[PATCH 0/3] x86/reboot: update docs and limit O990 quirk scope.

[PATCH 0/3] x86/reboot: update docs and limit O990 quirk scope.

[Paul Gortmaker]

When using an older Dell Optiplex 990 for boot testing, I found it quite
annoying that the stupid thing would power right down and then turn on
again a second or two later on every "normal" reboot.

After a bit of investigation, I found that it wasn't the machine that
was at fault, but that we had put in a reboot quirk about 10y ago when
the platform was new, and never bothered to check back if it was
required after the vendor did the first year worth of BIOS updates.

Along the way I found that we never properly documented how to avoid
using the reboot quirks, or the reboot=pci option so I fixed that too.

---

Cc: Borislav Petkov <bp@alien8.de>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Matthew Garrett <mjg@redhat.com>
Cc: Michael D Labriola <michael.d.labriola@gmail.com>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Thomas Renninger <trenn@suse.de>
Cc: x86@kernel.org

Paul Gortmaker (3):
  x86/reboot: document the "reboot=pci" option
  x86/reboot: document how to override DMI platform quirks
  x86/reboot: Limit Dell Optiplex 990 quirk to early BIOS versions

 Documentation/admin-guide/kernel-parameters.txt |  2 +-
 Documentation/x86/x86_64/boot-options.rst       | 11 ++++++++++-
 arch/x86/kernel/reboot.c                        |  3 ++-
 3 files changed, 13 insertions(+), 3 deletions(-)

-- 
2.25.1

[PATCH 1/3] x86/reboot: document the "reboot=pci" option

[Paul Gortmaker]

It is mentioned in the top level non-arch specific file but it was
overlooked here for x86.

Cc: Borislav Petkov <bp@alien8.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: x86@kernel.org
Signed-off-by: Paul Gortmaker <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 324cefff92e7..2d2810409cc8 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.
-- 
2.25.1

[PATCH 2/3] x86/reboot: document how to override DMI platform quirks

[Paul Gortmaker]

In commit 5955633e91bf ("x86/reboot: Skip DMI checks if reboot set
by user") we made it so that you didn't have 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 we didn't really document it outside the source
code, and so this information isn't really available to the average
user out there.

Here we tell a little white lie and invent "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 we don't
know what the future additions might be, we lay claim on "default"
since that is exactly what it achieves.

Cc: Borislav Petkov <bp@alien8.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Matthew Garrett <mjg@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Michael D Labriola <michael.d.labriola@gmail.com>
Cc: x86@kernel.org
Signed-off-by: Paul Gortmaker <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 29a116b590bd..63e391d7045c 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -4703,7 +4703,7 @@
 
 	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 2d2810409cc8..8593d4f87cf9 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: <name> series board detected. Selecting <type> 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
 =======================
 
-- 
2.25.1

[PATCH 3/3] x86/reboot: Limit Dell Optiplex 990 quirk to early BIOS versions

[Paul Gortmaker]

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 I saw the quirk in dmesg - and then disabled
it to find 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<ver>.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 I'm not going 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, I've limited 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")
Cc: stable@vger.kernel.org
Cc: Borislav Petkov <bp@alien8.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Thomas Renninger <trenn@suse.de>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: x86@kernel.org
Signed-off-by: Paul Gortmaker <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 */
-- 
2.25.1

[tip: x86/misc] x86/reboot: Limit Dell Optiplex 990 quirk to early BIOS versions

[tip-bot2 for Paul Gortmaker]

The following commit has been merged into the x86/misc branch of tip:

Commit-ID:     a729691b541f6e63043beae72e635635abe5dc09
Gitweb:        https://git.kernel.org/tip/a729691b541f6e63043beae72e635635abe5dc09
Author:        Paul Gortmaker <paul.gortmaker@windriver.com>
AuthorDate:    Sun, 30 May 2021 12:24:47 -04:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Thu, 12 Aug 2021 12:06:58 +02:00

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<ver>.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 <paul.gortmaker@windriver.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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 ebfb911..0a40df6 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 */

[tip: x86/misc] x86/reboot: Document how to override DMI platform quirks

[tip-bot2 for Paul Gortmaker]

The following commit has been merged into the x86/misc branch of tip:

Commit-ID:     12febc181886f0658ce3413f554203c255d338dd
Gitweb:        https://git.kernel.org/tip/12febc181886f0658ce3413f554203c255d338dd
Author:        Paul Gortmaker <paul.gortmaker@windriver.com>
AuthorDate:    Sun, 30 May 2021 12:24:46 -04:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Thu, 12 Aug 2021 12:06:58 +02:00

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 <paul.gortmaker@windriver.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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 bdb2200..34c8dd5 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 482f3b2..ccb7e86 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: <name> series board detected. Selecting <type> 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
 =======================
 

[tip: x86/misc] x86/reboot: Document the "reboot=pci" option

[tip-bot2 for Paul Gortmaker]

The following commit has been merged into the x86/misc branch of tip:

Commit-ID:     162a5284faf41b2441b8f686f9ac4771c7a8f669
Gitweb:        https://git.kernel.org/tip/162a5284faf41b2441b8f686f9ac4771c7a8f669
Author:        Paul Gortmaker <paul.gortmaker@windriver.com>
AuthorDate:    Sun, 30 May 2021 12:24:45 -04:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Thu, 12 Aug 2021 12:06:58 +02:00

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 <paul.gortmaker@windriver.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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 5f62b3b..482f3b2 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.