[Bug 211117] [oxygen] [virtuoso] route, dmix and other alsa plugins produce garbage output with mem_encrypt on Ryzen platform

[Bug 211117] [oxygen] [virtuoso] route, dmix and other alsa plugins produce garbage output with mem_encrypt on Ryzen platform

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=211117

Jaroslav Kysela (perex@perex.cz) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|Sound(ALSA)                 |Platform_x86
           Assignee|perex@perex.cz              |drivers_platform_x86@kernel
                   |                            |-bugs.osdl.org

--- Comment #15 from Jaroslav Kysela (perex@perex.cz) ---
It looks like an issue which is not related directly to audio, right?

Reassigning to Platform_X86 .

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[Bug 211117] dma_mmap_coherent() - garbage sound output with mem_encrypt on Ryzen platform

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=211117

Jaroslav Kysela (perex@perex.cz) changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |perex@perex.cz
            Summary|[oxygen] [virtuoso] route,  |dma_mmap_coherent() -
                   |dmix and other alsa plugins |garbage sound output with
                   |produce garbage output with |mem_encrypt on Ryzen
                   |mem_encrypt on Ryzen        |platform
                   |platform                    |

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[Bug 211117] dma_mmap_coherent() - garbage sound output with mem_encrypt on Ryzen platform

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=211117

--- Comment #16 from Takashi Iwai (tiwai@suse.de) ---
Yes, this must be a generic issue.  I'll ask Christoph at first.

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[Bug 211117] dma_mmap_coherent() - garbage sound output with mem_encrypt on Ryzen platform

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=211117

thomas.lendacky@amd.com changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |thomas.lendacky@amd.com

--- Comment #17 from thomas.lendacky@amd.com ---
This sounds like a mismatch between the encryption bit in the kernel and the
encryption bit in userspace. It looks like that should be taken care of by the
dma_pgprot() call in dma_mmap_attrs() or in iommu_dma_mmap(). But maybe the
force_dma_unencrypted() in arch/x86/mm/mem_encrypt.c needs to understand if the
IOMMU is doing the mapping. Since, even if the device doesn't support 48-bit or
higher DMA, it will still done encrypted because of the IOMMU. I don't see any
dmesg output, is the IOMMU enabled? What happens if you do iommu=pt on the
kernel command line?

Alternatively, if you want memory encryption for your bare-metal system, you
can see if the BIOS supports TSME (Transparent SME). Then you can remove
mem_encrypt=on or add mem_encrypt=off (if enabled by default), and still get
memory encryption.

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[Bug 211117] dma_mmap_coherent() - garbage sound output with mem_encrypt on Ryzen platform

[bugzilla-daemon]

https://bugzilla.kernel.org/show_bug.cgi?id=211117

--- Comment #18 from Triton Circonflexe (triton+enkelr@kumal.info) ---
Tested with iommu=pt (and no mem_encrypt option, so "on" by default): still
white noise.

Regarding the encryption, I don't really have a _need_ for that. If I use it,
it's in part because Virtualbox seems to require it in some use cases (not even
entirely sure about that) and mostly because it's activated by default (and I
like default settings to work correctly).
I checked the BIOS anyway but did not find any TSME or similar option (thanks
for the information, though).

Right now, I'm working with mem_encrypt=off and I can do everything I need for
now (no vbox for the moment).
I will continue to follow this bug because I can reproduce the problem easily
and do tests if required.

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