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Re: [PATCH v1] s390x/tcg: fix and optimize SPX (SET PREFIX)

From: Thomas Huth
Subject: Re: [PATCH v1] s390x/tcg: fix and optimize SPX (SET PREFIX)
Date: Fri, 6 Aug 2021 07:21:39 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.12.0

On 05/08/2021 14.59, David Hildenbrand wrote:
We not only invalidate the translation of the range 0x0-0x2000, we also
invalidate the translation of the new prefix range and the translation
of the old prefix range -- because real2abs would return different
results for all of these ranges when changing the prefix location.

This fixes the kvm-unit-tests "edat" test that just hangs before this
patch because we end up clearing the new prefix area instead of the old
prefix area.

While at it, let's not do anything in case the prefix doesn't change.

Cc: Richard Henderson <richard.henderson@linaro.org>
Cc: David Hildenbrand <david@redhat.com>
Cc: Cornelia Huck <cohuck@redhat.com>
Cc: Thomas Huth <thuth@redhat.com>
Cc: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: qemu-s390x@nongnu.org
Signed-off-by: David Hildenbrand <david@redhat.com>
  target/s390x/tcg/misc_helper.c | 15 ++++++++++++++-
  1 file changed, 14 insertions(+), 1 deletion(-)

diff --git a/target/s390x/tcg/misc_helper.c b/target/s390x/tcg/misc_helper.c
index 33e6999e15..aab9c47747 100644
--- a/target/s390x/tcg/misc_helper.c
+++ b/target/s390x/tcg/misc_helper.c
@@ -151,13 +151,26 @@ void HELPER(diag)(CPUS390XState *env, uint32_t r1, 
uint32_t r3, uint32_t num)
  /* Set Prefix */
  void HELPER(spx)(CPUS390XState *env, uint64_t a1)
+    const uint32_t prefix = a1 & 0x7fffe000;
+    const uint32_t old_prefix = env->psa;
      CPUState *cs = env_cpu(env);
-    uint32_t prefix = a1 & 0x7fffe000;
+    if (prefix == old_prefix) {
+        return;
+    }
env->psa = prefix;
      HELPER_LOG("prefix: %#x\n", prefix);
      tlb_flush_page(cs, 0);
      tlb_flush_page(cs, TARGET_PAGE_SIZE);
+    if (prefix != 0) {
+        tlb_flush_page(cs, prefix);
+        tlb_flush_page(cs, prefix + TARGET_PAGE_SIZE);
+    }
+    if (old_prefix != 0) {
+        tlb_flush_page(cs, old_prefix);
+        tlb_flush_page(cs, old_prefix + TARGET_PAGE_SIZE);
+    }

Sounds reasonable.

Reviewed-by: Thomas Huth <thuth@redhat.com>

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