From 162a5284faf41b2441b8f686f9ac4771c7a8f669 Mon Sep 17 00:00:00 2001 From: Paul Gortmaker Date: Sun, 30 May 2021 12:24:45 -0400 Subject: [PATCH 1/3] x86/reboot: Document the "reboot=pci" option It is mentioned in the top level non-arch specific file but it was overlooked here for x86. Signed-off-by: Paul Gortmaker Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/r/20210530162447.996461-2-paul.gortmaker@windriver.com --- Documentation/x86/x86_64/boot-options.rst | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/Documentation/x86/x86_64/boot-options.rst b/Documentation/x86/x86_64/boot-options.rst index 5f62b3b86357..482f3b29f99a 100644 --- a/Documentation/x86/x86_64/boot-options.rst +++ b/Documentation/x86/x86_64/boot-options.rst @@ -126,7 +126,7 @@ Idle loop Rebooting ========= - reboot=b[ios] | t[riple] | k[bd] | a[cpi] | e[fi] [, [w]arm | [c]old] + reboot=b[ios] | t[riple] | k[bd] | a[cpi] | e[fi] | p[ci] [, [w]arm | [c]old] bios Use the CPU reboot vector for warm reset warm @@ -145,6 +145,8 @@ Rebooting Use efi reset_system runtime service. If EFI is not configured or the EFI reset does not work, the reboot path attempts the reset using the keyboard controller. + pci + Use a write to the PCI config space register 0xcf9 to trigger reboot. Using warm reset will be much faster especially on big memory systems because the BIOS will not go through the memory check. From 12febc181886f0658ce3413f554203c255d338dd Mon Sep 17 00:00:00 2001 From: Paul Gortmaker Date: Sun, 30 May 2021 12:24:46 -0400 Subject: [PATCH 2/3] x86/reboot: Document how to override DMI platform quirks commit 5955633e91bf ("x86/reboot: Skip DMI checks if reboot set by user") made it so that it's not required to recompile the kernel in order to bypass broken reboot quirks compiled into an image: * This variable is used privately to keep track of whether or not * reboot_type is still set to its default value (i.e., reboot= hasn't * been set on the command line). This is needed so that we can * suppress DMI scanning for reboot quirks. Without it, it's * impossible to override a faulty reboot quirk without recompiling. However, at the time it was not eally documented outside the source code, and so this information isn't really available to the average user out there. The change is a little white lie and invented "reboot=default" since it is easy to remember, and documents well. The truth is that any random string that is *not* a currently accepted string will work. Since that doesn't document well for non-coders, and since it's unknown what the future additions might be, lay claim on "default" since that is exactly what it achieves. Signed-off-by: Paul Gortmaker Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/r/20210530162447.996461-3-paul.gortmaker@windriver.com --- Documentation/admin-guide/kernel-parameters.txt | 2 +- Documentation/x86/x86_64/boot-options.rst | 7 +++++++ 2 files changed, 8 insertions(+), 1 deletion(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index bdb22006f713..34c8dd54518e 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -4777,7 +4777,7 @@ reboot= [KNL] Format (x86 or x86_64): - [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] \ + [w[arm] | c[old] | h[ard] | s[oft] | g[pio]] | d[efault] \ [[,]s[mp]#### \ [[,]b[ios] | a[cpi] | k[bd] | t[riple] | e[fi] | p[ci]] \ [[,]f[orce] diff --git a/Documentation/x86/x86_64/boot-options.rst b/Documentation/x86/x86_64/boot-options.rst index 482f3b29f99a..ccb7e86bf8d9 100644 --- a/Documentation/x86/x86_64/boot-options.rst +++ b/Documentation/x86/x86_64/boot-options.rst @@ -157,6 +157,13 @@ Rebooting Don't stop other CPUs on reboot. This can make reboot more reliable in some cases. + reboot=default + There are some built-in platform specific "quirks" - you may see: + "reboot: series board detected. Selecting for reboots." + In the case where you think the quirk is in error (e.g. you have + newer BIOS, or newer board) using this option will ignore the built-in + quirk table, and use the generic default reboot actions. + Non Executable Mappings ======================= From a729691b541f6e63043beae72e635635abe5dc09 Mon Sep 17 00:00:00 2001 From: Paul Gortmaker Date: Sun, 30 May 2021 12:24:47 -0400 Subject: [PATCH 3/3] x86/reboot: Limit Dell Optiplex 990 quirk to early BIOS versions When this platform was relatively new in November 2011, with early BIOS revisions, a reboot quirk was added in commit 6be30bb7d750 ("x86/reboot: Blacklist Dell OptiPlex 990 known to require PCI reboot") However, this quirk (and several others) are open-ended to all BIOS versions and left no automatic expiry if/when the system BIOS fixed the issue, meaning that nobody is likely to come along and re-test. What is really problematic with using PCI reboot as this quirk does, is that it causes this platform to do a full power down, wait one second, and then power back on. This is less than ideal if one is using it for boot testing and/or bisecting kernels when legacy rotating hard disks are installed. It was only by chance that the quirk was noticed in dmesg - and when disabled it turned out that it wasn't required anymore (BIOS A24), and a default reboot would work fine without the "harshness" of power cycling the machine (and disks) down and up like the PCI reboot does. Doing a bit more research, it seems that the "newest" BIOS for which the issue was reported[1] was version A06, however Dell[2] seemed to suggest only up to and including version A05, with the A06 having a large number of fixes[3] listed. As is typical with a new platform, the initial BIOS updates come frequently and then taper off (and in this case, with a revival for CPU CVEs); a search for O990-A.exe reveals the following dates: A02 16 Mar 2011 A03 11 May 2011 A06 14 Sep 2011 A07 24 Oct 2011 A10 08 Dec 2011 A14 06 Sep 2012 A16 15 Oct 2012 A18 30 Sep 2013 A19 23 Sep 2015 A20 02 Jun 2017 A23 07 Mar 2018 A24 21 Aug 2018 While it's overkill to flash and test each of the above, it would seem likely that the issue was contained within A0x BIOS versions, given the dates above and the dates of issue reports[4] from distros. So rather than just throw out the quirk entirely, limit the scope to just those early BIOS versions, in case people are still running systems from 2011 with the original as-shipped early A0x BIOS versions. [1] https://lore.kernel.org/lkml/1320373471-3942-1-git-send-email-trenn@suse.de/ [2] https://www.dell.com/support/kbdoc/en-ca/000131908/linux-based-operating-systems-stall-upon-reboot-on-optiplex-390-790-990-systems [3] https://www.dell.com/support/home/en-ca/drivers/driversdetails?driverid=85j10 [4] https://bugs.launchpad.net/ubuntu/+source/linux/+bug/768039 Fixes: 6be30bb7d750 ("x86/reboot: Blacklist Dell OptiPlex 990 known to require PCI reboot") Signed-off-by: Paul Gortmaker Signed-off-by: Thomas Gleixner Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20210530162447.996461-4-paul.gortmaker@windriver.com --- arch/x86/kernel/reboot.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/x86/kernel/reboot.c b/arch/x86/kernel/reboot.c index ebfb91108232..0a40df66a40d 100644 --- a/arch/x86/kernel/reboot.c +++ b/arch/x86/kernel/reboot.c @@ -388,10 +388,11 @@ static const struct dmi_system_id reboot_dmi_table[] __initconst = { }, { /* Handle problems with rebooting on the OptiPlex 990. */ .callback = set_pci_reboot, - .ident = "Dell OptiPlex 990", + .ident = "Dell OptiPlex 990 BIOS A0x", .matches = { DMI_MATCH(DMI_SYS_VENDOR, "Dell Inc."), DMI_MATCH(DMI_PRODUCT_NAME, "OptiPlex 990"), + DMI_MATCH(DMI_BIOS_VERSION, "A0"), }, }, { /* Handle problems with rebooting on Dell 300's */