From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-oi1-f175.google.com (mail-oi1-f175.google.com [209.85.167.175]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 585DB4F5E9; Wed, 24 Jan 2024 11:35:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.167.175 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706096107; cv=none; b=uxiIYoXDLFTeM/mYxphh/7Un9SkJ/AbA03tW62R2Czw0MoPagY89qWSLZVSDGsOILQ41VS9yi0PPABKSTtKMPIA0yEwK0uleJCddHFe5apg+lCX3Apl47h5uytk7VGRZ3TmZ44B7IcyH/5CxWKnoq5FBFelgjbKu+TDCkRVCPgQ= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706096107; c=relaxed/simple; bh=P87B/NJmEx20+ry47oVcoCNzd+QWvtcpba/ysVCMEEc=; h=From:To:Cc:Subject:Date:Message-Id:MIME-Version; b=CP4JKz856rC99QC2iy2fwQIMCKqi8RtXzF05t5D5ICjGGjsJd7UHbEjOW5eS2VE5zoM7wdQjeUhS8xuIS6iNsINrIYXkT6puwW1SDO8uto3oOIwWbp5WUwjQKVsXzHchqY+cOIQadXNcjSHN2PP7ODzPqipYPIVcnJ4SKI3htk0= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=EVZPvN+v; arc=none smtp.client-ip=209.85.167.175 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="EVZPvN+v" Received: by mail-oi1-f175.google.com with SMTP id 5614622812f47-3bd9030d68fso3264249b6e.3; Wed, 24 Jan 2024 03:35:06 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1706096105; x=1706700905; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=C9dLmB1UBk2lcc6K0p3fcasn7wjRUeWpHrr479fQHwU=; b=EVZPvN+vjkGSqbk0xy1pNd30FiFLn+wCMmNxaisov4PUYZO0M651jiQU+1Yp+pZCIM EuL0YppZ2NVcuDDr+mpQrwVYugUD3lU/klLM4Fj3rKw6O8oVZZ0ZoQ6ZMQCsZsakk1SB 5niPPIvwOjzdf4mWbj+0VarasTrLv0kzXvAAWOoJCRkQbw6a3cHyXXmwmxww3mp6sc7+ 8PRL4lNAj01ZaQLeImX2i/Lvc4k6tMaF7m8FLsTmNznLFd2124a6kliyl8TVt2thezE0 44EGqsrsGZocF3BE/eEIjqOs/68cVa8+4PfTuAHSuVJP09cWEmgJAEdzIey7ih8o50G/ 77yA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1706096105; x=1706700905; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=C9dLmB1UBk2lcc6K0p3fcasn7wjRUeWpHrr479fQHwU=; b=WK46SV7WhWJ912BAVJERSbFahNE66UoNFz9jIVEizkLVefyMfzTdtdXSx/NjA4SoE6 bqgVO4nztkh4G3AbojeXm+WN6sy3zc9eBYbG4pW8jgO6M2jfz3/wlSgrxmEcslbxtwzM wWdeqCta8uCQGSiZ2XUnvIWtJkA+6FNE7rq5aVJEh4UgCet9O+1koSjkpml41Oin2Y6C WwPSMEJwEK7aJ2Iik1x6RAnrlsE2nNWKGzC1zwN8p7wxJHTKg1U2PT8VCLvOpUupPDYB +3wZ7qIOsgHNQwlQ4WQxhDU8eKLP39lB3ZHoAKV5SYccT+6cFPYsT4FRla/j+tzGGw88 Q5YQ== X-Gm-Message-State: AOJu0YwamzmT651cOwdhYP1a540I6f+O5JB6DgOcYEme8TOHRGJEPIfn lA0Qy/qKWXszp0EQiw0xYkkfVjdcx62nam+lywT78qIzzAoyfvBH X-Google-Smtp-Source: AGHT+IEt3aCxUIfMjDOEuHL1g4y3s4edufzn/iCQAQWHFDxaD8a0GWx+ZQUtTyZrxSqIBvLi9y7ivA== X-Received: by 2002:a05:6808:3a09:b0:3bd:4df7:db85 with SMTP id gr9-20020a0568083a0900b003bd4df7db85mr1859788oib.69.1706096105325; Wed, 24 Jan 2024 03:35:05 -0800 (PST) Received: from localhost.localdomain ([43.132.141.3]) by smtp.gmail.com with ESMTPSA id c15-20020a63d50f000000b00578b8fab907sm11727820pgg.73.2024.01.24.03.35.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 24 Jan 2024 03:35:04 -0800 (PST) From: Yi Wang X-Google-Original-From: Yi Wang To: seanjc@google.com, pbonzini@redhat.com, tglx@linutronix.de, mingo@redhat.com, bp@alien8.de, dave.hansen@linux.intel.com, x86@kernel.org, hpa@zytor.com, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, wanpengli@tencent.com, foxywang@tencent.com, oliver.upton@linux.dev, maz@kernel.org, anup@brainfault.org, atishp@atishpatra.org, borntraeger@linux.ibm.com, frankja@linux.ibm.com, imbrenda@linux.ibm.com Cc: up2wing@gmail.com Subject: [v3 0/3] KVM: irqchip: synchronize srcu only if needed Date: Wed, 24 Jan 2024 19:34:43 +0800 Message-Id: <20240124113446.2977003-1-foxywang@tencent.com> X-Mailer: git-send-email 2.39.3 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit From: Yi Wang We found that it may cost more than 20 milliseconds very accidentally to enable cap of KVM_CAP_SPLIT_IRQCHIP on a host which has many vms already. The reason is that when vmm(qemu/CloudHypervisor) invokes KVM_CAP_SPLIT_IRQCHIP kvm will call synchronize_srcu_expedited() and might_sleep and kworker of srcu may cost some delay during this period. One way makes sence is setup empty irq routing when creating vm and so that x86/s390 don't need to setup empty/dummy irq routing. Note: I have no s390 machine so the s390 patch has not been tested. Changelog: ---------- v3: - squash setup empty routing function and use of that into one commit - drop the comment in s390 part v2: - setup empty irq routing in kvm_create_vm - don't setup irq routing in x86 KVM_CAP_SPLIT_IRQCHIP - don't setup irq routing in s390 KVM_CREATE_IRQCHIP v1: https://lore.kernel.org/kvm/20240112091128.3868059-1-foxywang@tencent.com/ Yi Wang (3): KVM: setup empty irq routing when create vm KVM: x86: don't setup empty irq routing when KVM_CAP_SPLIT_IRQCHIP KVM: s390: don't setup dummy routing when KVM_CREATE_IRQCHIP arch/s390/kvm/kvm-s390.c | 9 +-------- arch/x86/kvm/irq.h | 1 - arch/x86/kvm/irq_comm.c | 5 ----- arch/x86/kvm/x86.c | 3 --- include/linux/kvm_host.h | 1 + virt/kvm/irqchip.c | 19 +++++++++++++++++++ virt/kvm/kvm_main.c | 4 ++++ 7 files changed, 25 insertions(+), 17 deletions(-) -- 2.39.3