Subject: Re: [PATCH v2 05/18] powerpc/85xx: Load all early TLB entries at once

From: Scott Wood <[email-masked]>
Date: Wed, 7 Oct 2015 14:57:48 -0500

On Wed, 2015-10-07 at 17:00 +0300, Laurentiu Tudor wrote:
> On 10/07/2015 06:48 AM, Scott Wood wrote:
> > Use an AS=1 trampoline TLB entry to allow all normal TLB1 entries to
> > be loaded at once.  This avoids the need to keep the translation that
> > code is executing from in the same TLB entry in the final TLB
> > configuration as during early boot, which in turn is helpful for
> > relocatable kernels (e.g. kdump) where the kernel is not running from
> > what would be the first TLB entry.
> > 
> > On e6500, we limit map_mem_in_cams() to the primary hwthread of a
> > core (the boot cpu is always considered primary, as a kdump kernel
> > can be entered on any cpu).  Each TLB only needs to be set up once,
> > and when we do, we don't want another thread to be running when we
> > create a temporary trampoline TLB1 entry.
> > 
> > Signed-off-by: Scott Wood <[email-masked]>
> > ---
> >  arch/powerpc/kernel/setup_64.c   |  8 +++++
> >  arch/powerpc/mm/fsl_booke_mmu.c  | 15 ++++++++--
> >  arch/powerpc/mm/mmu_decl.h       |  1 +
> >  arch/powerpc/mm/tlb_nohash.c     | 19 +++++++++++-
> >  arch/powerpc/mm/tlb_nohash_low.S | 63 
> > ++++++++++++++++++++++++++++++++++++++++
> >  5 files changed, 102 insertions(+), 4 deletions(-)
> > 
> > diff --git a/arch/powerpc/kernel/setup_64.c 
> > b/arch/powerpc/kernel/setup_64.c
> > index bdcbb71..505ec2c 100644
> > --- a/arch/powerpc/kernel/setup_64.c
> > +++ b/arch/powerpc/kernel/setup_64.c
> > @@ -108,6 +108,14 @@ static void setup_tlb_core_data(void)
> >     for_each_possible_cpu(cpu) {
> >             int first = cpu_first_thread_sibling(cpu);
> >  
> > +           /*
> > +            * If we boot via kdump on a non-primary thread,
> > +            * make sure we point at the thread that actually
> > +            * set up this TLB.
> > +            */
> > +           if (cpu_first_thread_sibling(boot_cpuid) == first)
> > +                   first = boot_cpuid;
> > +
> >             paca[cpu].tcd_ptr = &paca[first].tcd;
> >  
> >             /*
> > diff --git a/arch/powerpc/mm/fsl_booke_mmu.c 
> > b/arch/powerpc/mm/fsl_booke_mmu.c
> > index 354ba3c..36d3c55 100644
> > --- a/arch/powerpc/mm/fsl_booke_mmu.c
> > +++ b/arch/powerpc/mm/fsl_booke_mmu.c
> > @@ -105,8 +105,9 @@ unsigned long p_mapped_by_tlbcam(phys_addr_t pa)
> >   * an unsigned long (for example, 32-bit implementations cannot support a
> > 4GB
> >   * size).
> >   */
> > -static void settlbcam(int index, unsigned long virt, phys_addr_t phys,
> > -           unsigned long size, unsigned long flags, unsigned int pid)
> > +static void preptlbcam(int index, unsigned long virt, phys_addr_t phys,
> > +                  unsigned long size, unsigned long flags,
> > +                  unsigned int pid)
> >  {
> >     unsigned int tsize;
> >  
> > @@ -141,7 +142,13 @@ static void settlbcam(int index, unsigned long virt, 
> > phys_addr_t phys,
> >     tlbcam_addrs[index].start = virt;
> >     tlbcam_addrs[index].limit = virt + size - 1;
> >     tlbcam_addrs[index].phys = phys;
> > +}
> >  
> > +void settlbcam(int index, unsigned long virt, phys_addr_t phys,
> 
> 
> Nit: shouldn't this be left static? Also, now with this bulk TLB1 loading 
> is it still used? Maybe it can be dropped.

You're right, it's an unneeded leftover.  We might as well 
s/preptlbcam/settlbcam/ as well to reduce churn.

-Scott