linux-kernel - Re: [PATCH v5 1/5] hyperv: Define struct hv_output_get_vp

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Message-ID: <2234bf95-237c-4d73-a549-93877e0b6fb2@linux.microsoft.com>
Date: Wed, 8 Jan 2025 09:48:25 -0800
From: Roman Kisel <romank@...ux.microsoft.com>
To: Wei Liu <wei.liu@...nel.org>
Cc: Michael Kelley <mhklinux@...look.com>, "hpa@...or.com" <hpa@...or.com>,
 "kys@...rosoft.com" <kys@...rosoft.com>, "bp@...en8.de" <bp@...en8.de>,
 "dave.hansen@...ux.intel.com" <dave.hansen@...ux.intel.com>,
 "decui@...rosoft.com" <decui@...rosoft.com>,
 "eahariha@...ux.microsoft.com" <eahariha@...ux.microsoft.com>,
 "haiyangz@...rosoft.com" <haiyangz@...rosoft.com>,
 "mingo@...hat.com" <mingo@...hat.com>,
 "nunodasneves@...ux.microsoft.com" <nunodasneves@...ux.microsoft.com>,
 "tglx@...utronix.de" <tglx@...utronix.de>,
 "tiala@...rosoft.com" <tiala@...rosoft.com>,
 "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
 "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
 "x86@...nel.org" <x86@...nel.org>, "apais@...rosoft.com"
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 "sunilmut@...rosoft.com" <sunilmut@...rosoft.com>,
 "vdso@...bites.dev" <vdso@...bites.dev>
Subject: Re: [PATCH v5 1/5] hyperv: Define struct hv_output_get_vp_registers



On 1/7/2025 11:34 PM, Wei Liu wrote:
> On Mon, Jan 06, 2025 at 12:24:32PM -0800, Roman Kisel wrote:
>>
>>
>> On 1/6/2025 9:37 AM, Michael Kelley wrote:
>>> From: Roman Kisel <romank@...ux.microsoft.com> Sent: Monday, December 30, 2024 10:10 AM
>> [...]
>>>
>>> These bit field definitions don't look right. We want to "fill up"
>>> the field size, so that we're explicit about each bit, and not leave
>>> it to the compiler to add padding (which __packed tells the
>>> compiler not to do). So in aggregate, the "u64" bit fields should
>>> account for all 64 bits, but here you account for only 32 bits.
>>> There are two ways to fix this:
>>>
>>> 		u32 interruption_pending : 1;
>>> 		u32 interruption_type: 1;
>>> 		u32 reserved : 30;
>>> 		u32 error_code;
>>> Or
>>> 		u64 interruption_pending : 1;
>>> 		u64 interruption_type: 1;
>>> 		u64 reserved : 30;
>>> 		u64 error_code : 32;
>>>
>>>
>>> Nuno -- your thoughts?
>>
>> Quite a blunder on my side! Thank you very much for your help :)
>> GDB is my witness:
>>
>> (gdb) ptype /o union hv_arm64_pending_synthetic_exception_event
>> /* offset      |    size */  type = union
>> hv_arm64_pending_synthetic_exception_event {
>> /*                    16 */    u64 as_uint64[2];
>> /*                    13 */    struct {
>> /*      0: 0   |       4 */        u32 event_pending : 1;
>> /*      0: 1   |       4 */        u32 event_type : 3;
>> /*      0: 4   |       4 */        u32 reserved : 4;
>> /*      1      |       4 */        u32 exception_type;
>> /*      5      |       8 */        u64 context;
>>
>>                                     /* total size (bytes):   13 */
>>                                 };
>>
>>                                 /* total size (bytes):   16 */
>>                               }
>>
>> which looks messed up to me to put it mildly. Will fix next time.
> 
> We are pretty close to the next merge window (~2 weeks). Can you please
> resend a version this week or early next week?

Understood, will do!

> 
> Nuno, if you have any comments on this series, now it is the time to
> share them.
> 
> Thanks,
> Wei.

-- 
Thank you,
Roman