[Arm-dev] [PATCH v2] config-centos-sig: aarch64: Enable 48 bit VA

[Jeremy Linton]

On 11/18/2016 04:29 PM, Jeremy Linton wrote:
> The current RHELSA kernel is using a 42bit VA which
> is too limiting for possible near future workloads.
> Update this to 48 bits. This patch has a dependency
> on mozjs versions in the distro being patched to
> work with virtual address spaces >47 bits.

Just a quick comment. An easy way to verify that the kernel in use has 
48bit VA's is to check the /proc/xxx/maps of a userspace process.

A 48bit VA kernel will place shared libraries into addresses at the top 
of the userspace address region. For example:

ffffacbb0000-ffffacbc0000 r-xp 00000000 103:04 33858952 
/usr/lib64/libnss_files-2.17.so
ffffacbc0000-ffffacbd0000 r--p 00000000 103:04 33858952 
/usr/lib64/libnss_files-2.17.so
ffffacbd0000-ffffacbe0000 rw-p 00010000 103:04 33858952 
/usr/lib64/libnss_files-2.17.so
ffffacbf0000-ffffacc30000 r-xp 00000000 103:04 33644605 
/usr/lib64/libpcre.so.1.2.0
ffffacc30000-ffffacc40000 r--p 00030000 103:04 33644605 
/usr/lib64/libpcre.so.1.2.0
ffffacc40000-ffffacc50000 rw-p 00040000 103:04 33644605 
/usr/lib64/libpcre.so.1.2.0

>
> Signed-off-by: Jeremy Linton <jeremy.linton at arm.com>
> ---
>  SOURCES/config-centos-sig | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/SOURCES/config-centos-sig b/SOURCES/config-centos-sig
> index 15f60f4..33486a9 100644
> --- a/SOURCES/config-centos-sig
> +++ b/SOURCES/config-centos-sig
> @@ -9,4 +9,6 @@ CONFIG_XGENE_PMU=y
>  CONFIG_I2C_DESIGNWARE_CORE=m
>  CONFIG_I2C_DESIGNWARE_PLATFORM=m
>  CONFIG_I2C_DESIGNWARE_PCI=m
> +CONFIG_ARM64_VA_BITS_48=y
> +CONFIG_ARM64_VA_BITS=48
>
>