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Bochs/bochs/patches/patch.seg-checks
Bryce Denney e1df049256 - add patch submitted by Kevin Lawton on ML
2002-08-27 23:00:58 +00:00

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----------------------------------------------------------------------
Patch name: patch.seg-checks
Author: Kevin Lawton <kevinlawton2001@yahoo.com>
Date: Tue, 27 Aug 2002 15:47:14 -0700 (PDT)
Detailed description:
Here's some pretty simple mods that speed things up some.
The memory access routines in access.cc now skip the segment
type check if they've seen the same R or W operation on that
segment before, plus do their limit check if the access check
is not needed. This eliminates the call to write_virtual_checks()
and read_virtual_check() for most cases.
The limit check is a little faster as well.
There is a field in each segment cache called "valid". Since
this was always loaded with 0 or 1 when the segment is reloaded
or invalidated due to a context change, this made for an easy
place to store a couple extra bits to record when a read and
a write access to that seg has occurred. Other code that
sets "valid" to 0 or 1 wipes out the R&W bits, which is good,
since at least one new access check must occur before succeeding
accesses can eliminate it.
I'll let you folks benchmark the difference. One test
prog I ran gained 6%, but I'm not sure if it's register
intensive (and thus wouldn't gain much) vs memory access
intensive.
Patch was created with:
cvs diff -u
Apply patch to what version:
cvs checked out on DATE, release version VER
Instructions:
To patch, go to main bochs directory.
Type "patch -p0 < THIS_PATCH_FILE".
----------------------------------------------------------------------
Index: cpu/access.cc
===================================================================
RCS file: /cvsroot/bochs/bochs/cpu/access.cc,v
retrieving revision 1.12
diff -u -r1.12 access.cc
--- cpu/access.cc 3 Oct 2001 13:10:37 -0000 1.12
+++ cpu/access.cc 27 Aug 2002 22:28:19 -0000
@@ -38,14 +38,12 @@
-
void
BX_CPU_C::write_virtual_checks(bx_segment_reg_t *seg, Bit32u offset,
unsigned length)
{
Bit32u upper_limit;
-
if ( protected_mode() ) {
if ( seg->cache.valid==0 ) {
BX_ERROR(("seg = %s", BX_CPU_THIS_PTR strseg(seg)));
@@ -81,6 +79,16 @@
exception(int_number(seg), 0, 0);
return;
}
+ if (seg->cache.u.segment.limit_scaled >= 3) {
+ // Mark cache as being OK type for succeeding writes. The limit
+ // checks still needs to be done though, but is more simple. We
+ // could probably also optimize that out with a flag for the case
+ // when limit is the maximum 32bit value. Limit should accomodate
+ // at least a dword, since we subtract from it in the simple
+ // limit check in other functions, and we don't want the value to roll.
+ // Only normal segments (not expand down) are handled this way.
+ seg->cache.valid |= SegAccessWOK;
+ }
break;
case 6: case 7: /* read write, expand down */
@@ -109,6 +117,10 @@
if (seg == & BX_CPU_THIS_PTR sregs[2]) exception(BX_SS_EXCEPTION, 0, 0);
else exception(BX_GP_EXCEPTION, 0, 0);
}
+ if (seg->cache.u.segment.limit_scaled >= 3) {
+ // Mark cache as being OK type for succeeding writes. See notes above.
+ seg->cache.valid |= SegAccessWOK;
+ }
}
}
@@ -118,7 +130,6 @@
{
Bit32u upper_limit;
-
if ( protected_mode() ) {
if ( seg->cache.valid==0 ) {
BX_ERROR(("seg = %s", BX_CPU_THIS_PTR strseg(seg)));
@@ -148,6 +159,11 @@
exception(int_number(seg), 0, 0);
return;
}
+ if (seg->cache.u.segment.limit_scaled >= 3) {
+ // Mark cache as being OK type for succeeding writes. See notes for
+ // write checks; similar code.
+ seg->cache.valid |= SegAccessROK;
+ }
break;
case 2: case 3: /* read/write */
@@ -157,6 +173,11 @@
exception(int_number(seg), 0, 0);
return;
}
+ if (seg->cache.u.segment.limit_scaled >= 3) {
+ // Mark cache as being OK type for succeeding writes. See notes for
+ // write checks; similar code.
+ seg->cache.valid |= SegAccessROK;
+ }
break;
case 4: case 5: /* read only, expand down */
@@ -206,6 +227,11 @@
if (seg == & BX_CPU_THIS_PTR sregs[2]) exception(BX_SS_EXCEPTION, 0, 0);
else exception(BX_GP_EXCEPTION, 0, 0);
}
+ if (seg->cache.u.segment.limit_scaled >= 3) {
+ // Mark cache as being OK type for succeeding writes. See notes for
+ // write checks; similar code.
+ seg->cache.valid |= SegAccessROK;
+ }
return;
}
}
@@ -238,13 +264,19 @@
bx_segment_reg_t *seg;
seg = &BX_CPU_THIS_PTR sregs[s];
- write_virtual_checks(seg, offset, 1);
-
- laddr = seg->cache.u.segment.base + offset;
- BX_INSTR_MEM_DATA(laddr, 1, BX_WRITE);
+ if (seg->cache.valid & SegAccessWOK) {
+ if (offset <= seg->cache.u.segment.limit_scaled) {
+accessOK:
+ laddr = seg->cache.u.segment.base + offset;
+ BX_INSTR_MEM_DATA(laddr, 1, BX_WRITE);
- // all checks OK
- access_linear(laddr, 1, CPL==3, BX_WRITE, (void *) data);
+ // all checks OK
+ access_linear(laddr, 1, CPL==3, BX_WRITE, (void *) data);
+ return;
+ }
+ }
+ write_virtual_checks(seg, offset, 1);
+ goto accessOK;
}
void
@@ -254,13 +286,19 @@
bx_segment_reg_t *seg;
seg = &BX_CPU_THIS_PTR sregs[s];
- write_virtual_checks(seg, offset, 2);
+ if (seg->cache.valid & SegAccessWOK) {
+ if (offset < seg->cache.u.segment.limit_scaled) {
+accessOK:
+ laddr = seg->cache.u.segment.base + offset;
+ BX_INSTR_MEM_DATA(laddr, 2, BX_WRITE);
- laddr = seg->cache.u.segment.base + offset;
- BX_INSTR_MEM_DATA(laddr, 2, BX_WRITE);
-
- // all checks OK
- access_linear(laddr, 2, CPL==3, BX_WRITE, (void *) data);
+ // all checks OK
+ access_linear(laddr, 2, CPL==3, BX_WRITE, (void *) data);
+ return;
+ }
+ }
+ write_virtual_checks(seg, offset, 2);
+ goto accessOK;
}
void
@@ -270,13 +308,19 @@
bx_segment_reg_t *seg;
seg = &BX_CPU_THIS_PTR sregs[s];
- write_virtual_checks(seg, offset, 4);
+ if (seg->cache.valid & SegAccessWOK) {
+ if (offset < (seg->cache.u.segment.limit_scaled-2)) {
+accessOK:
+ laddr = seg->cache.u.segment.base + offset;
+ BX_INSTR_MEM_DATA(laddr, 4, BX_WRITE);
- laddr = seg->cache.u.segment.base + offset;
- BX_INSTR_MEM_DATA(laddr, 4, BX_WRITE);
-
- // all checks OK
- access_linear(laddr, 4, CPL==3, BX_WRITE, (void *) data);
+ // all checks OK
+ access_linear(laddr, 4, CPL==3, BX_WRITE, (void *) data);
+ return;
+ }
+ }
+ write_virtual_checks(seg, offset, 4);
+ goto accessOK;
}
void
@@ -286,13 +330,19 @@
bx_segment_reg_t *seg;
seg = &BX_CPU_THIS_PTR sregs[s];
- read_virtual_checks(seg, offset, 1);
+ if (seg->cache.valid & SegAccessROK) {
+ if (offset <= seg->cache.u.segment.limit_scaled) {
+accessOK:
+ laddr = seg->cache.u.segment.base + offset;
+ BX_INSTR_MEM_DATA(laddr, 1, BX_READ);
- laddr = seg->cache.u.segment.base + offset;
- BX_INSTR_MEM_DATA(laddr, 1, BX_READ);
-
- // all checks OK
- access_linear(laddr, 1, CPL==3, BX_READ, (void *) data);
+ // all checks OK
+ access_linear(laddr, 1, CPL==3, BX_READ, (void *) data);
+ return;
+ }
+ }
+ read_virtual_checks(seg, offset, 1);
+ goto accessOK;
}
@@ -303,13 +353,19 @@
bx_segment_reg_t *seg;
seg = &BX_CPU_THIS_PTR sregs[s];
- read_virtual_checks(seg, offset, 2);
-
- laddr = seg->cache.u.segment.base + offset;
- BX_INSTR_MEM_DATA(laddr, 2, BX_READ);
+ if (seg->cache.valid & SegAccessROK) {
+ if (offset < seg->cache.u.segment.limit_scaled) {
+accessOK:
+ laddr = seg->cache.u.segment.base + offset;
+ BX_INSTR_MEM_DATA(laddr, 2, BX_READ);
- // all checks OK
- access_linear(laddr, 2, CPL==3, BX_READ, (void *) data);
+ // all checks OK
+ access_linear(laddr, 2, CPL==3, BX_READ, (void *) data);
+ return;
+ }
+ }
+ read_virtual_checks(seg, offset, 2);
+ goto accessOK;
}
@@ -320,13 +376,19 @@
bx_segment_reg_t *seg;
seg = &BX_CPU_THIS_PTR sregs[s];
- read_virtual_checks(seg, offset, 4);
-
- laddr = seg->cache.u.segment.base + offset;
- BX_INSTR_MEM_DATA(laddr, 4, BX_READ);
+ if (seg->cache.valid & SegAccessROK) {
+ if (offset < (seg->cache.u.segment.limit_scaled-2)) {
+accessOK:
+ laddr = seg->cache.u.segment.base + offset;
+ BX_INSTR_MEM_DATA(laddr, 4, BX_READ);
- // all checks OK
- access_linear(laddr, 4, CPL==3, BX_READ, (void *) data);
+ // all checks OK
+ access_linear(laddr, 4, CPL==3, BX_READ, (void *) data);
+ return;
+ }
+ }
+ read_virtual_checks(seg, offset, 4);
+ goto accessOK;
}
//////////////////////////////////////////////////////////////
@@ -341,23 +403,29 @@
bx_segment_reg_t *seg;
seg = &BX_CPU_THIS_PTR sregs[s];
- write_virtual_checks(seg, offset, 1);
+ if (seg->cache.valid & SegAccessWOK) {
+ if (offset <= seg->cache.u.segment.limit_scaled) {
+accessOK:
+ laddr = seg->cache.u.segment.base + offset;
+ BX_INSTR_MEM_DATA(laddr, 1, BX_READ);
- laddr = seg->cache.u.segment.base + offset;
- BX_INSTR_MEM_DATA(laddr, 1, BX_READ);
-
- // all checks OK
+ // all checks OK
#if BX_CPU_LEVEL >= 3
- if (BX_CPU_THIS_PTR cr0.pg)
- access_linear(laddr, 1, CPL==3, BX_RW, (void *) data);
- else
+ if (BX_CPU_THIS_PTR cr0.pg)
+ access_linear(laddr, 1, CPL==3, BX_RW, (void *) data);
+ else
#endif
- {
- BX_CPU_THIS_PTR address_xlation.paddress1 = laddr;
- BX_INSTR_LIN_READ(laddr, laddr, 1);
- BX_INSTR_LIN_WRITE(laddr, laddr, 1);
- BX_CPU_THIS_PTR mem->read_physical(this, laddr, 1, (void *) data);
+ {
+ BX_CPU_THIS_PTR address_xlation.paddress1 = laddr;
+ BX_INSTR_LIN_READ(laddr, laddr, 1);
+ BX_INSTR_LIN_WRITE(laddr, laddr, 1);
+ BX_CPU_THIS_PTR mem->read_physical(this, laddr, 1, (void *) data);
+ }
+ return;
+ }
}
+ write_virtual_checks(seg, offset, 1);
+ goto accessOK;
}
@@ -368,23 +436,29 @@
bx_segment_reg_t *seg;
seg = &BX_CPU_THIS_PTR sregs[s];
- write_virtual_checks(seg, offset, 2);
-
- laddr = seg->cache.u.segment.base + offset;
- BX_INSTR_MEM_DATA(laddr, 2, BX_READ);
+ if (seg->cache.valid & SegAccessWOK) {
+ if (offset < seg->cache.u.segment.limit_scaled) {
+accessOK:
+ laddr = seg->cache.u.segment.base + offset;
+ BX_INSTR_MEM_DATA(laddr, 2, BX_READ);
- // all checks OK
+ // all checks OK
#if BX_CPU_LEVEL >= 3
- if (BX_CPU_THIS_PTR cr0.pg)
- access_linear(laddr, 2, CPL==3, BX_RW, (void *) data);
- else
+ if (BX_CPU_THIS_PTR cr0.pg)
+ access_linear(laddr, 2, CPL==3, BX_RW, (void *) data);
+ else
#endif
- {
- BX_CPU_THIS_PTR address_xlation.paddress1 = laddr;
- BX_INSTR_LIN_READ(laddr, laddr, 2);
- BX_INSTR_LIN_WRITE(laddr, laddr, 2);
- BX_CPU_THIS_PTR mem->read_physical(this, laddr, 2, data);
+ {
+ BX_CPU_THIS_PTR address_xlation.paddress1 = laddr;
+ BX_INSTR_LIN_READ(laddr, laddr, 2);
+ BX_INSTR_LIN_WRITE(laddr, laddr, 2);
+ BX_CPU_THIS_PTR mem->read_physical(this, laddr, 2, data);
+ }
+ return;
+ }
}
+ write_virtual_checks(seg, offset, 2);
+ goto accessOK;
}
void
@@ -394,23 +468,29 @@
bx_segment_reg_t *seg;
seg = &BX_CPU_THIS_PTR sregs[s];
- write_virtual_checks(seg, offset, 4);
-
- laddr = seg->cache.u.segment.base + offset;
- BX_INSTR_MEM_DATA(laddr, 4, BX_READ);
+ if (seg->cache.valid & SegAccessWOK) {
+ if (offset < (seg->cache.u.segment.limit_scaled-2)) {
+accessOK:
+ laddr = seg->cache.u.segment.base + offset;
+ BX_INSTR_MEM_DATA(laddr, 4, BX_READ);
- // all checks OK
+ // all checks OK
#if BX_CPU_LEVEL >= 3
- if (BX_CPU_THIS_PTR cr0.pg)
- access_linear(laddr, 4, CPL==3, BX_RW, (void *) data);
- else
+ if (BX_CPU_THIS_PTR cr0.pg)
+ access_linear(laddr, 4, CPL==3, BX_RW, (void *) data);
+ else
#endif
- {
- BX_CPU_THIS_PTR address_xlation.paddress1 = laddr;
- BX_INSTR_LIN_READ(laddr, laddr, 4);
- BX_INSTR_LIN_WRITE(laddr, laddr, 4);
- BX_CPU_THIS_PTR mem->read_physical(this, laddr, 4, data);
+ {
+ BX_CPU_THIS_PTR address_xlation.paddress1 = laddr;
+ BX_INSTR_LIN_READ(laddr, laddr, 4);
+ BX_INSTR_LIN_WRITE(laddr, laddr, 4);
+ BX_CPU_THIS_PTR mem->read_physical(this, laddr, 4, data);
+ }
+ return;
+ }
}
+ write_virtual_checks(seg, offset, 4);
+ goto accessOK;
}
void
Index: cpu/cpu.h
===================================================================
RCS file: /cvsroot/bochs/bochs/cpu/cpu.h,v
retrieving revision 1.22
diff -u -r1.22 cpu.h
--- cpu/cpu.h 5 Jun 2002 21:51:30 -0000 1.22
+++ cpu/cpu.h 27 Aug 2002 22:28:24 -0000
@@ -347,7 +347,13 @@
typedef struct {
- Boolean valid; /* 0 = invalid, 1 = valid */
+
+#define SegValidCache 0x1
+#define SegAccessROK 0x2
+#define SegAccessWOK 0x4
+ Boolean valid; // Holds above values, Or'd together. Used to
+ // hold only 0 or 1.
+
Boolean p; /* present */
Bit8u dpl; /* descriptor privilege level 0..3 */
Boolean segment; /* 0 = system/gate, 1 = data/code segment */
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