From 90b82dc43f04ece19e17a2b355baa02a63a47f4c Mon Sep 17 00:00:00 2001
From: xvanc <xvancm@gmail.com>
Date: Wed, 13 Sep 2023 09:38:47 -0500
Subject: [PATCH] riscv/vmm: use Svpbmt extension when available

---
 common/mm/vmm.c        | 13 +++++++++++++
 common/sys/cpu_riscv.c |  4 ++--
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/common/mm/vmm.c b/common/mm/vmm.c
index b46dba2e..2d456173 100644
--- a/common/mm/vmm.c
+++ b/common/mm/vmm.c
@@ -246,6 +246,7 @@ level4:
 #define PT_FLAG_USER        ((uint64_t)1 << 4)
 #define PT_FLAG_ACCESSED    ((uint64_t)1 << 6)
 #define PT_FLAG_DIRTY       ((uint64_t)1 << 7)
+#define PT_FLAG_PBMT_NC     ((uint64_t)1 << 62)
 #define PT_PADDR_MASK       ((uint64_t)0x003ffffffffffc00)
 
 #define PT_FLAG_RWX         (PT_FLAG_READ | PT_FLAG_WRITE | PT_FLAG_EXEC)
@@ -265,6 +266,8 @@ static uint64_t pt_to_vmm_flags_internal(pt_entry_t entry) {
         flags |= VMM_FLAG_WRITE;
     if (!(entry & PT_FLAG_EXEC))
         flags |= VMM_FLAG_NOEXEC;
+    if (entry & PT_FLAG_PBMT_NC)
+        flags |= VMM_FLAG_FB;
 
     return flags;
 }
@@ -331,11 +334,19 @@ done:
     return 6 + max_level;
 }
 
+static pt_entry_t pbmt_nc = 0;
+
 pagemap_t new_pagemap(int paging_mode) {
     pagemap_t pagemap;
     pagemap.paging_mode   = paging_mode;
     pagemap.max_page_size = paging_mode - 6;
     pagemap.top_level     = ext_mem_alloc(PT_SIZE);
+
+    if (riscv_check_isa_extension("svpbmt", NULL, NULL)) {
+        printv("riscv: Svpbmt extension is supported.\n");
+        pbmt_nc = PT_FLAG_PBMT_NC;
+    }
+
     return pagemap;
 }
 
@@ -351,6 +362,8 @@ void map_page(pagemap_t pagemap, uint64_t virt_addr, uint64_t phys_addr, uint64_
         ptflags |= PT_FLAG_WRITE;
     if (!(flags & VMM_FLAG_NOEXEC))
         ptflags |= PT_FLAG_EXEC;
+    if (flags & VMM_FLAG_FB)
+        ptflags |= pbmt_nc;
 
     // Start at the highest level.
     // The values of `enum page_size` map to the level index at which that size is mapped.
diff --git a/common/sys/cpu_riscv.c b/common/sys/cpu_riscv.c
index 37dcff90..41203b50 100644
--- a/common/sys/cpu_riscv.c
+++ b/common/sys/cpu_riscv.c
@@ -80,7 +80,7 @@ static inline struct rhct_hart_info *rhct_get_hart_info(struct rhct *rhct, uint3
     return NULL;
 }
 
-void riscv_init(void) {
+void init_riscv(void) {
     struct madt *madt = acpi_get_table("APIC", 0);
     struct rhct *rhct = acpi_get_table("RHCT", 0);
     if (madt == NULL || rhct == NULL) {
@@ -221,7 +221,7 @@ static bool parse_extension(const char **s, struct isa_extension *ext) {
 }
 
 static bool extension_matches(const struct isa_extension *ext, const char *name) {
-    for (size_t i = ext->name_len; i > 0; i--) {
+    for (size_t i = 0; i < ext->name_len; i++) {
         const char c1 = tolower(ext->name[i]);
         const char c2 = tolower(*name++);
         if (c2 == '\0' || c1 != c2) {