On Tue, 2017-03-28 at 12:38 +0300, Stas Sergeev wrote:
28.03.2017 02:46, Ricardo Neri пишет:
On Tue, 2017-03-14 at 00:25 +0300, Stas Sergeev wrote:
11.03.2017 02:59, Ricardo Neri пишет:
On Fri, 2017-03-10 at 14:33 +0300, Stas Sergeev wrote:
Why would you need one? Or do you really want to allow these instructions in v86 by the means of emulation? If so - this wasn't clearly stated in the patch description, neither it was properly discussed, it seems.
It str and sldt can be emulated in vm86 but as Andy mention, the behavior sould be the same with and without emulation.
Why would you do that? I looked up the dosemu2 CPU simulator code that is used under x86-64. It says this:
Stas, I apologize for the delayed reply; I missed your e-mail.
It only implements smsw. So maybe you can make your code much simpler and remove the unneeded emulation? Same is for prot mode.
Do you mean the unneeded emulation for SLDT and STR?
Not quite, I meant also sgdt and sidt in vm86. Yes that it will be a somewhat "incompatible" change, but if there is nothing to stay compatible with, then why to worry?
My idea of compatibility was to have the emulation code behave exactly as a processor without UMIP :)
Probably you could also remove the sldt and str emulation for protected mode, because, as I understand from this thread, wine does not need those.
I see. I would lean on keeping the emulation because I already implemented it :), for completeness, and because it is performed in a single switch. The bulk of the emulation code deals with operands.
Note that these days dosemu2 uses v86 mode set up under kvm rather than vm86(). Your patches affect that the same way as they do for vm86() syscall, or can there be some differences?
My code does not touch kvm at all. I would need to assess how kvm will behave.
Or should the UMIP be enabled under kvm by hands?
There was an attempt to emulate UMIP that was submitted a while ago: https://lkml.org/lkml/2016/7/12/644
You know the wine's requirements now - they are very small. And dosemu doesn't need anything at all but smsw. And even smsw is very rare.
But emulation is still needed for SMSW, right?
Likely so. If you want, I can enable the logging of this command and see if it is used by some of the DOS programs I have.
It would be great if you could do that, if you don't mind.
But at least dosemu implements it, so probably it is needed.
Right.
Of course if it is used by one of 100 DOS progs, then there is an option to just add its support to dosemu2 and pretend the compatibility problems did not exist. :)
Do you mean relaying the GP fault to dosemu instead of trapping it and emulating it in the kernel?
Thanks and BR, Ricardo