kernel.git/arch/powerpc/kernel/head_64.S, branch linux-2.6.21.y

[POWERPC] Fix performance monitor exception

2007-02-07T03:03:23Z

To the issue: some point during 2.6.20 development, Paul Mackerras introduced the "lazy IRQ disabling" patch (very cool work, BTW). In that patch, the performance monitor unit exception was marked as "maskable", in the sense that if interrupts were soft-disabled, that exception could be ignored. This broke my PowerPC profiling code. The symptom that I see is that a varying number of interrupts (from 0 to $n$, typically closer to 0) get delivered, when, in reality, it should always be very close to $n$. The issue stems from the way masking is being done. Masking in this fashion seems to work well with the decrementer and external interrupts, because they are raised again until "really" handled. For the PMU, however, this does not apply (at least on my Xserver machine with a 970FX processor). If the PMU exception is not handled, it will _not_ be re-raised (at least on my machine). The documentation states that the PMXE bit in MMCR0 is set to 0 when the PMU exception is raised. However, software must re-set the bit to re-enable PMU exceptions. If the exception is ignored (as currently) not only is that interrupt lost, but because software does not re-set PMXE, the PMU registers are "frozen" forever. [This patch means that performance monitor exceptions are taken and handled even if irqs are off, as long as some other interrupt hasn't come along and caused interrupts to be hard-disabled. In this sense the PMU exception becomes like an NMI. The oprofile code for most powerpc processors does nothing that is unsafe in an NMI context, but the Cell oprofile code does a spin_lock_irqsave. However, that turns out to be OK because Cell doesn't actually use the performance monitor exception; performance monitor interrupts come in as a regular interrupt on Cell, so will be disabled when irqs are off. -- paulus.] Signed-off-by: Paul Mackerras

[POWERPC] iSeries: Eliminate "exceeds stub group size" warnings

2006-12-04T09:41:31Z

Commit 3ccfc65c5004e5fe5cfbffe43b8acc686680b53e missed the same fixes for legacy iSeries specific code, so make some more symbols no longer global. Signed-off-by: Stephen Rothwell Signed-off-by: Paul Mackerras

Merge branch 'linux-2.6' into for-linus

2006-12-04T04:59:07Z

[PATCH] Remove occurences of PPC_MULTIPLATFORM in head_64.S

2006-11-13T03:44:58Z

Since iSeries is merged to MULTIPLATFORM, there is no way to build a 64bit kernel without MULTIPLATFORM, so PPC_MULTIPLATFORM can be removed in 64bit-only files. Signed-off-by: Sascha Hauer Acked-by: Benjamin Herrenschmidt Signed-off-by: Paul Mackerras

[PATCH] powerpc: Eliminate "exceeds stub group size" linker warning

2006-11-01T22:56:59Z

It turns out that the linker warnings on 64-bit powerpc about "section blah exceeds stub group size" were being triggered by conditional branches in head_64.S branching to global symbols, whether in head_64.S or in other files. This eliminates the warnings by making some global symbols in head_64.S no longer global, and by rearranging some branches. Signed-off-by: Paul Mackerras [ Yee-haa. Maybe I'll notice newly introduced real warnings now - Linus ] Signed-off-by: Linus Torvalds

[POWERPC] Make sure __cpu_preinit_ppc970 gets called on 970GX processors

2006-10-25T23:20:07Z

Add check for 970GX for __cpu_preinit_ppc970. Signed-off-by: Olof Johansson Signed-off-by: Paul Mackerras

[POWERPC] Consolidate feature fixup code

2006-10-25T01:42:10Z

There are currently two versions of the functions for applying the feature fixups, one for CPU features and one for firmware features. In addition, they are both in assembly and with separate implementations for 32 and 64 bits. identify_cpu() is also implemented in assembly and separately for 32 and 64 bits. This patch replaces them with a pair of C functions. The call sites are slightly moved on ppc64 as well to be called from C instead of from assembly, though it's a very small change, and thus shouldn't cause any problem. Signed-off-by: Benjamin Herrenschmidt Acked-by: Olof Johansson Signed-off-by: Paul Mackerras

[POWERPC] Make sure interrupt enable gets restored properly

2006-10-18T00:12:53Z

The lazy IRQ disable patch missed a couple of places where the interrupt enable flags need to be restored correctly. First, we weren't restoring the paca->hard_enabled flag on interrupt exit. Instead of saving it on entry, we compute it from the MSR_EE bit in the MSR we are restoring at exit. Secondly, the MMU hash miss code was clearing both paca->soft_enabled and paca->hard_enabled but not restoring them in the case where hash_page was able to resolve the miss from the Linux page tables. Signed-off-by: Paul Mackerras

[POWERPC] Lazy interrupt disabling for 64-bit machines

2006-10-16T06:31:36Z

This implements a lazy strategy for disabling interrupts. This means that local_irq_disable() et al. just clear the 'interrupts are enabled' flag in the paca. If an interrupt comes along, the interrupt entry code notices that interrupts are supposed to be disabled, and clears the EE bit in SRR1, clears the 'interrupts are hard-enabled' flag in the paca, and returns. This means that interrupts only actually get disabled in the processor when an interrupt comes along. When interrupts are enabled by local_irq_enable() et al., the code sets the interrupts-enabled flag in the paca, and then checks whether interrupts got hard-disabled. If so, it also sets the EE bit in the MSR to hard-enable the interrupts. This has the potential to improve performance, and also makes it easier to make a kernel that can boot on iSeries and on other 64-bit machines, since this lazy-disable strategy is very similar to the soft-disable strategy that iSeries already uses. This version renames paca->proc_enabled to paca->soft_enabled, and changes a couple of soft-disables in the kexec code to hard-disables, which should fix the crash that Michael Ellerman saw. This doesn't yet use a reserved CR field for the soft_enabled and hard_enabled flags. This applies on top of Stephen Rothwell's patches to make it possible to build a combined iSeries/other kernel. Signed-off-by: Paul Mackerras

[POWERPC] implement BEGIN/END_FW_FTR_SECTION

2006-10-03T06:50:21Z

and use it an all the obvious places in assembler code. Signed-off-by: Stephen Rothwell