From nobody Fri Dec 26 05:06:08 2025 Received: from mail-yb1-f201.google.com (mail-yb1-f201.google.com [209.85.219.201]) (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 5E4DE944F for ; Wed, 10 Jan 2024 00:39:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="eKOR2f2l" Received: by mail-yb1-f201.google.com with SMTP id 3f1490d57ef6-dbedc37d66cso3176653276.3 for ; Tue, 09 Jan 2024 16:39:49 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1704847188; x=1705451988; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:from:to:cc:subject:date:message-id:reply-to; bh=D4tvOVGYXZj07Mh3AbKScJlIRDF+gPUSkrxYwSocJBU=; b=eKOR2f2lty8vnakGYTNRzUplaVRRnXqedSIK3sreykitPI9o67BRVaBrxSgFLagtTX E7idXtH06VESju55/7pn2PyR9wabHnLKrg5hFMvFSPAUBTkBm0GI+QypdLjs+qCwUrkd Tr00OJcLOoRFHnPquwThbMR409+RjGDPa2clm160YkiOxvc3vjm8NNC0mPmNBFOulQpN pUunmH8MValLTymY4F4IUS2XDYXCzQ/GV6a4oGQ/P7ko0du8/zY5NfxmxWjypNQDV4Pf AxCYZDRc/nO9+8OaCOAOu+L839lOI1VXgGoH5etbh4FrviDVDQGYl4DsLckswoz7/7vG Y7hA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1704847188; x=1705451988; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:reply-to:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=D4tvOVGYXZj07Mh3AbKScJlIRDF+gPUSkrxYwSocJBU=; b=X8oxZisewDyqgKX6YWgr160pa2FmWJjBUw+EgFPpvKJHnX/XuaQ5PZnVWBBp7dtO4F NUD7K3roSQibAlh/2Hn/sO/+xCaSYP+XTzyATCkG4do2TNDSZhSXYR4hK4GARZf4SLfg NfUHubyYduzrG+XlDS55Dd7eiAiE3hH9sE/9vwo7kCFobU3Z4/OS6ysrENOMs16ZwS0s SXN8wk+bfZqhRYhbF3sYY/YvFIduBa1o/xY6Jm2XJtURMAuaeWwYM+dNaGf4ZMniPRwf LZudMEQItmDKCSPSsCABSGfWR8eVdbqOvgFp8YJr0J0loU6csMvuzUQpk1bS70Pk9Xkm Oiwg== X-Gm-Message-State: AOJu0Yxbcxz/pLmLDbdGawDJ7rgRii8JUbbz5Aei/INgbRM/B5d6fYd1 hxsYA4WgGQ2B8v24Vd/xs5cOBk9SEp2G6eP7fw== X-Google-Smtp-Source: AGHT+IFuJjrM+MDgoFfdbmi17tmfVjaKhqfjfC+jS0/h9snOExZty5PrssXn0VPV/aGi9MJjghmUZutE7hA= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a25:8749:0:b0:dbe:d426:c456 with SMTP id e9-20020a258749000000b00dbed426c456mr6512ybn.4.1704847188423; Tue, 09 Jan 2024 16:39:48 -0800 (PST) Reply-To: Sean Christopherson Date: Tue, 9 Jan 2024 16:39:38 -0800 In-Reply-To: <20240110003938.490206-1-seanjc@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20240110003938.490206-1-seanjc@google.com> X-Mailer: git-send-email 2.43.0.472.g3155946c3a-goog Message-ID: <20240110003938.490206-5-seanjc@google.com> Subject: [PATCH 4/4] KVM: Add a comment explaining the directed yield pending interrupt logic From: Sean Christopherson To: Sean Christopherson , Paolo Bonzini Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, Like Xu Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" Add a comment to explain why KVM treats vCPUs with pending interrupts as in-kernel when a vCPU wants to yield to a vCPU that was preempted while running in kernel mode. Signed-off-by: Sean Christopherson --- virt/kvm/kvm_main.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 6326852bfb3d..4a9e7513c585 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -4089,6 +4089,13 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me, bool yiel= d_to_kernel_mode) continue; if (kvm_vcpu_is_blocking(vcpu) && !vcpu_dy_runnable(vcpu)) continue; + + /* + * Treat the target vCPU as being in-kernel if it has a + * pending interrupt, as the vCPU trying to yield may + * be spinning waiting on IPI delivery, i.e. the target + * vCPU is in-kernel for the purposes of directed yield. + */ if (READ_ONCE(vcpu->preempted) && yield_to_kernel_mode && !kvm_arch_dy_has_pending_interrupt(vcpu) && !kvm_arch_vcpu_preempted_in_kernel(vcpu)) --=20 2.43.0.472.g3155946c3a-goog