From 628b61a0727e240be911ba9d01b41c58841b2c43 Mon Sep 17 00:00:00 2001
From: Aurelien Jarno <aurelien@aurel32.net>
Date: Tue, 2 Feb 2010 19:50:51 +0100
Subject: [PATCH] target-sh4: MMU: optimize UTLB accesses
With the current code, the QEMU TLB is setup to match the read/write
mode of the MMU fault. This means when read access is done, the page
is setup in read-only mode. When the page is later accessed in write
mode, an MMU fault happened, and the page is switch in write-only
mode. This flip-flop causes a lot of calls to the MMU code and slow
down the emulation.
This patch changes the MMU emulation, so that the QEMU TLB is setup
to match the UTLB protection key. This impressively increase the
speed of the emulation.
Signed-off-by: Aurelien Jarno <aurelien@aurel32.net>
---
target-sh4/helper.c | 38 ++++++++++++++------------------------
1 file changed, 14 insertions(+), 24 deletions(-)
diff --git a/target-sh4/helper.c b/target-sh4/helper.c
index 589efe40ad..2d00dfadd4 100644
--- a/target-sh4/helper.c
+++ b/target-sh4/helper.c
@@ -386,38 +386,28 @@ static int get_mmu_address(CPUState * env, target_ulong * physical,
n = find_utlb_entry(env, address, use_asid);
if (n >= 0) {
matching = &env->utlb[n];
- switch ((matching->pr << 1) | ((env->sr & SR_MD) ? 1 : 0)) {
- case 0: /* 000 */
- case 2: /* 010 */
- n = (rw == 1) ? MMU_DTLB_VIOLATION_WRITE :
- MMU_DTLB_VIOLATION_READ;
- break;
- case 1: /* 001 */
- case 4: /* 100 */
- case 5: /* 101 */
- if (rw == 1)
- n = MMU_DTLB_VIOLATION_WRITE;
- else
- *prot = PAGE_READ;
- break;
- case 3: /* 011 */
- case 6: /* 110 */
- case 7: /* 111 */
- *prot = (rw == 1)? PAGE_WRITE : PAGE_READ;
- break;
- }
+ if (!(env->sr & SR_MD) && !(matching->pr & 2)) {
+ n = (rw == 1) ? MMU_DTLB_VIOLATION_WRITE :
+ MMU_DTLB_VIOLATION_READ;
+ } else if ((rw == 1) && !(matching->pr & 1)) {
+ n = MMU_DTLB_VIOLATION_WRITE;
+ } else if ((rw == 1) & !matching->d) {
+ n = MMU_DTLB_INITIAL_WRITE;
+ } else {
+ *prot = PAGE_READ;
+ if ((matching->pr & 1) && matching->d) {
+ *prot |= PAGE_WRITE;
+ }
+ }
} else if (n == MMU_DTLB_MISS) {
n = (rw == 1) ? MMU_DTLB_MISS_WRITE :
MMU_DTLB_MISS_READ;
}
}
if (n >= 0) {
+ n = MMU_OK;
*physical = ((matching->ppn << 10) & ~(matching->size - 1)) |
(address & (matching->size - 1));
- if ((rw == 1) & !matching->d)
- n = MMU_DTLB_INITIAL_WRITE;
- else
- n = MMU_OK;
}
return n;
}