pmap nocache

[Christoph Egger <Christoph_Egger%gmx.de@localhost>]

Hi,

Attached x86_nocache.diff removes the TLB flush
when mapping dma-safe memory.

Attached pmap_md.diff adds a PMAP_MD_MASK.
For x86 PAT feature you need six MD PMAP types.

Comments?

Christoph

Index: sys/uvm/uvm_pmap.h
===================================================================
RCS file: /cvsroot/src/sys/uvm/uvm_pmap.h,v
retrieving revision 1.25
diff -u -p -r1.25 uvm_pmap.h
--- sys/uvm/uvm_pmap.h  10 Dec 2008 11:10:20 -0000      1.25
+++ sys/uvm/uvm_pmap.h  16 Apr 2009 20:26:53 -0000
@@ -99,6 +99,9 @@ typedef struct pmap_statistics        *pmap_sta
  */
 #define        PMAP_WIRED      0x00000010      /* wired mapping */
 #define        PMAP_CANFAIL    0x00000020      /* can fail if resource 
shortage */
+
+#define        PMAP_MD_MASK    0x0000ff00      /* Machine-dependent bits */
+
 /*
  * Flags passed to pmap_kenter_pa().  Note the bottom 3 bits are VM_PROT_*
  * bits, used to indicate the access type.

Index: sys/arch/x86/include/pmap.h
===================================================================
RCS file: /cvsroot/src/sys/arch/x86/include/pmap.h,v
retrieving revision 1.22
diff -u -p -r1.22 pmap.h
--- sys/arch/x86/include/pmap.h 21 Mar 2009 14:41:30 -0000      1.22
+++ sys/arch/x86/include/pmap.h 16 Apr 2009 20:26:51 -0000
@@ -176,6 +176,11 @@ struct pmap {
 #endif
 
 /*
+ * MD flags that we use for pmap_enter:
+ */
+#define PMAP_NOCACHE   0x00000100      /* set the non-cacheable bit */
+
+/*
  * global kernel variables
  */
 
Index: sys/arch/x86/x86/bus_dma.c
===================================================================
RCS file: /cvsroot/src/sys/arch/x86/x86/bus_dma.c,v
retrieving revision 1.49
diff -u -p -r1.49 bus_dma.c
--- sys/arch/x86/x86/bus_dma.c  14 Mar 2009 14:46:08 -0000      1.49
+++ sys/arch/x86/x86/bus_dma.c  16 Apr 2009 20:26:51 -0000
@@ -1017,26 +1017,23 @@ int
 _bus_dmamem_map(bus_dma_tag_t t, bus_dma_segment_t *segs, int nsegs,
     size_t size, void **kvap, int flags)
 {
-       vaddr_t sva, va, eva;
+       vaddr_t va;
        bus_addr_t addr;
        int curseg;
-       int nocache;
-       pt_entry_t *pte, opte, xpte;
        const uvm_flag_t kmflags =
            (flags & BUS_DMA_NOWAIT) != 0 ? UVM_KMF_NOWAIT : 0;
+       int pmapflags = PMAP_WIRED | VM_PROT_READ | VM_PROT_WRITE;
 
        size = round_page(size);
-       nocache = (flags & BUS_DMA_NOCACHE) != 0;
+       if (flags & BUS_DMA_NOCACHE)
+               pmapflags |= PMAP_NOCACHE;
 
        va = uvm_km_alloc(kernel_map, size, 0, UVM_KMF_VAONLY | kmflags);
 
        if (va == 0)
-               return (ENOMEM);
+               return ENOMEM;
 
        *kvap = (void *)va;
-       sva = va;
-       eva = sva + size;
-       xpte = 0;
 
        for (curseg = 0; curseg < nsegs; curseg++) {
                for (addr = segs[curseg].ds_addr;
@@ -1046,30 +1043,12 @@ _bus_dmamem_map(bus_dma_tag_t t, bus_dma
                                panic("_bus_dmamem_map: size botch");
                        _BUS_PMAP_ENTER(pmap_kernel(), va, addr,
                            VM_PROT_READ | VM_PROT_WRITE,
-                           PMAP_WIRED | VM_PROT_READ | VM_PROT_WRITE);
-                       /*
-                        * mark page as non-cacheable
-                        */
-                       if (nocache) {
-                               pte = kvtopte(va);
-                               opte = *pte;
-                               if ((opte & PG_N) == 0) {
-                                       pmap_pte_setbits(pte, PG_N);
-                                       xpte |= opte;
-                               }
-                       }
+                           pmapflags);
                }
        }
-#ifndef XEN    /* XXX */
-       if ((xpte & (PG_V | PG_U)) == (PG_V | PG_U)) {
-               kpreempt_disable();
-               pmap_tlb_shootdown(pmap_kernel(), sva, eva, xpte);
-               kpreempt_enable();
-       }
        pmap_update(pmap_kernel());
-#endif
 
-       return (0);
+       return 0;
 }
 
 /*
Index: sys/arch/x86/x86/pmap.c
===================================================================
RCS file: /cvsroot/src/sys/arch/x86/x86/pmap.c,v
retrieving revision 1.82
diff -u -p -r1.82 pmap.c
--- sys/arch/x86/x86/pmap.c     21 Mar 2009 22:55:08 -0000      1.82
+++ sys/arch/x86/x86/pmap.c     16 Apr 2009 20:26:52 -0000
@@ -4044,6 +4044,8 @@ pmap_enter(struct pmap *pmap, vaddr_t va
        npte = ma | protection_codes[prot] | PG_V;
        if (wired)
                npte |= PG_W;
+       if (flags & PMAP_NOCACHE)
+               npte |= PG_N;
        if (va < VM_MAXUSER_ADDRESS)
                npte |= PG_u;
        else if (va < VM_MAX_ADDRESS)