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[Qemu-devel] Re: [PATCH 1/2] Pad iommu with an empty slot (necessary for
From: |
Blue Swirl |
Subject: |
[Qemu-devel] Re: [PATCH 1/2] Pad iommu with an empty slot (necessary for SunOS 4.1.4) |
Date: |
Tue, 11 May 2010 00:05:37 +0300 |
On 5/10/10, Artyom Tarasenko <address@hidden> wrote:
> 2010/5/10 Blue Swirl <address@hidden>:
>
> > On 5/10/10, Artyom Tarasenko <address@hidden> wrote:
> >> 2010/5/9 Blue Swirl <address@hidden>:
> >> > On 5/9/10, Artyom Tarasenko <address@hidden> wrote:
> >> >> 2010/5/9 Blue Swirl <address@hidden>:
> >> >>
> >> >> > On 5/8/10, Artyom Tarasenko <address@hidden> wrote:
> >> >> >> On the real hardware (SS-5, LX) the MMU is not padded, but
> aliased.
> >> >> >> Software shouldn't use aliased addresses, neither should it crash
> >> >> >> when it uses (on the real hardware it wouldn't). Using empty_slot
> >> >> >> instead of aliasing can help with debugging such accesses.
> >> >> >
> >> >> > TurboSPARC Microprocessor User's Manual shows that there are
> >> >> > additional pages after the main IOMMU for AFX registers. So this is
> >> >> > not board specific, but depends on CPU/IOMMU versions.
> >> >>
> >> >>
> >> >> I checked it on the real hw: on LX and SS-5 these are aliased MMU
> addresses.
> >> >> SS-20 doesn't have any aliasing.
> >> >
> >> > But are your machines equipped with TurboSPARC or some other CPU?
> >>
> >>
> >> Good point, I must confess, I missed the word "Turbo" in your first
> >> answer. LX and SS-20 don't.
> >> But SS-5 must have a TurboSPARC CPU:
> >>
> >> ok cd /FMI,MB86904
> >> ok .attributes
> >> context-table 00 00 00 00 03 ff f0 00 00 00 10 00
> >> psr-implementation 00000000
> >> psr-version 00000004
> >> implementation 00000000
> >> version 00000004
> >> cache-line-size 00000020
> >> cache-nlines 00000200
> >> page-size 00001000
> >> dcache-line-size 00000010
> >> dcache-nlines 00000200
> >> dcache-associativity 00000001
> >> icache-line-size 00000020
> >> icache-nlines 00000200
> >> icache-associativity 00000001
> >> ncaches 00000002
> >> mmu-nctx 00000100
> >> sparc-version 00000008
> >> mask_rev 00000026
> >> device_type cpu
> >> name FMI,MB86904
> >>
> >> and still it behaves the same as TI,TMS390S10 from the LX. This is done
> on SS-5:
> >>
> >> ok 10000000 20 spacel@ .
> >> 4000009
> >> ok 14000000 20 spacel@ .
> >> 4000009
> >> ok 14000004 20 spacel@ .
> >> 23000
> >> ok 1f000004 20 spacel@ .
> >> 23000
> >> ok 10000008 20 spacel@ .
> >> 4000009
> >> ok 14000028 20 spacel@ .
> >> 4000009
> >> ok 1000000c 20 spacel@ .
> >> 23000
> >> ok 10000010 20 spacel@ .
> >> 4000009
> >>
> >>
> >> LX is the same except for the IOMMU-version:
> >>
> >> ok 10000000 20 spacel@ .
> >> 4000005
> >> ok 14000000 20 spacel@ .
> >> 4000005
> >> ok 18000000 20 spacel@ .
> >> 4000005
> >> ok 1f000000 20 spacel@ .
> >> 4000005
> >> ok 1ff00000 20 spacel@ .
> >> 4000005
> >> ok 1fff0004 20 spacel@ .
> >> 1fe000
> >> ok 10000004 20 spacel@ .
> >> 1fe000
> >> ok 10000108 20 spacel@ .
> >> 41000005
> >> ok 10000040 20 spacel@ .
> >> 41000005
> >> ok 1fff0040 20 spacel@ .
> >> 41000005
> >> ok 1fff0044 20 spacel@ .
> >> 1fe000
> >> ok 1fff0024 20 spacel@ .
> >> 1fe000
> >>
> >>
> >> >> At what address the additional AFX registers are located?
> >> >
> >> > Here's complete TurboSPARC IOMMU address map:
> >> > PA[30:0] Register Access
> >> > 1000_0000 IOMMU Control R/W
> >> > 1000_0004 IOMMU Base Address R/W
> >> > 1000_0014 Flush All IOTLB Entries W
> >> > 1000_0018 Address Flush W
> >> > 1000_1000 Asynchronous Fault Status R/W
> >> > 1000_1004 Asynchronous Fault Address R/W
> >> > 1000_1010 SBus Slot Configuration 0 R/W
> >> > 1000_1014 SBus Slot Configuration 1 R/W
> >> > 1000_1018 SBus Slot Configuration 2 R/W
> >> > 1000_101C SBus Slot Configuration 3 R/W
> >> > 1000_1020 SBus Slot Configuration 4 R/W
> >> > 1000_1050 Memory Fault Status R/W
> >> > 1000_1054 Memory Fault Address R/W
> >> > 1000_2000 Module Identification R/W
> >> > 1000_3018 Mask Identification R
> >> > 1000_4000 AFX Queue Level W
> >> > 1000_6000 AFX Queue Level R
> >> > 1000_7000 AFX Queue Status R
> >>
> >>
> >>
> >> But if I read it correctly 0x12fff294 (which makes SunOS crash with -m
> 32) is
> >> well above this limit.
> >
> > Oh, so I also misread something. You are not talking about the
> > adjacent pages, but 16MB increments.
> >
> > Earlier I sent a patch for a generic address alias device, would it be
> > useful for this?
>
>
> Should do as well. But I thought empty_slot is less overhead and
> easier to debug.
>
>
> > Maybe we have a general design problem, perhaps unassigned access
> > faults should only be triggered inside SBus slots and ignored
> > elsewhere. If this is true, generic Sparc32 unassigned access handler
> > should just ignore the access and special fault generating slots
> > should be installed for empty SBus address ranges.
>
>
> My impression was that SS-5 and SS-20 do unassigned accesses a bit
> differently.
> The current IOMMU implementation fits SS-20, which has no aliasing.
It's probably rather the board design than just IOMMU.
> >> >> > One approach would be that IOMMU_NREGS would be increased to cover
> >> >> > these registers (with the bump in savevm version field) and
> >> >> > iommu_init1() should check the version field to see how much MMIO
> to
> >> >> > provide.
> >> >>
> >> >>
> >> >> The problem I see here is that we already have too much registers: we
> >> >> emulate SS-20 IOMMU (I guess), while SS-5 and LX seem to have only
> >> >> 0x20 registers which are aliased all the way.
> >> >>
> >> >>
> >> >> > But in order to avoid the savevm version change, iommu_init1()
> could
> >> >> > just install dummy MMIO (in the TurboSPARC case), if OBP does not
> care
> >> >> > if the read back data matches what has been written earlier.
> Because
> >> >> > from OBP point of view this is identical to what your patch results
> >> >> > in, I'd suppose this approach would also work.
> >> >>
> >> >>
> >> >> OBP doesn't seem to care about these addresses at all. It's only the
> "MUNIX"
> >> >> SunOS 4.1.4 kernel who does. The "MUNIX" kernel is the only kernel
> available
> >> >> during the installation, so it is currently not possible to install
> 4.1.4.
> >> >> Surprisingly "GENERIC" kernel which is on the disk after the
> >> >> installation doesn't
> >> >> try to access these address ranges either, so a disk image taken
> from a live
> >> >> system works.
> >> >>
> >> >> Actually access to the non-connected/aliased addresses may also be a
> >> >> consequence of phys_page_find bug I mentioned before. When I run
> >> >> install with -m 64 and -m 256 it tries to access different
> >> >> non-connected addresses. May also be a SunOS bug of course. 256m used
> >> >> to be a lot back then.
> >> >
> >> > Perhaps with 256MB, memory probing advances blindly from memory to
> >> > IOMMU registers. Proll (used before OpenBIOS) did that once, with bad
> >> > results :-). If this is true, 64M, 128M and 192M should show identical
> >> > results and only with close or equal to 256M the accesses happen.
> >>
> >>
> >> 32m: 0x12fff294
> >> 64m: 0x14fff294
> >> 192m:0x1cfff294
> >> 256m:0x20fff294
> >>
> >> Memory probing? It would be strange that OS would do it itself. The OS
> >> could just
> >> ask OBP how much does it have. Here is the listing where it happens:
> >>
> >> _swift_vac_rgnflush: rd %psr, %g2
> >> _swift_vac_rgnflush+4: andn %g2, 0x20, %g5
> >> _swift_vac_rgnflush+8: mov %g5, %psr
> >> _swift_vac_rgnflush+0xc: nop
> >> _swift_vac_rgnflush+0x10: nop
> >> _swift_vac_rgnflush+0x14: mov 0x100, %g5
> >> _swift_vac_rgnflush+0x18: lda [%g5] 0x4, %g5
> >> _swift_vac_rgnflush+0x1c: sll %o2, 0x2, %g1
> >> _swift_vac_rgnflush+0x20: sll %g5, 0x4, %g5
> >> _swift_vac_rgnflush+0x24: add %g5, %g1, %g5
> >> _swift_vac_rgnflush+0x28: lda [%g5] 0x20, %g5
> >>
> >> _swift_vac_rgnflush+0x28: is the fatal one.
> >>
> >> kadb> $c
> >> _swift_vac_rgnflush(?)
> >> _vac_rgnflush() + 4
> >> _hat_setup_kas(0xc00,0xf0447000,0x43a000,0x400,0xf043a000,0x3c0) + 70
> >> _startup(0xfe000000,0x10000000,0xfa000000,0xf00e2bfc,0x10,0xdbc00) + 1414
> >> _main(0xf00e0fb4,0xf0007810,0x293ff49f,0xa805209c,0x200,0xf00d1d18) + 14
> >>
> >> Unfortunately (but not surprisingly) kadb doesn't allow debugging
> >> cache-flush code, so I can't check what is in
> >> [%g5] (aka sfar) on the real machine when this happens.
> >
> > Linux code for Swift/TurboSPARC VAC flush should be similar.
> >
> >> But the bug in phys_page_find would explain this accesses: sfar gets
> >> the wrong address, and then the secondary access happens on this wrong
> >> address instead of the original one.
> >
> > I doubt phys_page_find can be buggy, it is so vital for all architecture.
>
>
> But you've seen the example of buggy behaviour I posted last Friday, right?
> If it's not phys_page_find, it's either cpu_physical_memory_rw (which
> is also pretty generic), or
> the way SS-20 registers devices. Can it be that all the pages must be
> registered in the proper order?
How about unassigned access handler, could it be suspected?
> I think it's a pretty rare use case where you have a memory fault (not
> a translation fault) on an unknown address. You may have such fault
> during device probing, but in such case you know what address you are
> probing, so you don't care about the sync fault address register.
>
> Besides, do all architectures have sync fault address register?
No, I think system level checks like that and IOMMU-like controls on
most architectures are very poor compared to Sparc32. Server and
mainframe systems may be a bit better.
> >> fwiw the routine is called only once on the real hardware. It sort of
> >> speaks for your hypothesis about the memory probing. Although it may
> >> not necessarily probe for memory...
> >>
> >>
>
> --
> Regards,
> Artyom Tarasenko
>
> solaris/sparc under qemu blog: http://tyom.blogspot.com/
>
- [Qemu-devel] [PATCH 1/2] Pad iommu with an empty slot (necessary for SunOS 4.1.4), Artyom Tarasenko, 2010/05/08
- [Qemu-devel] [PATCH 2/2] reformatted SS-5 and LX definitions, Artyom Tarasenko, 2010/05/08
- [Qemu-devel] Re: [PATCH 1/2] Pad iommu with an empty slot (necessary for SunOS 4.1.4), Blue Swirl, 2010/05/09
- [Qemu-devel] Re: [PATCH 1/2] Pad iommu with an empty slot (necessary for SunOS 4.1.4), Artyom Tarasenko, 2010/05/09
- [Qemu-devel] Re: [PATCH 1/2] Pad iommu with an empty slot (necessary for SunOS 4.1.4), Blue Swirl, 2010/05/09
- [Qemu-devel] Re: [PATCH 1/2] Pad iommu with an empty slot (necessary for SunOS 4.1.4), Artyom Tarasenko, 2010/05/09
- [Qemu-devel] Re: [PATCH 1/2] Pad iommu with an empty slot (necessary for SunOS 4.1.4), Blue Swirl, 2010/05/10
- [Qemu-devel] Re: [PATCH 1/2] Pad iommu with an empty slot (necessary for SunOS 4.1.4), Artyom Tarasenko, 2010/05/10
- [Qemu-devel] Re: [PATCH 1/2] Pad iommu with an empty slot (necessary for SunOS 4.1.4),
Blue Swirl <=
- [Qemu-devel] Re: [PATCH 1/2] Pad iommu with an empty slot (necessary for SunOS 4.1.4), Artyom Tarasenko, 2010/05/21
- [Qemu-devel] Re: [PATCH 1/2] Pad iommu with an empty slot (necessary for SunOS 4.1.4), Blue Swirl, 2010/05/21
- [Qemu-devel] Re: [PATCH 1/2] Pad iommu with an empty slot (necessary for SunOS 4.1.4), Artyom Tarasenko, 2010/05/25
- [Qemu-devel] Re: [PATCH 1/2] Pad iommu with an empty slot (necessary for SunOS 4.1.4), Blue Swirl, 2010/05/25
- [Qemu-devel] Re: [PATCH 1/2] Pad iommu with an empty slot (necessary for SunOS 4.1.4), Artyom Tarasenko, 2010/05/26
- Re: [Qemu-devel] Re: [PATCH 1/2] Pad iommu with an empty slot (necessary for SunOS 4.1.4), Bob Breuer, 2010/05/27
- [Qemu-devel] Re: [PATCH 1/2] Pad iommu with an empty slot (necessary for SunOS 4.1.4), Artyom Tarasenko, 2010/05/28
- [Qemu-devel] Re: [PATCH 1/2] Pad iommu with an empty slot (necessary for SunOS 4.1.4), Blue Swirl, 2010/05/29