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

[Claudio Imbrenda <imbrenda@linux.ibm.com>]

On Thu,  5 Aug 2021 14:59:38 +0200
David Hildenbrand <david@redhat.com> 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.

looks like a good idea

> 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.

also looks like a good idea

Reviewed-by: Claudio Imbrenda <imbrenda@linux.ibm.com>
 
> 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);
> +    }
>  }
>  
>  static void update_ckc_timer(CPUS390XState *env)