Commit 2e3cf820 authored by Oliver Upton's avatar Oliver Upton
Browse files

KVM: arm64: nv: Ensure correct VL is loaded before saving SVE state 



It is possible that the guest hypervisor has selected a smaller VL than
the maximum for its nested guest. As such, ZCR_EL2 may be configured for
a different VL when exiting a nested guest.

Set ZCR_EL2 (via the EL1 alias) to the maximum VL for the VM before
saving SVE state as the SVE save area is dimensioned by the max VL.

Reviewed-by: default avatarMarc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20240620164653.1130714-8-oliver.upton@linux.dev


Signed-off-by: default avatarOliver Upton <oliver.upton@linux.dev>
parent 9092aca9

arch/arm64/kvm/fpsimd.c

+7 −4
Original line number Diff line number Diff line
@@ -195,11 +195,14 @@ void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu) 
			 * Note that this means that at guest exit ZCR_EL1 is

			 * not necessarily the same as on guest entry.

			 *

			 * Restoring the VL isn't needed in VHE mode since

			 * ZCR_EL2 (accessed via ZCR_EL1) would fulfill the same

			 * role when doing the save from EL2.

			 * ZCR_EL2 holds the guest hypervisor's VL when running

			 * a nested guest, which could be smaller than the

			 * max for the vCPU. Similar to above, we first need to

			 * switch to a VL consistent with the layout of the

			 * vCPU's SVE state. KVM support for NV implies VHE, so

			 * using the ZCR_EL1 alias is safe.

			 */

			if (!has_vhe())

			if (!has_vhe() || (vcpu_has_nv(vcpu) && !is_hyp_ctxt(vcpu)))

				sve_cond_update_zcr_vq(vcpu_sve_max_vq(vcpu) - 1,

						       SYS_ZCR_EL1);

		}