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Mon, 17 Aug 2026 12:00:08 -0400 X-MC-Unique: OtzTCRPgMr2QHUMKyw4kuQ-1 X-Mimecast-MFC-AGG-ID: OtzTCRPgMr2QHUMKyw4kuQ_1786982406 Received: from mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.93]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 126F51800651; Mon, 17 Aug 2026 16:00:05 +0000 (UTC) Received: from [100.90.56.12] (headnet05.pony-001.prod.iad2.dc.redhat.com [10.2.32.117]) by mx-prod-int-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id 692ED1800347; Mon, 17 Aug 2026 15:59:59 +0000 (UTC) Message-ID: <55cc8357-daeb-4315-9f3a-8be7a59c355b@redhat.com> Date: Mon, 17 Aug 2026 17:59:57 +0200 Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 11/16] accel/kvm: Consistently return CPU halt state from process_async_events To: =?UTF-8?Q?Philippe_Mathieu-Daud=C3=A9?= , qemu-devel@nongnu.org Cc: Daniel Henrique Barboza , Pierrick Bouvier , Mohamed Mediouni , Alexander Graf , qemu-ppc@nongnu.org, qemu-riscv@nongnu.org, kvm@vger.kernel.org, Richard Henderson , qemu-arm@nongnu.org, Magnus Kulke , Peter Maydell , Palmer Dabbelt , Alistair Francis , Weiwei Li , Liu Zhiwei , Chao Liu References: <20260813181640.6537-1-philmd@oss.qualcomm.com> <20260813181640.6537-12-philmd@oss.qualcomm.com> From: Paolo Bonzini Content-Language: en-US Autocrypt: addr=pbonzini@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.93 On 8/13/26 20:16, Philippe Mathieu-Daudé wrote: > When comparing the KVM implementations, RISCV and ARM differ > from S390x / PPC and LoongArch. The caller expects a non-zero > value to return pausing execution with the EXCP_HLT exception: > > 3427 int kvm_cpu_exec(CPUState *cpu) > 3428 { > ... > 3434 if (kvm_arch_process_async_events(cpu)) { > 3435 return EXCP_HLT; > 3436 } > 3437 > 3438 bql_unlock(); > 3439 cpu_exec_start(cpu); > 3440 > 3441 /* Inner vCPU loop */ > 3442 do { > ... Your patch is correct because, even if cpu_thread_is_idle() sees cpu->halted == false, the flag could become true during process_queued_cpu_work() because it releases the BQL. However, I think the better fix is to remove the return code, and check cpu->halted in kvm_cpu_exec(). Thanks, Paolo > Change ARM and RISC-V to return cs->halted for consistent behavior. > > Signed-off-by: Philippe Mathieu-Daudé > --- > target/arm/kvm.c | 2 +- > target/riscv/kvm/kvm-cpu.c | 2 +- > 2 files changed, 2 insertions(+), 2 deletions(-) > > diff --git a/target/arm/kvm.c b/target/arm/kvm.c > index d40a6a98591..5caabfab63f 100644 > --- a/target/arm/kvm.c > +++ b/target/arm/kvm.c > @@ -1575,7 +1575,7 @@ bool kvm_arch_stop_on_emulation_error(CPUState *cs) > > int kvm_arch_process_async_events(CPUState *cs) > { > - return 0; > + return cs->halted; > } > > /** > diff --git a/target/riscv/kvm/kvm-cpu.c b/target/riscv/kvm/kvm-cpu.c > index 97069bf597a..1a61cd5ef37 100644 > --- a/target/riscv/kvm/kvm-cpu.c > +++ b/target/riscv/kvm/kvm-cpu.c > @@ -1568,7 +1568,7 @@ int kvm_arch_irqchip_create(KVMState *s) > > int kvm_arch_process_async_events(CPUState *cs) > { > - return 0; > + return cs->halted; > } > > void kvm_arch_pre_run(CPUState *cs, struct kvm_run *run)