Date: Thu, 14 Apr 2016 10:53:56 -0600 From: Warner Losh <imp@bsdimp.com> To: John Baldwin <jhb@freebsd.org> Cc: Warner Losh <imp@freebsd.org>, src-committers <src-committers@freebsd.org>, "svn-src-all@freebsd.org" <svn-src-all@freebsd.org>, "svn-src-head@freebsd.org" <svn-src-head@freebsd.org> Subject: Re: svn commit: r297954 - in head/sys: boot/efi/loader/arch/amd64 boot/i386/libi386 x86/acpica Message-ID: <CANCZdfp_uEUbc0YUobJQVdt5UWA-YKJpD47kNF_Hz-w7EnosyQ@mail.gmail.com> In-Reply-To: <41810993.gdbbayOUgu@ralph.baldwin.cx> References: <201604140459.u3E4xpYv038183@repo.freebsd.org> <41810993.gdbbayOUgu@ralph.baldwin.cx>
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On Thu, Apr 14, 2016 at 10:40 AM, John Baldwin <jhb@freebsd.org> wrote: > On Thursday, April 14, 2016 04:59:51 AM Warner Losh wrote: > > Author: imp > > Date: Thu Apr 14 04:59:51 2016 > > New Revision: 297954 > > URL: https://svnweb.freebsd.org/changeset/base/297954 > > > > Log: > > Deprecate using hints.acpi.0.rsdp to communicate the RSDP to the > > system. This uses the hints mechnanism. This mostly works today > > because when there's no static hints (the default), this value can be > > fetched from the hint. When there is a static hints file, the hint > > passed from the boot loader to the kernel is ignored, but for the BIOS > > case we're able to find it anyway. However, with UEFI, the fallback > > doesn't work, so we get a panic instead. > > > > Switch to acpi.rsdp and use TUNABLE_ULONG_FETCH instead. Continue to > > generate the old values to allow for transitions. In addition, fall > > back to the old method if the new method isn't present. > > > > Add comments about all this. > > I still think this is a bit of a band-aid. At least acpidump in userland > also > uses the hints I believe. I still think a better long term approach is to > fix static hints + loader one way or another. > Sure, but this data never should have been passed as a hint. > One approach would be to teach the hint code to "merge" dynamic and static > hints by looking in the dynamic hints first. However, while that is fairly > trivial for resource_*_value() that request values by name, it would be a > PITA > to handle the part of the hints API that iterates to find all the possible > device names (though this could perhaps iterate over dynamic then static). > Yes, we could do that, or we could not abuse 'hints' mechanism and instead realize it can and will be overridden and use a different method to pass this critical data. I like module data better than the environment, but was short on time. That's where this should be passed in, and a sysctl to export it to userland should be done instead of acpidump reading hints. I freely admit that my kenv hack just made things better without fully fixing the problem. The second approach would be to desupport using static hints for kernels > booted via the loader and relegate it to something that only systems using > uboot or the like use. Anything in static hints can be moved into either > /boot/device.hints, /boot/loader.conf{,.local} or into a /boot/foo.hints > that is added to the list of loader conf files in > /boot/loader.conf{,.local}. > I would add a big, fat WARNING message (like we have for WITNESS) that > prints > out during kernel boot if we detect static hints being used when a kernel > environment is present. > Seems like an over-reaction to using the wrong mechanism > I probably lean towards the second. We never shipped a release that used > static hints for a kernel on platforms where /boot/loader is supported > (GENERIC on i386 only used static hints for about a month after the hints > code was added pre-5.0 before the hints moved out to /boot/device.hints > instead). Moving your static hints out into a loader config file means > that > you also have more flexibility to during recovery situations as you could, > at least in theory, adjust the values pre-boot from the loader. I see no reason to desupport anything. Warner
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