Messages in this thread | | | Date | Mon, 28 Feb 2022 19:33:53 +0300 | From | "Kirill A. Shutemov" <> | Subject | Re: [PATCHv4 15/30] x86/boot: Allow to hook up alternative port I/O helpers |
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On Sun, Feb 27, 2022 at 02:02:19PM -0800, Josh Poimboeuf wrote: > On Thu, Feb 24, 2022 at 06:56:15PM +0300, Kirill A. Shutemov wrote: > > Port I/O instructions trigger #VE in the TDX environment. In response to > > the exception, kernel emulates these instructions using hypercalls. > > > > But during early boot, on the decompression stage, it is cumbersome to > > deal with #VE. It is cleaner to go to hypercalls directly, bypassing #VE > > handling. > > > > Add a way to hook up alternative port I/O helpers in the boot stub. > > > > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> > > I think you missed my comment from v3.
I did not missed it, but I failed to acknowledge it.
To me it is a judgement call. Either way has right to live. I talked to Borislav on this and we suggested to keep it as. Rework later as needed.
> Repeating it here: > > At least from reading the commit message it's not self-evident why #VE > handling would be worse, especially since there's already #VC support in > boot. It would help to give more info about that in the commit message. > > The current approach also seems fragile, doesn't it require all future > code to remember to not do i/o directly? How do we make sure that > doesn't happen going forward? > > How does it fail if some code accidentally does i/o directly? Or > triggers #VE some other way? Is the error understandable and > actionable?
Dealing with failure in decompression code is a pain. We don't have usual infrastructure there. The patch deals with port I/O which is the only way to communicate issue to the user. If it fails for whatever reason we are screwed. And it doesn't depend on how it was implemented.
-- Kirill A. Shutemov
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