[PATCH 0/4] crypto: ccp - Make sev_cmd_mutex more granular

[Michael Roth <michael.roth@amd.com>]

This patchset is also available at:

  https://github.com/amdese/linux/commits/ccp-mutex-rework-v1

and is based on cryptodev-2.6 master.


OVERVIEW
--------

The current code makes very coarse usage of the sev_cmd_mutex; for SEV
firmware ioctls, it is essentially taken upon entry, and ends up wrapping
a lot of potentially time-consuming prep/cleanup work that may need to be
done before/after issuing the actual firmware call, which is the main
thing the mutex is meant to protect.

Additionally, some of that prep work involves
copy_from_user()/copy_to_user() calls which can generate page faults and
unecessarily lead to potential deadlock scenarios. No known case exists
in current upstream, but with the upcoming KVM/guest_memfd support for
in-place conversion of the same PFN between shared/private state (which
is currently targeted for kernel 7.4), a special fault handler is added
that could theoretically deadlock if a malicious user tries to use
guest_memfd pages as the source/target of target of said
copy_from_user()/copy_to_user() scenarios[1].

So this series is a prereq to enabling the above-mentioned KVM/guest_memfd
in-place conversion support on SNP-enabled hosts, as well as a cleanup
for SEV ioctls in general.

Thank you to Sean for suggesting this approach and Ackerley for wrangling
the changes into a (hopefully) presentable patchset.


REFERENCES
----------

[1] https://lore.kernel.org/kvm/asz8GKNO9aQANr5E@google.com/


Thanks!

-Mike


----------------------------------------------------------------
Ackerley Tng (3):
      crypto: ccp - Shut down SEV firmware before copying to user
      crypto: ccp - Check SNP initialization state after copying user inputs
      crypto: ccp - Make usage of sev_cmd_mutex more granular

Michael Roth (1):
      crypto: ccp - Allocate status page outside sev_cmd_mutex in SNP_PLATFORM_STATUS

 drivers/crypto/ccp/sev-dev.c | 165 ++++++++++++++++++++++++-------------------
 1 file changed, 94 insertions(+), 71 deletions(-)