From: Chen Gang <gang.chen@asianux•com>
To: Paul Mackerras <paulus@samba•org>, Mike Qiu <qiudayu@linux•vnet.ibm.com>
Cc: linuxppc-dev@ozlabs•org, Michael Neuling <mikey@neuling•org>,
"sfr@canb•auug.org.au" <sfr@canb•auug.org.au>
Subject: Re: [PATCH] powerpc: Fix "attempt to move .org backwards" error
Date: Fri, 26 Apr 2013 12:13:43 +0800 [thread overview]
Message-ID: <5179FEF7.8080903@asianux.com> (raw)
In-Reply-To: <20130426035140.GA5796@drongo>
On 2013年04月26日 11:51, Paul Mackerras wrote:
> Building a 64-bit powerpc kernel with PR KVM enabled currently gives
> this error:
>
> AS arch/powerpc/kernel/head_64.o
> arch/powerpc/kernel/exceptions-64s.S: Assembler messages:
> arch/powerpc/kernel/exceptions-64s.S:258: Error: attempt to move .org backwards
> make[2]: *** [arch/powerpc/kernel/head_64.o] Error 1
>
> This happens because the MASKABLE_EXCEPTION_PSERIES macro turns into
> 33 instructions, but we only have space for 32 at the decrementer
> interrupt vector (from 0x900 to 0x980).
>
> In the code generated by the MASKABLE_EXCEPTION_PSERIES macro, we
> currently have two instances of the HMT_MEDIUM macro, which has the
> effect of setting the SMT thread priority to medium. One is the
> first instruction, and is overwritten by a no-op on processors where
> we save the PPR (processor priority register), that is, POWER7 or
> later. The other is after we have saved the PPR.
>
> In order to reduce the code at 0x900 by one instruction, we omit the
> first HMT_MEDIUM. On processors without SMT this will have no effect
> since HMT_MEDIUM is a no-op there. On POWER5 and RS64 machines this
> will mean that the first few instructions take a little longer in the
> case where a decrementer interrupt occurs when the hardware thread is
> running at low SMT priority. On POWER6 and later machines, the
> hardware automatically boosts the thread priority when a decrementer
> interrupt is taken if the thread priority was below medium, so this
> change won't make any difference.
>
> The alternative would be to branch out of line after saving the CFAR.
> However, that would incur an extra overhead on all processors, whereas
> the approach adopted here only adds overhead on older threaded processors.
>
> Signed-off-by: Paul Mackerras <paulus@samba•org>
> ---
Hello Mike:
Please try Paul's patch, firstly.
:-)
Thanks.
> arch/powerpc/include/asm/exception-64s.h | 2 +-
> arch/powerpc/kernel/exceptions-64s.S | 7 ++++++-
> 2 files changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/arch/powerpc/include/asm/exception-64s.h b/arch/powerpc/include/asm/exception-64s.h
> index 05e6d2e..8e5fae8 100644
> --- a/arch/powerpc/include/asm/exception-64s.h
> +++ b/arch/powerpc/include/asm/exception-64s.h
> @@ -414,7 +414,6 @@ label##_relon_hv: \
> #define SOFTEN_NOTEST_HV(vec) _SOFTEN_TEST(EXC_HV, vec)
>
> #define __MASKABLE_EXCEPTION_PSERIES(vec, label, h, extra) \
> - HMT_MEDIUM_PPR_DISCARD; \
> SET_SCRATCH0(r13); /* save r13 */ \
> EXCEPTION_PROLOG_0(PACA_EXGEN); \
> __EXCEPTION_PROLOG_1(PACA_EXGEN, extra, vec); \
> @@ -427,6 +426,7 @@ label##_relon_hv: \
> . = loc; \
> .globl label##_pSeries; \
> label##_pSeries: \
> + HMT_MEDIUM_PPR_DISCARD; \
> _MASKABLE_EXCEPTION_PSERIES(vec, label, \
> EXC_STD, SOFTEN_TEST_PR)
>
> diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
> index 56bd923..574db3f 100644
> --- a/arch/powerpc/kernel/exceptions-64s.S
> +++ b/arch/powerpc/kernel/exceptions-64s.S
> @@ -235,6 +235,7 @@ instruction_access_slb_pSeries:
> .globl hardware_interrupt_hv;
> hardware_interrupt_pSeries:
> hardware_interrupt_hv:
> + HMT_MEDIUM_PPR_DISCARD
> BEGIN_FTR_SECTION
> _MASKABLE_EXCEPTION_PSERIES(0x502, hardware_interrupt,
> EXC_HV, SOFTEN_TEST_HV)
> @@ -254,7 +255,11 @@ hardware_interrupt_hv:
> STD_EXCEPTION_PSERIES(0x800, 0x800, fp_unavailable)
> KVM_HANDLER_PR(PACA_EXGEN, EXC_STD, 0x800)
>
> - MASKABLE_EXCEPTION_PSERIES(0x900, 0x900, decrementer)
> + . = 0x900
> + .globl decrementer_pSeries
> +decrementer_pSeries:
> + _MASKABLE_EXCEPTION_PSERIES(0x900, decrementer, EXC_STD, SOFTEN_TEST_PR)
> +
> STD_EXCEPTION_HV(0x980, 0x982, hdecrementer)
>
> MASKABLE_EXCEPTION_PSERIES(0xa00, 0xa00, doorbell_super)
>
--
Chen Gang
Asianux Corporation
next prev parent reply other threads:[~2013-04-26 4:35 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-04-26 3:51 [PATCH] powerpc: Fix "attempt to move .org backwards" error Paul Mackerras
2013-04-26 4:13 ` Chen Gang [this message]
2013-04-27 9:34 ` Mike Qiu
-- strict thread matches above, loose matches on Subject: below --
2013-12-09 19:10 Mahesh J Salgaonkar
2013-12-09 23:10 ` Stephen Rothwell
2013-12-09 23:26 ` Benjamin Herrenschmidt
2014-02-12 5:22 ` Stephen Rothwell
2014-02-15 18:02 ` Guenter Roeck
2014-08-09 5:22 Guenter Roeck
2014-08-11 0:20 ` Stephen Rothwell
2014-08-11 16:25 ` Guenter Roeck
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