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

Claire Chang
2021-05-31T17:06:28Z

On Fri, May 28, 2021 at 12:32 AM Tom Lendacky <thomas.lendacky@amd.com> wrote:
>
> 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. Will add a flag to skip set_memory_decrypted() in v9.

>
> Thanks,
> Tom
>
> >
> > Thanks,
> > Tom
> >
> >>