Re: [PATCH v3 15/15] Drivers: hv: Add modules to expose /dev/mshv to VMMs running on Hyper-V

[Nuno Das Neves]

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On 9/23/2023 12:58 AM, Greg KH wrote:
> On Fri, Sep 22, 2023 at 11:38:35AM -0700, Nuno Das Neves wrote:
> > +static int mshv_vtl_get_vsm_regs(void)
> > +{
> > +	struct hv_register_assoc registers[2];
> > +	union hv_input_vtl input_vtl;
> > +	int ret, count = 2;
> > +
> > +	input_vtl.as_uint8 = 0;
> > +	registers[0].name = HV_REGISTER_VSM_CODE_PAGE_OFFSETS;
> > +	registers[1].name = HV_REGISTER_VSM_CAPABILITIES;
> > +
> > +	ret = hv_call_get_vp_registers(HV_VP_INDEX_SELF, HV_PARTITION_ID_SELF,
> > +				       count, input_vtl, registers);
> > +	if (ret)
> > +		return ret;
> > +
> > +	mshv_vsm_page_offsets.as_uint64 = registers[0].value.reg64;
> > +	mshv_vsm_capabilities.as_uint64 = registers[1].value.reg64;
> > +
> > +	pr_debug("%s: VSM code page offsets: %#016llx\n", __func__,
> > +		 mshv_vsm_page_offsets.as_uint64);
> > +	pr_info("%s: VSM capabilities: %#016llx\n", __func__,
> > +		mshv_vsm_capabilities.as_uint64);
>
> When drivers are working properly, they are quiet.  This is very noisy
> and probably is leaking memory addresses to userspace?

I will remove these, thanks.

> Also, there is NEVER a need for __func__ in a pr_debug() line, it has
> that for you automatically.

Thank you, I didn't know this.

> Also, drivers should never call pr_*() calls, always use the proper
> dev_*() calls instead.

We only use struct device in one place in this driver, I think that is 
the only place it makes sense to use dev_*() over pr_*() calls.
> > +
> > +	return ret;
> > +}
> > +
> > +static int mshv_vtl_configure_vsm_partition(void)
> > +{
> > +	union hv_register_vsm_partition_config config;
> > +	struct hv_register_assoc reg_assoc;
> > +	union hv_input_vtl input_vtl;
> > +
> > +	config.as_u64 = 0;
> > +	config.default_vtl_protection_mask = HV_MAP_GPA_PERMISSIONS_MASK;
> > +	config.enable_vtl_protection = 1;
> > +	config.zero_memory_on_reset = 1;
> > +	config.intercept_vp_startup = 1;
> > +	config.intercept_cpuid_unimplemented = 1;
> > +
> > +	if (mshv_vsm_capabilities.intercept_page_available) {
> > +		pr_debug("%s: using intercept page", __func__);
>
> Again, __func__ is not needed, you are providing it twice here for no
> real reason except to waste storage space :)

Thanks, I will review all the uses of pr_debug().

> > +		config.intercept_page = 1;
> > +	}
> > +
> > +	reg_assoc.name = HV_REGISTER_VSM_PARTITION_CONFIG;
> > +	reg_assoc.value.reg64 = config.as_u64;
> > +	input_vtl.as_uint8 = 0;
> > +
> > +	return hv_call_set_vp_registers(HV_VP_INDEX_SELF, HV_PARTITION_ID_SELF,
> > +				       1, input_vtl, &reg_assoc);
>
>
> None of this needs to be unwound if initialization fails later on?

I think unwinding this is not needed, not 100% sure.
Saurabh, can you comment?

Thanks,
Nuno

> thanks,
>
> greg k-h