linux-kernel - Re: [PATCH v2 12/12] x86/traps: Fix up invalid PASID

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Date:   Mon, 15 Jun 2020 21:09:28 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Fenghua Yu <fenghua.yu@...el.com>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        H Peter Anvin <hpa@...or.com>,
        David Woodhouse <dwmw2@...radead.org>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Frederic Barrat <fbarrat@...ux.ibm.com>,
        Andrew Donnellan <ajd@...ux.ibm.com>,
        Felix Kuehling <Felix.Kuehling@....com>,
        Joerg Roedel <joro@...tes.org>,
        Dave Hansen <dave.hansen@...el.com>,
        Tony Luck <tony.luck@...el.com>,
        Ashok Raj <ashok.raj@...el.com>,
        Jacob Jun Pan <jacob.jun.pan@...el.com>,
        Dave Jiang <dave.jiang@...el.com>,
        Yu-cheng Yu <yu-cheng.yu@...el.com>,
        Sohil Mehta <sohil.mehta@...el.com>,
        Ravi V Shankar <ravi.v.shankar@...el.com>,
        linux-kernel <linux-kernel@...r.kernel.org>,
        x86 <x86@...nel.org>, iommu@...ts.linux-foundation.org,
        amd-gfx <amd-gfx@...ts.freedesktop.org>,
        linuxppc-dev <linuxppc-dev@...ts.ozlabs.org>
Subject: Re: [PATCH v2 12/12] x86/traps: Fix up invalid PASID

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