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