Re: [PATCH v3 5/5] KVM: arm64: selftests: Test for setting ID register from usersapce

[Itaru Kitayama <itaru.kitayama@linux.dev>]

On Mon, Jan 08, 2024 at 10:40:11PM +0000, Oliver Upton wrote:
> Hi Zenghui,
> 
> On Fri, Jan 05, 2024 at 05:07:08PM +0800, Zenghui Yu wrote:
> > On 2023/10/19 16:38, Eric Auger wrote:
> > 
> > > > +static const struct reg_ftr_bits ftr_id_aa64dfr0_el1[] = {
> > > > +	S_REG_FTR_BITS(FTR_LOWER_SAFE, ID_AA64DFR0_EL1, PMUVer, 0),
> > >
> > > Strictly speaking this is not always safe to have a lower value. For
> > > instance: From Armv8.1, if FEAT_PMUv3 is implemented, the value 0b0001
> > > is not permitted. But I guess this consistency is to be taken into
> > > account by the user space. But may be wort a comment. Here and below
> > > 
> > > You may at least clarify what does mean 'safe'
> > >
> > > > +	REG_FTR_BITS(FTR_LOWER_SAFE, ID_AA64DFR0_EL1, DebugVer, 0),
> > 
> > I've seen the following failure on Cortex A72 where
> > ID_AA64DFR0_EL1.DebugVer is 6.
> 
> Ah, yes, the test is wrong. KVM enforces a minimum value of 0x6 on this
> field, yet get_safe_value() returns 0x5 for the field.

This is observed with the RevC AEM FVP as well.

Thanks,
Itaru.

> 
> Jing, do you have time to check this test for similar failures and send
> out a fix for Zenghui's observations?
> 
> > # ./aarch64/set_id_regs
> > TAP version 13
> > 1..79
> > ok 1 ID_AA64DFR0_EL1_PMUVer
> > ==== Test Assertion Failure ====
> >   include/kvm_util_base.h:553: !ret
> >   pid=2288505 tid=2288505 errno=22 - Invalid argument
> >      1	0x0000000000402787: vcpu_set_reg at kvm_util_base.h:553
> > (discriminator 6)
> >      2	 (inlined by) test_reg_set_success at set_id_regs.c:342
> > (discriminator 6)
> >      3	 (inlined by) test_user_set_reg at set_id_regs.c:413 (discriminator
> > 6)
> >      4	0x0000000000401943: main at set_id_regs.c:475
> >      5	0x0000ffffbdd5d03b: ?? ??:0
> >      6	0x0000ffffbdd5d113: ?? ??:0
> >      7	0x0000000000401a2f: _start at ??:?
> >   KVM_SET_ONE_REG failed, rc: -1 errno: 22 (Invalid argument)
> 
> -- 
> Thanks,
> Oliver