KVM: arm64: Skip fixed-feature state flush for protected vCPUs

flush_hyp_vcpu() copies the host's mdcr_el2, TWI/TWE and debug state
into the hyp vCPU on every entry, so for a protected vCPU the host's
trap configuration overrides the one pkvm_vcpu_init_traps() computed
at EL2. Move the mdcr_el2 and TWI/TWE copies into the non-protected
branch, and return early from flush_debug_state() and
sync_debug_state() for a protected vCPU: its debug registers are
hypervisor-owned, and it takes the host's TWI/TWE at vCPU load.
MDCR_EL2.TDA traps only the guest's own accesses; it doesn't stop the
world switch from loading host-supplied breakpoints and MDSCR_EL1.

EL2's mdcr_el2 starts from 0, and HPMN == 0 is reserved without
FEAT_HPMN0. Set HPMN at vCPU load to PMCR_EL0.N on a PE whose
ID_AA64DFR0_EL1 implements PMUv3, the value the host's copy carried,
read as kvm_init_host_debug_data() reads it: the PMUv3 cpucap is
system-wide and off without CONFIG_HW_PERF_EVENTS. A protected guest's
PMU accesses trap regardless.

Signed-off-by: Fuad Tabba <fuad.tabba@linux.dev>
Link: https://patch.msgid.link/20261001135711.1640520-7-fuad.tabba@linux.dev
Signed-off-by: Marc Zyngier <maz@kernel.org>

0 files changed, 0 insertions, 0 deletions