mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
synced 2026-08-20 13:00:09 -04:00
cdc69269b1
KVM tracks when EFER.SVME is set and cleared to initialize and tear down
nested state. However, it doesn't differentiate if EFER.SVME is getting
toggled in L1 or L2+. If L2 clears EFER.SVME, and L1 does not intercept
the EFER write, KVM exits guest mode and tears down nested state while
L2 is running, executing L1 without injecting a proper #VMEXIT.
According to the APM:
The effect of turning off EFER.SVME while a guest is running is
undefined; therefore, the VMM should always prevent guests from
writing EFER.
Since the behavior is architecturally undefined, KVM gets to choose what
to do. Inject a triple fault into L1 as a more graceful option that
running L1 with corrupted state.
Co-developed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Yosry Ahmed <yosry.ahmed@linux.dev>
base-commit: 95deaec3557dced322e2540bfa426e60e5373d46
Link: https://patch.msgid.link/20260209195142.2554532-2-yosry.ahmed@linux.dev
Signed-off-by: Sean Christopherson <seanjc@google.com>