linux-kernel - Re: [PATCH v7 01/15] swiotlb: Refactor swiotlb init functions

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Date:   Thu, 27 May 2021 11:32:01 -0500
From:   Tom Lendacky <thomas.lendacky@....com>
To:     Christoph Hellwig <hch@....de>,
        Florian Fainelli <f.fainelli@...il.com>
Cc:     Claire Chang <tientzu@...omium.org>,
        Rob Herring <robh+dt@...nel.org>, mpe@...erman.id.au,
        Joerg Roedel <joro@...tes.org>, Will Deacon <will@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        boris.ostrovsky@...cle.com, jgross@...e.com,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        benh@...nel.crashing.org, paulus@...ba.org,
        "list@....net:IOMMU DRIVERS" <iommu@...ts.linux-foundation.org>,
        sstabellini@...nel.org, Robin Murphy <robin.murphy@....com>,
        grant.likely@....com, xypron.glpk@....de,
        Thierry Reding <treding@...dia.com>, mingo@...nel.org,
        bauerman@...ux.ibm.com, peterz@...radead.org,
        Greg KH <gregkh@...uxfoundation.org>,
        Saravana Kannan <saravanak@...gle.com>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        heikki.krogerus@...ux.intel.com,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Randy Dunlap <rdunlap@...radead.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Bartosz Golaszewski <bgolaszewski@...libre.com>,
        linux-devicetree <devicetree@...r.kernel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        linuxppc-dev@...ts.ozlabs.org, xen-devel@...ts.xenproject.org,
        Nicolas Boichat <drinkcat@...omium.org>,
        Jim Quinlan <james.quinlan@...adcom.com>, tfiga@...omium.org,
        bskeggs@...hat.com, bhelgaas@...gle.com, chris@...is-wilson.co.uk,
        daniel@...ll.ch, airlied@...ux.ie, dri-devel@...ts.freedesktop.org,
        intel-gfx@...ts.freedesktop.org, jani.nikula@...ux.intel.com,
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        linux-pci@...r.kernel.org, maarten.lankhorst@...ux.intel.com,
        matthew.auld@...el.com, rodrigo.vivi@...el.com,
        thomas.hellstrom@...ux.intel.com
Subject: Re: [PATCH v7 01/15] swiotlb: Refactor swiotlb init functions

On 5/27/21 9:41 AM, Tom Lendacky wrote:
> On 5/27/21 8:02 AM, Christoph Hellwig wrote:
>> On Wed, May 19, 2021 at 11:50:07AM -0700, Florian Fainelli wrote:
>>> You convert this call site with swiotlb_init_io_tlb_mem() which did not
>>> do the set_memory_decrypted()+memset(). Is this okay or should
>>> swiotlb_init_io_tlb_mem() add an additional argument to do this
>>> conditionally?
>>
>> The zeroing is useful and was missing before.  I think having a clean
>> state here is the right thing.
>>
>> Not sure about the set_memory_decrypted, swiotlb_update_mem_attributes
>> kinda suggests it is too early to set the memory decrupted.
>>
>> Adding Tom who should now about all this.
> 
> The reason for adding swiotlb_update_mem_attributes() was because having
> the call to set_memory_decrypted() in swiotlb_init_with_tbl() triggered a
> BUG_ON() related to interrupts not being enabled yet during boot. So that
> call had to be delayed until interrupts were enabled.

I pulled down and tested the patch set and booted with SME enabled. The
following was seen during the boot:

[    0.134184] BUG: Bad page state in process swapper  pfn:108002
[    0.134196] page:(____ptrval____) refcount:0 mapcount:-128 mapping:0000000000000000 index:0x0 pfn:0x108002
[    0.134201] flags: 0x17ffffc0000000(node=0|zone=2|lastcpupid=0x1fffff)
[    0.134208] raw: 0017ffffc0000000 ffff88847f355e28 ffff88847f355e28 0000000000000000
[    0.134210] raw: 0000000000000000 0000000000000001 00000000ffffff7f 0000000000000000
[    0.134212] page dumped because: nonzero mapcount
[    0.134213] Modules linked in:
[    0.134218] CPU: 0 PID: 0 Comm: swapper Not tainted 5.13.0-rc2-sos-custom #3
[    0.134221] Hardware name: ...
[    0.134224] Call Trace:
[    0.134233]  dump_stack+0x76/0x94
[    0.134244]  bad_page+0xa6/0xf0
[    0.134252]  __free_pages_ok+0x331/0x360
[    0.134256]  memblock_free_all+0x158/0x1c1
[    0.134267]  mem_init+0x1f/0x14c
[    0.134273]  start_kernel+0x290/0x574
[    0.134279]  secondary_startup_64_no_verify+0xb0/0xbb

I see this about 40 times during the boot, each with a different PFN. The
system boots (which seemed odd), but I don't know if there will be side
effects to this (I didn't stress the system).

I modified the code to add a flag to not do the set_memory_decrypted(), as
suggested by Florian, when invoked from swiotlb_init_with_tbl(), and that
eliminated the bad page state BUG.

Thanks,
Tom

> 
> Thanks,
> Tom
> 
>>