On Fri, Dec 01, 2017 at 03:49:07PM +0000, Richard Purdie wrote: > Occasionally in Linux guests on x86_64 we're seeing logs like: > > ppc_set_irq: 0x55b4e0d562f0 n_IRQ 8 level 1 => pending 00000100req 00000004 > > when they should read: > > ppc_set_irq: 0x55b4e0d562f0 n_IRQ 8 level 1 => pending 00000100req 00000002 > > The "00000004" is CPU_INTERRUPT_EXITTB yet the code calls > cpu_interrupt(cs, CPU_INTERRUPT_HARD) ("00000002") in this function > just before the log message. Something is causing the HARD bit setting > to get lost. > > The knock on effect of losing that bit is the decrementer timer interrupts > don't get delivered which causes the guest to sit idle in its idle handler > and 'hang'. > > The issue occurs due to races from code which sets CPU_INTERRUPT_EXITTB. > > Rather than poking directly into cs->interrupt_request, that code needs to: > > a) hold BQL > b) use the cpu_interrupt() helper > > This patch fixes the call sites to do this, fixing the hang. > > Signed-off-by: Richard Purdie <richard.pur...@linuxfoundation.org>
I strongly suspect there's a better way to do this long term - a lot of that old ppc TCG code is really crufty. But as best I can tell, this is certainly a fix over what we had. So, applied to ppc-for-2.11. > --- > target/ppc/excp_helper.c | 16 +++++++++++++--- > target/ppc/helper_regs.h | 10 ++++++++-- > 2 files changed, 21 insertions(+), 5 deletions(-) > > v2: Fixes a compile issue with master and ensures BQL is held in one case > where it potentially wasn't. > > diff --git a/target/ppc/excp_helper.c b/target/ppc/excp_helper.c > index e6009e7..8040277 100644 > --- a/target/ppc/excp_helper.c > +++ b/target/ppc/excp_helper.c > @@ -207,7 +207,13 @@ static inline void powerpc_excp(PowerPCCPU *cpu, int > excp_model, int excp) > "Entering checkstop state\n"); > } > cs->halted = 1; > - cs->interrupt_request |= CPU_INTERRUPT_EXITTB; > + if (!qemu_mutex_iothread_locked()) { > + qemu_mutex_lock_iothread(); > + cpu_interrupt(cs, CPU_INTERRUPT_EXITTB); > + qemu_mutex_unlock_iothread(); > + } else { > + cpu_interrupt(cs, CPU_INTERRUPT_EXITTB); > + } > } > if (env->msr_mask & MSR_HVB) { > /* ISA specifies HV, but can be delivered to guest with HV clear > @@ -940,7 +946,9 @@ void helper_store_msr(CPUPPCState *env, target_ulong val) > > if (excp != 0) { > CPUState *cs = CPU(ppc_env_get_cpu(env)); > - cs->interrupt_request |= CPU_INTERRUPT_EXITTB; > + qemu_mutex_lock_iothread(); > + cpu_interrupt(cs, CPU_INTERRUPT_EXITTB); > + qemu_mutex_unlock_iothread(); > raise_exception(env, excp); > } > } > @@ -995,7 +1003,9 @@ static inline void do_rfi(CPUPPCState *env, target_ulong > nip, target_ulong msr) > /* No need to raise an exception here, > * as rfi is always the last insn of a TB > */ > - cs->interrupt_request |= CPU_INTERRUPT_EXITTB; > + qemu_mutex_lock_iothread(); > + cpu_interrupt(cs, CPU_INTERRUPT_EXITTB); > + qemu_mutex_unlock_iothread(); > > /* Reset the reservation */ > env->reserve_addr = -1; > diff --git a/target/ppc/helper_regs.h b/target/ppc/helper_regs.h > index 2627a70..0beaad5 100644 > --- a/target/ppc/helper_regs.h > +++ b/target/ppc/helper_regs.h > @@ -20,6 +20,8 @@ > #ifndef HELPER_REGS_H > #define HELPER_REGS_H > > +#include "qemu/main-loop.h" > + > /* Swap temporary saved registers with GPRs */ > static inline void hreg_swap_gpr_tgpr(CPUPPCState *env) > { > @@ -114,11 +116,15 @@ static inline int hreg_store_msr(CPUPPCState *env, > target_ulong value, > } > if (((value >> MSR_IR) & 1) != msr_ir || > ((value >> MSR_DR) & 1) != msr_dr) { > - cs->interrupt_request |= CPU_INTERRUPT_EXITTB; > + qemu_mutex_lock_iothread(); > + cpu_interrupt(cs, CPU_INTERRUPT_EXITTB); > + qemu_mutex_unlock_iothread(); > } > if ((env->mmu_model & POWERPC_MMU_BOOKE) && > ((value >> MSR_GS) & 1) != msr_gs) { > - cs->interrupt_request |= CPU_INTERRUPT_EXITTB; > + qemu_mutex_lock_iothread(); > + cpu_interrupt(cs, CPU_INTERRUPT_EXITTB); > + qemu_mutex_unlock_iothread(); > } > if (unlikely((env->flags & POWERPC_FLAG_TGPR) && > ((value ^ env->msr) & (1 << MSR_TGPR)))) { -- David Gibson | I'll have my music baroque, and my code david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_ | _way_ _around_! http://www.ozlabs.org/~dgibson
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