linux_dsm_epyc7002/arch
Sricharan R f52bb72254 ARM: mm: Correct virt_to_phys patching for 64 bit physical addresses
The current phys_to_virt patching mechanism works only for 32 bit
physical addresses and this patch extends the idea for 64bit physical
addresses.

The 64bit v2p patching mechanism patches the higher 8 bits of physical
address with a constant using 'mov' instruction and lower 32bits are patched
using 'add'. While this is correct, in those platforms where the lowmem addressable
physical memory spawns across 4GB boundary, a carry bit can be produced as a
result of addition of lower 32bits. This has to be taken in to account and added
in to the upper. The patched __pv_offset and va are added in lower 32bits, where
__pv_offset can be in two's complement form when PA_START < VA_START and that can
result in a false carry bit.

e.g
    1) PA = 0x80000000; VA = 0xC0000000
       __pv_offset = PA - VA = 0xC0000000 (2's complement)

    2) PA = 0x2 80000000; VA = 0xC000000
       __pv_offset = PA - VA = 0x1 C0000000

So adding __pv_offset + VA should never result in a true overflow for (1).
So in order to differentiate between a true carry, a __pv_offset is extended
to 64bit and the upper 32bits will have 0xffffffff if __pv_offset is
2's complement. So 'mvn #0' is inserted instead of 'mov' while patching
for the same reason. Since mov, add, sub instruction are to patched
with different constants inside the same stub, the rotation field
of the opcode is using to differentiate between them.

So the above examples for v2p translation becomes for VA=0xC0000000,
    1) PA[63:32] = 0xffffffff
       PA[31:0] = VA + 0xC0000000 --> results in a carry
       PA[63:32] = PA[63:32] + carry

       PA[63:0] = 0x0 80000000

    2) PA[63:32] = 0x1
       PA[31:0] = VA + 0xC0000000 --> results in a carry
       PA[63:32] = PA[63:32] + carry

       PA[63:0] = 0x2 80000000

The above ideas were suggested by Nicolas Pitre <nico@linaro.org> as
part of the review of first and second versions of the subject patch.

There is no corresponding change on the phys_to_virt() side, because
computations on the upper 32-bits would be discarded anyway.

Cc: Russell King <linux@arm.linux.org.uk>

Reviewed-by: Nicolas Pitre <nico@linaro.org>
Signed-off-by: Sricharan R <r.sricharan@ti.com>
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>
2013-10-10 20:25:06 -04:00
..
alpha Remove GENERIC_HARDIRQ config option 2013-09-13 15:09:52 +02:00
arc Remove GENERIC_HARDIRQ config option 2013-09-13 15:09:52 +02:00
arm ARM: mm: Correct virt_to_phys patching for 64 bit physical addresses 2013-10-10 20:25:06 -04:00
arm64 arm64: Widen hwcap to be 64 bit 2013-09-20 09:56:07 +01:00
avr32 Remove GENERIC_HARDIRQ config option 2013-09-13 15:09:52 +02:00
blackfin Merge branch 'genirq' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux 2013-09-13 07:31:38 -07:00
c6x Remove GENERIC_HARDIRQ config option 2013-09-13 15:09:52 +02:00
cris Remove GENERIC_HARDIRQ config option 2013-09-13 15:09:52 +02:00
frv Remove GENERIC_HARDIRQ config option 2013-09-13 15:09:52 +02:00
h8300 Remove GENERIC_HARDIRQ config option 2013-09-13 15:09:52 +02:00
hexagon Remove GENERIC_HARDIRQ config option 2013-09-13 15:09:52 +02:00
ia64 Remove GENERIC_HARDIRQ config option 2013-09-13 15:09:52 +02:00
m32r Remove GENERIC_HARDIRQ config option 2013-09-13 15:09:52 +02:00
m68k Remove GENERIC_HARDIRQ config option 2013-09-13 15:09:52 +02:00
metag Remove GENERIC_HARDIRQ config option 2013-09-13 15:09:52 +02:00
microblaze Remove GENERIC_HARDIRQ config option 2013-09-13 15:09:52 +02:00
mips MIPS: Fix invalid symbolic link file 2013-09-19 17:04:35 +02:00
mn10300 Remove GENERIC_HARDIRQ config option 2013-09-13 15:09:52 +02:00
openrisc Remove GENERIC_HARDIRQ config option 2013-09-13 15:09:52 +02:00
parisc Remove GENERIC_HARDIRQ config option 2013-09-13 15:09:52 +02:00
powerpc Remove GENERIC_HARDIRQ config option 2013-09-13 15:09:52 +02:00
s390 Remove GENERIC_HARDIRQ config option 2013-09-13 15:09:52 +02:00
score Remove GENERIC_HARDIRQ config option 2013-09-13 15:09:52 +02:00
sh Remove GENERIC_HARDIRQ config option 2013-09-13 15:09:52 +02:00
sparc Remove GENERIC_HARDIRQ config option 2013-09-13 15:09:52 +02:00
tile tile: remove stray blank space 2013-09-16 15:47:32 -04:00
um Remove GENERIC_HARDIRQ config option 2013-09-13 15:09:52 +02:00
unicore32 Remove GENERIC_HARDIRQ config option 2013-09-13 15:09:52 +02:00
x86 Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2013-09-18 11:26:17 -05:00
xtensa Xtensa patchset for v3.12 2013-09-13 10:57:48 -07:00
.gitignore
Kconfig microblaze: fix clone syscall 2013-08-13 17:57:48 -07:00