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Re: [PATCH v2 63/93] tcg/tci: Use ffi for calls


From: Stefan Weil
Subject: Re: [PATCH v2 63/93] tcg/tci: Use ffi for calls
Date: Tue, 9 Feb 2021 22:15:12 +0100
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.16; rv:78.0) Gecko/20100101 Thunderbird/78.7.1

Am 09.02.21 um 21:46 schrieb Richard Henderson:

On 2/8/21 2:55 PM, Richard Henderson wrote:
Ok, I've reproduced something on a T3 (gcc102.fsffrance.org).
Running the same code side-by-side vs the T5, I get different results.
Brown paper bag time: the T5 build dir lost the --enable-tcg-interpreter flag,
so was testing tcg native.

Big-endian bug wrt an odd api wart in libffi.  Fixed thus.


Thanks for solving this. The patch works for me.

BIOS boot time with qemu-system-i386 is about 41 s (with my code which lacks thread support and ffi it was 40 s).

With qemu-system-x86_64 it is twice as fast, so it looks like in my last report where I said that the new code had doubled the speed I compared different system emulations.

Apropos "slow" TCI: on Apple's M1 it is faster than native TCG on most of my Intel / AMD machines. And it works with current git master while native TCG still waits for pending patches which fix the memory access.

Stefan






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