From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:35645) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eHCPn-00068p-WC for qemu-devel@nongnu.org; Tue, 21 Nov 2017 12:32:58 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eHCPm-0001hh-TP for qemu-devel@nongnu.org; Tue, 21 Nov 2017 12:32:56 -0500 From: Richard Purdie Date: Tue, 21 Nov 2017 17:32:18 +0000 Message-Id: <1511285538-22883-1-git-send-email-richard.purdie@linuxfoundation.org> Subject: [Qemu-devel] [PATCH] target/ppc: Fix system lockups caused by interrupt_request state corruption List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org, david@gibson.dropbear.id.au Cc: qemu-ppc@nongnu.org, Richard Purdie 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 --- target/ppc/excp_helper.c | 12 +++++++++--- target/ppc/helper_regs.h | 8 ++++++-- 2 files changed, 15 insertions(+), 5 deletions(-) diff --git a/target/ppc/excp_helper.c b/target/ppc/excp_helper.c index e6009e7..f175c21 100644 --- a/target/ppc/excp_helper.c +++ b/target/ppc/excp_helper.c @@ -207,7 +207,9 @@ 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; + qemu_mutex_lock_iothread(); + cpu_interrupt(cs, CPU_INTERRUPT_EXITTB); + qemu_mutex_unlock_iothread(); } if (env->msr_mask & MSR_HVB) { /* ISA specifies HV, but can be delivered to guest with HV clear @@ -940,7 +942,9 @@ 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 +999,9 @@ 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..13dd0b8 100644 --- a/target/ppc/helper_regs.h +++ b/target/ppc/helper_regs.h @@ -114,11 +114,15 @@ 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)))) { -- 2.7.4