[PATCH v5 5/7] powerpc/pseries: flush SLB contents on SLB MCE errors.

[Michal Suchánek]

On Tue, 3 Jul 2018 08:08:14 +1000
Nicholas Piggin <npiggin at gmail.com> wrote:

> On Mon, 02 Jul 2018 11:17:06 +0530
> Mahesh J Salgaonkar <mahesh at linux.vnet.ibm.com> wrote:
> 
> > From: Mahesh Salgaonkar <mahesh at linux.vnet.ibm.com>
> > 
> > On pseries, as of today system crashes if we get a machine check
> > exceptions due to SLB errors. These are soft errors and can be
> > fixed by flushing the SLBs so the kernel can continue to function
> > instead of system crash. We do this in real mode before turning on
> > MMU. Otherwise we would run into nested machine checks. This patch
> > now fetches the rtas error log in real mode and flushes the SLBs on
> > SLB errors.
> > 
> > Signed-off-by: Mahesh Salgaonkar <mahesh at linux.vnet.ibm.com>
> > ---
> >  arch/powerpc/include/asm/book3s/64/mmu-hash.h |    1 
> >  arch/powerpc/include/asm/machdep.h            |    1 
> >  arch/powerpc/kernel/exceptions-64s.S          |   42
> > +++++++++++++++++++++ arch/powerpc/kernel/mce.c
> > |   16 +++++++- arch/powerpc/mm/slb.c                         |
> > 6 +++ arch/powerpc/platforms/powernv/opal.c         |    1 
> >  arch/powerpc/platforms/pseries/pseries.h      |    1 
> >  arch/powerpc/platforms/pseries/ras.c          |   51
> > +++++++++++++++++++++++++
> > arch/powerpc/platforms/pseries/setup.c        |    1 9 files
> > changed, 116 insertions(+), 4 deletions(-) 
> 
> 
> > +TRAMP_REAL_BEGIN(machine_check_pSeries_early)
> > +BEGIN_FTR_SECTION
> > +	EXCEPTION_PROLOG_1(PACA_EXMC, NOTEST, 0x200)
> > +	mr	r10,r1			/* Save r1 */
> > +	ld	r1,PACAMCEMERGSP(r13)	/* Use MC emergency
> > stack */
> > +	subi	r1,r1,INT_FRAME_SIZE	/* alloc stack
> > frame		*/
> > +	mfspr	r11,SPRN_SRR0		/* Save SRR0 */
> > +	mfspr	r12,SPRN_SRR1		/* Save SRR1 */
> > +	EXCEPTION_PROLOG_COMMON_1()
> > +	EXCEPTION_PROLOG_COMMON_2(PACA_EXMC)
> > +	EXCEPTION_PROLOG_COMMON_3(0x200)
> > +	addi	r3,r1,STACK_FRAME_OVERHEAD
> > +	BRANCH_LINK_TO_FAR(machine_check_early) /* Function call
> > ABI */  
> 
> Is there any reason you can't use the existing
> machine_check_powernv_early code to do all this?

Code sharing is nice but if we envision this going to stable kernels
butchering the existing handler is going to be a nightmare. The code is
quite a bit different between kernel versions.

This code as is requires the bit that introduces
EXCEPTION_PROLOG_COMMON_1 and then should work on Linux 3.14+

Thanks

Michal