[PATCH 0/4] KVM: arm64: pKVM SVE vCPU init fixes

[Fuad Tabba <fuad.tabba@linux.dev>]

Hi folks,

If it's not the GIC, it's SVE. I found these while preparing the
follow-up to the pKVM core series [1].

Patch 1 was posted on its own [2] and carries Marc's Reviewed-by. It is
unchanged and included here because it has not been picked up yet and
the rest of the series does not apply without it.

Patches 2 and 4 are two ways to reach the same broken state, a vCPU
whose sve_state is NULL while vcpu_has_sve() is true, so the world
switch loads the guest's SVE state from it. EL2 keeps two answers to
"does this guest have SVE": KVM_ARCH_FLAG_GUEST_HAS_SVE, which the
world switch reads, and KVM_ARM_VCPU_SVE, which pkvm_vcpu_init_sve()
reads. Patch 2 stops EL2 desynchronising them itself on an init
failure. Patch 4 stops the host handing them over already
desynchronised. Patch 3 keys the unpin on the state it unpins rather
than on the feature bit, which agree for any vCPU that completed init.

All of it needs a host that misreports its own vCPU state, so none of
it is reachable from host userspace.

Based on Linux 7.2, and applies cleanly to kvmarm/next.

Cheers,
/fuad

[1] https://lore.kernel.org/all/178552142335.30097.18179093757678605679.b4-ty@kernel.org/
[2] https://lore.kernel.org/all/20260818093117.2379344-1-fuad.tabba@linux.dev/

Fuad Tabba (4):
  KVM: arm64: Validate the SVE vector length in pkvm_vcpu_init_sve()
  KVM: arm64: Do not clear VM-wide SVE feature on vCPU init failure
  KVM: arm64: Key unpin_host_sve_state() on the state it unpins
  KVM: arm64: Derive GUEST_HAS_SVE from the SVE feature bit at EL2

 arch/arm64/kvm/hyp/nvhe/pkvm.c | 29 +++++++++++++----------------
 1 file changed, 13 insertions(+), 16 deletions(-)

-- 
2.39.5