Wrong defaults in 3.7-rc3
Hi!
Supervisor Mode Access Prevention (X86_SMAP) [Y/n/?] (NEW)
...Slows stuff down, eats memory, only works on unreleased Intel CPUs (from 2013!) perhaps should be off by default?
"Supervisor Mode Access Prevention (SMAP) is a security feature in newer Intel processors. There is a small performance cost if this enabled and turned on; there is also a small increase in the kernel size if this is enabled."
Perhaps help text should mention what processors support it?
DiBcom DiB0070 silicon base-band tuner (DVB_TUNER_DIB0070) [M/n/y/?] (NEW) n
DiBcom DiB0090 silicon base-band tuner (DVB_TUNER_DIB0090) [M/n/y/?] (NEW) n
M is never good config default.
Pavel
Signature · 2 lines
(english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
Em Thu, 15 Nov 2012 12:06:20 +0100
Pavel Machek <[email protected]> escreveu:
Quoted 6 lines
DiBcom DiB0070 silicon base-band tuner (
DVB_TUNER_DIB0070) [M/n/y/?] (NEW) n
DiBcom DiB0090 silicon base-band tuner (DVB_TUNER_DIB0090) [M/n/y/?] (NEW) nM is never good config default.
Had you ever seen the Kconfig logic for tuners? They're not enabled by default.
config MEDIA_SUBDRV_AUTOSELECT
bool "Autoselect tuners and i2c modules to build"
depends on MEDIA_ANALOG_TV_SUPPORT || MEDIA_DIGITAL_TV_SUPPORT || MEDIA_CAMERA_SUPPORT default y
help
By default, a media driver auto-selects all possible i2c
devices that are used by any of the supported devices.
This is generally the right thing to do, except when there are strict constraints with regards to the kernel size, like on embedded systems.
Use this option with care, as deselecting ancillary drivers which are, in fact, necessary will result in the lack of the needed functionality for your device (it may not tune or may not have the need demodulers).
If unsure say Y.
...
menu "Customise DVB Frontends"
visible if !MEDIA_SUBDRV_AUTOSELECT
comment "Multistandard (satellite) frontends"
depends on DVB_CORE
...
config DVB_TUNER_DIB0070
tristate "DiBcom DiB0070 silicon base-band tuner" depends on I2C
default m if !MEDIA_SUBDRV_AUTOSELECT
help
A driver for the silicon baseband tuner DiB0070 from DiBcom. This device is only used inside a SiP called together with a demodulator for now.
People should never disable MEDIA_SUBDRV_AUTOSELECT, except if they know exactly what they're doing and they have very strict diskspace constraints, as the DVB driver may stop working without support for the needed ancillary chips present at the DVB card.
The default "M" is there to prevent people to open NOT_A_BUG bugzillas when they do stupid things like disabling MEDIA_SUBDRV_AUTOSELECT without knowing that this can break the driver for their cards.
Signature · 2 lines
Regards, Mauro
Quoted 4 lines · Pavel Machek
Hi!
Supervisor Mode Access Prevention (
X86_SMAP) [Y/n/?] (NEW)
Quoted 8 lines
...Slows stuff down, eats memory, only works on unreleased Intel CPUs (from 2013!) perhaps should be off by default?
"Supervisor Mode Access Prevention (SMAP) is a security feature in newer Intel processors. There is a small performance cost if this enabled and turned on; there is also a small increase in the kernel size if this is enabled."
*Extremely* small. Unless you are targeting a specific processor there is no point in disabling it. If anyone can find a non-SMAP processor on which the overhead is measurable I would be highly surprised, except perhaps some embedded 486 clone.
-hpa