Date: Thu, 14 Apr 2016 09:40:33 -0700 From: John Baldwin <jhb@freebsd.org> To: Warner Losh <imp@freebsd.org> Cc: src-committers@freebsd.org, svn-src-all@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: <41810993.gdbbayOUgu@ralph.baldwin.cx> In-Reply-To: <201604140459.u3E4xpYv038183@repo.freebsd.org> References: <201604140459.u3E4xpYv038183@repo.freebsd.org>
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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. 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). 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. 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. -- John Baldwin
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