svn commit: r307626 - head/sys/ufs/ffs

[Konstantin Belousov]

On Sun, Nov 13, 2016 at 12:12:02AM -0700, Warner Losh wrote:
> On Sat, Nov 12, 2016 at 11:58 PM, Konstantin Belousov
> <kostikbel at gmail.com> wrote:
> > On Sat, Nov 12, 2016 at 03:19:13PM -0800, Adrian Chadd wrote:
> >> hi!
> >>
> >> This broke freebsd on mips24k.
> >>
> >> BAD_PAGE_FAULT: pid 1 tid 100001 (init), uid 0: pc 0x4002a4 got a read
> >> fault (type 0x2) at 0
> >> Trapframe Register Dump:
> >>     zero: 0    at: 0    v0: 0    v1: 0
> >>     a0: 0x7fffeecc    a1: 0    a2: 0    a3: 0
> >>     t0: 0    t1: 0    t2: 0    t3: 0
> >>     t4: 0    t5: 0    t6: 0    t7: 0
> >>     t8: 0    t9: 0x400260    s0: 0x10    s1: 0x2
> >>     s2: 0x7fffeed0    s3: 0    s4: 0    s5: 0
> >>     s6: 0    s7: 0    k0: 0    k1: 0
> >>     gp: 0x4d55d0    sp: 0x7ffeee90    s8: 0    ra: 0
> >>     sr: 0xfc13    mullo: 0    mulhi: 0    badvaddr: 0
> >>     cause: 0x8    pc: 0x4002a4
> >> Page table info for pc address 0x4002a4: pde = 0x809be000, pte = 0xa001acda
> >> Dumping 4 words starting at pc address 0x4002a4:
> >> 8c420000 14400003 00908021 8f828024
> >> Page table info for bad address 0: pde = 0, pte = 0
> > MIPS24k has split I/D caches, and both are VIPT, am I right ?
> > I was not able to find the handling of cache aliasing in mips/pmap.c.
> >
> > Still, I am curious whether setting the loader tunable vfs.buf_pager_relbuf
> > to 1 change anything.
> 
> MIPS caches are such that creating two virtual mappings to the same
> physical page will cause corruption. It's simply not allowed, at least
> for the class of MIPS machines I used to bring up the port originally.

Yes, caches are VIPT on 24k, according to the "MIPS32(R) 24K(R)
Processor Core Family Software User's Manual " rev 3.11.  My question is,
how is that handled in the mips pmap.c.  I was not able to locate
the alias detection and prevention code, or e.g. switching to uncached mode
for the page when aliasing is detected, after browsing pmap.

Does FreeBSD/mips run with the caches enabled ?