linux-kernel - Re: [PATCH v2 5/6] KVM: arm64: show writable masks for feature registers

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Message-ID: <eee2b0c4-2245-15d4-b887-122e080813e9@redhat.com>
Date: Fri, 3 May 2024 13:03:15 +0200 (CEST)
From: Sebastian Ott <sebott@...hat.com>
To: Oliver Upton <oliver.upton@...ux.dev>
cc: linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev, 
    linux-kernel@...r.kernel.org, Marc Zyngier <maz@...nel.org>, 
    James Morse <james.morse@....com>, 
    Suzuki K Poulose <suzuki.poulose@....com>, 
    Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>
Subject: Re: [PATCH v2 5/6] KVM: arm64: show writable masks for feature
 registers

On Wed, 1 May 2024, Oliver Upton wrote:

> On Fri, Apr 26, 2024 at 12:49:49PM +0200, Sebastian Ott wrote:
>> Instead of using ~0UL provide the actual writable mask for
>> non-id feature registers in the output of the
>> KVM_ARM_GET_REG_WRITABLE_MASKS ioctl.
>
> Urgh, yeah in retrospect I think we should've constrained this to the
> registers KVM considers "id regs" (the space occupied by known registers
> or otherwise RAZ).
>
>> Explicitely set the mask for CLIDR_EL1 to make sure we present
>> the same value to userspace than before.
>
> typo: explicitly
>
> Also, we know the set of mutable bits for CLIDR_EL1 as it is handled in
> set_clidr(). The mask really should match that, since the UAPI is
> documented as "allowing userspace to know what fields can be changed for
> the system register"

Done for the next revision.

Thanks,
Sebastian