KVM: arm64: Pin the host vCPU before adjusting its PC under pKVM

Under pKVM, a page the host shares with EL2 is mapped at EL2 only while
it's pinned, and the host vCPU is pinned at its first KVM_RUN.
KVM_SET_VCPU_EVENTS with ext_dabt_pending reaches __kvm_adjust_pc() at
EL2 before that, and dereferencing the unmapped host vCPU panics the
hypervisor. Any process holding /dev/kvm on a pKVM host can trigger it.

Pin the host vCPU around the adjustment when no hyp vCPU is loaded for
it. A loaded hyp vCPU implies it's pinned. A pin fails only for memory
the host isn't sharing, and the request is then dropped like any other
bad host pointer.

Fixes: efa1368ba9f4b ("KVM: arm64: Commit exceptions from KVM_SET_VCPU_EVENTS immediately")
Reviewed-by: Vincent Donnefort <vdonnefort@google.com>
Reviewed-by: Joey Gouly <joey.gouly@arm.com>
Cc: stable@vger.kernel.org
Signed-off-by: Fuad Tabba <fuad.tabba@linux.dev>
Link: https://patch.msgid.link/20261001135711.1640520-4-fuad.tabba@linux.dev
Signed-off-by: Marc Zyngier <maz@kernel.org>

0 files changed, 0 insertions, 0 deletions