrapper PATCH v2 07/13] Rework common init C code Mark Rutland
2022-01-17 16:23   ` Andre Przywara
2022-01-14 10:56 ` [bootwrapper PATCH v2 08/13] Announce boot-wrapper mode / exception level Mark Rutland
2022-01-17 14:39   ` Andre Przywara
2022-01-17 15:50     ` Mark Rutland
2022-01-14 10:56 ` [bootwrapper PATCH v2 09/13] aarch64: move the bulk of EL3 initialization to C Mark Rutland
2022-01-17 14:31   ` Andre Przywara
2022-01-17 18:08     ` Mark Rutland
2022-01-17 18:31       ` Andre Przywara
2022-01-18 16:50         ` Mark Brown
2022-01-19 15:22           ` Mark Rutland
2022-01-14 10:56 ` [bootwrapper PATCH v2 10/13] aarch32: move the bulk of Secure PL1 " Mark Rutland
2022-01-17 14:52   ` Andre Przywara
2022-01-14 10:56 ` [bootwrapper PATCH v2 11/13] Announce locations of memory objects Mark Rutland
2022-01-14 15:30   ` Andre Przywara
2022-01-14 16:04     ` Robin Murphy
2022-01-14 16:30       ` Mark Rutland
2022-01-14 16:21     ` Mark Rutland
2022-01-17 14:59   ` Andre Przywara
2022-01-14 10:56 ` [bootwrapper PATCH v2 12/13] Rework bootmethod initialization Mark Rutland
2022-01-17 17:43   ` Andre Przywara
2022-01-25 14:00     ` Mark Rutland
2022-01-14 10:56 ` [bootwrapper PATCH v2 13/13] Unify start_el3 & start_no_el3 Mark Rutland
2022-01-17 17:43   ` Andre Przywara
2022-01-14 15:09 ` [bootwrapper PATCH v2 00/13] Cleanups and improvements Andre Przywara
2022-01-14 15:23   ` Mark Rutland

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