From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 92370364043 for ; Fri, 14 Aug 2026 16:26:05 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786724767; cv=none; b=AZoXt30d0vC2yFzlnkmV48JORDoqKMtbmS+iE7bgttuNB7ZPBF6k6G7DfaQxEQRsikkKNfMaUzfeMiqW1JgS6ukUrOiLFJkPP2m+V2qeD6vbpy0qWCZb5tmK5bV+4tPhOIzciWHze/lhUCN6aN0LbwQZuyj88V2iwYyrwMEBBqs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1786724767; c=relaxed/simple; bh=MTPBOHQFJvYtb+AHcGvBZoYpVjfEnZJvBa0lWB+9N4g=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=COUSpz7vFmaW/sMyJhPz1Tgcl7eDncm9kApj/SysJTaqYNXeoUy7OmMExKRla0yzSjFyLNmS+VqxdVZvEqmxAQYMzNrlGBFuNO8btdwbf5VhJStMs+F6XPIEng8gAJMRVHj2ulRiXX3uUc8SGcG2j7EaX/qTb4gSoVf0/RDzG/I= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=DWgoTJHq; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="DWgoTJHq" Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 175141596; Fri, 14 Aug 2026 09:26:01 -0700 (PDT) Received: from raptor (usa-sjc-mx-foss1.foss.arm.com [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id DC3FF3F632; Fri, 14 Aug 2026 09:26:02 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1786724765; bh=MTPBOHQFJvYtb+AHcGvBZoYpVjfEnZJvBa0lWB+9N4g=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=DWgoTJHqOCjad3GIisdj3ANJUPRHIZpHgG+PT2LH+0PtFsBB96Dx1ZWBk/dLSVIz+ lWRVVd6FJRFZeOnqUQYcjh+8S6wGBxgK1yknbk6JSYoFK6km4YAdjMZ7aIaOXQKrjf JFfOrlqAtKTXo1ga4xKDGaXnVaQRHXeH2UegfyMA= Date: Fri, 14 Aug 2026 17:26:00 +0100 From: Alexandru Elisei To: Sean Christopherson Cc: David Hildenbrand , Mark Rutland , pbonzini@redhat.com, kvm@vger.kernel.org, maz@kernel.org, oupton@kernel.org, joey.gouly@arm.com, seiden@linux.ibm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, fuad.tabba@linux.dev Subject: Re: [RFC PATCH 0/3] KVM: Dirty page logging for guest_memfd-only memslots Message-ID: References: <487aa57c-72ad-453b-971d-ca24a8380429@arm.com> Precedence: bulk X-Mailing-List: kvmarm@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Hi, On Fri, Aug 14, 2026 at 09:04:46AM -0700, Sean Christopherson wrote: > On Fri, Aug 14, 2026, Alexandru Elisei wrote: > > On Fri, Aug 14, 2026 at 06:03:54AM -0700, Sean Christopherson wrote: > > > > That would be in contrast to user space having to guess that page migration on > > > > the current hardware with the current guest_memfd implementation does not > > > > support page migration, to then disable exactly that. > > > > If guest_memfd picks up support for another feature that might lead to > > memory being unmapped from stage 2 without userspace initiating it, would > > you be ok with that feature being gated by another guest_memfd flag? > > Yes, absolutely. FWIW, if I get my way and reclaim is driven by userspace, then > hopefully such a feature never comes along. But if guest_memfd does gain some > feature that triggers invalidations, then yeah, at the very least it would need > to have some knowledge of whether or not the associated VM supports said feature. > > > I get the feeling we're all on the same page, that guest_memfd will support > > a mode where memory isn't unmapped from stage 2, and right now the > > discussion is more about how that will be implemented. > > Ya. That's great, thanks for confirming. Alex