[PATCH v7 06/18] accel/tcg: Suppress auto-invalidate in probe_access_internal

From: Richard Henderson <richard.henderson@linaro.org>
To: qemu-devel@nongnu.org
Cc: alex.bennee@linaro.org, David Hildenbrand <david@redhat.com>,
	Peter Maydell <peter.maydell@linaro.org>
Subject: [PATCH v7 06/18] accel/tcg: Suppress auto-invalidate in probe_access_internal
Date: Tue,  4 Oct 2022 07:10:39 -0700	[thread overview]
Message-ID: <20221004141051.110653-7-richard.henderson@linaro.org> (raw)
In-Reply-To: <20221004141051.110653-1-richard.henderson@linaro.org>

When PAGE_WRITE_INV is set when calling tlb_set_page,
we immediately set TLB_INVALID_MASK in order to force
tlb_fill to be called on the next lookup.  Here in
probe_access_internal, we have just called tlb_fill
and eliminated true misses, thus the lookup must be valid.

This allows us to remove a warning comment from s390x.
There doesn't seem to be a reason to change the code though.

Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: David Hildenbrand <david@redhat.com>
Reviewed-by: Peter Maydell <peter.maydell@linaro.org>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>
---
 accel/tcg/cputlb.c            | 10 +++++++++-
 target/s390x/tcg/mem_helper.c |  4 ----
 2 files changed, 9 insertions(+), 5 deletions(-)

diff --git a/accel/tcg/cputlb.c b/accel/tcg/cputlb.c
index d06ff44ce9..264f84a248 100644
--- a/accel/tcg/cputlb.c
+++ b/accel/tcg/cputlb.c
@@ -1533,6 +1533,7 @@ static int probe_access_internal(CPUArchState *env, target_ulong addr,
     }
     tlb_addr = tlb_read_ofs(entry, elt_ofs);
 
+    flags = TLB_FLAGS_MASK;
     page_addr = addr & TARGET_PAGE_MASK;
     if (!tlb_hit_page(tlb_addr, page_addr)) {
         if (!victim_tlb_hit(env, mmu_idx, index, elt_ofs, page_addr)) {
@@ -1547,10 +1548,17 @@ static int probe_access_internal(CPUArchState *env, target_ulong addr,
 
             /* TLB resize via tlb_fill may have moved the entry.  */
             entry = tlb_entry(env, mmu_idx, addr);
+
+            /*
+             * With PAGE_WRITE_INV, we set TLB_INVALID_MASK immediately,
+             * to force the next access through tlb_fill.  We've just
+             * called tlb_fill, so we know that this entry *is* valid.
+             */
+            flags &= ~TLB_INVALID_MASK;
         }
         tlb_addr = tlb_read_ofs(entry, elt_ofs);
     }
-    flags = tlb_addr & TLB_FLAGS_MASK;
+    flags &= tlb_addr;
 
     /* Fold all "mmio-like" bits into TLB_MMIO.  This is not RAM.  */
     if (unlikely(flags & ~(TLB_WATCHPOINT | TLB_NOTDIRTY))) {
diff --git a/target/s390x/tcg/mem_helper.c b/target/s390x/tcg/mem_helper.c
index fc52aa128b..3758b9e688 100644
--- a/target/s390x/tcg/mem_helper.c
+++ b/target/s390x/tcg/mem_helper.c
@@ -148,10 +148,6 @@ static int s390_probe_access(CPUArchState *env, target_ulong addr, int size,
 #else
     int flags;
 
-    /*
-     * For !CONFIG_USER_ONLY, we cannot rely on TLB_INVALID_MASK or haddr==NULL
-     * to detect if there was an exception during tlb_fill().
-     */
     env->tlb_fill_exc = 0;
     flags = probe_access_flags(env, addr, access_type, mmu_idx, nonfault, phost,
                                ra);
-- 
2.34.1


