linux-kernel - Re: [PATCH 3/3] KVM: arm64: nv: Handle all _EL02 and

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Message-ID: <9D7F3DC3-9AB4-4FDB-9E9F-B491D3350392@oracle.com>
Date:   Mon, 25 Sep 2023 11:04:07 +0000
From:   Miguel Luis <miguel.luis@...cle.com>
To:     Marc Zyngier <maz@...nel.org>
CC:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Oliver Upton <oliver.upton@...ux.dev>,
        James Morse <james.morse@....com>,
        Suzuki K Poulose <suzuki.poulose@....com>,
        Zenghui Yu <yuzenghui@...wei.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kvmarm@...ts.linux.dev" <kvmarm@...ts.linux.dev>
Subject: Re: [PATCH 3/3] KVM: arm64: nv: Handle all _EL02 and _EL12 registers

Hi Marc,

> On 18 Sep 2023, at 12:56, Marc Zyngier <maz@...nel.org> wrote:
> 
> On Mon, 18 Sep 2023 13:41:45 +0100,
> Miguel Luis <miguel.luis@...cle.com> wrote:
>> 
>> Hi Marc,
>> 
>>> On 18 Sep 2023, at 09:44, Marc Zyngier <maz@...nel.org> wrote:
>>> 
>>> On Wed, 13 Sep 2023 19:52:08 +0100,
>>> Miguel Luis <miguel.luis@...cle.com> wrote:
>>>> 
>>>> Specify both _EL02 and _EL12 system registers.
>>>> 
>>>> Signed-off-by: Miguel Luis <miguel.luis@...cle.com>
>>>> ---
>>>> arch/arm64/kvm/emulate-nested.c | 35 +++++++++++++++++++++++++++++----
>>>> 1 file changed, 31 insertions(+), 4 deletions(-)
>>>> 
>>>> diff --git a/arch/arm64/kvm/emulate-nested.c b/arch/arm64/kvm/emulate-nested.c
>>>> index 9aa1c06abdb7..957afd97e488 100644
>>>> --- a/arch/arm64/kvm/emulate-nested.c
>>>> +++ b/arch/arm64/kvm/emulate-nested.c
>>>> @@ -690,10 +690,37 @@ static const struct encoding_to_trap_config encoding_to_cgt[] __initconst = {
>>>> SR_RANGE_TRAP(sys_reg(3, 4, 14, 0, 3),
>>>> sys_reg(3, 4, 14, 5, 2), CGT_HCR_NV),
>>>> /* All _EL02, _EL12 registers */
>>>> - SR_RANGE_TRAP(sys_reg(3, 5, 0, 0, 0),
>>>> -       sys_reg(3, 5, 10, 15, 7), CGT_HCR_NV),
>>>> - SR_RANGE_TRAP(sys_reg(3, 5, 12, 0, 0),
>>>> -       sys_reg(3, 5, 14, 15, 7), CGT_HCR_NV),
>>>> + SR_TRAP(SYS_SCTLR_EL12, CGT_HCR_NV),
>>>> + SR_TRAP(SYS_CPACR_EL12, CGT_HCR_NV),
>>>> + SR_TRAP(SYS_SCTLR2_EL12, CGT_HCR_NV),
>>>> + SR_TRAP(SYS_ZCR_EL12, CGT_HCR_NV),
>>>> + SR_TRAP(SYS_TRFCR_EL12, CGT_HCR_NV),
>>>> + SR_TRAP(SYS_SMCR_EL12, CGT_HCR_NV),
>>>> + SR_TRAP(SYS_TTBR0_EL12, CGT_HCR_NV),
>>>> + SR_TRAP(SYS_TTBR1_EL12, CGT_HCR_NV),
>>>> + SR_TRAP(SYS_TCR_EL12, CGT_HCR_NV),
>>>> + SR_TRAP(SYS_TCR2_EL12, CGT_HCR_NV),
>>>> + SR_TRAP(SYS_SPSR_EL12, CGT_HCR_NV),
>>>> + SR_TRAP(SYS_ELR_EL12, CGT_HCR_NV),
>>>> + SR_TRAP(SYS_AFSR0_EL12, CGT_HCR_NV),
>>>> + SR_TRAP(SYS_AFSR1_EL12, CGT_HCR_NV),
>>>> + SR_TRAP(SYS_ESR_EL12, CGT_HCR_NV),
>>>> + SR_TRAP(SYS_TFSR_EL12, CGT_HCR_NV),
>>>> + SR_TRAP(SYS_FAR_EL12, CGT_HCR_NV),
>>>> + SR_TRAP(SYS_BRBCR_EL12, CGT_HCR_NV),
>>>> + SR_TRAP(SYS_PMSCR_EL12, CGT_HCR_NV),
>>>> + SR_TRAP(SYS_MAIR_EL12, CGT_HCR_NV),
>>>> + SR_TRAP(SYS_AMAIR_EL12, CGT_HCR_NV),
>>>> + SR_TRAP(SYS_VBAR_EL12, CGT_HCR_NV),
>>>> + SR_TRAP(SYS_CONTEXTIDR_EL12, CGT_HCR_NV),
>>>> + SR_TRAP(SYS_SCXTNUM_EL12, CGT_HCR_NV),
>>>> + SR_TRAP(SYS_CNTKCTL_EL12, CGT_HCR_NV),
>>>> + SR_TRAP(SYS_CNTP_TVAL_EL02, CGT_HCR_NV),
>>>> + SR_TRAP(SYS_CNTP_CTL_EL02, CGT_HCR_NV),
>>>> + SR_TRAP(SYS_CNTP_CVAL_EL02, CGT_HCR_NV),
>>>> + SR_TRAP(SYS_CNTV_TVAL_EL02, CGT_HCR_NV),
>>>> + SR_TRAP(SYS_CNTV_CTL_EL02, CGT_HCR_NV),
>>>> + SR_TRAP(SYS_CNTV_CVAL_EL02, CGT_HCR_NV),
>>>> SR_TRAP(OP_AT_S1E2R, CGT_HCR_NV),
>>>> SR_TRAP(OP_AT_S1E2W, CGT_HCR_NV),
>>>> SR_TRAP(OP_AT_S12E1R, CGT_HCR_NV),
>>> 
>>> While I could see the problem with the EL2 registers, I'm not
>>> convinced by this patch. Is there an actual case for non _EL02, non
>>> _EL12 registers that are included in the two ranges above?
>>> 
>> 
>> Having DDI0487Ja as reference, there is none. It is not clear to me having two
>> separate ranges. If it is to cover _EL02 and _EL12 ranges separately then the
>> second range is covering both aliases. I couldn't find the reason for these
>> aliases start and end other than SYS_SCTLR_EL12 and SYS_CNTV_CVAL_EL02,
>> respectively.
> 
> The reason we have two ranges is to explicitly exclude the IMPDEF
> range, which is trapped by HCR_EL2.TIDCP:
> 
> SR_RANGE_TRAP(sys_reg(3, 5, 11, 0, 0),
>       sys_reg(3, 5, 11, 15, 7), CGT_HCR_TIDCP),
> 

OK. I’m dropping this patch from the series.
The current approach satisfies the purpose.

Thanks
Miguel

> Thanks,
> 
> M.
> 
> -- 
> Without deviation from the norm, progress is not possible.