[PATCH v3 21/42] KVM: arm64: Compute FGT masks from KVM's own FGT tables

[Marc Zyngier <maz@kernel.org>]

In the process of decoupling KVM's view of the FGT bits from the
wider architectural state, use KVM's own FGT tables to build
a synthetic view of what is actually known.

This allows for some checking along the way.

Signed-off-by: Marc Zyngier <maz@kernel.org>
---
 arch/arm64/include/asm/kvm_host.h |  14 ++++
 arch/arm64/kvm/emulate-nested.c   | 106 ++++++++++++++++++++++++++++++
 2 files changed, 120 insertions(+)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index 7a1ef5be7efb2..95fedd27f4bb8 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -607,6 +607,20 @@ struct kvm_sysreg_masks {
 	} mask[NR_SYS_REGS - __SANITISED_REG_START__];
 };
 
+struct fgt_masks {
+	const char	*str;
+	u64		mask;
+	u64		nmask;
+	u64		res0;
+};
+
+extern struct fgt_masks hfgrtr_masks;
+extern struct fgt_masks hfgwtr_masks;
+extern struct fgt_masks hfgitr_masks;
+extern struct fgt_masks hdfgrtr_masks;
+extern struct fgt_masks hdfgwtr_masks;
+extern struct fgt_masks hafgrtr_masks;
+
 struct kvm_cpu_context {
 	struct user_pt_regs regs;	/* sp = sp_el0 */
 
diff --git a/arch/arm64/kvm/emulate-nested.c b/arch/arm64/kvm/emulate-nested.c
index 52a2d63a667c9..528b33fcfcfd6 100644
--- a/arch/arm64/kvm/emulate-nested.c
+++ b/arch/arm64/kvm/emulate-nested.c
@@ -2033,6 +2033,105 @@ static u32 encoding_next(u32 encoding)
 	return sys_reg(op0 + 1, 0, 0, 0, 0);
 }
 
+#define FGT_MASKS(__n, __m)						\
+	struct fgt_masks __n = { .str = #__m, .res0 = __m, }
+
+FGT_MASKS(hfgrtr_masks, HFGRTR_EL2_RES0);
+FGT_MASKS(hfgwtr_masks, HFGWTR_EL2_RES0);
+FGT_MASKS(hfgitr_masks, HFGITR_EL2_RES0);
+FGT_MASKS(hdfgrtr_masks, HDFGRTR_EL2_RES0);
+FGT_MASKS(hdfgwtr_masks, HDFGWTR_EL2_RES0);
+FGT_MASKS(hafgrtr_masks, HAFGRTR_EL2_RES0);
+
+static __init bool aggregate_fgt(union trap_config tc)
+{
+	struct fgt_masks *rmasks, *wmasks;
+
+	switch (tc.fgt) {
+	case HFGRTR_GROUP:
+		rmasks = &hfgrtr_masks;
+		wmasks = &hfgwtr_masks;
+		break;
+	case HDFGRTR_GROUP:
+		rmasks = &hdfgrtr_masks;
+		wmasks = &hdfgwtr_masks;
+		break;
+	case HAFGRTR_GROUP:
+		rmasks = &hafgrtr_masks;
+		wmasks = NULL;
+		break;
+	case HFGITR_GROUP:
+		rmasks = &hfgitr_masks;
+		wmasks = NULL;
+		break;
+	}
+
+	/*
+	 * A bit can be reserved in either the R or W register, but
+	 * not both.
+	 */
+	if ((BIT(tc.bit) & rmasks->res0) &&
+	    (!wmasks || (BIT(tc.bit) & wmasks->res0)))
+		return false;
+
+	if (tc.pol)
+		rmasks->mask |= BIT(tc.bit) & ~rmasks->res0;
+	else
+		rmasks->nmask |= BIT(tc.bit) & ~rmasks->res0;
+
+	if (wmasks) {
+		if (tc.pol)
+			wmasks->mask |= BIT(tc.bit) & ~wmasks->res0;
+		else
+			wmasks->nmask |= BIT(tc.bit) & ~wmasks->res0;
+	}
+
+	return true;
+}
+
+static __init int check_fgt_masks(struct fgt_masks *masks)
+{
+	unsigned long duplicate = masks->mask & masks->nmask;
+	u64 res0 = masks->res0;
+	int ret = 0;
+
+	if (duplicate) {
+		int i;
+
+		for_each_set_bit(i, &duplicate, 64) {
+			kvm_err("%s[%d] bit has both polarities\n",
+				masks->str, i);
+		}
+
+		ret = -EINVAL;
+	}
+
+	masks->res0 = ~(masks->mask | masks->nmask);
+	if (masks->res0 != res0)
+		kvm_info("Implicit %s = %016llx, expecting %016llx\n",
+			 masks->str, masks->res0, res0);
+
+	return ret;
+}
+
+static __init int check_all_fgt_masks(int ret)
+{
+	static struct fgt_masks * const masks[] __initconst = {
+		&hfgrtr_masks,
+		&hfgwtr_masks,
+		&hfgitr_masks,
+		&hdfgrtr_masks,
+		&hdfgwtr_masks,
+		&hafgrtr_masks,
+	};
+	int err = 0;
+
+	for (int i = 0; i < ARRAY_SIZE(masks); i++)
+		err |= check_fgt_masks(masks[i]);
+
+	return ret ?: err;
+}
+
 int __init populate_nv_trap_config(void)
 {
 	int ret = 0;
@@ -2097,8 +2196,15 @@ int __init populate_nv_trap_config(void)
 			ret = xa_err(prev);
 			print_nv_trap_error(fgt, "Failed FGT insertion", ret);
 		}
+
+		if (!aggregate_fgt(tc)) {
+			ret = -EINVAL;
+			print_nv_trap_error(fgt, "FGT bit is reserved", ret);
+		}
 	}
 
+	ret = check_all_fgt_masks(ret);
+
 	kvm_info("nv: %ld fine grained trap handlers\n",
 		 ARRAY_SIZE(encoding_to_fgt));
 
-- 
2.39.2