KVM: arm64: Add system register reset framework for protected VMs

Add kvm_reset_pvm_sys_regs() and the pvm_sys_reg_reset_vals[] table
that drives it, and call it from init_pkvm_hyp_vcpu() for protected
vCPUs. The table holds the registers KVM resets that EL2 loads for a
protected vCPU: the ones __sysreg_restore_state_nvhe() restores, and
CNTV_CTL_EL0, which flush_hyp_timer_state() loads from a copy the
host's kvm_timer_vcpu_reset() doesn't write. The ptrauth keys, which
entry.S loads, are not in the table: sys_regs.c resets them to
UNKNOWN, and a vCPU that CPU_ON brings back keeps the keys the guest
last set, one UNKNOWN value in place of another.

A register that resets to 0 still takes an entry: a later patch calls
kvm_reset_pvm_sys_regs() again for PSCI CPU_ON at EL2, on a context
that has run.

A poison value stands in where sys_regs.c resets to UNKNOWN, and for
VBAR_EL1 and CONTEXTIDR_EL1 in place of the 0 it uses.

MPIDR_EL1 is derived from vcpu_id, as for any KVM guest.

AMAIR_EL1 resets to 0 where sys_regs.c reads the hardware: the host
writes it freely before the hypercall, and it's loaded on every guest
entry.

Until the per-EC marshalling patch removes the host's full-context
copy from flush_hyp_vcpu(), that copy overwrites these values on every
entry. It preserves CNTV_CTL_EL0, whose entry writes the zero the page
already holds. So this patch has no observable effect on its own.

No functional change intended.

Reviewed-by: Joey Gouly <joey.gouly@arm.com>
Signed-off-by: Fuad Tabba <fuad.tabba@linux.dev>
Link: https://patch.msgid.link/20261001135711.1640520-9-fuad.tabba@linux.dev
Signed-off-by: Marc Zyngier <maz@kernel.org>

0 files changed, 0 insertions, 0 deletions