On Thu, Oct 06, 2016 at 11:47:36AM +0100, Peter Maydell wrote: > On 6 October 2016 at 04:45, David Gibson <da...@gibson.dropbear.id.au> wrote: > > On Wed, Oct 05, 2016 at 07:20:52AM -0700, Peter Maydell wrote: > >> On 5 October 2016 at 07:00, Cédric Le Goater <c...@kaod.org> wrote: > >> > On 10/05/2016 03:53 PM, Peter Maydell wrote: > >> >> Which tswap? Last time I worked through the stack of > >> >> what happens I thought that we had the right set of > >> >> swaps in the right places. > >> > > >> > The one I am talking about are under qtest_process_command(), > >> > see below. > >> > >> Those are correct and required, and they do not change > >> the overall behaviour of the system depending on the host > >> endianness. (They convert 32-bit values to "bag of > >> bytes in guest order" which is what the cpu_physical_memory_* > >> functions want.) > > > > These functions are correct for the defined semantics of the > > readw/readl operations, but those semantics are not useful. > > ?? They're the most obvious and required semantics: "act > like the CPU just did a word/halfword/byte read/write".
The CPU with what mode and options?
> There's a reason we've got this far without needing anything
> else, and it's that this is the most straightforward use case.
No, I'm pretty sure we've got this far because most of the tests
haven't yet been enabled for a traditionally BE target.
> > This proposal is introducing alternate functions with the more useful
> > semantics which are "convert a 32-bit value to a bag of bytes in LE
> > order" or "convert a 32-bit value to a bag of bytes in BE order"
> > depending on which variant you choose.
>
> It's adding functions whose semantics are "act like the
> CPU wrote this value to some RAM and then memcpy()ed it to
> the device". I think devices whose usage model is "memcpy bytes
> to me" are rare to nonexistent.
Uh, that's not the intention. I have some comments on this elsewhere.
The intended semantics are that we do a single atomic write to an
address, but with a specific endianness.
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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