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

Nuno Das Neves
2023-09-26T00:07:25Z

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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