[PATCH v4 0/4] Enable writable for idregs DFR0,PFR0, MMFR{0,1,2}

Oliver Upton oliver.upton at linux.dev
Mon Jun 26 13:52:46 PDT 2023


Hi Jing,

On Wed, Jun 07, 2023 at 07:45:50PM +0000, Jing Zhang wrote:
> 
> This patch series enable userspace writable for below idregs:
> ID_AA64DFR0_EL1, ID_DFR0_EL1, ID_AA64PFR0_EL1, ID_AA64MMFR{0, 1, 2}_EL1.
> 
> It is based on below series [2] which add infrastructure for writable idregs.

Could you implement some tests for these changes? We really need to see
that userspace is only allowed to select a subset of features that're
provided by the host, and that the CPU feature set never exceeds what
the host can support.

Additionally, there are places in the kernel where we use host ID
register values for the sake of emulation (DBGDIDR, LORegion). These
both should instead be using the _guest_ ID register values.

-- 
Thanks,
Oliver



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