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

[Adrian Chadd]

On 12 November 2016 at 23:12, Warner Losh <imp at bsdimp.com> 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.

Hi,

Right - the bulk of MIPS hardware (including 24k/74k) are VIPT, and
we're not allowed to do cache aliasing in that manner.



-adrian