From: Michael Ellerman <patch-notifications@ellerman.id.au>
To: Nicholas Piggin <npiggin@gmail.com>, linuxppc-dev@lists.ozlabs.org
Cc: Nicholas Piggin <npiggin@gmail.com>
Subject: Re: [PATCH 1/5] powerpc/64s/exception: remove bad stack branch
Date: Fri, 5 Jul 2019 01:52:51 +1000 (AEST) [thread overview]
Message-ID: <45fjDM3kMWz9sPM@ozlabs.org> (raw)
In-Reply-To: <20190628063322.11628-2-npiggin@gmail.com>
On Fri, 2019-06-28 at 06:33:18 UTC, Nicholas Piggin wrote:
> The bad stack test in interrupt handlers has a few problems. For
> performance it is taken in the common case, which is a fetch bubble
> and a waste of i-cache.
>
> For code development and maintainence, it requires yet another stack
> frame setup routine, and that constrains all exception handlers to
> follow the same register save pattern which inhibits future
> optimisation.
>
> Remove the test/branch and replace it with a trap. Teach the program
> check handler to use the emergency stack for this case.
>
> This does not result in quite so nice a message, however the SRR0 and
> SRR1 of the crashed interrupt can be seen in r11 and r12, as is the
> original r1 (adjusted by INT_FRAME_SIZE). These are the most important
> parts to debugging the issue.
>
> The original r9-12 and cr0 is lost, which is the main downside.
>
> kernel BUG at linux/arch/powerpc/kernel/exceptions-64s.S:847!
> Oops: Exception in kernel mode, sig: 5 [#1]
> BE SMP NR_CPUS=2048 NUMA PowerNV
> Modules linked in:
> CPU: 0 PID: 1 Comm: swapper/0 Not tainted
> NIP: c000000000009108 LR: c000000000cadbcc CTR: c0000000000090f0
> REGS: c0000000fffcbd70 TRAP: 0700 Not tainted
> MSR: 9000000000021032 <SF,HV,ME,IR,DR,RI> CR: 28222448 XER: 20040000
> CFAR: c000000000009100 IRQMASK: 0
> GPR00: 000000000000003d fffffffffffffd00 c0000000018cfb00 c0000000f02b3166
> GPR04: fffffffffffffffd 0000000000000007 fffffffffffffffb 0000000000000030
> GPR08: 0000000000000037 0000000028222448 0000000000000000 c000000000ca8de0
> GPR12: 9000000002009032 c000000001ae0000 c000000000010a00 0000000000000000
> GPR16: 0000000000000000 0000000000000000 0000000000000000 0000000000000000
> GPR20: c0000000f00322c0 c000000000f85200 0000000000000004 ffffffffffffffff
> GPR24: fffffffffffffffe 0000000000000000 0000000000000000 000000000000000a
> GPR28: 0000000000000000 0000000000000000 c0000000f02b391c c0000000f02b3167
> NIP [c000000000009108] decrementer_common+0x18/0x160
> LR [c000000000cadbcc] .vsnprintf+0x3ec/0x4f0
> Call Trace:
> Instruction dump:
> 996d098a 994d098b 38610070 480246ed 48005518 60000000 38200000 718a4000
> 7c2a0b78 3821fd00 41c20008 e82d0970 <0981fd00> f92101a0 f9610170 f9810178
>
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Series applied to powerpc next, thanks.
https://git.kernel.org/powerpc/c/0a882e28468f48ab3d9a36dde0a5723ea29ed1ed
cheers
next prev parent reply other threads:[~2019-07-04 16:05 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-06-28 6:33 [PATCH 0/5] rework bad stack, sreset, hmi handling Nicholas Piggin
2019-06-28 6:33 ` [PATCH 1/5] powerpc/64s/exception: remove bad stack branch Nicholas Piggin
2019-07-04 15:52 ` Michael Ellerman [this message]
2019-06-28 6:33 ` [PATCH 2/5] powerpc/64s/exception: optimise system_reset for idle, clean up non-idle case Nicholas Piggin
2019-06-28 6:33 ` [PATCH 3/5] powerpc/64s/exception: sreset move trampoline ahead of common code Nicholas Piggin
2019-06-28 6:33 ` [PATCH 4/5] powerpc/64s/exception: hmi remove special case macro Nicholas Piggin
2019-06-28 6:33 ` [PATCH 5/5] powerpc/64s/exception: simplify hmi control flow Nicholas Piggin
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