Re: [RFC PATCH] powerpc/64/ftrace: mprofile-kernel patch out mflr

2019-05-17 Thread Naveen N. Rao
Nicholas Piggin wrote: Naveen N. Rao's on May 17, 2019 4:22 am: While enabling ftrace, we will first need to patch the preceding 'mflr r0' (which would now be a 'nop') with 'b +8', then use synchronize_rcu_tasks() and finally patch in 'bl _mcount()' followed by 'mflr r0'. I think that's wha

Re: [RFC PATCH] powerpc/64/ftrace: mprofile-kernel patch out mflr

2019-05-17 Thread Nicholas Piggin
Naveen N. Rao's on May 17, 2019 4:22 am: > Nicholas Piggin wrote: >> Naveen N. Rao's on May 14, 2019 6:32 pm: >>> Michael Ellerman wrote: "Naveen N. Rao" writes: > Michael Ellerman wrote: >> Nicholas Piggin writes: >>> The new mprofile-kernel mcount sequence is >>> >>>

Re: [RFC PATCH] powerpc/64/ftrace: mprofile-kernel patch out mflr

2019-05-16 Thread Naveen N. Rao
Nicholas Piggin wrote: Naveen N. Rao's on May 14, 2019 6:32 pm: Michael Ellerman wrote: "Naveen N. Rao" writes: Michael Ellerman wrote: Nicholas Piggin writes: The new mprofile-kernel mcount sequence is mflr r0 bl_mcount Dynamic ftrace patches the branch instruction with a noop,

Re: [RFC PATCH] powerpc/64/ftrace: mprofile-kernel patch out mflr

2019-05-15 Thread Nicholas Piggin
Naveen N. Rao's on May 14, 2019 6:32 pm: > Michael Ellerman wrote: >> "Naveen N. Rao" writes: >>> Michael Ellerman wrote: Nicholas Piggin writes: > The new mprofile-kernel mcount sequence is > > mflrr0 > bl _mcount > > Dynamic ftrace patches the branch in

Re: [RFC PATCH] powerpc/64/ftrace: mprofile-kernel patch out mflr

2019-05-15 Thread Michael Ellerman
"Naveen N. Rao" writes: > Michael Ellerman wrote: >> "Naveen N. Rao" writes: >>> Michael Ellerman wrote: Nicholas Piggin writes: > The new mprofile-kernel mcount sequence is > > mflrr0 > bl _mcount > > Dynamic ftrace patches the branch instruction with a

Re: [RFC PATCH] powerpc/64/ftrace: mprofile-kernel patch out mflr

2019-05-14 Thread Naveen N. Rao
Michael Ellerman wrote: "Naveen N. Rao" writes: Michael Ellerman wrote: Nicholas Piggin writes: The new mprofile-kernel mcount sequence is mflr r0 bl_mcount Dynamic ftrace patches the branch instruction with a noop, but leaves the mflr. mflr is executed by the branch unit that can

Re: [RFC PATCH] powerpc/64/ftrace: mprofile-kernel patch out mflr

2019-05-13 Thread Michael Ellerman
"Naveen N. Rao" writes: > Michael Ellerman wrote: >> Nicholas Piggin writes: >>> The new mprofile-kernel mcount sequence is >>> >>> mflr r0 >>> bl_mcount >>> >>> Dynamic ftrace patches the branch instruction with a noop, but leaves >>> the mflr. mflr is executed by the branch uni

Re: [RFC PATCH] powerpc/64/ftrace: mprofile-kernel patch out mflr

2019-05-12 Thread Naveen N. Rao
Michael Ellerman wrote: Nicholas Piggin writes: The new mprofile-kernel mcount sequence is mflr r0 bl_mcount Dynamic ftrace patches the branch instruction with a noop, but leaves the mflr. mflr is executed by the branch unit that can only execute one per cycle on POWER9 and shared wi

Re: [RFC PATCH] powerpc/64/ftrace: mprofile-kernel patch out mflr

2019-05-12 Thread Michael Ellerman
Nicholas Piggin writes: > The new mprofile-kernel mcount sequence is > > mflrr0 > bl _mcount > > Dynamic ftrace patches the branch instruction with a noop, but leaves > the mflr. mflr is executed by the branch unit that can only execute one > per cycle on POWER9 and shared with branch

Re: [RFC PATCH] powerpc/64/ftrace: mprofile-kernel patch out mflr

2019-04-15 Thread Naveen N. Rao
Hi Nick, Nicholas Piggin wrote: The new mprofile-kernel mcount sequence is mflr r0 bl_mcount Dynamic ftrace patches the branch instruction with a noop, but leaves the mflr. mflr is executed by the branch unit that can only execute one per cycle on POWER9 and shared with branches, so i