[Skiboot] [PATCH] external/mambo: add helper for machine checks

[Nicholas Piggin]

On Mon, 01 May 2017 14:02:17 +1000
Stewart Smith <stewart at linux.vnet.ibm.com> wrote:

> Nicholas Piggin <npiggin at gmail.com> writes:
> > Add helpers to construct machine checks with registers set up properly.
> > exc_mce raises a machine check exception that can be stepped into. This
> > is useful for testing the machine check handler.
> >
> > Also add a similar exc_sreset for system reset.
> >
> > inject_mce does the same but runs immediately and stops when the
> > instruction reaches the NIP (which can get tangled up if machine check
> > re-enters this code). This is useful for testing robustness to
> > interleaving machine checks.
> >
> > inject_mce_step allows injecting MCEs between each instruction and stepping
> > over them. inject_mce_step_ri does the same but only when MSR has RI set.
> > This can be useful to test correctness of low level code. For example,
> > testing system call vs machine check:
> >
> > systemsim % b 0xC000000000004c00
> > systemsim % c
> > 0xC000000000004C00 (0x0000000000004C00) Enc:0xA64BB17D : mtspr   HSPRG1,r13
> > systemsim % inject_mce_step_ri 100
> > 0xC000000000004C04 (0x0000000000004C04) Enc:0xA64AB07D : mfspr   r13,HSPRG0
> > 0xC000000000004C08 (0x0000000000004C08) Enc:0x80002DF9 : std     r9,0x80(r13)
> > 0xC000000000004C0C (0x0000000000004C0C) Enc:0xA6E2207D : mfspr   r9,PPR
> > 0xC000000000004C10 (0x0000000000004C10) Enc:0x7813427C : mr      r2,r2
> > 0xC000000000004C14 (0x0000000000004C14) Enc:0x88004DF9 : std     r10,0x88(r13)
> > 0xC000000000004C18 (0x0000000000004C18) Enc:0xD8002DF9 : std     r9,0xD8(r13)
> > 0xC000000000004C1C (0x0000000000004C1C) Enc:0x2600207D : mfcr    r9
> > 0xC000000000004C20 (0x0000000000004C20) Enc:0xE8074D89 : lbz     r10,0x7E8(r13)
> > 0xC000000000004C24 (0x0000000000004C24) Enc:0x00000A2C : cmpwi   cr0,r10,0
> > 0xC000000000004C28 (0x0000000000004C28) Enc:0xA80F8240 : bne     cr0,$+0xFA8  (bc 0x4,0x2,0xFA8,0,0)
> > 0xC000000000004C2C (0x0000000000004C2C) Enc:0xA64AB17D : mfspr   r13,HSPRG1
> > 0xC000000000004C30 (0x0000000000004C30) Enc:0xBE1E202C : cmpdi   cr0,r0,7870
> > 0xC000000000004C34 (0x0000000000004C34) Enc:0x2000C241 : beq     cr0,$+0x20  (bc 0xE,0x2,0x20,0,0)
> > 0xC000000000004C38 (0x0000000000004C38) Enc:0x786BA97D : mr      r9,r13
> > 0xC000000000004C3C (0x0000000000004C3C) Enc:0xA64AB07D : mfspr   r13,HSPRG0
> > 0xC000000000004C40 (0x0000000000004C40) Enc:0xA6027A7D : mfspr   r11,SRR0
> > 0xC000000000004C44 (0x0000000000004C44) Enc:0xA6029B7D : mfspr   r12,SRR1
> > 0xC000000000004C48 (0x0000000000004C48) Enc:0x02004039 : li      r10,2
> > 0xC000000000004C4C (0x0000000000004C4C) Enc:0x6401417D : mtmsrd  r10,1
> > 0xC000000000004C50 (0x0000000000004C50) Enc:0xB0620048 : b       $+0x62B0
> > 236380163: (212143620): Disabling lock debugging due to kernel taint
> > 0xC000000000004C50 (0x0000000000004C50) Enc:0xB0620048 : b       $+0x62B0
> > 0xC00000000000AF00 (0x000000000000AF00) Enc:0xE1F78A79 : rldicl. r10,r12,30,63,63 (0x0000000000000001)
> > 0xC00000000000AF00 (0x000000000000AF00) Enc:0xE1F78A79 : rldicl. r10,r12,30,63,63 (0x0000000000000001)
> > [...]
> >
> > Every instruction after 0xC000000000004C4C is getting an interleaving
> > MCE, and continuing after this injection the kernel prints a lot of MCE
> > reports and continues working properly.
> >
> > Signed-off-by: Nicholas Piggin <npiggin at gmail.com>
> > ---
> > Hi,
> >
> > If anybody would find this useful or has a better way to do it, let me
> > know. This is a polished up and improved version of what I've been using
> > for testing.
> >
> > It should be noted that upstream mambo currently does not quite work
> > properly with this because of a quirk in how it injects MCE interrupts.
> > I was kind-of hacking around that in the script but took out that code
> > because the mambo developers will be fixing that or giving us an option
> > to change behaviour soon.
> >
> > Thanks,
> > Nick  
> 
> Thanks, merged to master as of 6e6d5417ec67797b1dc52c8e30e9b1b4cf64e74f
> 

Thanks. BTW., if it wasn't mentioned, this did actually find a bug in Linux.

This may just need a couple of minor tweaks with the recent simulator
changes to exception injection that's been made for us, which is working
its way into the next sim release.

I think it should work, but I'll go through it again and re-test it all. I'll
also look at adding canned test cases for Linux that we can run as regression
tests so everything stays working.

Thanks,
Nick