From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-f200.google.com (mail-pf1-f200.google.com [209.85.210.200]) (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 E76624A3D4F for ; Mon, 21 Sep 2026 14:06:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.200 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789999613; cv=none; b=tGL41x+DI6uvxpV729Qd3aiTm0DVhTmD2/KDBmy21SJDXsdOqw0W6pPyxudAP13RPfC8RZORi0jZEXREWdsJWTYGWBSgw9HRXI53VAcNCIa5LIFJ27CIC+6TdufReieugN0/nUgsOSjgN3Vh5bdOJzazxyjfKHHj3xwaVDseH2Q= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789999613; c=relaxed/simple; bh=9DbB+fO0at60/guM4JWrHQTN+GOYW1w48uWzZv0KR1E=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=Dd1S7DEi3FNEWucMb07BaXmAMA6FnLhjy3eIl/foPCRt84HF5kiXHHkYlKlIO735tv2BuXFj4HXxCVj68YBBplCNiwhKVAJdMuQkggLYxV24GRiR91nVn7U4ACnC3PzMsBN8C/WsY9XfYJriGql0ckfBPGlieKRV2IA2whqgEzg= 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=WEMoeZAH; arc=none smtp.client-ip=209.85.210.200 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="WEMoeZAH" Received: by mail-pf1-f200.google.com with SMTP id d2e1a72fcca58-877ef1457aeso2177202b3a.1 for ; Mon, 21 Sep 2026 07:06:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1789999611; x=1790604411; darn=vger.kernel.org; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:from:to:cc:subject:date:message-id:reply-to :content-type; bh=VFozjASAAkxsRNEYPT4IGxp7pcPM6/9Z8WMRlei3dvA=; b=WEMoeZAHwJK/fyROSc9nMcsaz84dgSNKbS7raiQ7bGA4MBDV8KkfSo/2AaCvnzgxRo IAcb2gCsyVNbi547cRbkYkjFC4QCoqJp7gnPEtQDCMJIUFA5FhGHOi+jbJgOn8ekg8Q8 i+CisiD2u970bZnTJwSbSU1snAK9t+sEoySOv8cX71+hbGCKzxcYL2eO6hNdxSKBkU7g NDGqovPt1YKmjn1R7GD/Y8kemkshbO2ti6nqlKNx/mSa010+v4NgHaN7dibjWu3eqU/k w7v+7IDEGkXaCHzeSE/sqnsMII/NulSV3wAXuDlH8Kwgn7gb2dt9uEmxmSOn95qb+vAe U4lA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1789999611; x=1790604411; h=content-type: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:content-type; bh=VFozjASAAkxsRNEYPT4IGxp7pcPM6/9Z8WMRlei3dvA=; b=Q9REPGlz4xIfZ0cOAeoRvu7VTZpOT7BVIAbwHHhmevvN+ZxHZBuz+SQ6o7OKIE/LEe pAzlIbZrncauB1u8hOjg8KAixliEaSNl8pub+qx6RE58eftAITdJcye22vToSHXgLVvD FNYwQX7btZ79hKTqfOsGSyG9hy81IqHMWT1ekpmewR/y/y+w+CPzYNtOnSU46IBXJVPe t9GhtIKWfT3osl854CyGGfMKRH2dya1l7/jHFjCLprhfeAcBKRtbK1S2GtB2osI9yXg0 4l6kW7//VJkc75BlL7lh2Tih1I1wq9RE52aM7r7Cl4zgnjChW/USA4WQCh6FswiBQu6e gh4A== X-Forwarded-Encrypted: i=1; AKwUvBx6dkfYccVEgTtLUZZQG7fs5XhXvvMrXw/Hk2YhvYxLQ+D/6GPfLPRYlPzZC6c16amaH4zNvJUA1LxD8QE=@vger.kernel.org X-Gm-Message-State: AFuF++kw1o/nWwDbgNAIOmUIgFWM3JS6x9jqo8b7w7pN1pChLkXGqdl/ OwSeJG6ChpWdTmA8O53Qv8/6dpFkysWglPwpYdwBlddy4ymuI9IKFczB+3532lv9e4EddZuTewZ MtDLhBA== X-Received: from pfiv14.prod.google.com ([2002:aa7:99ce:0:b0:853:9149:8801]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a00:2990:b0:874:705d:f646 with SMTP id d2e1a72fcca58-874de80468cmr13965258b3a.40.1789999610928; Mon, 21 Sep 2026 07:06:50 -0700 (PDT) Date: Mon, 21 Sep 2026 07:05:22 -0700 In-Reply-To: <20260902211759.2700289-1-seanjc@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260902211759.2700289-1-seanjc@google.com> X-Mailer: git-send-email 2.55.0.1082.g2b9226bbc0-goog Message-ID: <178999884535.741435.243109419293478594.b4-ty@google.com> Subject: Re: [PATCH] KVM: x86/mmu: Always guard rmaps with mmu_lock on PREEMPT_RT=y kernels From: Sean Christopherson To: Sean Christopherson , Paolo Bonzini Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org, David Woodhouse Content-Type: text/plain; charset="utf-8" On Wed, 02 Sep 2026 14:17:59 -0700, Sean Christopherson wrote: > For all intents and purposes, revert KVM's ability to walk rmaps outside of > mmu_lock when running on a realtime (PREEMPT_RT=y) kernel. I.e. don't use > a non-sleepable bit-spinlock to protect rmap entries, as realtime kernels > are highly unlikely to benefit from increased aging throughput and reduced > jitter for memory-overcommitted nested VMs, whereas using a non-sleepable > lock is currently buggy and goes against the spirit of realtime kernels. > > [...] Applied to kvm-x86 mmu, thanks! [1/1] KVM: x86/mmu: Always guard rmaps with mmu_lock on PREEMPT_RT=y kernels https://github.com/kvm-x86/linux/commit/df269c8e097f -- https://github.com/kvm-x86/linux/tree/next