Re: [PATCH] acpi, spcr: Make SPCR available to x86

[Prarit Bhargava]

On 02/12/2018 10:44 AM, Peter Zijlstra wrote:
> On Mon, Feb 12, 2018 at 10:18:06AM -0500, Prarit Bhargava wrote:
>>> But when I specify "earlyprintk=serial,ttyS0,115200" this SPCR crud will
>>> not interfere?
>>>
>>
>> I tested "earlyprintk=serial,ttyS0,115200" on a system which is known to 
>> have a
>> functional console with "console=ttyS0,1152008N1" both with and without
>> CONFIG_ACPI_SPCR_TABLE enabled.
> 
> OK, but my point was that SPCR will never override explicit earlyprintk
> stuff. There is absolutely nothing worse than breaking working setups.
> 

Oh, I see.  SPCR will not override earlyprintk config.

P.
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Re: [PATCH] acpi, spcr: Make SPCR available to x86

[Peter Zijlstra]

On Mon, Feb 12, 2018 at 10:18:06AM -0500, Prarit Bhargava wrote:
> > But when I specify "earlyprintk=serial,ttyS0,115200" this SPCR crud will
> > not interfere?
> > 
> 
> I tested "earlyprintk=serial,ttyS0,115200" on a system which is known to have 
> a
> functional console with "console=ttyS0,1152008N1" both with and without
> CONFIG_ACPI_SPCR_TABLE enabled.

OK, but my point was that SPCR will never override explicit earlyprintk
stuff. There is absolutely nothing worse than breaking working setups.
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Re: [PATCH] acpi, spcr: Make SPCR available to x86

[Prarit Bhargava]

On 02/12/2018 09:56 AM, Peter Zijlstra wrote:
> On Mon, Feb 12, 2018 at 08:47:57AM -0500, Prarit Bhargava wrote:
>>
>>
>> On 02/12/2018 08:34 AM, Peter Zijlstra wrote:
>>> On Thu, Jan 18, 2018 at 10:09:51AM -0500, Prarit Bhargava wrote:
  config ACPI_SPCR_TABLE
 +  bool "ACPI Serial Port Console Redirection Support"
 +  default y if X86
 +  help
 +Enable support for Serial Port Console Redirection (SPCR) Table.
 +This table provides information about the configuration of the
 +earlycon console.
>>>
>>> I just got asked this by oldconfig, which left me rather puzzled, WTF
>>> does this do?
>>
>> Odd -- I thought I had taken care of that :(  My apologies Peter.
>>
>> ACPI SPCR is used by a vendor to define the serial console for a system.  If
>> SPCR exists a user can add kernel parameter "earlycon" (no extra kernel
>> parameters) and the console will work out-of-the-box.
>>
>> The serial console configuration varies from vendor to vendor.  This takes 
>> the
>> guess-work out of defining a serial console.
> 
> But when I specify "earlyprintk=serial,ttyS0,115200" this SPCR crud will
> not interfere?
> 

I tested "earlyprintk=serial,ttyS0,115200" on a system which is known to have a
functional console with "console=ttyS0,1152008N1" both with and without
CONFIG_ACPI_SPCR_TABLE enabled.

I do not see any significant difference in output.

diff of boot logs:

--- earlyprintk_no_spcr_enable  2018-02-12 10:11:00.477288423 -0500
+++ earlyprintk_spcr_enable 2018-02-12 10:16:02.282574797 -0500
@@ -1,5 +1,5 @@
 microcode: microcode updated early to revision 0x235, date = 2017-10-17
-Linux version 4.15.0+ (r...@intel-purley-lr-02.khw.lab.eng.bos.redhat.com) (gcc
version 4.8.5 20150623 (Red Hat 4.8.5-28) (GCC)) #5 SMP Mon Feb 12 10:06:08 EST 
2018
+Linux version 4.15.0+ (r...@intel-purley-lr-02.khw.lab.eng.bos.redhat.com) (gcc
version 4.8.5 20150623 (Red Hat 4.8.5-28) (GCC)) #6 SMP Mon Feb 12 10:11:42 EST 
2018
 Command line: BOOT_IMAGE=/vmlinuz-4.15.0+
root=/dev/mapper/rhel_intel--purley--lr--02-root ro crashkernel=auto
rd.lvm.lv=rhel_intel-purley-lr-02/root rd.lvm.lv=rhel_intel-purley-lr-02/swap
earlyprintk=serial,ttyS0,115200 LANG=en_US.UTF-8
 x86/fpu: Supporting XSAVE feature 0x001: 'x87 floating point registers'
 x86/fpu: Supporting XSAVE feature 0x002: 'SSE registers'
@@ -205,7 +205,7 @@
 e820: last_pfn = 0x6f800 max_arch_pfn = 0x4
 Using GB pages for direct mapping
 Secure boot disabled
-RAMDISK: [mem 0x3a563000-0x3bba2fff]
+RAMDISK: [mem 0x3a5da000-0x3bba2fff]
 ACPI: Early table checksum verification disabled
 ACPI: RSDP 0x6922A014 24 (v02 INTEL )
 ACPI: XSDT 0x690DD188 000114 (v01 INTEL  EDK2   
0113)
@@ -519,6 +519,8 @@
 ACPI: INT_SRC_OVR (bus 0 bus_irq 9 global_irq 9 high level)
 Using ACPI (MADT) for SMP configuration information
 ACPI: HPET id: 0x8086a701 base: 0xfed0
+ACPI: SPCR: SPCR table version 1
+ACPI: SPCR: console: uart,io,0x3f8,115200
 smpboot: Allowing 432 CPUs, 224 hotplug CPUs
 PM: Registered nosave memory: [mem 0x-0x0fff]
 PM: Registered nosave memory: [mem 0x000a-0x000f]
@@ -555,10 +557,10 @@
 log_buf_len total cpu_extra contributions: 1765376 bytes
 log_buf_len min size: 524288 bytes
 log_buf_len: 4194304 bytes
-early log buf free: 477984(91%)
-Memory: 394593504K/401282564K available (10252K kernel code, 2147K rwdata,
3664K rodata, 2504K init, 1800K bss, 6689060K reserved, 0K cma-reserved)
+early log buf free: 477876(91%)
+Memory: 394593976K/401282564K available (10252K kernel code, 2147K rwdata,
3664K rodata, 2504K init, 1800K bss, 6688588K reserved, 0K cma-reserved)
 Kernel/User page tables isolation: enabled
-ftrace: allocating 35205 entries in 138 pages
+ftrace: allocating 35206 entries in 138 pages
 Hierarchical RCU implementation.
RCU restricting CPUs from NR_CPUS=8192 to nr_cpu_ids=432.
Tasks RCU enabled.

P.

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Re: [PATCH] acpi, spcr: Make SPCR available to x86

[Timur Tabi]

On 2/12/18 8:49 AM, Prarit Bhargava wrote:

That's true on ARM64.  I specifically did not enable the console by default on
x86.  There are users who do not want a console active during boot & runtime.


H... That's a good point.  On ARM systems with SPCR, you get a 
console whether you like it or not.


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Re: [PATCH] acpi, spcr: Make SPCR available to x86

[Peter Zijlstra]

On Mon, Feb 12, 2018 at 08:47:57AM -0500, Prarit Bhargava wrote:
> 
> 
> On 02/12/2018 08:34 AM, Peter Zijlstra wrote:
> > On Thu, Jan 18, 2018 at 10:09:51AM -0500, Prarit Bhargava wrote:
> >>  config ACPI_SPCR_TABLE
> >> +  bool "ACPI Serial Port Console Redirection Support"
> >> +  default y if X86
> >> +  help
> >> +Enable support for Serial Port Console Redirection (SPCR) Table.
> >> +This table provides information about the configuration of the
> >> +earlycon console.
> > 
> > I just got asked this by oldconfig, which left me rather puzzled, WTF
> > does this do?
> 
> Odd -- I thought I had taken care of that :(  My apologies Peter.
> 
> ACPI SPCR is used by a vendor to define the serial console for a system.  If
> SPCR exists a user can add kernel parameter "earlycon" (no extra kernel
> parameters) and the console will work out-of-the-box.
> 
> The serial console configuration varies from vendor to vendor.  This takes the
> guess-work out of defining a serial console.

But when I specify "earlyprintk=serial,ttyS0,115200" this SPCR crud will
not interfere?
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Re: [PATCH] acpi, spcr: Make SPCR available to x86

[Prarit Bhargava]

On 02/12/2018 09:43 AM, Timur Tabi wrote:
> On 2/12/18 7:47 AM, Prarit Bhargava wrote:
>> ACPI SPCR is used by a vendor to define the serial console for a system.  If
>> SPCR exists a user can add kernel parameter "earlycon" (no extra kernel
>> parameters) and the console will work out-of-the-box.
> 
> "earlycon" is needed only for an *early* console.  You don't need any command
> line parameters for a normal console to work with SPCR.

That's true on ARM64.  I specifically did not enable the console by default on
x86.  There are users who do not want a console active during boot & runtime.

P.

> 
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Re: [PATCH] acpi, spcr: Make SPCR available to x86

[Timur Tabi]

On 2/12/18 7:47 AM, Prarit Bhargava wrote:

ACPI SPCR is used by a vendor to define the serial console for a system.  If
SPCR exists a user can add kernel parameter "earlycon" (no extra kernel
parameters) and the console will work out-of-the-box.


"earlycon" is needed only for an *early* console.  You don't need any 
command line parameters for a normal console to work with SPCR.


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Re: [PATCH] acpi, spcr: Make SPCR available to x86

[Prarit Bhargava]

On 02/12/2018 08:34 AM, Peter Zijlstra wrote:
> On Thu, Jan 18, 2018 at 10:09:51AM -0500, Prarit Bhargava wrote:
>>  config ACPI_SPCR_TABLE
>> +bool "ACPI Serial Port Console Redirection Support"
>> +default y if X86
>> +help
>> +  Enable support for Serial Port Console Redirection (SPCR) Table.
>> +  This table provides information about the configuration of the
>> +  earlycon console.
> 
> I just got asked this by oldconfig, which left me rather puzzled, WTF
> does this do?

Odd -- I thought I had taken care of that :(  My apologies Peter.

ACPI SPCR is used by a vendor to define the serial console for a system.  If
SPCR exists a user can add kernel parameter "earlycon" (no extra kernel
parameters) and the console will work out-of-the-box.

The serial console configuration varies from vendor to vendor.  This takes the
guess-work out of defining a serial console.

P.

> 
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Re: [PATCH] acpi, spcr: Make SPCR available to x86

[Peter Zijlstra]

On Thu, Jan 18, 2018 at 10:09:51AM -0500, Prarit Bhargava wrote:
>  config ACPI_SPCR_TABLE
> + bool "ACPI Serial Port Console Redirection Support"
> + default y if X86
> + help
> +   Enable support for Serial Port Console Redirection (SPCR) Table.
> +   This table provides information about the configuration of the
> +   earlycon console.

I just got asked this by oldconfig, which left me rather puzzled, WTF
does this do?
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Re: [PATCH] acpi, spcr: Make SPCR available to x86

[Prarit Bhargava]

On 01/22/2018 04:49 PM, Timur Tabi wrote:
> On 01/18/2018 09:09 AM, Prarit Bhargava wrote:
>>   if (acpi_disabled) {
>> -if (earlycon_init_is_deferred)
>> +if (earlycon_acpi_spcr_enable)
> 
> This patch works for me, so I can ACK it, but first you might want to rename
> earlycon_acpi_spcr_enable, because these two lines don't make much sense.
> 
> "If ACPI is disabled, and ACPI SCPR is enabled, then "
> 
> If ACPI is disabled, then how can a variable called 
> "earlycon_acpi_spcr_enable"
> be true?
> 
> Would it make more sense to rename it to earlycon_spcr_enable?
> 

acpi_disabled is a global runtime flag that can be set via "acpi=off" on the
command line.  It does not disable the tables, only the reading and interpreting
of the data in the tables.

P.
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Re: [PATCH] acpi, spcr: Make SPCR available to x86

[Ingo Molnar]

* Prarit Bhargava  wrote:

> Note on testing:  I've tested this on several ARM64 and x86 boxes (only
> earlycon, console=ttyS0,115200, and with both options), verified that
> functionality on ARM64 has not changed (ie, CONFIG_ACPI_SPCR_TABLE is
> always =y), and verified functionality when !CONFIG_ACPI_SPCR_TABLE on
> x86.
> 
> P.
> 
> 8<
> 
> SPCR is currently only enabled or ARM64 and x86 can use SPCR to setup an
> early console.
> 
> General fixes include updating Documentation & Kconfig (for x86), updating
> comments, and changing parse_spcr() to acpi_parse_spcr(), and
> earlycon_init_is_deferred to earlycon_acpi_spcr_enable to be more
> descriptive.
> 
> On x86, many systems have a valid SPCR table but the table version is not
> 2 so the table version check must be a warning.
> 
> On ARM64 when the kernel parameter earlycon is used both the early console
> and console are enabled.  On x86, only the earlycon should be enabled by
> by default.  Modify acpi_parse_spcr() to allow options for initializing
> the early console and console separately.
> 
> Signed-off-by: Prarit Bhargava 
> Cc: linux-a...@vger.kernel.org
> Cc: linux-doc@vger.kernel.org
> Cc: linux-arm-ker...@lists.infradead.org
> Cc: linux...@vger.kernel.org
> Cc: linux-ser...@vger.kernel.org
> Cc: Bhupesh Sharma 
> Cc: Lv Zheng 
> Cc: Thomas Gleixner 
> Cc: Ingo Molnar 
> Cc: "H. Peter Anvin" 
> Cc: x...@kernel.org
> Cc: Jonathan Corbet 
> Cc: Catalin Marinas 
> Cc: Will Deacon 
> Cc: "Rafael J. Wysocki" m...@rjwysocki.net>
> Cc: Timur Tabi 
> Cc: graeme.greg...@linaro.org
> Cc: mark.sal...@redhat.com
> ---
>  Documentation/admin-guide/kernel-parameters.txt |  9 +---
>  arch/arm64/kernel/acpi.c|  4 ++--
>  arch/x86/kernel/acpi/boot.c |  3 +++
>  drivers/acpi/Kconfig|  7 +-
>  drivers/acpi/spcr.c | 29 
> +
>  drivers/tty/serial/earlycon.c   | 15 +
>  include/linux/acpi.h|  7 --
>  include/linux/serial_core.h |  4 ++--
>  8 files changed, 44 insertions(+), 34 deletions(-)

I'm fine with the x86 aspect of this:

Acked-by: Ingo Molnar 

>   earlycon=   [KNL] Output early console device and options.
>  
> - When used with no options, the early console is
> - determined by the stdout-path property in device
> - tree's chosen node.
> + [ARM64] The early console is determined by the
> + stdout-path property in device tree's chosen node,
> + or determined by the ACPI SPCR table.

s/in device tree's chosen node
 /in the device tree's chosen node

Thanks,

Ingo
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[PATCH] acpi, spcr: Make SPCR available to x86

[Prarit Bhargava]

Note on testing:  I've tested this on several ARM64 and x86 boxes (only
earlycon, console=ttyS0,115200, and with both options), verified that
functionality on ARM64 has not changed (ie, CONFIG_ACPI_SPCR_TABLE is
always =y), and verified functionality when !CONFIG_ACPI_SPCR_TABLE on
x86.

P.

8<

SPCR is currently only enabled or ARM64 and x86 can use SPCR to setup an
early console.

General fixes include updating Documentation & Kconfig (for x86), updating
comments, and changing parse_spcr() to acpi_parse_spcr(), and
earlycon_init_is_deferred to earlycon_acpi_spcr_enable to be more
descriptive.

On x86, many systems have a valid SPCR table but the table version is not
2 so the table version check must be a warning.

On ARM64 when the kernel parameter earlycon is used both the early console
and console are enabled.  On x86, only the earlycon should be enabled by
by default.  Modify acpi_parse_spcr() to allow options for initializing
the early console and console separately.

Signed-off-by: Prarit Bhargava 
Cc: linux-a...@vger.kernel.org
Cc: linux-doc@vger.kernel.org
Cc: linux-arm-ker...@lists.infradead.org
Cc: linux...@vger.kernel.org
Cc: linux-ser...@vger.kernel.org
Cc: Bhupesh Sharma 
Cc: Lv Zheng 
Cc: Thomas Gleixner 
Cc: Ingo Molnar 
Cc: "H. Peter Anvin" 
Cc: x...@kernel.org
Cc: Jonathan Corbet 
Cc: Catalin Marinas 
Cc: Will Deacon 
Cc: "Rafael J. Wysocki" m...@rjwysocki.net>
Cc: Timur Tabi 
Cc: graeme.greg...@linaro.org
Cc: mark.sal...@redhat.com
---
 Documentation/admin-guide/kernel-parameters.txt |  9 +---
 arch/arm64/kernel/acpi.c|  4 ++--
 arch/x86/kernel/acpi/boot.c |  3 +++
 drivers/acpi/Kconfig|  7 +-
 drivers/acpi/spcr.c | 29 +
 drivers/tty/serial/earlycon.c   | 15 +
 include/linux/acpi.h|  7 --
 include/linux/serial_core.h |  4 ++--
 8 files changed, 44 insertions(+), 34 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt 
b/Documentation/admin-guide/kernel-parameters.txt
index 46b26bfee27b..6f519230ed34 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -915,9 +915,12 @@
 
earlycon=   [KNL] Output early console device and options.
 
-   When used with no options, the early console is
-   determined by the stdout-path property in device
-   tree's chosen node.
+   [ARM64] The early console is determined by the
+   stdout-path property in device tree's chosen node,
+   or determined by the ACPI SPCR table.
+
+   [X86] When used with no options the early console is
+   determined by the ACPI SPCR table.
 
cdns,[,options]
Start an early, polled-mode console on a Cadence
diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
index b3162715ed78..2aa5609def27 100644
--- a/arch/arm64/kernel/acpi.c
+++ b/arch/arm64/kernel/acpi.c
@@ -230,10 +230,10 @@ void __init acpi_boot_table_init(void)
 
 done:
if (acpi_disabled) {
-   if (earlycon_init_is_deferred)
+   if (earlycon_acpi_spcr_enable)
early_init_dt_scan_chosen_stdout();
} else {
-   parse_spcr(earlycon_init_is_deferred);
+   acpi_parse_spcr(earlycon_acpi_spcr_enable, true);
if (IS_ENABLED(CONFIG_ACPI_BGRT))
acpi_table_parse(ACPI_SIG_BGRT, acpi_parse_bgrt);
}
diff --git a/arch/x86/kernel/acpi/boot.c b/arch/x86/kernel/acpi/boot.c
index f4c463df8b08..0bf6a58f7a6d 100644
--- a/arch/x86/kernel/acpi/boot.c
+++ b/arch/x86/kernel/acpi/boot.c
@@ -36,6 +36,7 @@
 #include 
 #include 
 #include 
+#include 
 
 #include 
 #include 
@@ -1626,6 +1627,8 @@ int __init acpi_boot_init(void)
if (!acpi_noirq)
x86_init.pci.init = pci_acpi_init;
 
+   /* Do not enable ACPI SPCR console by default */
+   acpi_parse_spcr(earlycon_acpi_spcr_enable, false);
return 0;
 }
 
diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
index 46505396869e..ddcb5f40e8ee 100644
--- a/drivers/acpi/Kconfig
+++ b/drivers/acpi/Kconfig
@@ -79,7 +79,12 @@ config ACPI_DEBUGGER_USER
 endif
 
 config ACPI_SPCR_TABLE
-   bool
+   bool "ACPI Serial Port Console Redirection Support"
+   default y if X86
+   help
+ Enable support for Serial Port Console Redirection (SPCR) Table.
+ This table provides information about the configuration of the
+ earlycon console.
 
 config