linux-kernel - Re: [PATCH 1/1] iommu/vt-d: Fix lockdep splat in intel_pasid_get

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Message-ID: <YFRqG3DW8k0Zrk0w@8bytes.org>
Date:   Fri, 19 Mar 2021 10:08:43 +0100
From:   Joerg Roedel <joro@...tes.org>
To:     Lu Baolu <baolu.lu@...ux.intel.com>
Cc:     Will Deacon <will@...nel.org>, Dave Jiang <dave.jiang@...el.com>,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] iommu/vt-d: Fix lockdep splat in
 intel_pasid_get_entry()

Hi Baolu,

On Fri, Mar 19, 2021 at 09:02:34AM +0800, Lu Baolu wrote:
> This code modifies the pasid directory entry. The pasid directory
> entries are allocated on demand and will never be freed.
> 
> > What you need to do here is to retry the whole path by adding a goto
> > to before  the first get_pasid_table_from_pde() call.
> 
> Yes. Retrying by adding a goto makes the code clearer.
> 
> > 
> > Btw, what makes sure that the pasid_entry does not go away when it is
> > returned here?
> 
> As explained above, it handles the pasid directory table entry which
> won't go away.

Okay, I think the goto is a good idea anyway, in case this changes
someday. Please also add a comment to this code stating that the entries
are never freed.

Regards,

	Joerg