linux-kernel - Re: [PATCH RFC 01/13] x86: Move posted interrupt descriptor out of vmx code

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Message-ID: <20231208152116.1c09a17c@jacob-builder>
Date:   Fri, 8 Dec 2023 15:21:16 -0800
From:   Jacob Pan <jacob.jun.pan@...ux.intel.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>, X86 Kernel <x86@...nel.org>,
        iommu@...ts.linux.dev, Lu Baolu <baolu.lu@...ux.intel.com>,
        kvm@...r.kernel.org, Dave Hansen <dave.hansen@...el.com>,
        Joerg Roedel <joro@...tes.org>,
        "H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...en8.de>,
        Ingo Molnar <mingo@...hat.com>,
        Raj Ashok <ashok.raj@...el.com>,
        "Tian, Kevin" <kevin.tian@...el.com>, maz@...nel.org,
        peterz@...radead.org, seanjc@...gle.com,
        Robin Murphy <robin.murphy@....com>,
        jacob.jun.pan@...ux.intel.com
Subject: Re: [PATCH RFC 01/13] x86: Move posted interrupt descriptor out of
 vmx code

Hi Thomas,

On Fri, 08 Dec 2023 10:31:20 +0100, Thomas Gleixner <tglx@...utronix.de>
wrote:

> On Thu, Dec 07 2023 at 20:54, Jacob Pan wrote:
> > On Wed, 06 Dec 2023 17:33:28 +0100, Thomas Gleixner <tglx@...utronix.de>
> > wrote:  
> >> On Sat, Nov 11 2023 at 20:16, Jacob Pan wrote:
> >> 	u32			rsvd[6];
> >> } __aligned(64);
> >>   
> > It seems bit-fields cannot pass type check. I got these compile error.  
> 
> And why are you telling me that instead if simply fixing it?
My point is that I am not sure this change is worthwhile unless I don't do
the per CPU pointer check.

gcc cannot take bit-field address afaik. So the problem is that with this
bit-field change we don't have individual members anymore to check pointers.

e.g.
./include/linux/percpu-defs.h:363:20: error: cannot take address of
bit-field ‘nv’ 363 |  __verify_pcpu_ptr(&(variable));  


Thanks,

Jacob