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From: Florian Weimer <fweimer@redhat.com>
To: Richard Henderson <richard.henderson@linaro.org>
Cc: qemu-devel@nongnu.org
Subject: Re: Emulating CPUs with larger atomic accesses
Date: Tue, 24 May 2022 11:27:24 +0200	[thread overview]
Message-ID: <87sfozuvpf.fsf@oldenburg.str.redhat.com> (raw)
In-Reply-To: <37f4c866-4344-37ba-b64b-fd338dc96887@linaro.org> (Richard Henderson's message of "Sat, 21 May 2022 18:07:33 -0700")

* Richard Henderson:

> On 5/13/22 03:00, Florian Weimer wrote:
>> What's QEMU's approach to emulating CPU instructions that atomatically
>> operate on values larger than what is supported by the host CPU?
>> I assume that for full system emulation, this is not a problem, but
>> qemu-user will not achieve atomic behavior on shared memory mappings.
>> How much of a problem is this in practice?
>
> Well, it doesn't work, no.  In practice, x86_64 supports 128-bit
> atomic operations, and guest requires more than that.  No one really
> cares anymore about 32-bit hosts with smaller atomic operations.

Which part doesn't work?  Full-system emulation?

Do guests really require wider-than-128 atomics?  That's quite
surprising?

Thanks,
Florian



  reply	other threads:[~2022-05-24  9:48 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-05-13 10:00 Emulating CPUs with larger atomic accesses Florian Weimer
2022-05-22  1:07 ` Richard Henderson
2022-05-24  9:27   ` Florian Weimer [this message]
2022-05-24 11:48     ` Richard Henderson
2022-05-24 11:51       ` Florian Weimer

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