On Tue, Nov 01, 2022 at 01:33:16PM +0000, Marc Zyngier wrote:
> Mark Brown <broonie@xxxxxxxxxx> wrote:
> > - if (cpus_have_final_cap(ARM64_SME))
> > + if (cpus_have_final_cap(ARM64_SME)) {
> > write_sysreg(read_sysreg(sctlr_el2) & ~SCTLR_ELx_ENTP2,
> > sctlr_el2);
> I still question this. As far as I can tell, it only affects the host
> context (HCR_EL2.{E2H,TGE}={1,1}).
> This is outlined in the description of the HFGWTR_EL2.nTPIDR2_EL0 bit:
Oh, I see what you meant there - I was purely focusing on the new code
with the fine grained traps, not the existing code.
> So I can only conclude that messing with SCTLR_EL2 is superfluous and
> doesn't affect the execution in a guest context.
Yes, if you look at the pseudocode for TPIDR2_EL0 that's the case. It's
either EnTP2 for HCR_EL2.<E2H,TGE> == '11' or the fine grained trap
otherwise.
> > + /*
> > + * Enable access to SMPRI_EL1 - we don't need to
> > + * control nTPIDR2_EL0 in VHE mode.
> > + */
> This comment is factually wrong.
Bah, I fixed one but not the other sorry :/
> Date: Tue, 1 Nov 2022 12:19:51 +0000
> Subject: [PATCH] KVM: arm64: Fix SMPRI_EL1/TPIDR2_EL0 trapping on VHE
>
> The trapping of SMPRI_EL1 and TPIDR2_EL0 currently only really
> work on nVHE, as only this mode uses the fine-grained trapping
> that controls these two registers.
>
> Move the trapping enable/disable code into
> __{de,}activate_traps_common(), allowing it to be called when it
> actually matters on VHE, and remove the flipping of EL2 control
> for TPIDR2_EL0, which only affects the host access of this
> register.
>
> Fixes: 861262ab8627 ("KVM: arm64: Handle SME host state when running guests")
> Signed-off-by: Marc Zyngier <maz@xxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
Reported-by: Mark Brown <broonie@xxxxxxxxxx>
Reviewed-by: Mark Brown <broonie@xxxxxxxxxx>
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