KVM: arm64: Use KVM-specific HCRX_EL2 RES0 mask

We do not have a computed table for HCRX_EL2, so statically define
the bits we know about. A warning will fire if the architecture
grows bits that are not handled yet.

Reviewed-by: Joey Gouly <[email protected]>
Signed-off-by: Marc Zyngier <[email protected]>

Author: Marc Zyngier

arch/arm64/include/asm/kvm_arm.h

@@ -315,10 +315,20 @@
 				 GENMASK(19, 18) |	\
 				 GENMASK(15, 0))
 
-/* Polarity masks for HCRX_EL2 */
-#define __HCRX_EL2_RES0         HCRX_EL2_RES0
-#define __HCRX_EL2_MASK		(BIT(6))
-#define __HCRX_EL2_nMASK	~(__HCRX_EL2_RES0 | __HCRX_EL2_MASK)
+/*
+ * Polarity masks for HCRX_EL2, limited to the bits that we know about
+ * at this point in time. It doesn't mean that we actually *handle*
+ * them, but that at least those that are not advertised to a guest
+ * will be RES0 for that guest.
+ */
+#define __HCRX_EL2_MASK		(BIT_ULL(6))
+#define __HCRX_EL2_nMASK	(GENMASK_ULL(24, 14) | \
+				 GENMASK_ULL(11, 7)  | \
+				 GENMASK_ULL(5, 0))
+#define __HCRX_EL2_RES0		~(__HCRX_EL2_nMASK | __HCRX_EL2_MASK)
+#define __HCRX_EL2_RES1		~(__HCRX_EL2_nMASK | \
+				  __HCRX_EL2_MASK  | \
+				  __HCRX_EL2_RES0)
 
 /* Hyp Prefetch Fault Address Register (HPFAR/HDFAR) */
 #define HPFAR_MASK	(~UL(0xf))

arch/arm64/kvm/emulate-nested.c

@@ -2157,6 +2157,7 @@ int __init populate_nv_trap_config(void)
 	BUILD_BUG_ON(__NR_CGT_GROUP_IDS__ > BIT(TC_CGT_BITS));
 	BUILD_BUG_ON(__NR_FGT_GROUP_IDS__ > BIT(TC_FGT_BITS));
 	BUILD_BUG_ON(__NR_FG_FILTER_IDS__ > BIT(TC_FGF_BITS));
+	BUILD_BUG_ON(__HCRX_EL2_MASK & __HCRX_EL2_nMASK);
 
 	for (int i = 0; i < ARRAY_SIZE(encoding_to_cgt); i++) {
 		const struct encoding_to_trap_config *cgt = &encoding_to_cgt[i];
@@ -2182,6 +2183,10 @@ int __init populate_nv_trap_config(void)
 		}
 	}
 
+	if (__HCRX_EL2_RES0 != HCRX_EL2_RES0)
+		kvm_info("Sanitised HCR_EL2_RES0 = %016llx, expecting %016llx\n",
+			 __HCRX_EL2_RES0, HCRX_EL2_RES0);
+
 	kvm_info("nv: %ld coarse grained trap handlers\n",
 		 ARRAY_SIZE(encoding_to_cgt));
 

arch/arm64/kvm/nested.c

@@ -1058,8 +1058,8 @@ int kvm_init_nv_sysregs(struct kvm_vcpu *vcpu)
 	set_sysreg_masks(kvm, HCR_EL2, res0, res1);
 
 	/* HCRX_EL2 */
-	res0 = HCRX_EL2_RES0;
-	res1 = HCRX_EL2_RES1;
+	res0 = __HCRX_EL2_RES0;
+	res1 = __HCRX_EL2_RES1;
 	if (!kvm_has_feat(kvm, ID_AA64ISAR3_EL1, PACM, TRIVIAL_IMP))
 		res0 |= HCRX_EL2_PACMEn;
 	if (!kvm_has_feat(kvm, ID_AA64PFR2_EL1, FPMR, IMP))