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

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Date:   Mon, 15 Jun 2020 09:53:13 +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 Fri, Jun 12, 2020 at 05:41:33PM -0700, Fenghua Yu wrote:
> @@ -447,6 +458,18 @@ dotraplinkage void do_general_protection(struct pt_regs *regs, long error_code)
>  	int ret;
>  
>  	RCU_LOCKDEP_WARN(!rcu_is_watching(), "entry code didn't wake RCU");
> +
> +	/*
> +	 * Perform the check for a user mode PASID exception before enable
> +	 * interrupts. Doing this here ensures that the PASID MSR can be simply
> +	 * accessed because the contents are known to be still associated
> +	 * with the current process.
> +	 */
> +	if (user_mode(regs) && fixup_pasid_exception()) {
> +		cond_local_irq_enable(regs);
> +		return;

OK, so we're done with the exception, lets enable interrupts?

> +	}