From f1fb1d5c901797b80e17d5c1d2a38aee6b63fcd2 Mon Sep 17 00:00:00 2001
From: Andrew Turner <andrew@FreeBSD.org>
Date: Fri, 18 Oct 2024 10:16:41 +0100
Subject: [PATCH] arm64: Support more ID register field types

Add MRS_EXACT_IF_DIFFERENT, MRS_HIGHER_OR_ZERO, and MRS_HIGHER.

These will be used to handle the cache CTR_EL0 register, and make some
ID register values safer.

They are:
 - MRS_EXACT_IF_DIFFERENT: If the field is the same on all CPUs then
                           use this value, otherwise use the safe value.
 - MRS_HIGHER_OR_ZERO: Use the highest value, or zero if seen,
 - MRS_HIGHER: Use the highest value.

Reviewed by:	imp
Sponsored by:	Arm Ltd
Differential Revision:	https://reviews.freebsd.org/D47122
---
 sys/arm64/arm64/identcpu.c | 35 ++++++++++++++++++++++++++++++-----
 1 file changed, 30 insertions(+), 5 deletions(-)

diff --git a/sys/arm64/arm64/identcpu.c b/sys/arm64/arm64/identcpu.c
index 83d934af345e..48ac5c59274d 100644
--- a/sys/arm64/arm64/identcpu.c
+++ b/sys/arm64/arm64/identcpu.c
@@ -292,7 +292,10 @@ const struct cpu_implementers cpu_implementers[] = {
 #define	MRS_TYPE_MASK		0xf
 #define	MRS_INVALID		0
 #define	MRS_EXACT		1
-#define	MRS_LOWER		2
+#define	MRS_EXACT_IF_DIFFERENT	2
+#define	MRS_LOWER		3
+#define	MRS_HIGHER_OR_ZERO	4
+#define	MRS_HIGHER		5
 #define	MRS_SAFE_SHIFT		4
 #define	MRS_SAFE_MASK		(0xfu << MRS_SAFE_SHIFT)
 #define	MRS_SAFE(x)		(((x) << MRS_SAFE_SHIFT) & MRS_SAFE_MASK)
@@ -2175,19 +2178,41 @@ static uint64_t
 update_special_reg_field(uint64_t user_reg, u_int type, uint64_t value,
     u_int width, u_int shift, bool sign)
 {
+	uint64_t cur, mask, new_val;
+
+	mask = ((1ul << width) - 1) << shift;
+	cur = user_reg & mask;
+	new_val = value & mask;
+
 	switch (type & MRS_TYPE_MASK) {
+	case MRS_EXACT_IF_DIFFERENT:
+		if (mrs_field_cmp(cur, new_val, shift, width, sign) != 0)
+			break;
+		/* FALLTHROUGH */
 	case MRS_EXACT:
-		user_reg &= ~(0xful << shift);
-		user_reg |= (uint64_t)MRS_SAFE(type) << shift;
+		cur = (uint64_t)MRS_SAFE_VAL(type) << shift;
 		break;
 	case MRS_LOWER:
-		user_reg = update_lower_register(user_reg, value, shift, width,
-		    sign);
+		if (mrs_field_cmp(cur, new_val, shift, width, sign) < 0)
+			cur = new_val;
+		break;
+	case MRS_HIGHER_OR_ZERO:
+		if (cur == 0 || new_val == 0) {
+			cur = 0;
+			break;
+		}
+		/* FALLTHROUGH */
+	case MRS_HIGHER:
+		if (mrs_field_cmp(cur, new_val, shift, width, sign) > 0)
+			cur = new_val;
 		break;
 	default:
 		panic("Invalid field type: %d", type);
 	}
 
+	user_reg &= ~mask;
+	user_reg |= cur;
+
 	return (user_reg);
 }