linux-kernel - Re: [PATCH 1/2] hyperv: Fix pointer type for the output of the hypercall in get

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Message-ID: <00986b68-3784-4087-af83-36e5db1a76c9@linux.microsoft.com>
Date: Thu, 19 Dec 2024 11:11:49 -0800
From: Roman Kisel <romank@...ux.microsoft.com>
To: Nuno Das Neves <nunodasneves@...ux.microsoft.com>, hpa@...or.com,
 kys@...rosoft.com, bp@...en8.de, dave.hansen@...ux.intel.com,
 decui@...rosoft.com, eahariha@...ux.microsoft.com, haiyangz@...rosoft.com,
 mingo@...hat.com, mhklinux@...look.com, tglx@...utronix.de,
 tiala@...rosoft.com, wei.liu@...nel.org, linux-hyperv@...r.kernel.org,
 linux-kernel@...r.kernel.org, x86@...nel.org
Cc: apais@...rosoft.com, benhill@...rosoft.com, ssengar@...rosoft.com,
 sunilmut@...rosoft.com, vdso@...bites.dev
Subject: Re: [PATCH 1/2] hyperv: Fix pointer type for the output of the
 hypercall in get_vtl(void)



On 12/19/2024 10:40 AM, Nuno Das Neves wrote:
> On 12/18/2024 12:54 PM, Roman Kisel wrote:
>> Commit bc905fa8b633 ("hyperv: Switch from hyperv-tlfs.h to hyperv/hvhdk.h")
>> changed the type of the output pointer to `struct hv_register_assoc` from
>> `struct hv_get_vp_registers_output`. That leads to an incorrect computation,
>> and leaves the system broken.
>>
> My bad! But, lets not use `struct hv_get_registers_output`. Instead, use
> `struct hv_register_value`, since that is the more complete definition of a
> register value. The output of the get_vp_registers hypercall is just an array
> of these values.
> 
> Ideally we remove `struct hv_get_vp_registers_output` at some point, since
> it serves the same role as `struct hv_register_value` but in a more limited
> capacity.
Nuno, thank you very much for your help! Agreed, I will use `struct
  hv_register_value` in v2.

> 
> Thanks
> Nuno
Thank you,
Roman

> 
>> Use the correct pointer type for the output of the GetVpRegisters hypercall.
>>
>> Fixes: bc905fa8b633 ("hyperv: Switch from hyperv-tlfs.h to hyperv/hvhdk.h")
>> Signed-off-by: Roman Kisel <romank@...ux.microsoft.com>
>> ---
>>   arch/x86/hyperv/hv_init.c   | 6 +++---
>>   include/hyperv/hvgdk_mini.h | 3 ---
>>   2 files changed, 3 insertions(+), 6 deletions(-)
>>
>> diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
>> index 3cf2a227d666..c7185c6a290b 100644
>> --- a/arch/x86/hyperv/hv_init.c
>> +++ b/arch/x86/hyperv/hv_init.c
>> @@ -416,13 +416,13 @@ static u8 __init get_vtl(void)
>>   {
>>   	u64 control = HV_HYPERCALL_REP_COMP_1 | HVCALL_GET_VP_REGISTERS;
>>   	struct hv_input_get_vp_registers *input;
>> -	struct hv_register_assoc *output;
>> +	struct hv_get_vp_registers_output *output;
>>   	unsigned long flags;
>>   	u64 ret;
>>   
>>   	local_irq_save(flags);
>>   	input = *this_cpu_ptr(hyperv_pcpu_input_arg);
>> -	output = (struct hv_register_assoc *)input;
>> +	output = (struct hv_get_vp_registers_output *)input;
>>   
>>   	memset(input, 0, struct_size(input, names, 1));
>>   	input->partition_id = HV_PARTITION_ID_SELF;
>> @@ -432,7 +432,7 @@ static u8 __init get_vtl(void)
>>   
>>   	ret = hv_do_hypercall(control, input, output);
>>   	if (hv_result_success(ret)) {
>> -		ret = output->value.reg8 & HV_X64_VTL_MASK;
>> +		ret = output->as64.low & HV_X64_VTL_MASK;
>>   	} else {
>>   		pr_err("Failed to get VTL(error: %lld) exiting...\n", ret);
>>   		BUG();
>> diff --git a/include/hyperv/hvgdk_mini.h b/include/hyperv/hvgdk_mini.h
>> index db3d1aaf7330..0b1a10828f33 100644
>> --- a/include/hyperv/hvgdk_mini.h
>> +++ b/include/hyperv/hvgdk_mini.h
>> @@ -1107,7 +1107,6 @@ union hv_register_value {
>>   	union hv_x64_pending_interruption_register pending_interruption;
>>   };
>>   
>> -#if defined(CONFIG_ARM64)
>>   /* HvGetVpRegisters returns an array of these output elements */
>>   struct hv_get_vp_registers_output {
>>   	union {
>> @@ -1124,8 +1123,6 @@ struct hv_get_vp_registers_output {
>>   	};
>>   };
>>   
>> -#endif /* CONFIG_ARM64 */
>> -
>>   struct hv_register_assoc {
>>   	u32 name;			/* enum hv_register_name */
>>   	u32 reserved1;

-- 
Thank you,
Roman