From: Richard Henderson <richard.henderson@linaro.org>
To: "Alex Bennée" <alex.bennee@linaro.org>
Cc: "open list:S390 TCG CPUs" <qemu-s390x@nongnu.org>,
Thomas Huth <thuth@redhat.com>, Cornelia Huck <cohuck@redhat.com>,
qemu-devel@nongnu.org, David Hildenbrand <david@redhat.com>
Subject: Re: [RFC PATCH] target/s390x: don't double ld_code() when reading instructions
Date: Tue, 12 Oct 2021 08:38:29 -0700 [thread overview]
Message-ID: <615facec-1751-778d-2187-b6a93afff9eb@linaro.org> (raw)
In-Reply-To: <87lf2ywap4.fsf@linaro.org>
On 10/12/21 7:52 AM, Alex Bennée wrote:
>> I think the plugin stuff could be more clever, knowing where the read
>> occurs within the sequence. Otherwise, we should simplify the
>> interface so that it is not possible to make this mistake.
>
> It's plugin_insn_append which is doing the tracking here so we could
> extend the interface to include the current pc of the load and make the
> appropriate adjustments. That said it's a bunch hoops to jump every
> instruction when we could just as easily add an assert and fix up any
> cases where we do. I guess it comes down to how prevalent double dipping
> in the instruction stream is when constructing a translation?
Yes, which is why I suggested simplifying the interface to translate_ld*. It currently
takes the DisasContextBase; it could potentially read from pc_next, and increment it. It
would completely eliminate the problem you're encountering.
> What happens if the protection of the code area changes half way through
> a translation? Could a mapping change in flight?
No, we hold mmap_lock.
r~
prev parent reply other threads:[~2021-10-12 15:39 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-12 9:31 [RFC PATCH] target/s390x: don't double ld_code() when reading instructions Alex Bennée
2021-10-12 12:07 ` Richard Henderson
2021-10-12 12:10 ` Richard Henderson
2021-10-12 14:52 ` Alex Bennée
2021-10-12 15:38 ` Richard Henderson [this message]
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