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4356e9f8 |
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09-Feb-2024 |
Linus Torvalds <torvalds@linux-foundation.org> |
work around gcc bugs with 'asm goto' with outputs We've had issues with gcc and 'asm goto' before, and we created a 'asm_volatile_goto()' macro for that in the past: see commits 3f0116c3238a ("compiler/gcc4: Add quirk for 'asm goto' miscompilation bug") and a9f180345f53 ("compiler/gcc4: Make quirk for asm_volatile_goto() unconditional"). Then, much later, we ended up removing the workaround in commit 43c249ea0b1e ("compiler-gcc.h: remove ancient workaround for gcc PR 58670") because we no longer supported building the kernel with the affected gcc versions, but we left the macro uses around. Now, Sean Christopherson reports a new version of a very similar problem, which is fixed by re-applying that ancient workaround. But the problem in question is limited to only the 'asm goto with outputs' cases, so instead of re-introducing the old workaround as-is, let's rename and limit the workaround to just that much less common case. It looks like there are at least two separate issues that all hit in this area: (a) some versions of gcc don't mark the asm goto as 'volatile' when it has outputs: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98619 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110420 which is easy to work around by just adding the 'volatile' by hand. (b) Internal compiler errors: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110422 which are worked around by adding the extra empty 'asm' as a barrier, as in the original workaround. but the problem Sean sees may be a third thing since it involves bad code generation (not an ICE) even with the manually added 'volatile'. but the same old workaround works for this case, even if this feels a bit like voodoo programming and may only be hiding the issue. Reported-and-tested-by: Sean Christopherson <seanjc@google.com> Link: https://lore.kernel.org/all/20240208220604.140859-1-seanjc@google.com/ Cc: Nick Desaulniers <ndesaulniers@google.com> Cc: Uros Bizjak <ubizjak@gmail.com> Cc: Jakub Jelinek <jakub@redhat.com> Cc: Andrew Pinski <quic_apinski@quicinc.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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6fee1302 |
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06-Apr-2023 |
Michael Ellerman <mpe@ellerman.id.au> |
powerpc/64: Don't call trace_hardirqs_on() in prep_irq_for_idle() Since commit a01353cf1896 ("cpuidle: Fix ct_idle_*() usage"), the cpuidle entry code calls trace_hardirqs_on() (actually trace_hardirqs_on_prepare()) in ct_cpuidle_enter() before calling into the cpuidle driver. Suggested-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://msgid.link/20230406144535.3786008-2-mpe@ellerman.id.au
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7640854d |
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06-Apr-2023 |
Michael Ellerman <mpe@ellerman.id.au> |
powerpc/64: Mark prep_irq_for_idle() __cpuidle Code in the idle path is not allowed to be instrumented because RCU is disabled, see commit 0e985e9d2286 ("cpuidle: Add comments about noinstr/__cpuidle usage"). Mark prep_irq_for_idle() __cpuidle, which is equivalent to noinstr, to enforce that. Suggested-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://msgid.link/20230406144535.3786008-1-mpe@ellerman.id.au
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4f8e0910 |
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05-Feb-2023 |
Rohan McLure <rmclure@linux.ibm.com> |
powerpc/kcsan: Prevent recursive instrumentation with IRQ save/restores Instrumented memory accesses provided by KCSAN will access core-local memories (which will save and restore IRQs) as well as restoring IRQs directly. Avoid recursive instrumentation by applying __no_kcsan annotation to IRQ restore routines. Signed-off-by: Rohan McLure <rmclure@linux.ibm.com> [mpe: Resolve merge conflict with IRQ replay recursion changes] Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20230206021801.105268-5-rmclure@linux.ibm.com
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5746ca13 |
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21-Jan-2023 |
Nicholas Piggin <npiggin@gmail.com> |
powerpc/64: Don't recurse irq replay Interrupt handlers called by soft-pending irq replay code can run softirqs, softirq replay enables and disables local irqs, which allows interrupts to come in including soft-masked interrupts, and it can cause pending irqs to be replayed again. That makes the soft irq replay state machine and possible races more complicated and fragile than it needs to be. Use irq_enter/irq_exit around irq replay to prevent softirqs running while interrupts are being replayed. Softirqs will now be run at the irq_exit() call after all the irq replaying is done. This prevents irqs being replayed while irqs are being replayed, and should hopefully make things simpler and easier to think about and debug. A new PACA_IRQ_REPLAYING is added to prevent asynchronous interrupt handlers hard-enabling EE while pending irqs are being replayed, because that causes new pending irqs to arrive which is also a complexity. This means pending irqs won't be profiled quite so well because perf irqs can't be taken. Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20230121102618.2824429-1-npiggin@gmail.com
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1da5351f |
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25-Sep-2022 |
Nicholas Piggin <npiggin@gmail.com> |
powerpc/64/irq: tidy soft-masked irq replay and improve documentation irq replay is quite complicated because of softirq processing which itself enables and disables irqs. Several considerations need to be accounted for due to this, and they are not clearly documented. Refactor the irq replay code a bit to tidy and deduplicate some common functions. Add comments, debug checks. This has a minor functional change that irq tracing enable/disable is done after each interrupt replayed, rather than after a batch. It also re-sets state to IRQS_ALL_DISABLED after an interrupt, which doesn't matter much because interrupts are hard disabled at this point, but it is more consistent with how interrupt handlers are called. Signed-off-by: Nicholas Piggin <npiggin@gmail.com> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/20220926054305.2671436-8-npiggin@gmail.com
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98552307 |
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18-May-2022 |
Christophe Leroy <christophe.leroy@csgroup.eu> |
powerpc/irq64: Remove get_irq_happened() No need to open code the read of local_paca->irq_happened in assembly, we have READ_ONCE() for doing the same. Replace get_irq_happened() by READ_ONCE(local_paca->irq_happened). Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/af511b53e4eb51f8fbc51eda7f5597175e68dce6.1652859593.git.christophe.leroy@csgroup.eu
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7d7b28b3 |
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18-May-2022 |
Christophe Leroy <christophe.leroy@csgroup.eu> |
powerpc/irq: Split irq.c More than half of irq.c is dedicated to PPC64. Move PPC64 code out of irq.c into irq_64.c Signed-off-by: Christophe Leroy <christophe.leroy@csgroup.eu> Signed-off-by: Michael Ellerman <mpe@ellerman.id.au> Link: https://lore.kernel.org/r/9f1a47de80f78d3dd270a7a72f69f55f581c4054.1652859593.git.christophe.leroy@csgroup.eu
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