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

[Oliver Upton <oliver.upton@linux.dev>]

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.

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