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Re: [Qemu-ppc] [Qemu-devel] [PATCH v7 00/42] Invert Endian bit in SPARCv

From: Philippe Mathieu-Daudé
Subject: Re: [Qemu-ppc] [Qemu-devel] [PATCH v7 00/42] Invert Endian bit in SPARCv9 MMU TTE
Date: Fri, 16 Aug 2019 11:58:05 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.7.0

Hi Tony,

On 8/16/19 8:28 AM, address@hidden wrote:
> This patchset implements the IE (Invert Endian) bit in SPARCv9 MMU TTE.
> v7:
> - Re-declared many native endian devices as little or big endian. This is why
>   v7 has +16 patches.

Why are you doing that? What is the rational?

Anyhow if this not required by your series, you should split it out of
it, and send it on your principal changes are merged.
I'm worried because this these new patches involve many subsystems (thus
maintainers) and reviewing them will now take a fair amount of time.

> For each device declared with DEVICE_NATIVE_ENDIAN, find the set of
> targets from the set of target/hw/*/device.o.
> If the set of targets are all little or all big endian, re-declare
> the device endianness as DEVICE_LITTLE_ENDIAN or DEVICE_BIG_ENDIAN
> respectively.

If only little endian targets use a device, that doesn't mean the device
is designed in little endian...

Then if a big endian target plan to use this device, it will require
more work and you might have introduced regressions...

I'm not sure this is a safe move.

> This *naive* deduction may result in genuinely native endian devices
> being incorrectly declared as little or big endian, but should not
> introduce regressions for current targets.



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