linux-kernel - Re: [PATCH v2 1/3] hyperv: Convert hypercall statuses to linux error codes

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Message-ID: <61b11926-3e85-4fd5-92a9-ca7c7e4b4c7c@linux.microsoft.com>
Date: Thu, 20 Feb 2025 13:59:17 -0800
From: Nuno Das Neves <nunodasneves@...ux.microsoft.com>
To: Easwar Hariharan <eahariha@...ux.microsoft.com>
Cc: linux-hyperv@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org,
 iommu@...ts.linux.dev, mhklinux@...look.com, kys@...rosoft.com,
 haiyangz@...rosoft.com, wei.liu@...nel.org, decui@...rosoft.com,
 catalin.marinas@....com, will@...nel.org, tglx@...utronix.de,
 mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com, x86@...nel.org,
 hpa@...or.com, daniel.lezcano@...aro.org, joro@...tes.org,
 robin.murphy@....com, arnd@...db.de, jinankjain@...ux.microsoft.com,
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Subject: Re: [PATCH v2 1/3] hyperv: Convert hypercall statuses to linux error
 codes

On 2/20/2025 10:49 AM, Easwar Hariharan wrote:
> On 2/20/2025 10:33 AM, Nuno Das Neves wrote:
>> Return linux-friendly error codes from hypercall helper functions,
>> which allows them to be used more flexibly.
>>
>> Introduce hv_result_to_errno() for this purpose, which also handles
>> the special value U64_MAX returned from hv_do_hypercall().
>>
>> Signed-off-by: Nuno Das Neves <nunodasneves@...ux.microsoft.com>
>> ---
>>  drivers/hv/hv_common.c         | 34 ++++++++++++++++++++++++++++++++++
>>  drivers/hv/hv_proc.c           |  6 +++---
>>  include/asm-generic/mshyperv.h |  1 +
>>  3 files changed, 38 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/hv/hv_common.c b/drivers/hv/hv_common.c
>> index ee3083937b4f..2120aead98d9 100644
>> --- a/drivers/hv/hv_common.c
>> +++ b/drivers/hv/hv_common.c
>> @@ -683,3 +683,37 @@ u64 __weak hv_tdx_hypercall(u64 control, u64 param1, u64 param2)
>>  	return HV_STATUS_INVALID_PARAMETER;
>>  }
>>  EXPORT_SYMBOL_GPL(hv_tdx_hypercall);
>> +
>> +/* Convert a hypercall result into a linux-friendly error code. */
>> +int hv_result_to_errno(u64 status)
>> +{
>> +	/* hv_do_hypercall() may return U64_MAX, hypercalls aren't possible */
>> +	if (unlikely(status == U64_MAX))
>> +		return -EOPNOTSUPP;
>> +	/*
>> +	 * A failed hypercall is usually only recoverable (or loggable) near
>> +	 * the call site where the HV_STATUS_* code is known. So the errno
>> +	 * it gets converted to is not too useful further up the stack.
>> +	 * Provice a few mappings that could be useful, and revert to -EIO
> 
> Typo: Provide
> 
Yep, looks like there will be a v3, I'll fix it there.
Thanks for the review!

> Otherwise, looks good to me.
> 
> Reviewed-by: Easwar Hariharan <eahariha@...ux.microsoft.com>
> 
> Thanks,
> Easwar (he/him)