[PATCH v2 0/2] Fix arm64 CONFIG_CMDLINE handling and remove CMDLINE_EXTEND

[PATCH v2 0/2] Fix arm64 CONFIG_CMDLINE handling and remove CMDLINE_EXTEND

[Will Deacon]

Hi again,

This is version two of the series I previously posted here:

	https://lore.kernel.org/r/20210225125921.13147-1-will@kernel.org

The main change since v1 is that, rather than "fix" the FDT code to
follow the documented behaviour for CMDLINE_EXTEND, I've opted to remove
the thing entirely for arm64 while a less ambiguous and generic
replacement is developed, probably based on either [1] or [2].

I've left the first-patch as-is so that it's easier to incorporate
whatever ends up replacing CMDLINE_EXTEND in future.

Cheers,

Will

[1] https://patchwork.ozlabs.org/project/linuxppc-dev/cover/cover.1554195798.git.christophe.leroy@c-s.fr/
[2] https://patchwork.ozlabs.org/project/linuxppc-dev/patch/20190319232448.45964-2-danielwa@cisco.com/

--->8

Cc: Max Uvarov <muvarov@gmail.com>
Cc: Rob Herring <robh@kernel.org>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Doug Anderson <dianders@chromium.org>
Cc: Tyler Hicks <tyhicks@linux.microsoft.com>
Cc: Frank Rowand <frowand.list@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: <kernel-team@android.com>
Cc: <linux-arm-kernel@lists.infradead.org>
Cc: <devicetree@vger.kernel.org>

Will Deacon (2):
  arm64: cpufeatures: Fix handling of CONFIG_CMDLINE for idreg overrides
  arm64: Drop support for CMDLINE_EXTEND

 arch/arm64/Kconfig                 |  6 -----
 arch/arm64/kernel/idreg-override.c | 43 ++++++++++++++++--------------
 2 files changed, 23 insertions(+), 26 deletions(-)

-- 
2.30.1.766.gb4fecdf3b7-goog

[PATCH v2 0/2] Fix arm64 CONFIG_CMDLINE handling and remove CMDLINE_EXTEND

[Will Deacon]

Hi again,

This is version two of the series I previously posted here:

	https://lore.kernel.org/r/20210225125921.13147-1-will@kernel.org

The main change since v1 is that, rather than "fix" the FDT code to
follow the documented behaviour for CMDLINE_EXTEND, I've opted to remove
the thing entirely for arm64 while a less ambiguous and generic
replacement is developed, probably based on either [1] or [2].

I've left the first-patch as-is so that it's easier to incorporate
whatever ends up replacing CMDLINE_EXTEND in future.

Cheers,

Will

[1] https://patchwork.ozlabs.org/project/linuxppc-dev/cover/cover.1554195798.git.christophe.leroy@c-s.fr/
[2] https://patchwork.ozlabs.org/project/linuxppc-dev/patch/20190319232448.45964-2-danielwa@cisco.com/

--->8

Cc: Max Uvarov <muvarov@gmail.com>
Cc: Rob Herring <robh@kernel.org>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Doug Anderson <dianders@chromium.org>
Cc: Tyler Hicks <tyhicks@linux.microsoft.com>
Cc: Frank Rowand <frowand.list@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Palmer Dabbelt <palmer@dabbelt.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: <kernel-team@android.com>
Cc: <linux-arm-kernel@lists.infradead.org>
Cc: <devicetree@vger.kernel.org>

Will Deacon (2):
  arm64: cpufeatures: Fix handling of CONFIG_CMDLINE for idreg overrides
  arm64: Drop support for CMDLINE_EXTEND

 arch/arm64/Kconfig                 |  6 -----
 arch/arm64/kernel/idreg-override.c | 43 ++++++++++++++++--------------
 2 files changed, 23 insertions(+), 26 deletions(-)

-- 
2.30.1.766.gb4fecdf3b7-goog


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

[PATCH v2 1/2] arm64: cpufeatures: Fix handling of CONFIG_CMDLINE for idreg overrides

[Will Deacon]

The built-in kernel commandline (CONFIG_CMDLINE) can be configured in
three different ways:

  1. CMDLINE_FORCE: Use CONFIG_CMDLINE instead of any bootloader args
  2. CMDLINE_EXTEND: Append the bootloader args to CONFIG_CMDLINE
  3. CMDLINE_FROM_BOOTLOADER: Only use CONFIG_CMDLINE if there aren't
     any bootloader args.

The early cmdline parsing to detect idreg overrides gets (2) and (3)
slightly wrong: in the case of (2) the bootloader args are parsed first
and in the case of (3) the CMDLINE is always parsed.

Fix these issues by moving the bootargs parsing out into a helper
function and following the same logic as that used by the EFI stub.

Reviewed-by: Marc Zyngier <maz@kernel.org>
Fixes: 33200303553d ("arm64: cpufeature: Add an early command-line cpufeature override facility")
Signed-off-by: Will Deacon <will@kernel.org>
---
 arch/arm64/kernel/idreg-override.c | 44 +++++++++++++++++-------------
 1 file changed, 25 insertions(+), 19 deletions(-)

diff --git a/arch/arm64/kernel/idreg-override.c b/arch/arm64/kernel/idreg-override.c
index dffb16682330..cc071712c6f9 100644
--- a/arch/arm64/kernel/idreg-override.c
+++ b/arch/arm64/kernel/idreg-override.c
@@ -163,33 +163,39 @@ static __init void __parse_cmdline(const char *cmdline, bool parse_aliases)
 	} while (1);
 }
 
-static __init void parse_cmdline(void)
+static __init const u8 *get_bootargs_cmdline(void)
 {
-	if (!IS_ENABLED(CONFIG_CMDLINE_FORCE)) {
-		const u8 *prop;
-		void *fdt;
-		int node;
+	const u8 *prop;
+	void *fdt;
+	int node;
 
-		fdt = get_early_fdt_ptr();
-		if (!fdt)
-			goto out;
+	fdt = get_early_fdt_ptr();
+	if (!fdt)
+		return NULL;
 
-		node = fdt_path_offset(fdt, "/chosen");
-		if (node < 0)
-			goto out;
+	node = fdt_path_offset(fdt, "/chosen");
+	if (node < 0)
+		return NULL;
 
-		prop = fdt_getprop(fdt, node, "bootargs", NULL);
-		if (!prop)
-			goto out;
+	prop = fdt_getprop(fdt, node, "bootargs", NULL);
+	if (!prop)
+		return NULL;
 
-		__parse_cmdline(prop, true);
+	return strlen(prop) ? prop : NULL;
+}
 
-		if (!IS_ENABLED(CONFIG_CMDLINE_EXTEND))
-			return;
+static __init void parse_cmdline(void)
+{
+	const u8 *prop = get_bootargs_cmdline();
+
+	if (IS_ENABLED(CONFIG_CMDLINE_EXTEND) ||
+	    IS_ENABLED(CONFIG_CMDLINE_FORCE) ||
+	    !prop) {
+		__parse_cmdline(CONFIG_CMDLINE, true);
 	}
 
-out:
-	__parse_cmdline(CONFIG_CMDLINE, true);
+	if (!IS_ENABLED(CONFIG_CMDLINE_FORCE) && prop)
+		__parse_cmdline(prop, true);
 }
 
 /* Keep checkers quiet */
-- 
2.30.1.766.gb4fecdf3b7-goog

[PATCH v2 1/2] arm64: cpufeatures: Fix handling of CONFIG_CMDLINE for idreg overrides

[Will Deacon]

The built-in kernel commandline (CONFIG_CMDLINE) can be configured in
three different ways:

  1. CMDLINE_FORCE: Use CONFIG_CMDLINE instead of any bootloader args
  2. CMDLINE_EXTEND: Append the bootloader args to CONFIG_CMDLINE
  3. CMDLINE_FROM_BOOTLOADER: Only use CONFIG_CMDLINE if there aren't
     any bootloader args.

The early cmdline parsing to detect idreg overrides gets (2) and (3)
slightly wrong: in the case of (2) the bootloader args are parsed first
and in the case of (3) the CMDLINE is always parsed.

Fix these issues by moving the bootargs parsing out into a helper
function and following the same logic as that used by the EFI stub.

Reviewed-by: Marc Zyngier <maz@kernel.org>
Fixes: 33200303553d ("arm64: cpufeature: Add an early command-line cpufeature override facility")
Signed-off-by: Will Deacon <will@kernel.org>
---
 arch/arm64/kernel/idreg-override.c | 44 +++++++++++++++++-------------
 1 file changed, 25 insertions(+), 19 deletions(-)

diff --git a/arch/arm64/kernel/idreg-override.c b/arch/arm64/kernel/idreg-override.c
index dffb16682330..cc071712c6f9 100644
--- a/arch/arm64/kernel/idreg-override.c
+++ b/arch/arm64/kernel/idreg-override.c
@@ -163,33 +163,39 @@ static __init void __parse_cmdline(const char *cmdline, bool parse_aliases)
 	} while (1);
 }
 
-static __init void parse_cmdline(void)
+static __init const u8 *get_bootargs_cmdline(void)
 {
-	if (!IS_ENABLED(CONFIG_CMDLINE_FORCE)) {
-		const u8 *prop;
-		void *fdt;
-		int node;
+	const u8 *prop;
+	void *fdt;
+	int node;
 
-		fdt = get_early_fdt_ptr();
-		if (!fdt)
-			goto out;
+	fdt = get_early_fdt_ptr();
+	if (!fdt)
+		return NULL;
 
-		node = fdt_path_offset(fdt, "/chosen");
-		if (node < 0)
-			goto out;
+	node = fdt_path_offset(fdt, "/chosen");
+	if (node < 0)
+		return NULL;
 
-		prop = fdt_getprop(fdt, node, "bootargs", NULL);
-		if (!prop)
-			goto out;
+	prop = fdt_getprop(fdt, node, "bootargs", NULL);
+	if (!prop)
+		return NULL;
 
-		__parse_cmdline(prop, true);
+	return strlen(prop) ? prop : NULL;
+}
 
-		if (!IS_ENABLED(CONFIG_CMDLINE_EXTEND))
-			return;
+static __init void parse_cmdline(void)
+{
+	const u8 *prop = get_bootargs_cmdline();
+
+	if (IS_ENABLED(CONFIG_CMDLINE_EXTEND) ||
+	    IS_ENABLED(CONFIG_CMDLINE_FORCE) ||
+	    !prop) {
+		__parse_cmdline(CONFIG_CMDLINE, true);
 	}
 
-out:
-	__parse_cmdline(CONFIG_CMDLINE, true);
+	if (!IS_ENABLED(CONFIG_CMDLINE_FORCE) && prop)
+		__parse_cmdline(prop, true);
 }
 
 /* Keep checkers quiet */
-- 
2.30.1.766.gb4fecdf3b7-goog


_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

[PATCH v2 2/2] arm64: Drop support for CMDLINE_EXTEND

[Will Deacon]

The documented behaviour for CMDLINE_EXTEND is that the arguments from
the bootloader are appended to the built-in kernel command line. This
also matches the option parsing behaviour for the EFI stub and early ID
register overrides.

Bizarrely, the fdt behaviour is the other way around: appending the
built-in command line to the bootloader arguments, resulting in a
command-line that doesn't necessarily line-up with the parsing order and
definitely doesn't line-up with the documented behaviour.

As it turns out, there is a proposal [1] to replace CMDLINE_EXTEND with
CMDLINE_PREPEND and CMDLINE_APPEND options which should hopefully make
the intended behaviour much clearer. While we wait for those to land,
drop CMDLINE_EXTEND for now as there appears to be little enthusiasm for
changing the current FDT behaviour.

[1] https://lore.kernel.org/lkml/20190319232448.45964-2-danielwa@cisco.com/

Cc: Max Uvarov <muvarov@gmail.com>
Cc: Rob Herring <robh@kernel.org>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Doug Anderson <dianders@chromium.org>
Cc: Tyler Hicks <tyhicks@linux.microsoft.com>
Cc: Frank Rowand <frowand.list@gmail.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/CAL_JsqJX=TCCs7=gg486r9TN4NYscMTCLNfqJF9crskKPq-bTg@mail.gmail.com
Signed-off-by: Will Deacon <will@kernel.org>
---
 arch/arm64/Kconfig                 | 6 ------
 arch/arm64/kernel/idreg-override.c | 5 +----
 2 files changed, 1 insertion(+), 10 deletions(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 1f212b47a48a..f15418332d16 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -1855,12 +1855,6 @@ config CMDLINE_FROM_BOOTLOADER
 	  the boot loader doesn't provide any, the default kernel command
 	  string provided in CMDLINE will be used.
 
-config CMDLINE_EXTEND
-	bool "Extend bootloader kernel arguments"
-	help
-	  The command-line arguments provided by the boot loader will be
-	  appended to the default kernel command string.
-
 config CMDLINE_FORCE
 	bool "Always use the default kernel command string"
 	help
diff --git a/arch/arm64/kernel/idreg-override.c b/arch/arm64/kernel/idreg-override.c
index cc071712c6f9..83f1c4b92095 100644
--- a/arch/arm64/kernel/idreg-override.c
+++ b/arch/arm64/kernel/idreg-override.c
@@ -188,11 +188,8 @@ static __init void parse_cmdline(void)
 {
 	const u8 *prop = get_bootargs_cmdline();
 
-	if (IS_ENABLED(CONFIG_CMDLINE_EXTEND) ||
-	    IS_ENABLED(CONFIG_CMDLINE_FORCE) ||
-	    !prop) {
+	if (IS_ENABLED(CONFIG_CMDLINE_FORCE) || !prop)
 		__parse_cmdline(CONFIG_CMDLINE, true);
-	}
 
 	if (!IS_ENABLED(CONFIG_CMDLINE_FORCE) && prop)
 		__parse_cmdline(prop, true);
-- 
2.30.1.766.gb4fecdf3b7-goog

[PATCH v2 2/2] arm64: Drop support for CMDLINE_EXTEND

[Will Deacon]

The documented behaviour for CMDLINE_EXTEND is that the arguments from
the bootloader are appended to the built-in kernel command line. This
also matches the option parsing behaviour for the EFI stub and early ID
register overrides.

Bizarrely, the fdt behaviour is the other way around: appending the
built-in command line to the bootloader arguments, resulting in a
command-line that doesn't necessarily line-up with the parsing order and
definitely doesn't line-up with the documented behaviour.

As it turns out, there is a proposal [1] to replace CMDLINE_EXTEND with
CMDLINE_PREPEND and CMDLINE_APPEND options which should hopefully make
the intended behaviour much clearer. While we wait for those to land,
drop CMDLINE_EXTEND for now as there appears to be little enthusiasm for
changing the current FDT behaviour.

[1] https://lore.kernel.org/lkml/20190319232448.45964-2-danielwa@cisco.com/

Cc: Max Uvarov <muvarov@gmail.com>
Cc: Rob Herring <robh@kernel.org>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Doug Anderson <dianders@chromium.org>
Cc: Tyler Hicks <tyhicks@linux.microsoft.com>
Cc: Frank Rowand <frowand.list@gmail.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Link: https://lore.kernel.org/r/CAL_JsqJX=TCCs7=gg486r9TN4NYscMTCLNfqJF9crskKPq-bTg@mail.gmail.com
Signed-off-by: Will Deacon <will@kernel.org>
---
 arch/arm64/Kconfig                 | 6 ------
 arch/arm64/kernel/idreg-override.c | 5 +----
 2 files changed, 1 insertion(+), 10 deletions(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 1f212b47a48a..f15418332d16 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -1855,12 +1855,6 @@ config CMDLINE_FROM_BOOTLOADER
 	  the boot loader doesn't provide any, the default kernel command
 	  string provided in CMDLINE will be used.
 
-config CMDLINE_EXTEND
-	bool "Extend bootloader kernel arguments"
-	help
-	  The command-line arguments provided by the boot loader will be
-	  appended to the default kernel command string.
-
 config CMDLINE_FORCE
 	bool "Always use the default kernel command string"
 	help
diff --git a/arch/arm64/kernel/idreg-override.c b/arch/arm64/kernel/idreg-override.c
index cc071712c6f9..83f1c4b92095 100644
--- a/arch/arm64/kernel/idreg-override.c
+++ b/arch/arm64/kernel/idreg-override.c
@@ -188,11 +188,8 @@ static __init void parse_cmdline(void)
 {
 	const u8 *prop = get_bootargs_cmdline();
 
-	if (IS_ENABLED(CONFIG_CMDLINE_EXTEND) ||
-	    IS_ENABLED(CONFIG_CMDLINE_FORCE) ||
-	    !prop) {
+	if (IS_ENABLED(CONFIG_CMDLINE_FORCE) || !prop)
 		__parse_cmdline(CONFIG_CMDLINE, true);
-	}
 
 	if (!IS_ENABLED(CONFIG_CMDLINE_FORCE) && prop)
 		__parse_cmdline(prop, true);
-- 
2.30.1.766.gb4fecdf3b7-goog


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http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

Re: [PATCH v2 1/2] arm64: cpufeatures: Fix handling of CONFIG_CMDLINE for idreg overrides

[Rob Herring]

On Wed, Mar 3, 2021 at 7:50 AM Will Deacon <will@kernel.org> wrote:
>
> The built-in kernel commandline (CONFIG_CMDLINE) can be configured in
> three different ways:
>
>   1. CMDLINE_FORCE: Use CONFIG_CMDLINE instead of any bootloader args
>   2. CMDLINE_EXTEND: Append the bootloader args to CONFIG_CMDLINE
>   3. CMDLINE_FROM_BOOTLOADER: Only use CONFIG_CMDLINE if there aren't
>      any bootloader args.
>
> The early cmdline parsing to detect idreg overrides gets (2) and (3)
> slightly wrong: in the case of (2) the bootloader args are parsed first
> and in the case of (3) the CMDLINE is always parsed.
>
> Fix these issues by moving the bootargs parsing out into a helper
> function and following the same logic as that used by the EFI stub.
>
> Reviewed-by: Marc Zyngier <maz@kernel.org>
> Fixes: 33200303553d ("arm64: cpufeature: Add an early command-line cpufeature override facility")
> Signed-off-by: Will Deacon <will@kernel.org>
> ---
>  arch/arm64/kernel/idreg-override.c | 44 +++++++++++++++++-------------
>  1 file changed, 25 insertions(+), 19 deletions(-)

It bothers me a bit having command line handling here. It means how
the command line is assembled in 2 places. I guess if we get rid of
ambiguous 'extend' then it's better, but perhaps a better
implementation would be an api get a specific command line parameter.
The main downside would be searching the DT again for each parameter
if we can't store any data in between calls, but there's ways around
that. PowerPC also needs similar functionality in
disabled_on_cmdline().

Anyways, that's all beyond the scope of this.

Rob

Re: [PATCH v2 1/2] arm64: cpufeatures: Fix handling of CONFIG_CMDLINE for idreg overrides

[Rob Herring]

On Wed, Mar 3, 2021 at 7:50 AM Will Deacon <will@kernel.org> wrote:
>
> The built-in kernel commandline (CONFIG_CMDLINE) can be configured in
> three different ways:
>
>   1. CMDLINE_FORCE: Use CONFIG_CMDLINE instead of any bootloader args
>   2. CMDLINE_EXTEND: Append the bootloader args to CONFIG_CMDLINE
>   3. CMDLINE_FROM_BOOTLOADER: Only use CONFIG_CMDLINE if there aren't
>      any bootloader args.
>
> The early cmdline parsing to detect idreg overrides gets (2) and (3)
> slightly wrong: in the case of (2) the bootloader args are parsed first
> and in the case of (3) the CMDLINE is always parsed.
>
> Fix these issues by moving the bootargs parsing out into a helper
> function and following the same logic as that used by the EFI stub.
>
> Reviewed-by: Marc Zyngier <maz@kernel.org>
> Fixes: 33200303553d ("arm64: cpufeature: Add an early command-line cpufeature override facility")
> Signed-off-by: Will Deacon <will@kernel.org>
> ---
>  arch/arm64/kernel/idreg-override.c | 44 +++++++++++++++++-------------
>  1 file changed, 25 insertions(+), 19 deletions(-)

It bothers me a bit having command line handling here. It means how
the command line is assembled in 2 places. I guess if we get rid of
ambiguous 'extend' then it's better, but perhaps a better
implementation would be an api get a specific command line parameter.
The main downside would be searching the DT again for each parameter
if we can't store any data in between calls, but there's ways around
that. PowerPC also needs similar functionality in
disabled_on_cmdline().

Anyways, that's all beyond the scope of this.

Rob

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Re: [PATCH v2 1/2] arm64: cpufeatures: Fix handling of CONFIG_CMDLINE for idreg overrides

[Will Deacon]

On Wed, Mar 03, 2021 at 04:30:21PM -0600, Rob Herring wrote:
> On Wed, Mar 3, 2021 at 7:50 AM Will Deacon <will@kernel.org> wrote:
> >
> > The built-in kernel commandline (CONFIG_CMDLINE) can be configured in
> > three different ways:
> >
> >   1. CMDLINE_FORCE: Use CONFIG_CMDLINE instead of any bootloader args
> >   2. CMDLINE_EXTEND: Append the bootloader args to CONFIG_CMDLINE
> >   3. CMDLINE_FROM_BOOTLOADER: Only use CONFIG_CMDLINE if there aren't
> >      any bootloader args.
> >
> > The early cmdline parsing to detect idreg overrides gets (2) and (3)
> > slightly wrong: in the case of (2) the bootloader args are parsed first
> > and in the case of (3) the CMDLINE is always parsed.
> >
> > Fix these issues by moving the bootargs parsing out into a helper
> > function and following the same logic as that used by the EFI stub.
> >
> > Reviewed-by: Marc Zyngier <maz@kernel.org>
> > Fixes: 33200303553d ("arm64: cpufeature: Add an early command-line cpufeature override facility")
> > Signed-off-by: Will Deacon <will@kernel.org>
> > ---
> >  arch/arm64/kernel/idreg-override.c | 44 +++++++++++++++++-------------
> >  1 file changed, 25 insertions(+), 19 deletions(-)
> 
> It bothers me a bit having command line handling here. It means how
> the command line is assembled in 2 places.

It's more than 2 places, it's also done in the EFI stub; see efi_pe_entry()
in drivers/firmware/efi/libstub/efi-stub.c. That's why I'm pushing on this,
because at the moment the command-line reported by /proc/cmdline doesn't
match the command-line that was parsed there because they stitch it together
in opposite orders when CMDLINE_EXTEND is used.

> I guess if we get rid of ambiguous 'extend' then it's better, but perhaps
> a better implementation would be an api get a specific command line
> parameter.  The main downside would be searching the DT again for each
> parameter if we can't store any data in between calls, but there's ways
> around that. PowerPC also needs similar functionality in
> disabled_on_cmdline().

Christophe's patches at least aim to put the assembling all in one place,
although we'll have to see whether or not it can be used in the EFI stub
environment.

Will

Re: [PATCH v2 1/2] arm64: cpufeatures: Fix handling of CONFIG_CMDLINE for idreg overrides

[Will Deacon]

On Wed, Mar 03, 2021 at 04:30:21PM -0600, Rob Herring wrote:
> On Wed, Mar 3, 2021 at 7:50 AM Will Deacon <will@kernel.org> wrote:
> >
> > The built-in kernel commandline (CONFIG_CMDLINE) can be configured in
> > three different ways:
> >
> >   1. CMDLINE_FORCE: Use CONFIG_CMDLINE instead of any bootloader args
> >   2. CMDLINE_EXTEND: Append the bootloader args to CONFIG_CMDLINE
> >   3. CMDLINE_FROM_BOOTLOADER: Only use CONFIG_CMDLINE if there aren't
> >      any bootloader args.
> >
> > The early cmdline parsing to detect idreg overrides gets (2) and (3)
> > slightly wrong: in the case of (2) the bootloader args are parsed first
> > and in the case of (3) the CMDLINE is always parsed.
> >
> > Fix these issues by moving the bootargs parsing out into a helper
> > function and following the same logic as that used by the EFI stub.
> >
> > Reviewed-by: Marc Zyngier <maz@kernel.org>
> > Fixes: 33200303553d ("arm64: cpufeature: Add an early command-line cpufeature override facility")
> > Signed-off-by: Will Deacon <will@kernel.org>
> > ---
> >  arch/arm64/kernel/idreg-override.c | 44 +++++++++++++++++-------------
> >  1 file changed, 25 insertions(+), 19 deletions(-)
> 
> It bothers me a bit having command line handling here. It means how
> the command line is assembled in 2 places.

It's more than 2 places, it's also done in the EFI stub; see efi_pe_entry()
in drivers/firmware/efi/libstub/efi-stub.c. That's why I'm pushing on this,
because at the moment the command-line reported by /proc/cmdline doesn't
match the command-line that was parsed there because they stitch it together
in opposite orders when CMDLINE_EXTEND is used.

> I guess if we get rid of ambiguous 'extend' then it's better, but perhaps
> a better implementation would be an api get a specific command line
> parameter.  The main downside would be searching the DT again for each
> parameter if we can't store any data in between calls, but there's ways
> around that. PowerPC also needs similar functionality in
> disabled_on_cmdline().

Christophe's patches at least aim to put the assembling all in one place,
although we'll have to see whether or not it can be used in the EFI stub
environment.

Will

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Re: [PATCH v2 0/2] Fix arm64 CONFIG_CMDLINE handling and remove CMDLINE_EXTEND

[Will Deacon]

On Wed, 3 Mar 2021 13:49:25 +0000, Will Deacon wrote:
> This is version two of the series I previously posted here:
> 
> 	https://lore.kernel.org/r/20210225125921.13147-1-will@kernel.org
> 
> The main change since v1 is that, rather than "fix" the FDT code to
> follow the documented behaviour for CMDLINE_EXTEND, I've opted to remove
> the thing entirely for arm64 while a less ambiguous and generic
> replacement is developed, probably based on either [1] or [2].
> 
> [...]

Applied to arm64 (for-next/fixes), thanks!

[1/2] arm64: cpufeatures: Fix handling of CONFIG_CMDLINE for idreg overrides
      https://git.kernel.org/arm64/c/df304c2d0dfd
[2/2] arm64: Drop support for CMDLINE_EXTEND
      https://git.kernel.org/arm64/c/cae118b6acc3

Cheers,
-- 
Will

https://fixes.arm64.dev
https://next.arm64.dev
https://will.arm64.dev

Re: [PATCH v2 0/2] Fix arm64 CONFIG_CMDLINE handling and remove CMDLINE_EXTEND

[Will Deacon]

On Wed, 3 Mar 2021 13:49:25 +0000, Will Deacon wrote:
> This is version two of the series I previously posted here:
> 
> 	https://lore.kernel.org/r/20210225125921.13147-1-will@kernel.org
> 
> The main change since v1 is that, rather than "fix" the FDT code to
> follow the documented behaviour for CMDLINE_EXTEND, I've opted to remove
> the thing entirely for arm64 while a less ambiguous and generic
> replacement is developed, probably based on either [1] or [2].
> 
> [...]

Applied to arm64 (for-next/fixes), thanks!

[1/2] arm64: cpufeatures: Fix handling of CONFIG_CMDLINE for idreg overrides
      https://git.kernel.org/arm64/c/df304c2d0dfd
[2/2] arm64: Drop support for CMDLINE_EXTEND
      https://git.kernel.org/arm64/c/cae118b6acc3

Cheers,
-- 
Will

https://fixes.arm64.dev
https://next.arm64.dev
https://will.arm64.dev

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