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

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Message-ID: <Z34qdI3puoSe9PiR@liuwe-devbox-debian-v2>
Date: Wed, 8 Jan 2025 07:34:12 +0000
From: Wei Liu <wei.liu@...nel.org>
To: Roman Kisel <romank@...ux.microsoft.com>
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>,
	"wei.liu@...nel.org" <wei.liu@...nel.org>,
	"linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
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	"benhill@...rosoft.com" <benhill@...rosoft.com>,
	"ssengar@...rosoft.com" <ssengar@...rosoft.com>,
	"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 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?

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

Thanks,
Wei.