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Date: Mon, 12 Jan 2009 21:53:15 +0100
From: Jakub Jermar <jakub@jermar.eu>
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Subject: [Qemu-devel] sparc64's get_physical_address_code should not fault
 on TTE's with V=0
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To: Blue Swirl <blauwirbel@gmail.com>
Cc: qemu-devel@nongnu.org

Hi,

when I make the following change to helper.c, get_physical_address_code:

-        // ctx match, vaddr match?
+        // ctx match, vaddr match, valid?
         if (env->dmmuregs[1] == (env->itlb_tag[i] & 0x1fff) &&
-            (address & mask) == (env->itlb_tag[i] & ~0x1fffULL)) {
-            // valid, access ok?
-            if ((env->itlb_tte[i] & 0x8000000000000000ULL) == 0 ||
-                ((env->itlb_tte[i] & 0x4) && is_user)) {
+            (address & mask) == (env->itlb_tag[i] & ~0x1fffULL) &&
+            env->itlb_tte[i] & 0x8000000000000000ULL) {
+            // access ok?
+            if ((env->itlb_tte[i] & 0x4) && is_user) {

HelenOS gets a little bit further than without this change and seems
to panic more or less gracefully later.

In short, non-valid entries should be skipped by the loop in
get_physical_address_code instead of causing TFAULT, because
the ITLB can contain a valid entry for the same address. The
same is true for DTLB.

Can you confirm this?

Thanks,
Jakub