Changeset de96d3b in mainline for kernel/arch/amd64/src/amd64.c

Timestamp:

2024-01-03T16:54:15Z (4 months ago)

Author:

Jiří Zárevúcky <zarevucky.jiri@…>

Branches:

master, topic/simplify-dev-export

Children:

00e6288, 25e1490

Parents:

7130754

git-author:

Jiří Zárevúcky <zarevucky.jiri@…> (2024-01-01 04:12:52)

git-committer:

Jiří Zárevúcky <zarevucky.jiri@…> (2024-01-03 16:54:15)

Message:

On x86 CPUs supporting it, use write-combining memory mode for framebuffer

With this, kernel printouts are about three times faster in QEMU.

File:

• kernel/arch/amd64/src/amd64.c (modified) (2 diffs)

kernel/arch/amd64/src/amd64.c

@@ -60 +60 @@
 #include <arch/vreg.h>
 #include <arch/kseg.h>
+#include <arch/mm/pat.h>
 #include <genarch/pic/pic_ops.h>
 
@@ -115 +116 @@
         /* Disable alignment check */
         write_cr0(read_cr0() & ~CR0_AM);
+
+        /* Use PCD+PWT bit combination in PTE to mean write-combining mode. */
+        if (pat_supported())
+                pat_set_mapping(false, true, true, PAT_TYPE_WRITE_COMBINING);
 
         if (config.cpu_active == 1) {