[v2] igvm/sev: apply the IGVM guest policy before launch

[PATCH v2 0/5] igvm/sev: apply the IGVM guest policy before launch

Luigi Leonardi posted 5 patches 2 weeks, 5 days ago

Diff against v1
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git fetch https://github.com/patchew-project/qemu tags/patchew/20260907-fix._5Figvm._5Fpolicy-v2-0-c8c50f1dbfda@redhat.com

Maintainers: Gerd Hoffmann <kraxel@redhat.com>, Stefano Garzarella <sgarzare@redhat.com>, Ani Sinha <anisinha@redhat.com>, Paolo Bonzini <pbonzini@redhat.com>, Zhao Liu <zhao1.liu@intel.com>, Marcelo Tosatti <mtosatti@redhat.com>

backends/confidential-guest-support.c       |  24 +++-
backends/igvm.c                             |  91 ++++++------
include/system/confidential-guest-support.h |  36 +++--
include/system/igvm-internal.h              |   3 -
target/i386/sev.c                           | 215 ++++++++++++++++++----------
5 files changed, 230 insertions(+), 139 deletions(-)

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[PATCH v2 0/5] igvm/sev: apply the IGVM guest policy before launch

Posted by Luigi Leonardi 2 weeks, 5 days ago

The guest policy from an IGVM file never actually made it to the platform
before launch. The callback that was supposed to forward it ran after
LAUNCH_START, so it did nothing and the guest was launched with the
default policy instead of the one requested by the file.

The policy is part of the attestation report, so this quietly breaks
attestation: the resulting measurement does not match what the IGVM file
was built for.

Patches 1 to 4 are cleanups needed to get there: dropping an overloaded
callback, moving the SNP ID block handling, giving the policy properties
proper accessors, and adding a way to read back the platform's current
guest policy. Patch 5 is the actual fix.

One thing worth calling out: if a policy is also passed on the command
line and it differs from the IGVM one, the command-line value takes
precedence and we print a warning instead of silently picking one over
the other.

Signed-off-by: Luigi Leonardi <leonardi@redhat.com>
---
Changes in v2:
- Rework the callback split. Now we don't have an unimplemented callback [Stefano, Gerd]
- Reject a command-line/IGVM policy that doesn't fit in the 32-bit
  SEV/SEV-ES policy field instead of truncating it [Stefano]
- On a mismatch between the command-line and IGVM policy, print a warning and
  keep the command-line value instead of returning an error. [Daniel,
  Gerd, Stefano]
- Picked up RoB
- Rebased to latest upstream
- Link to v1: https://lore.kernel.org/qemu-devel/20260901-fix_igvm_policy-v1-0-e93a6cf8c5ac@redhat.com

---
Luigi Leonardi (5):
      sev: split set_guest_policy into set_guest_policy and set_id_block
      igvm: move set_id_block call into the SNP ID block directive handler
      i386/sev: convert the guest policy properties to custom accessors
      i386/sev: add a get_guest_policy callback
      igvm/sev: forward the IGVM guest policy to the platform before launch

 backends/confidential-guest-support.c       |  24 +++-
 backends/igvm.c                             |  91 ++++++------
 include/system/confidential-guest-support.h |  36 +++--
 include/system/igvm-internal.h              |   3 -
 target/i386/sev.c                           | 215 ++++++++++++++++++----------
 5 files changed, 230 insertions(+), 139 deletions(-)
---
base-commit: cacd3462963a0a4f5bab4263ce79c2aa4b32692d
change-id: 20260831-fix_igvm_policy-0b92de52dd6a

Best regards,
-- 
Luigi Leonardi <leonardi@redhat.com>