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KVM: arm64: Finalize ID registers only once per VM

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Owing to the ID registers being global to the VM, there is no point
in computing them more than once.  However, recent changes making
use of kvm_set_vm_id_reg() outlined that we repeatedly hammer
the ID registers when we shouldn't.

Gate the ID reg update on the VM having never run.

Fixes: 50e7cce81b ("KVM: arm64: Limit clearing of ID_{AA64PFR0,PFR1}_EL1.GIC to userspace irqchip")
Fixes: 5cb57a1aff ("KVM: arm64: Zero ID_AA64PFR0_EL1.GIC when no GICv3 is presented to the guest")
Closes: https://lore.kernel.org/r/aRHf6x5umkTYhYJ3@finisterre.sirena.org.uk
Reported-by: Mark Brown <broonie@kernel.org>
Tested-by: Mark Brown <broonie@kernel.org>
Link: https://patch.msgid.link/20251110173010.1918424-1-maz@kernel.org
Signed-off-by: Marc Zyngier <maz@kernel.org>
This commit is contained in:
Marc Zyngier
2025-11-10 17:30:10 +00:00
parent 4af235bf64
commit 0f559cd91e
1 changed files with 5 additions and 1 deletions
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6
arch/arm64/kvm/sys_regs.c
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@@ -5609,7 +5609,11 @@ int kvm_finalize_sys_regs(struct kvm_vcpu *vcpu)
guard(mutex)(&kvm->arch.config_lock);
if (!irqchip_in_kernel(kvm)) {
/*
* This hacks into the ID registers, so only perform it when the
* first vcpu runs, or the kvm_set_vm_id_reg() helper will scream.
*/
if (!irqchip_in_kernel(kvm) && !kvm_vm_has_ran_once(kvm)) {
u64 val;
val = kvm_read_vm_id_reg(kvm, SYS_ID_AA64PFR0_EL1) & ~ID_AA64PFR0_EL1_GIC;