[ Cc'ing Tom Lendacky which I forgot to do earlier. Sorry about that. ]

Hello Halil,

Thanks for the quick review.

Halil Pasic [off-list ref] writes:

On Fri, 12 Jul 2019 02:36:31 -0300
Thiago Jung Bauermann [off-list ref] wrote:

quoted

Secure Encrypted Virtualization is an x86-specific feature, so it shouldn't
appear in generic kernel code because it forces non-x86 architectures to
define the sev_active() function, which doesn't make a lot of sense.

sev_active() might be just bad (too specific) name for a general
concept. s390 code defines it drives the right behavior in
kernel/dma/direct.c (which uses it).

I thought about that but couldn't put my finger on a general concept.
Is it "guest with memory inaccessible to the host"?

Since your proposed definiton for force_dma_unencrypted() is simply to
make it equivalent to sev_active(), I thought it was more
straightforward to make each arch define force_dma_unencrypted()
directly.

Also, does sev_active() drive the right behavior for s390 in
elfcorehdr_read() as well?

quoted

To solve this problem, add an x86 elfcorehdr_read() function to override
the generic weak implementation. To do that, it's necessary to make
read_from_oldmem() public so that it can be used outside of vmcore.c.

Signed-off-by: Thiago Jung Bauermann <redacted>
---
 arch/x86/kernel/crash_dump_64.c |  5 +++++
 fs/proc/vmcore.c                |  8 ++++----
 include/linux/crash_dump.h      | 14 ++++++++++++++
 include/linux/mem_encrypt.h     |  1 -
 4 files changed, 23 insertions(+), 5 deletions(-)

Does not seem to apply to today's or yesterdays master.

It assumes the presence of the two patches I mentioned in the cover
letter. Only one of them is in master.

I hadn't realized the s390 virtio patches were on their way to upstream.
I was keeping an eye on the email thread but didn't see they were picked
up in the s390 pull request. I'll add a new patch to this series making
the corresponding changes to s390's <asm/mem_encrypt.h> as well.

--
Thiago Jung Bauermann
IBM Linux Technology Center