Re: [Qemu-devel] [PATCH v2 06/27] target/sh4: Handle user-space atomics

[John Paul Adrian Glaubitz]

On 07/16/2017 12:14 AM, Aurelien Jarno wrote:
> Do you have actually have a good documentation about gUSA? I have found
> a few documents (some of them in Japanese), the most complete one being
> the LinuxTag paper. The ABI is also described in the kernel and the
> glibc. That said I am missing the following informations:
> - What kind of instructions are allowed in the atomic sequence? Your
>   patch takes into account branches, but are there allowed? used in
>   practice? What about FP instructions?
> - Does the atomic sequence is actually allowed to cross pages?
> - Is there any alignement required? The paper mention adding a nop to
>   gUSA_exchange_and_add to align the end point to 4 bytes.

The best person to answer this is Yutaka Niibe as he is actually the
person who came up with the design. I'll drop him a message and see
if he can join the discussion.

Adrian

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