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

On Fri, May 28, 2021 at 12:32 AM Tom Lendacky [off-list ref] wrote:

On 5/27/21 9:41 AM, Tom Lendacky wrote:

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On 5/27/21 8:02 AM, Christoph Hellwig wrote:

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On Wed, May 19, 2021 at 11:50:07AM -0700, Florian Fainelli wrote:

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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. Will add a flag to skip set_memory_decrypted() in v9.

Thanks,
Tom

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Thanks,
Tom

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