[PATCH 20/28] KVM: arm64: Add sanitisation for NVHCR_EL2

[Marc Zyngier]

Just like any other VNCR-based register, NVHCR_EL2 requires some
level of sanitisation. Being specified as a live copy of HCR_EL2,
it adopts the exact same format, but depends on FEAT_NV3 instead.

A subtle aspect is that we only want to apply the sanitisation if
FEAT_NV3 is actually present, as the VNCR location is otherwise
used to back accesses to HCR_EL2.

Signed-off-by: Marc Zyngier <maz at kernel.org>
---
 arch/arm64/kvm/config.c | 15 +++++++++++++++
 arch/arm64/kvm/nested.c |  4 ++++
 2 files changed, 19 insertions(+)

diff --git a/arch/arm64/kvm/config.c b/arch/arm64/kvm/config.c
index b9a9d65b973e6..7e86479142723 100644
--- a/arch/arm64/kvm/config.c
+++ b/arch/arm64/kvm/config.c
@@ -1017,6 +1017,9 @@ static const struct reg_bits_to_feat_map hcr_feat_map[] = {
 static const DECLARE_FEAT_MAP(hcr_desc, HCR_EL2,
 			      hcr_feat_map, FEAT_AA64EL2);
 
+static const DECLARE_FEAT_MAP(nvhcr_desc, NVHCR_EL2,
+			      hcr_feat_map, FEAT_NV3);
+
 static const struct reg_bits_to_feat_map sctlr2_feat_map[] = {
 	NEEDS_FEAT(SCTLR2_EL1_NMEA	|
 		   SCTLR2_EL1_EASE,
@@ -1391,6 +1394,7 @@ void __init check_feature_map(void)
 	check_reg_desc(&hdfgwtr2_desc);
 	check_reg_desc(&hcrx_desc);
 	check_reg_desc(&hcr_desc);
+	check_reg_desc(&nvhcr_desc);
 	check_reg_desc(&sctlr2_desc);
 	check_reg_desc(&tcr2_el2_desc);
 	check_reg_desc(&sctlr_el1_desc);
@@ -1590,6 +1594,17 @@ struct resx get_reg_fixed_bits(struct kvm *kvm, enum vcpu_sysreg reg)
 	case HCR_EL2:
 		resx = compute_reg_resx_bits(kvm, &hcr_desc, 0, 0);
 		break;
+	case NVHCR_EL2:
+		/*
+		 * Only apply sanitisation if we do have FEAT_NV3.
+		 * Otherwise, the register aliases with HCR_EL2 in VNCR,
+		 * and we're better off relying on data transfers between
+		 * NVHCR_EL2 and HCR_EL2 to sanitise things.
+		 */
+		resx = (kvm_has_nv3(kvm) ?
+			compute_reg_resx_bits(kvm, &nvhcr_desc, 0, 0) :
+			(typeof(resx)){});
+		break;
 	case SCTLR2_EL1:
 	case SCTLR2_EL2:
 		resx = compute_reg_resx_bits(kvm, &sctlr2_desc, 0, 0);
diff --git a/arch/arm64/kvm/nested.c b/arch/arm64/kvm/nested.c
index 9972dea42d12a..c9bf04944f9cb 100644
--- a/arch/arm64/kvm/nested.c
+++ b/arch/arm64/kvm/nested.c
@@ -1830,6 +1830,10 @@ int kvm_init_nv_sysregs(struct kvm_vcpu *vcpu)
 	resx = get_reg_fixed_bits(kvm, HCR_EL2);
 	set_sysreg_masks(kvm, HCR_EL2, resx);
 
+	/* NVHCR_EL2 */
+	resx = get_reg_fixed_bits(kvm, NVHCR_EL2);
+	set_sysreg_masks(kvm, NVHCR_EL2, resx);
+
 	/* HCRX_EL2 */
 	resx = get_reg_fixed_bits(kvm, HCRX_EL2);
 	set_sysreg_masks(kvm, HCRX_EL2, resx);
-- 
2.47.3