Date: Fri, 5 Feb 2021 22:33:02 +0200 From: Toomas Soome <tsoome@me.com> To: Warner Losh <imp@bsdimp.com> Cc: Toomas Soome <tsoome@freebsd.org>, src-committers <src-committers@freebsd.org>, "<dev-commits-src-all@freebsd.org>" <dev-commits-src-all@freebsd.org>, dev-commits-src-branches@freebsd.org Subject: Re: git: 0c839497c174 - stable/13 - loader.efi: There are systems without ConOut, also use ConOutDev Message-ID: <68A78067-CE19-4024-B6A9-D924F8972A35@me.com> In-Reply-To: <CANCZdfo-pRUQhw_7=MN6VPOcsgvRoP47PUC44yjbZbzopdtJSw@mail.gmail.com> References: <CANCZdfqXU7Syo4wvxJ17Gt%2B0E2Kw8yOU_nrTNA%2Beu=z-ZwTKow@mail.gmail.com> <CF59D855-228A-4BC1-AC4B-0C54417EF3BF@me.com> <CANCZdfrdpMXTxJbzY6w2NE_DtwZ1eBuMm%2B1rr6d0a22R2QKaCQ@mail.gmail.com> <97F5C09F-7AE3-4763-AD32-BFEA25101CE5@me.com> <CANCZdfpf6KAyPCnxJnxPAg2K4POK7okkp1m3O28VvAcrK1tzag@mail.gmail.com> <014891C8-7B1F-4908-9495-2ED1A5FAABCF@me.com> <CANCZdfo-pRUQhw_7=MN6VPOcsgvRoP47PUC44yjbZbzopdtJSw@mail.gmail.com>
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> On 5. Feb 2021, at 22:21, Warner Losh <imp@bsdimp.com> wrote: >=20 >=20 >=20 > On Fri, Feb 5, 2021 at 1:09 PM Toomas Soome <tsoome@me.com = <mailto:tsoome@me.com>> wrote: >=20 >=20 >> On 5. Feb 2021, at 21:43, Warner Losh <imp@bsdimp.com = <mailto:imp@bsdimp.com>> wrote: >>=20 >>=20 >>=20 >> On Fri, Feb 5, 2021 at 10:24 AM Toomas Soome <tsoome@me.com = <mailto:tsoome@me.com>> wrote: >>=20 >>=20 >>> On 5. Feb 2021, at 18:44, Warner Losh <imp@bsdimp.com = <mailto:imp@bsdimp.com>> wrote: >>>=20 >>>=20 >>>=20 >>> On Thu, Feb 4, 2021 at 11:38 PM Toomas Soome <tsoome@me.com = <mailto:tsoome@me.com>> wrote: >>>=20 >>>=20 >>>> On 5. Feb 2021, at 01:56, Warner Losh <imp@bsdimp.com = <mailto:imp@bsdimp.com>> wrote: >>>>=20 >>>> =EF=BB=BF >>>> And why the instaMFC? Changes are supposed to cook force days = before merging... I have questions about the wisdom of this change... >>>>=20 >>>> Warner=20 >>>>=20 >>>=20 >>> Reason is in PR. There is someone with the system without ConOut but = ConOutDev is set. Instead of falling back to arbitrary device (which in = this case was totally wrong choice), we can try the possible devices = list. We do not change the ConOut parsing. >>>=20 >>> We could have the same effect defaulting to Video. This bug should = have been discussed / reviewed before it was committed. >>=20 >> How is is different from defaulting to serial, it is just as bad? we = can not guess there, thats why we do have ConOutDev list. >>=20 >>=20 >>>=20 >>> If it would appear, there are systems with unusable devices listed = in ConOutDev, then we need to think how to handle such case. >>>=20 >>> Yes. We fall back to the arbitrary device... It's just a flag that = can be overridden. We can easily fall back to video too. >>=20 >> We *should not* fall back on arbitrary devices when there is source = for alternate options. And that option is from specification: >>=20 >> "The ConInDev, ConOutDev, and ErrOutDev variables each contain an = EFI_DEVICE_PATH_PROTOCOL descriptor that defines all the possible = default devices to use on boot. These variables are volatile, and are = set dynamically on every boot. ConIn, ConOut, and ErrOut are always = proper subsets of ConInDev, ConOutDev, and ErrOutDev.=E2=80=9D >>=20 >> Right. Except they aren't a proper subset in this case. Since they = aren't a proper subset, can you count on them having any meaningful = meaning? In the cases you found they do, but it's just as arbitrary. >=20 > Well, we can argue if empty set is or is not subset of (any) other = set. But, we do have specification. And we should not arbitrary pick = what part we are going to follow and what not. >=20 > The empty set isn't a proper subset. It is a subset, but not a proper = subset, by definition. Therefore, it's not standards complaint. >> =20 >> UEFI Spec 2.8A, Page 82. >>=20 >> There may or may not be Video (or Serial) device listed. If not, = there are good chance we will be in trouble because the firmware = internals may not be set up properly and we can just as well end up in = hung system. >>=20 >> For x86, there's almost always Video. For !x86 it gets more = troublesome. >=20 > There is almost always ConOut as well. Except when there is not. And = in this case, there is not. >=20 > I still do not get what it is we are arguing about. Do we have case = where ConOut is not set and ConOutDev does have garbage? >=20 > We have one sighting of 'ConOut' being missing. Any extrapolation from = there is tricky. We know in this one case the info appears to be good. = But this is not standards compliant, so how can we be sure that others = will be similar? >=20 > Warner It is tricky, agree. But we also have other assumptions. Like we can = get handles for all devices (vmware devs at one point in time did decide = to only give handles for devices used at boot time - no handles fot = non-boot disks, serial ports and such). But we are not going to tell user to buy better computer, do we?:) = Otherwise, we should tell the same for other non-standard cases we = already do know about=E2=80=A6 Thanks for all the feedback, toomas
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