From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj1-f74.google.com (mail-pj1-f74.google.com [209.85.216.74]) (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 0257738F232 for ; Wed, 25 Feb 2026 13:55:24 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.74 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772027726; cv=none; b=ZNM/RyDKlqsrfyeSFxAvMnjiGWd7UtlCe/y5aXUcynLAyIrDLzp3r02J0r7foFjZh4O/K8TLukNIQzz0/4wcjM+gyNy9d21ij9H3EpKJ57luYGkiNZkTt3VaM9S8rhOb7bqrr6VmCFTaWeQYKYPB/p+VDoKERajRY6zjpc5Vwh0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772027726; c=relaxed/simple; bh=j8QD+YOKTudOlbEWjrHGAEdh2xgoRTUdHV6Nf6Pmn5U=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=asDpk21VIl/VaO4dF4wy+HmyzkCMl3ftiU6wJsDIWijRJ/sz206EpCWgMP+pK5UL6feNiAh+Y4Wn+eaOSBYTt5ruGsZ+q/OUigjSy6oHCg8rVXaQ4IM8dUKkgAeW/sNo1aWzlOMvb0ruUfFCnnDKaYGVqTW6mMQLCqbCWHTIbWA= 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=DS2dKdsU; arc=none smtp.client-ip=209.85.216.74 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="DS2dKdsU" Received: by mail-pj1-f74.google.com with SMTP id 98e67ed59e1d1-3545b891dd1so38131024a91.1 for ; Wed, 25 Feb 2026 05:55:24 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1772027724; x=1772632524; darn=lists.linux.dev; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=hj5kWs8x13Nc52H5YwkoGAX7bER0Qj5o5LwtSPL8HY8=; b=DS2dKdsUjm0MVmeD9nNNxBtflBOUj7LZklLJbyMgyZnTpKnA9CTYDgJJ7F2lMtxL7/ RtuvAvfY5XRQ/I5PySPbWGyF9GAV+LsgQxsQHLEzC2g0mqbyUr2y8fJMSxPhutai5rYM +TXv2Sz8NUWXPJGQx3xAVJAEkpogaQ43twP0dTMqelUTp2p9k4p0rsNxklKxW01UmVVe 9TOIk5RPGEq/ud+yfUkSEvC1LWUnBQQPeedyt21iM9SMlqNpPsYKcjGzw2H5LLQqwnUW 6Dd3bfTkttv7wj96pARQxrCiA/HP71jOTRSHeXTeK6dNKxOY8N/IOqwnVnNrWhGZ4LWv SnNA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1772027724; x=1772632524; 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=hj5kWs8x13Nc52H5YwkoGAX7bER0Qj5o5LwtSPL8HY8=; b=fZZWJJyNBBPhtuN7XbR+zcI8j108INXuqOwFz1neDAYoMKotD79w+B5kuzXJlEIFXr wbMOXj5VnwyLQCy9sMiU8ckdL7ktlMWou5mO51hLdHMpxBeBijF30tarfvScACRfCEyz MblnMFPY0mS8uk3zp6IHrBJjZ0+xnJQFIzGhTOxyxT0LulbImi5awD7y8azOThgQFI3v D5YZkoODkCelgXoTcxQfERMVxpG3AyhdhVpVQQbn7bWFs8eGQgJ0ywwZLU6Ra+W0/chX +EjPH+94BwIe+msMb/UIcS45fiibstaYeq6+b496Mg0+1WIrgepx+HLpVxZRa1S9J+tQ GhsA== X-Forwarded-Encrypted: i=1; AJvYcCX+2ffpeV+4WknEsjTzzm1DCOBgLTJSE0v/EkjdMTfPnpp15jOyONTOLb2kJ93sedzStktoUMH2NKQ6@lists.linux.dev X-Gm-Message-State: AOJu0YyA6iPwgLh9QquQwhaLCSwxc6mCb//TtqPGf7irPgTnEshlsjqp CTMsGb3Z97VePloCh20sumkvCX4jk/a7LcN19qIHeIa7W18DEMP0bXtlallmisWjLyfTQSqdoDZ lXxlHhQ== X-Received: from pjbee5.prod.google.com ([2002:a17:90a:fc45:b0:34f:96fa:45e]) (user=seanjc job=prod-delivery.src-stubby-dispatcher) by 2002:a17:90b:3147:b0:354:a065:ec3b with SMTP id 98e67ed59e1d1-358ae8d5edbmr14072256a91.27.1772027724097; Wed, 25 Feb 2026 05:55:24 -0800 (PST) Date: Wed, 25 Feb 2026 05:55:22 -0800 In-Reply-To: <20260225075211.3353194-1-aik@amd.com> Precedence: bulk X-Mailing-List: linux-coco@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260225075211.3353194-1-aik@amd.com> Message-ID: Subject: Re: [RFC PATCH kernel] iommufd: Allow mapping from KVM's guest_memfd From: Sean Christopherson To: Alexey Kardashevskiy Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org, Jason Gunthorpe , Kevin Tian , Joerg Roedel , Will Deacon , Robin Murphy , Paolo Bonzini , Steve Sistare , Nicolin Chen , iommu@lists.linux.dev, linux-coco@lists.linux.dev, Dan Williams , Santosh Shukla , "Pratik R . Sampat" , Ackerley Tng , Fuad Tabba , Xu Yilun , "Aneesh Kumar K . V" Content-Type: text/plain; charset="us-ascii" On Wed, Feb 25, 2026, Alexey Kardashevskiy wrote: > For the new guest_memfd type, no additional reference is taken as > pinning is guaranteed by the KVM guest_memfd library. > > There is no KVM-GMEMFD->IOMMUFD direct notification mechanism as > the assumption is that: > 1) page stage change events will be handled by VMM which is going > to call IOMMUFD to remap pages; > 2) shrinking GMEMFD equals to VM memory unplug and VMM is going to > handle it. The VMM is outside of the kernel's effective TCB. Assuming the VMM will always do the right thing is a non-starter.