linux-kernel - Re: [RFC v2 14/17] x86/apic: Add kexec support for Secure AVIC

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Message-ID: <87frirwx76.ffs@tglx>
Date: Tue, 01 Apr 2025 20:31:09 +0200
From: Thomas Gleixner <tglx@...utronix.de>
To: Neeraj Upadhyay <Neeraj.Upadhyay@....com>, linux-kernel@...r.kernel.org
Cc: bp@...en8.de, mingo@...hat.com, dave.hansen@...ux.intel.com,
 Thomas.Lendacky@....com, nikunj@....com, Santosh.Shukla@....com,
 Vasant.Hegde@....com, Suravee.Suthikulpanit@....com, David.Kaplan@....com,
 x86@...nel.org, hpa@...or.com, peterz@...radead.org, seanjc@...gle.com,
 pbonzini@...hat.com, kvm@...r.kernel.org, kirill.shutemov@...ux.intel.com,
 huibo.wang@....com, naveen.rao@....com
Subject: Re: [RFC v2 14/17] x86/apic: Add kexec support for Secure AVIC

On Tue, Apr 01 2025 at 16:05, Neeraj Upadhyay wrote:

> On 3/21/2025 9:18 PM, Thomas Gleixner wrote:
>> On Wed, Feb 26 2025 at 14:35, Neeraj Upadhyay wrote:
>>>  
>>> +/*
>>> + * Unregister GPA of the Secure AVIC backing page.
>>> + *
>>> + * @apic_id: APIC ID of the vCPU. Use -1ULL for the current vCPU
>> 
>> Yes, -1ULL is really a sensible value - NOT. Ever thought about
>> signed/unsigned?
> 
>
> In table "Table 7: List of Supported Non-Automatic Events" of GHCB spec [1],
> 0xffff_ffff_ffff_ffff is used for Secure AVIC GHCB event
>
> "RAX will have the APIC ID of the target vCPU or 0xffff_ffff_ffff_ffff
>  for the vCPU doing the call"
>
> I am using -1ULL for that here.

Which is a horrible construct, while  ~0ULL is not.