[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [PATCH for-4.16] x86/passthrough: Fix hvm_gsi_eoi() build with GCC 12


  • To: Jan Beulich <jbeulich@xxxxxxxx>
  • From: Roger Pau Monné <roger.pau@xxxxxxxxxx>
  • Date: Thu, 18 Nov 2021 10:34:59 +0100
  • Arc-authentication-results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=citrix.com; dmarc=pass action=none header.from=citrix.com; dkim=pass header.d=citrix.com; arc=none
  • Arc-message-signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=GoWQ71HXUd+cJ3hMxF7fMYUXTE8CKyFN8s2LY//+xMA=; b=VP678NmbTX9gS/f1JDqoP1qqUGbGSRDhE8RobpCWSmemN4LnbPH7w0E4PoBqvhWQZRD54/vSD1ZKUm55yI2inqLXvmXCigTGz3FHuJnH/5edFACKDXiTHrzbJP7z5y+tgbU5D8K0De1zqJPsJ/X21PRKkCD39BIPdyj/8mujlfIR/mrylr+JjafmuTOUFqi1+Ny8CZ4zmnBHQXMe6I3rXiBt9UtkTlGrjO9cMHo+D04s1xoquDKQ5TBSNc1ECOWsV6ZmM0wWgNM3zLNJsuMXC4KSHYR5F6UzgIkhPZO8vrd9Iat/E5ovLZPw/l3g5OLwA7k8pp3TAGt6pQTNelMnDw==
  • Arc-seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=AAG+Us73IbODWmvfcJuFYpSR0iEBenx+rVfODkBXn7q535l6j/H8kyPoMw4AIOxsLokK2Qt6ZniMH1GlhPPisSCFf0tBkl5GcWtKchNaTc5Ney/2C3vVLV4JX0MC+U4+CSSxoi/QxGkR8BEI6RhHxFaBeYmtRys9xdBxFFXHzIdpjkVfMNGeCBiGZ1cSB+dofB9YzDbw9N55PPNHm4CJetZOVetqFEkCbs16KVlPAz0l8lawcVb7Fpav8ZyZxlmsxogfpazfFutZ9Jhah6OkmuHTIJeHcgFhVRNIKnPAr3nyjhvrZYgceSTxR3x4X25xOfDDAcCxhphacMZYNyjmFA==
  • Authentication-results: esa3.hc3370-68.iphmx.com; dkim=pass (signature verified) header.i=@citrix.onmicrosoft.com
  • Cc: Wei Liu <wl@xxxxxxx>, Ian Jackson <iwj@xxxxxxxxxxxxxx>, Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>
  • Delivery-date: Thu, 18 Nov 2021 09:35:19 +0000
  • Ironport-data: A9a23:lTdNH6/YQZrtKdUdJVCqDrUDa3mTJUtcMsCJ2f8bNWPcYEJGY0x3z WtMDzyGb63bNDTxKt5wbIjl9BwDupWAzt9gQQtl/n88E34SpcT7XtnIdU2Y0wF+jyHgoOCLy +1EN7Es+ehtFie0Si9AttENlFEkvU2ybuOU5NXsZ2YhGmeIdA970Ug6wrdg0tYy6TSEK1jlV e3a8pW31GCNg1aYAkpMg05UgEoy1BhakGpwUm0WPZinjneH/5UmJMt3yZWKB2n5WuFp8tuSH I4v+l0bElTxpH/BAvv9+lryn9ZjrrT6ZWBigVIOM0Sub4QrSoXfHc/XOdJFAXq7hQllkPh36 NNmuJfscDw1GZfnyMEXXSJUAx1XaPguFL/veRBTsOSWxkzCNXDt3+9vHAc9OohwFuRfWD8Us 6ZCcXZUM07F17neLLGTE4GAguw5K8bmJsUHs2xIxjDFF/c2B5vERs0m4PcFjG5r3pwXQp4yY eJCbgVEdjWRZyRrJ3kLC5gklfqpjFbgJmgwRFW9+vNsvjm7IBZK+LnyMvLFd9qSX8JXk02E4 GXc8AzREhwccdCS1zeB2natnfPU2zP2XpoIE7+1/eIsh0ecrkQRAhALUVqwodGil1WzHdlYL iQ85S4GvaU0skuxQbHAswaQ+SDe+ERGApwJTrN8uFrlJrfoDxixAEgCZTNKNOUdqOgMbmwP3 FGyk8PVLGk62FGKck61+rCRpDK0HCEaK24eeCMJJTc4D8nfTJIb1UyWEIs6eEKhppisQGyrn WjWxMQrr+xL1ZZj6kmtwbzQb9tATLDtRxV92AjYV3nNAuhRNN/8PNzABbQ2AJ99wGelorup4 Chsdyu2trlm4XSxeMqlGrll8FaBvajtDdEkqQQzd6TNDhz0k5JZQahe4StlOGBiOdsedDnib Sf74F0Ku8YMYCb2PfInOepd7vjGK4C6SbwJsdiOMLJzjmVZLlfbrEmCm2bOt4wSrKTcuf5mY srKGSpdJX0bFb5m3FKLqxQ1itcWKtQF7TqLH/jTlk3/uZLHPSL9YepVYTOmM7FihIvZ8Vq9z jqqH5bTo/mpeLalOXe/HE96BQ1iEEXX8riq8ZEKLbDafVI9cIzjYteIqY4cl0Vet/09vs/D/ 22nW18ez1z6hHbdLh6NZGwlY7TqNauTZ1piVcD1FVr3iXUlf6i166ITK8k+cbU9rbQxxv9oV fgVPc6HB60XGDjA/j0ca7j7rZBjK0v31V7fYXL9bWhtZYNkSizI5sTgIlnl+h4RA3flrsA5u bChiF/WGMJRWwR4Ac/KQ/uz1Fft72MFked/UhKQcNlecUnh6qZwLCn1gqNlKs0AM0yblDCby xyXEVETouyU+90599zAhKalqYa1ErQhQhoGTjeDtbvvbHvU5Guux4NEQd2kRzGFWTOm4rima MVU0+r4bK8NkmFVvtcuCL1s168/uYfi/ucI0gR+EXzXRF23Ebc8cGKe1MxCu6ARlL9UvQy6B hCG9tVAYOjbPcrkFBgaJRY/b/TF3vYRw2GA4fMwKUT8xSl24LvYDhkCY0jS0HRQfOlvLYco4 eY9o8pHuQWwhy0jPsuCki0JpX+HKWYNUvl/u5wXaGMxZtHHFr2WjUTgNxLL
  • Ironport-hdrordr: A9a23:yilI/6/tKOKVeIF21sRuk+FCdb1zdoMgy1knxilNoENuHfBwxv rDoB1E73LJYVYqOU3Jmbi7Sc69qFfnhORICO4qTMqftWjdyRCVxeRZg7cKrAeQeREWmtQtsJ uINpIOdOEYbmIK/PoSgjPIaurIqePvmMvD5Za8vgdQpENRGtldBm9Ce3im+yZNNW977PQCZf 6hDp0tnUveRZ1bVLXwOlA1G8z44/HbnpPvZhALQzYh9Qm1lDutrJr3CQKR0BsyWy5Ghe5Kyx mIryXJooGY992rwB7V0GHeq7xQhdva09NGQOiBkNIcJDnAghuhIK5hR7qBljYop/zH0idmrP D85zMbe+hj4XLYeW+45TPrxgnbyT4rr0TvzFeJ6EGT6PDRdXYfMY5slIhZehzW5w4Lp9dnyp 9G2Gqfqt5+EQ7AtD6V3amIazha0m6P5VYym+8aiHJSFaEEbqVKkIAZ9ERJVL8dASPB7pw9Gu UGNrCT2B9vSyLYU5nlhBgs/DT1NU5DWytuA3Jy9fB96gIm3EyQlCAjtYgidnRpzuNKd3AL3Z WCDk1SrsA9ciYhV9MLOA4we7rFNoXze2O4DIuzGyWuKEhVAQOHl3bIiI9FkN1CPqZ4iqcPpA ==
  • Ironport-sdr: eXJCbs6qfnyGdrIiwY8kvaYmNYONRZldlCvG4TEh6OF53MWvVqL/esGqum+zC+8iNcImYOwKar IoxmW46Ox0wHmzvp7C/4mpSfIaCxQZrPr+0fUivLKRdu7Y5dSC3NBB/pCSjDvUtASeP6BTxJWi BXOOzF2axDsGZYpPllDOl/V0OiQ0rFSbj6qp5xUFFjwSgbFwrp9390DwTbmssya1vby4ASmCJP WjSdfgVrW+9Qqpyk9Yy7BLjqWfMAr8+Bkcb2rfnwBsmd/y36etz8lq6riTAZ8SciNhrMiEcyh0 xKMhqKWCuM/iwlEeqdTJiQZ6
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On Thu, Nov 18, 2021 at 09:51:52AM +0100, Jan Beulich wrote:
> On 18.11.2021 09:33, Roger Pau Monné wrote:
> > On Thu, Nov 04, 2021 at 01:17:53PM +0100, Jan Beulich wrote:
> >> On 04.11.2021 11:48, Andrew Cooper wrote:
> >>> If your answer is "well actually, we didn't mean to say 'if a GSI is
> >>> mapped' in the comment, and here's a different predicate which actually
> >>> inspects the state of a dpci object for validity", then fine -  that
> >>> will shut the compiler up because you're no longer checking for the
> >>> NULLness of a pointer to a sub-object of a non-NULL pointer, but that's
> >>> a bugfix which needs backporting several releases too.
> >>>
> >>> The current logic is not correct, and does not become correct by trying
> >>> pass blame to the compiler.
> >>
> >> I have yet to understand in which way you deem the current logic to not
> >> be correct. I'm sorry for being dense.
> >>
> >>> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=102967 is the GCC bug, but
> >>> the result of it was them persuading me that the diagnostic was
> >>> legitimate, even if currently expressed badly.  They've agreed to fix
> >>> how it is expressed, but I doubt you'll persuade them that the trigger
> >>> for the diagnostic in the first place was wrong.
> >>
> >> Well, thanks for the pointer in any event. I've commented there as well.
> > 
> > Did we get any resolution out of this?
> 
> I don't think we did. I'm still struggling to understand Andrew's way
> of thinking.

What about the GCC bug report?

Ultimately we need GCC people to make the check less restrictive or we
need a way to rework the code in a way that doesn't trigger it, either
Andrew's proposal or something else.

> > It would be good IMO if we could build out of the box with GCC 12
> > instead of having to backport fixes later on.
> 
> I guess gcc12 is too far from getting released that there could be any
> guarantee for no further issues to get exposed by that point. It has
> also been common for us to backport fixes and workarounds when new
> compiler versions appear.
> 
> I could agree to being proactive if the change to make to our code was
> uncontroversial.

OK, but unless GCC changes their mind we are likely to have this
conversation again in the future, so we might be just delaying the
inevitable.

Thanks, Roger.



 


Rackspace

Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.