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From: Michal Orzel <michal.orzel@arm.com>
To: Julien Grall <julien@xen.org>, xen-devel@lists.xenproject.org
Cc: Stefano Stabellini <sstabellini@kernel.org>,
	Volodymyr Babchuk <Volodymyr_Babchuk@epam.com>,
	bertrand.marquis@arm.com
Subject: Re: [PATCH v2 03/10] arm: Modify type of actlr to register_t
Date: Thu, 29 Apr 2021 09:10:35 +0200	[thread overview]
Message-ID: <9c2f6d85-2b03-0360-ffa6-a3433a30a9bd@arm.com> (raw)
In-Reply-To: <160ccd79-1a6e-059f-82a7-996c8bcc68f3@xen.org>

Hi Julien,

On 27.04.2021 11:47, Julien Grall wrote:
> Hi Michal,
> 
> On 27/04/2021 10:35, Michal Orzel wrote:
>> AArch64 registers are 64bit whereas AArch32 registers
>> are 32bit or 64bit. MSR/MRS are expecting 64bit values thus
>> we should get rid of helpers READ/WRITE_SYSREG32
>> in favour of using READ/WRITE_SYSREG.
>> We should also use register_t type when reading sysregs
>> which can correspond to uint64_t or uint32_t.
>> Even though many AArch64 registers have upper 32bit reserved
>> it does not mean that they can't be widen in the future.
> 
> This is a pretty generic message but doesn't really explain the change itself and point out this is a bug (possibly latent on current HW) because it is implementation defined. IOW a CPU implementer may already have decided to use the top 32-bit without our knowledge.
> 
> Cheers,
> Is the following ok?
"
AArch64 registers are 64bit whereas AArch32 registers
are 32bit or 64bit. MSR/MRS are expecting 64bit values thus
we should get rid of helpers READ/WRITE_SYSREG32
in favour of using READ/WRITE_SYSREG.
We should also use register_t type when reading sysregs
which can correspond to uint64_t or uint32_t.
Even though many AArch64 registers have upper 32bit reserved
it does not mean that they can't be widen in the future.

ACTLR_EL1 system register bits are implementation defined
which means it is possibly a bug on current HW as the CPU
implementer may already have decided to use the top 32bit.
"

Cheers
Michal


  reply	other threads:[~2021-04-29  7:10 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-27  9:35 [PATCH v2 00/10] Get rid of READ/WRITE_SYSREG32 Michal Orzel
2021-04-27  9:35 ` [PATCH v2 01/10] arm64/vfp: " Michal Orzel
2021-04-27  9:35 ` [PATCH v2 02/10] arm/domain: " Michal Orzel
2021-04-27  9:45   ` Julien Grall
2021-04-29  6:58     ` Michal Orzel
2021-04-27  9:35 ` [PATCH v2 03/10] arm: Modify type of actlr to register_t Michal Orzel
2021-04-27  9:47   ` Julien Grall
2021-04-29  7:10     ` Michal Orzel [this message]
2021-04-27  9:35 ` [PATCH v2 04/10] arm/gic: Remove member hcr of structure gic_v3 Michal Orzel
2021-04-27  9:48   ` Julien Grall
2021-04-27  9:35 ` [PATCH v2 05/10] arm/gic: Get rid of READ/WRITE_SYSREG32 Michal Orzel
2021-04-27 10:02   ` Julien Grall
2021-04-29  7:14     ` Michal Orzel
2021-04-27  9:35 ` [PATCH v2 06/10] arm/p2m: " Michal Orzel
2021-04-27  9:35 ` [PATCH v2 07/10] arm/mm: " Michal Orzel
2021-04-27  9:59   ` Julien Grall
2021-04-29  7:16     ` Michal Orzel
2021-04-27  9:35 ` [PATCH v2 08/10] arm/page: " Michal Orzel
2021-04-27  9:35 ` [PATCH v2 09/10] arm/time,vtimer: " Michal Orzel
2021-04-27 10:09   ` Julien Grall
2021-04-27  9:35 ` [PATCH v2 10/10] arm64: Change type of hsr, cpsr, spsr_el1 to uint64_t Michal Orzel
2021-04-27 11:09   ` Julien Grall
2021-04-29  8:53     ` Michal Orzel
2021-04-29 10:31       ` Tamas K Lengyel
2021-04-29 10:35         ` Julien Grall

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