From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f202.google.com (mail-pl1-f202.google.com [209.85.214.202]) (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 B6B4533985 for ; Fri, 21 Nov 2025 00:35:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.202 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763685322; cv=none; b=Ds/Q36T1Y/Ers/MCokrMNlD2snQKibUHKWm3zWsK82GGKkAGY95I81fSewgJkSmFO79w0bHIeXiGG7BdMkVTz061cdVhBBKSPFTAZnsH48u+8lvORDkTsPtY5H0eyNO7RbcHEZyglckGQ0PW86dpTELcSn1PE4V90QtTj3k7GSA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1763685322; c=relaxed/simple; bh=3OChlrmQKATxVpYpuB+oz/ry9O2xVPknjT8fb666zsQ=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=GRkV5CmKuPf/ipAwuqs73qVt1/n1q0TnQlPWTjGBQ4ZP38+rwx2wjCcynYUVhX0i3EIYiebp6xopWjTT0DlKQC3vEq1ErYdVTSJfLw7JJ91eT3EMufe2CI09mBYzlnxrIA2EQ7wwVhTDLCyfY6l/G1BCNtG1RQhAucqNkhb3TQw= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--seanjc.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=cQiUfifF; arc=none smtp.client-ip=209.85.214.202 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="cQiUfifF" Received: by mail-pl1-f202.google.com with SMTP id d9443c01a7336-297df52c960so43235085ad.1 for ; Thu, 20 Nov 2025 16:35:20 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1763685320; x=1764290120; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=cHLDZszmr1TnFL0JXaFkeoodC4elnYIqQNnTDiuHk4M=; b=cQiUfifFiRfglklHqjeHO+rreKtUXzA5XLVLeH0pfzLStshTHFxU905y9P1IWkSj+W Eo47isAQP19ynNwARyJgMb11/A1U6xaTj/vjkMwe4WzGt1FtWIG4Q8YdcrJCjpwTCw0l FFEf/9kAFK6VdiWPeq5FAlV1t8cK3Xq1wcqV89vfhSvxDw4GS/uWf9Vo/E8mE7UxVjpb ZNcfVrYlerKf+kpI9O5x4FlYveIqDBAL15ULciCw1y4iJPWVJII4igcNX6m2tfcYK7Ca x194st4h3XYxFQYbw8fsQSTqZFgvmIBW6v6UKxmBwjuGxv6AoqQNTjnZWBGoKfGzYtVf iUyQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1763685320; x=1764290120; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=cHLDZszmr1TnFL0JXaFkeoodC4elnYIqQNnTDiuHk4M=; b=Q2HfCX9D7kJS4IjB1mNRJhF/Nrs4n+nh/pyXaHmpH+nurnvS9Z7c0oaqcWE+YNrlUE xdVXH3jWiLmExrutATKwcAjFoe7sM9lXl4+Qny8VC0By08npoGmwQ5czrGsyyI4wPxNE leXUsjZMMC0WxS7Uqay2GHpvG1X9q/Xwtv2jPNrpM9itM479k9hwyfFZSV9cYnOgqZWd ZrppOelNNaxoWpoFOBIKei7PL8jFTVyYgSHUd7Fe/meZmjLOgcX5Wqx8I5/kACFptH5W BmoVb7CvOhYqQ0W//QvZ7GPcep8GuIpLejTyHrKUF2kRypnj0ROnJPLufEzvvMkZ8oB5 7g1w== X-Forwarded-Encrypted: i=1; AJvYcCVVibKZPm/PGRNHKm7Be1v0+fJXPmLw2aw3lH1eN8BEIOMudLD892J9JpCZe9Ldwyhppv4=@vger.kernel.org X-Gm-Message-State: AOJu0YxHb2KAajWVzsT3AwbMKoYqE6MhgllODuyfniBw9Lu59dlamXB2 IDL/kQoxLsv7sscdreJ1PJda4+qTUBk+hcppgJK8C4ZB2HrJh2xv+3D/5BcpZWAO6Y6oZvrd9cd kFK/gkw== X-Google-Smtp-Source: AGHT+IHPHoFCt0OdGLSJm5S3SSaQjefM37ka4yIBV1HYsyIu1JyRdfUA1VLCBXD1D2PGR5lTfTIjhoJ7N5E= X-Received: from pjod1.prod.google.com ([2002:a17:90a:8d81:b0:33b:b692:47b0]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:903:907:b0:295:6122:5c42 with SMTP id d9443c01a7336-29b6becc972mr6327525ad.24.1763685320008; Thu, 20 Nov 2025 16:35:20 -0800 (PST) Date: Thu, 20 Nov 2025 16:35:18 -0800 In-Reply-To: <20251110033232.12538-7-kernellwp@gmail.com> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20251110033232.12538-1-kernellwp@gmail.com> <20251110033232.12538-7-kernellwp@gmail.com> Message-ID: Subject: Re: [PATCH 06/10] KVM: Fix last_boosted_vcpu index assignment bug From: Sean Christopherson To: Wanpeng Li Cc: Peter Zijlstra , Ingo Molnar , Thomas Gleixner , Paolo Bonzini , Steven Rostedt , Vincent Guittot , Juri Lelli , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Wanpeng Li Content-Type: text/plain; charset="us-ascii" On Mon, Nov 10, 2025, Wanpeng Li wrote: > From: Wanpeng Li > > From: Wanpeng Li Something might be off in your email scripts. Speaking of email, mostly as an FYI, your @tencent email was bouncing as of last year, and prompted commit b018589013d6 ("MAINTAINERS: Drop Wanpeng Li as a Reviewer for KVM Paravirt support"). > In kvm_vcpu_on_spin(), the loop counter 'i' is incorrectly written to > last_boosted_vcpu instead of the actual vCPU index 'idx'. This causes > last_boosted_vcpu to store the loop iteration count rather than the > vCPU index, leading to incorrect round-robin behavior in subsequent > directed yield operations. > > Fix this by using 'idx' instead of 'i' in the assignment. Fixes: 7e513617da71 ("KVM: Rework core loop of kvm_vcpu_on_spin() to use a single for-loop") Cc: stable@vger.kernel.org Reviewed-by: Sean Christopherson Please, please don't bury fixes like this in a large-ish series, especially in a series that's going to be quite contentious and thus likely to linger on-list for quite some time. It's pretty much dumb luck on my end that I saw this. That said, thank you for fixing my goof :-) Paolo, do you want to grab this for 6.19? Or just wait for 6.20? > Signed-off-by: Wanpeng Li > --- > virt/kvm/kvm_main.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index b7a0ae2a7b20..cde1eddbaa91 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -4026,7 +4026,7 @@ void kvm_vcpu_on_spin(struct kvm_vcpu *me, bool yield_to_kernel_mode) > > yielded = kvm_vcpu_yield_to(vcpu); > if (yielded > 0) { > - WRITE_ONCE(kvm->last_boosted_vcpu, i); > + WRITE_ONCE(kvm->last_boosted_vcpu, idx); > break; > } else if (yielded < 0 && !--try) { > break; > -- > 2.43.0 >