Re: [PATCH] KVM: arm64: Fix the name of sys_reg_desc related to PMU

[Marc Zyngier <maz@kernel.org>]

On Thu, 13 Jul 2023 03:35:39 +0100,
"chenxiang (M)" <chenxiang66@hisilicon.com> wrote:
> 
> Hi Marc,
> 
> 
> 在 2023/7/12 星期三 16:36, Marc Zyngier 写道:
> > On Wed, 12 Jul 2023 08:55:05 +0100,
> > chenxiang <chenxiang66@hisilicon.com> wrote:
> >> From: Xiang Chen <chenxiang66@hisilicon.com>
> >> 
> >> For those PMU system registers defined in sys_reg_descs[], use macro
> >> PMU_SYS_REG() / PMU_PMEVCNTR_EL0 / PMU_PMEVTYPER_EL0 to define them, and
> >> later two macros call macro PMU_SYS_REG() actually.
> >> Currently the input parameter of PMU_SYS_REG() is other macro which is
> >> calculation formula of the value of system registers, so for example, if
> >> we want to "SYS_PMINTENSET_EL1" as the name of sys register, actually
> >> the name will be as following:
> >> (((3) << 19) | ((0) << 16) | ((9) << 12) | ((14) << 8) | ((1) << 5))
> >> 
> >> To fix the issue, use the name as a input parameter of PMU_SYS_REG like
> >> MTE_REG or EL2_REG.
> > Why is the name relevant? Is this related to tracing?
> I think It is not related to tracing. I find the issue when i want to
> know which system reigsters are set
> when on live migration and printk the name of sys_reg_desc in function
> kvm_sys_reg_set_user,
> find the name of some registers are abnormal as followings:
> 
> [  227.145540] kvm_sys_reg_set_user 3427:SYS_FAR_EL1
> [  227.158057] kvm_sys_reg_set_user 3427:SYS_PAR_EL1
> [  227.170574] kvm_sys_reg_set_user 3427:(((3) << 19) | ((0) << 16) |
> ((9) << 12) | ((14) << 8) | ((1) << 5))
> [  227.188037] kvm_sys_reg_set_user 3427:(((3) << 19) | ((0) << 16) |
> ((9) << 12) | ((14) << 8) | ((2) << 5))
> [  227.205511] kvm_sys_reg_set_user 3427:SYS_MAIR_EL1
> [  227.218117] kvm_sys_reg_set_user 3427:SYS_PIRE0_EL1

So what is this if not some form of tracing?

I agree that it would be good to fix it, at least because the register
name is smaller than the encoding, but the commit message should at
least mention what this is used for.

Thanks,

	M.

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