[gentoo-user] re: NX (Execute Disable) protection cannot be enabled: non-PAE kernel! [dmesg]

[gentoo-user] re: NX (Execute Disable) protection cannot be enabled: non-PAE kernel! [dmesg]

[Alexander Kapshuk]

Is the message below I should do something about?

box0=; dmesg|grep -i PAE
[    0.000000] Notice: NX (Execute Disable) protection cannot be
enabled: non-PAE kernel!


My CPU seems to have support for it.
box0=; grep pae /proc/cpuinfo
flags        : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca
cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx lm
constant_tsc arch_perfmon pebs bts aperfmperf pni dtes64 monitor ds_cpl
est tm2 ssse3 cx16 xtpr pdcm lahf_lm dtherm
flags        : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca
cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx lm
constant_tsc arch_perfmon pebs bts aperfmperf pni dtes64 monitor ds_cpl
est tm2 ssse3 cx16 xtpr pdcm lahf_lm dtherm

But not my kernel, as far as I can tell.
box0=; uname -a
Linux box0 3.10.7-gentoo-r1 #1 SMP Sat Oct 5 23:57:58 EEST 2013 i686
Intel(R) Pentium(R) Dual CPU T3400 @ 2.16GHz GenuineIntel GNU/Linux

box0=; grep -i pae .config
box0=; echo $?
1

Thanks.

Re: [gentoo-user] re: NX (Execute Disable) protection cannot be enabled: non-PAE kernel! [dmesg]

[Alan McKinnon]

On 07/10/2013 21:28, Alexander Kapshuk wrote:
> Is the message below I should do something about?
> 
> box0=; dmesg|grep -i PAE
> [    0.000000] Notice: NX (Execute Disable) protection cannot be
> enabled: non-PAE kernel!
> 
> 
> My CPU seems to have support for it.
> box0=; grep pae /proc/cpuinfo
> flags        : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca
> cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx lm
> constant_tsc arch_perfmon pebs bts aperfmperf pni dtes64 monitor ds_cpl
> est tm2 ssse3 cx16 xtpr pdcm lahf_lm dtherm
> flags        : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca
> cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx lm
> constant_tsc arch_perfmon pebs bts aperfmperf pni dtes64 monitor ds_cpl
> est tm2 ssse3 cx16 xtpr pdcm lahf_lm dtherm
> 
> But not my kernel, as far as I can tell.
> box0=; uname -a
> Linux box0 3.10.7-gentoo-r1 #1 SMP Sat Oct 5 23:57:58 EEST 2013 i686
> Intel(R) Pentium(R) Dual CPU T3400 @ 2.16GHz GenuineIntel GNU/Linux
> 
> box0=; grep -i pae .config
> box0=; echo $?
> 1
> 
> Thanks.
> 
> 


Symbol: ARM_LPAE [=ARM_LPAE]
Type  : unknown

Symbol: X86_PAE [=n]
Type  : boolean
Prompt: PAE (Physical Address Extension) Support
  Location:
(1) -> Processor type and features
  Defined at arch/x86/Kconfig:1213
  Depends on: X86_32 [=n] && !HIGHMEM4G [=n]
  Selected by: HIGHMEM64G [=n] && <choice> && !M486 [=n]


-- 
Alan McKinnon
alan.mckinnon@gmail.com

Re: [gentoo-user] re: NX (Execute Disable) protection cannot be enabled: non-PAE kernel! [dmesg]

[Alexander Kapshuk]

On 10/07/2013 10:42 PM, Alan McKinnon wrote:
> On 07/10/2013 21:28, Alexander Kapshuk wrote:
>> Is the message below I should do something about?
>>
>> box0=; dmesg|grep -i PAE
>> [    0.000000] Notice: NX (Execute Disable) protection cannot be
>> enabled: non-PAE kernel!
>>
>>
>> My CPU seems to have support for it.
>> box0=; grep pae /proc/cpuinfo
>> flags        : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca
>> cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx lm
>> constant_tsc arch_perfmon pebs bts aperfmperf pni dtes64 monitor ds_cpl
>> est tm2 ssse3 cx16 xtpr pdcm lahf_lm dtherm
>> flags        : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca
>> cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx lm
>> constant_tsc arch_perfmon pebs bts aperfmperf pni dtes64 monitor ds_cpl
>> est tm2 ssse3 cx16 xtpr pdcm lahf_lm dtherm
>>
>> But not my kernel, as far as I can tell.
>> box0=; uname -a
>> Linux box0 3.10.7-gentoo-r1 #1 SMP Sat Oct 5 23:57:58 EEST 2013 i686
>> Intel(R) Pentium(R) Dual CPU T3400 @ 2.16GHz GenuineIntel GNU/Linux
>>
>> box0=; grep -i pae .config
>> box0=; echo $?
>> 1
>>
>> Thanks.
>>
>>
>
> Symbol: ARM_LPAE [=ARM_LPAE]
> Type  : unknown
>
> Symbol: X86_PAE [=n]
> Type  : boolean
> Prompt: PAE (Physical Address Extension) Support
>   Location:
> (1) -> Processor type and features
>   Defined at arch/x86/Kconfig:1213
>   Depends on: X86_32 [=n] && !HIGHMEM4G [=n]
>   Selected by: HIGHMEM64G [=n] && <choice> && !M486 [=n]
>
>
Thanks. I did a little research into the whole PAE business, as
obviously my knowledge of the matter in question was limited.

If I understood it correctly, PAE is a method that allows 32-bit kernels
access 4 or more Gb of RAM, which is normally the domain of 64-bit kernels.

Seeing I've got 3 Gb of RAM, I arrived at the conclusion I don't need
PAE enabled, do I?

box0=; sed 1q /proc/meminfo
MemTotal:        3107668 kB

Thanks.

Re: [gentoo-user] re: NX (Execute Disable) protection cannot be enabled: non-PAE kernel! [dmesg]

[Alan McKinnon]

On 08/10/2013 19:04, Alexander Kapshuk wrote:
> On 10/07/2013 10:42 PM, Alan McKinnon wrote:
>> On 07/10/2013 21:28, Alexander Kapshuk wrote:
>>> Is the message below I should do something about?
>>>
>>> box0=; dmesg|grep -i PAE
>>> [    0.000000] Notice: NX (Execute Disable) protection cannot be
>>> enabled: non-PAE kernel!
>>>
>>>
>>> My CPU seems to have support for it.
>>> box0=; grep pae /proc/cpuinfo
>>> flags        : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca
>>> cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx lm
>>> constant_tsc arch_perfmon pebs bts aperfmperf pni dtes64 monitor ds_cpl
>>> est tm2 ssse3 cx16 xtpr pdcm lahf_lm dtherm
>>> flags        : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca
>>> cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx lm
>>> constant_tsc arch_perfmon pebs bts aperfmperf pni dtes64 monitor ds_cpl
>>> est tm2 ssse3 cx16 xtpr pdcm lahf_lm dtherm
>>>
>>> But not my kernel, as far as I can tell.
>>> box0=; uname -a
>>> Linux box0 3.10.7-gentoo-r1 #1 SMP Sat Oct 5 23:57:58 EEST 2013 i686
>>> Intel(R) Pentium(R) Dual CPU T3400 @ 2.16GHz GenuineIntel GNU/Linux
>>>
>>> box0=; grep -i pae .config
>>> box0=; echo $?
>>> 1
>>>
>>> Thanks.
>>>
>>>
>>
>> Symbol: ARM_LPAE [=ARM_LPAE]
>> Type  : unknown
>>
>> Symbol: X86_PAE [=n]
>> Type  : boolean
>> Prompt: PAE (Physical Address Extension) Support
>>   Location:
>> (1) -> Processor type and features
>>   Defined at arch/x86/Kconfig:1213
>>   Depends on: X86_32 [=n] && !HIGHMEM4G [=n]
>>   Selected by: HIGHMEM64G [=n] && <choice> && !M486 [=n]
>>
>>
> Thanks. I did a little research into the whole PAE business, as
> obviously my knowledge of the matter in question was limited.
> 
> If I understood it correctly, PAE is a method that allows 32-bit kernels
> access 4 or more Gb of RAM, which is normally the domain of 64-bit kernels.
> 
> Seeing I've got 3 Gb of RAM, I arrived at the conclusion I don't need
> PAE enabled, do I?
> 
> box0=; sed 1q /proc/meminfo
> MemTotal:        3107668 kB


That is correct, with 3G physica RAM, you will not benefit from using
PAE at all. I don't think it interferes with anything if you do have it,
I recall a time when RedHat shipped 32 bit kernels that were PAE-enabled.

Briefly, the way it works is that the kernel assigns blocks of memory to
different processes. So a single process can still only access 4G of
memory, but two different process don't anymore have to address the same
4G of memory like you must do without PAE. But you still don't get to
give your 32 bit database more than 4g of RAM




-- 
Alan McKinnon
alan.mckinnon@gmail.com

Re: [gentoo-user] re: NX (Execute Disable) protection cannot be enabled: non-PAE kernel! [dmesg]

[gottlieb]

On Tue, Oct 08 2013, Alan McKinnon wrote:

> That is correct, with 3G physica RAM, you will not benefit from using
> PAE at all. I don't think it interferes with anything if you do have it,
> I recall a time when RedHat shipped 32 bit kernels that were PAE-enabled.
>
> Briefly, the way it works is that the kernel assigns blocks of memory to
> different processes. So a single process can still only access 4G of
> memory, but two different process don't anymore have to address the same
> 4G of memory like you must do without PAE. But you still don't get to
> give your 32 bit database more than 4g of RAM

Agreed.  Virtual addresses refer to those in the program (really
process).  Physical addresses address refer to those in the hardware
(i.e. addresses in the RAM itself).  To have a single process able to
access extra memory would be to increase the *virtual* address range.
PAE (*physical* address extension) enables more RAM to be accessed (by
the hardware not by a single process), but does not increase the virtual
address range.

When pdp-11s added I and D space, that increased the virtual address
range by a factor of two.  The I/D bit (instruction/data) was
essentially an extra bit of virtual address.

allan

Re: [gentoo-user] re: NX (Execute Disable) protection cannot be enabled: non-PAE kernel! [dmesg]

[Alexander Kapshuk]

On 10/09/2013 05:17 AM, gottlieb@nyu.edu wrote:
> On Tue, Oct 08 2013, Alan McKinnon wrote:
>
>> That is correct, with 3G physica RAM, you will not benefit from using
>> PAE at all. I don't think it interferes with anything if you do have it,
>> I recall a time when RedHat shipped 32 bit kernels that were PAE-enabled.
>>
>> Briefly, the way it works is that the kernel assigns blocks of memory to
>> different processes. So a single process can still only access 4G of
>> memory, but two different process don't anymore have to address the same
>> 4G of memory like you must do without PAE. But you still don't get to
>> give your 32 bit database more than 4g of RAM
> Agreed.  Virtual addresses refer to those in the program (really
> process).  Physical addresses address refer to those in the hardware
> (i.e. addresses in the RAM itself).  To have a single process able to
> access extra memory would be to increase the *virtual* address range.
> PAE (*physical* address extension) enables more RAM to be accessed (by
> the hardware not by a single process), but does not increase the virtual
> address range.
>
> When pdp-11s added I and D space, that increased the virtual address
> range by a factor of two.  The I/D bit (instruction/data) was
> essentially an extra bit of virtual address.
>
> allan
>
Thanks a lot for the explanation. Much appreciated.

Re: [gentoo-user] re: NX (Execute Disable) protection cannot be enabled: non-PAE kernel! [dmesg]

[gottlieb]

On Wed, Oct 09 2013, Alexander Kapshuk wrote:

> On 10/09/2013 05:17 AM, gottlieb@nyu.edu wrote:
>> On Tue, Oct 08 2013, Alan McKinnon wrote:
>>
>>> That is correct, with 3G physica RAM, you will not benefit from using
>>> PAE at all. I don't think it interferes with anything if you do have it,
>>> I recall a time when RedHat shipped 32 bit kernels that were PAE-enabled.
>>>
>>> Briefly, the way it works is that the kernel assigns blocks of memory to
>>> different processes. So a single process can still only access 4G of
>>> memory, but two different process don't anymore have to address the same
>>> 4G of memory like you must do without PAE. But you still don't get to
>>> give your 32 bit database more than 4g of RAM
>> Agreed.  Virtual addresses refer to those in the program (really
>> process).  Physical addresses address refer to those in the hardware
>> (i.e. addresses in the RAM itself).  To have a single process able to
>> access extra memory would be to increase the *virtual* address range.
>> PAE (*physical* address extension) enables more RAM to be accessed (by
>> the hardware not by a single process), but does not increase the virtual
>> address range.
>>
>> When pdp-11s added I and D space, that increased the virtual address
>> range by a factor of two.  The I/D bit (instruction/data) was
>> essentially an extra bit of virtual address.
>>
>> allan
>>
> Thanks a lot for the explanation. Much appreciated.

You are quite welcome.
allan