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Date:   Wed, 17 Jun 2020 10:31:16 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Fenghua Yu <fenghua.yu@intel.com>
Cc:     Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        H Peter Anvin <hpa@zytor.com>,
        David Woodhouse <dwmw2@infradead.org>,
        Lu Baolu <baolu.lu@linux.intel.com>,
        Frederic Barrat <fbarrat@linux.ibm.com>,
        Andrew Donnellan <ajd@linux.ibm.com>,
        Felix Kuehling <Felix.Kuehling@amd.com>,
        Joerg Roedel <joro@8bytes.org>,
        Dave Hansen <dave.hansen@intel.com>,
        Tony Luck <tony.luck@intel.com>,
        Ashok Raj <ashok.raj@intel.com>,
        Jacob Jun Pan <jacob.jun.pan@intel.com>,
        Dave Jiang <dave.jiang@intel.com>,
        Yu-cheng Yu <yu-cheng.yu@intel.com>,
        Sohil Mehta <sohil.mehta@intel.com>,
        Ravi V Shankar <ravi.v.shankar@intel.com>,
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        x86 <x86@kernel.org>, iommu@lists.linux-foundation.org,
        amd-gfx <amd-gfx@lists.freedesktop.org>,
        linuxppc-dev <linuxppc-dev@lists.ozlabs.org>
Subject: Re: [PATCH v2 12/12] x86/traps: Fix up invalid PASID
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On Tue, Jun 16, 2020 at 04:23:46PM -0700, Fenghua Yu wrote:
> Hi, Peter,
> 
> On Mon, Jun 15, 2020 at 09:09:28PM +0200, Peter Zijlstra wrote:
> > On Mon, Jun 15, 2020 at 11:55:29AM -0700, Fenghua Yu wrote:
> > 
> > > Or do you suggest to add a random new flag in struct thread_info instead
> > > of a TIF flag?
> > 
> > Why thread_info? What's wrong with something simple like the below. It
> > takes a bit from the 'strictly current' flags word.
> > 
> > 
> > diff --git a/include/linux/sched.h b/include/linux/sched.h
> > index b62e6aaf28f0..fca830b97055 100644
> > --- a/include/linux/sched.h
> > +++ b/include/linux/sched.h
> > @@ -801,6 +801,9 @@ struct task_struct {
> >  	/* Stalled due to lack of memory */
> >  	unsigned			in_memstall:1;
> >  #endif
> > +#ifdef CONFIG_PCI_PASID
> > +	unsigned			has_valid_pasid:1;
> > +#endif
> >  
> >  	unsigned long			atomic_flags; /* Flags requiring atomic access. */
> >  
> > diff --git a/kernel/fork.c b/kernel/fork.c
> > index 142b23645d82..10b3891be99e 100644
> > --- a/kernel/fork.c
> > +++ b/kernel/fork.c
> > @@ -955,6 +955,10 @@ static struct task_struct *dup_task_struct(struct task_struct *orig, int node)
> >  	tsk->use_memdelay = 0;
> >  #endif
> >  
> > +#ifdef CONFIG_PCI_PASID
> > +	tsk->has_valid_pasid = 0;
> > +#endif
> > +
> >  #ifdef CONFIG_MEMCG
> >  	tsk->active_memcg = NULL;
> >  #endif
> 
> Can I add "Signed-off-by: Peter Zijlstra <peterz@infradead.org>"
> to this patch? I will send this patch in the next version of the series.

Sure, n/p.