From 0ee738ef8c34d5494265b8a14435333f45b96dc6 Mon Sep 17 00:00:00 2001
From: cinap_lenrek <cinap_lenrek@felloff.net>
Date: Wed, 2 Oct 2019 00:58:46 +0200
Subject: [PATCH] vgai81x: use vmap() for uncached access to cursor data
 instead of manipulating kernel page table

on 386, the kernel memory region is mapped using huge 4MB pages
(when supported by the cpu). so the uncached pte manipulation
does not work to map the cursor data with uncached attribute.

instead, we allocate a memory page using newpage() and map
it globally using vmap(), which maps it uncached.
---
 sys/src/9/pc/vgai81x.c | 33 ++++++++++++++++-----------------
 1 file changed, 16 insertions(+), 17 deletions(-)

diff --git a/sys/src/9/pc/vgai81x.c b/sys/src/9/pc/vgai81x.c
index 07b8b489d..735f33915 100644
--- a/sys/src/9/pc/vgai81x.c
+++ b/sys/src/9/pc/vgai81x.c
@@ -56,7 +56,7 @@ i81xenable(VGAscr* scr)
 	Pcidev *p;
 	int size;
 	Mach *mach0;
-	ulong *pgtbl, *rp, cursor, *pte, fbuf, fbend;
+	ulong *pgtbl, *rp, fbuf, fbend;
 	
 	if(scr->mmio)
 		return;
@@ -90,18 +90,7 @@ i81xenable(VGAscr* scr)
 		fbuf += BY2PG;
 	}
 
-	/*
-	 * allocate space for the cursor data in system memory.
-	 * must be uncached.
-	 */
-	cursor = (ulong)xspanalloc(BY2PG, BY2PG, 0);
-	mach0 = MACHP(0);
-	pte = mmuwalk(mach0->pdb, cursor, 2, 0);
-	if(pte == nil)
-		panic("i81x cursor mmuwalk");
-	*pte |= PTEUNCACHED;
-	scr->storage = cursor;
-
+	scr->storage = 0;
 	scr->blank = i81xblank;
 }
 
@@ -123,7 +112,7 @@ i81xcurload(VGAscr* scr, Cursor* curs)
 	uchar *p;
 	CursorI81x *hwcurs;
 
-	if(scr->mmio == 0)
+	if(scr->mmio == 0 || scr->storage == 0)
 		return;
 	hwcurs = (void*)((uchar*)scr->mmio+hwCur);
 
@@ -192,23 +181,33 @@ i81xcurenable(VGAscr* scr)
 {
 	int i;
 	uchar *p;
-	CursorI81x *hwcurs;
 
 	i81xenable(scr);
 	if(scr->mmio == 0)
 		return;
-	hwcurs = (void*)((uchar*)scr->mmio+hwCur);
+
+	if(scr->storage == 0){
+		CursorI81x *hwcurs;
+		Page *pg = newpage(0, nil, 0);
+		scr->storage = (uintptr)vmap(pg->pa, BY2PG);
+		if(scr->storage == 0){
+			putpage(pg);
+			return;
+		}
+		hwcurs = (void*)((uchar*)scr->mmio+hwCur);
+		hwcurs->base = pg->pa;
+	}
 
 	/*
 	 * Initialise the 32x32 cursor to be transparent in 2bpp mode.
 	 */
-	hwcurs->base = PADDR(scr->storage);
 	p = (uchar*)scr->storage;
 	for(i = 0; i < 32/2; i++) {
 		memset(p, 0xff, 8);
 		memset(p+8, 0, 8);
 		p += 16;
 	}
+
 	/*
 	 * Load, locate and enable the 32x32 cursor in 2bpp mode.
 	 */