linux-kernel - Re: [PATCH] x86/iommu: Fix two minimal issues in check_iommu

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Date:   Mon, 4 Jan 2021 13:43:53 +0800
From:   Zhenzhong Duan <zhenzhong.duan@...il.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     linux-kernel <linux-kernel@...r.kernel.org>, zhongjiang@...wei.com,
        joe@...ches.com, konrad.wilk@...cle.com,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        iommu@...ts.linux-foundation.org,
        David Woodhouse <dwmw2@...radead.org>,
        Lu Baolu <baolu.lu@...ux.intel.com>,
        Joerg Roedel <joro@...tes.org>, will@...nel.org
Subject: Re: [PATCH] x86/iommu: Fix two minimal issues in check_iommu_entries()

On Wed, Dec 30, 2020 at 3:02 PM Borislav Petkov <bp@...en8.de> wrote:
>
> On Wed, Dec 23, 2020 at 02:24:12PM +0800, Zhenzhong Duan wrote:
> > check_iommu_entries() checks for cyclic dependency in iommu entries
> > and fixes the cyclic dependency by setting x->depend to NULL. But
> > this repairing isn't correct if q is in front of p, there will be
> > "EXECUTION ORDER INVALID!" report following. Fix it by NULLing
> > whichever in the front.
>
> When does "q is in front of p" happen? How does it happen?

Sorry, just realized it never happen.
>
> > The second issue is about the report of exectuion order reverse,
> > the order is reversed incorrectly in the report, fix it.
>
> I have no clue what that means.

I mean if p depends on q, then q->detect should be called before p->detect.
The message generated by printk() is wrong.

Regards
Zhenzhong