linux-kernel - Re: [PATCH 4/8] x86/traps: Demand-populate PASID MSR via #GP

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Date:   Wed, 22 Sep 2021 23:39:26 +0000
From:   Fenghua Yu <fenghua.yu@...el.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Andy Lutomirski <luto@...nel.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Joerg Roedel <joro@...tes.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Jacob Jun Pan <jacob.jun.pan@...el.com>,
        Ashok Raj <ashok.raj@...el.com>,
        Ravi V Shankar <ravi.v.shankar@...el.com>,
        iommu@...ts.linux-foundation.org, x86 <x86@...nel.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 4/8] x86/traps: Demand-populate PASID MSR via #GP

Hi, Peter,

On Wed, Sep 22, 2021 at 11:07:22PM +0200, Peter Zijlstra wrote:
> On Mon, Sep 20, 2021 at 07:23:45PM +0000, Fenghua Yu wrote:
> >  
> > +	if (user_mode(regs) && fixup_pasid_exception())
> > +		goto exit;
> > +
> >  	if (static_cpu_has(X86_FEATURE_UMIP)) {
> >  		if (user_mode(regs) && fixup_umip_exception(regs))
> >  			goto exit;
> 
> So you're eating any random #GP that might or might not be PASID
> related. And all that witout a comment... Enlighten?

I will add a comment here.

Thanks.

-Fenghua