From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id EC90C1A9F82 for ; Sat, 20 Jun 2026 05:06:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781931963; cv=none; b=vAb8OA5W9I5wKPSWTebDmcL0tNLurCk3FDwK7PY6WCSuS4lX7HCXo1KrEzEO9ecJN3oKBIvbMFpJNv15WvOfnbfzvQasaqKiK9QYs4SHB5XOBMHelLu1/HpplZNWRrxFmS98oyLB4ASW/Wl/ZepNwD8GBQojgUXjtTG863QAyeM= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1781931963; c=relaxed/simple; bh=LGoovJRM/Ms0TIqQ/cWFmXwCqudJ4LAo2WIXZtcjJ64=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=XPUst/M+ONPlcqWuugqD1AVpw73DWSAJvceAQp7nVRDHtv4mC41Nxu7AfKg+km6gJe3T/Z477ajHz+OioxpFta+7bccuSTNK9grQybOHL7ePnv2os7s59iDLGVnAeDhKAk4JY0X6xbIoVP5AggNIntZhmb7fG8L0VBwbvJdrc+8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=sjX8kIpR; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="sjX8kIpR" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 02C871F000E9; Sat, 20 Jun 2026 05:06:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linuxfoundation.org; s=korg; t=1781931962; bh=WK8UnMA+KGe3WYmTlWEGp+/drI9scmiSoxdlJ5oGPJE=; h=Date:From:To:Cc:Subject:References:In-Reply-To; b=sjX8kIpR4uWG0sxZpwL8L2kxuU6yKvmkHqJj7+MplPNOi6gAurFAsH5ZgJgiZPKFX mfebW5S2UIXqfWnf3MQTpI+sn7w0SXqCibuP07stfs2R6tRB9Hf+0I65oO7yBrrLDA YtrixefwVz3R68ESV5m/zs5gQtLN4SZMSyuBnZFo= Date: Sat, 20 Jun 2026 07:04:55 +0200 From: Greg KH To: Rishi Chhibber Cc: arnd@arndb.de, linux-kernel@vger.kernel.org, ajay.kaher@broadcom.com, alexey.makhalov@broadcom.com, vamsi-krishna.brahmajosyula@broadcom.com, yin.ding@broadcom.com, tapas.kundu@broadcom.com Subject: Re: [PATCH] misc: vmw_zerocopy: Add VMware zero-copy buffer sharing driver Message-ID: <2026062044-crib-commodore-bea7@gregkh> References: <20260617203125.397427-1-rishi.chhibber@broadcom.com> <20260619182710.2498154-1-rishi.chhibber@broadcom.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260619182710.2498154-1-rishi.chhibber@broadcom.com> On Fri, Jun 19, 2026 at 11:27:10AM -0700, Rishi Chhibber wrote: > This driver implements a misc character device (/dev/vmw_zc) that allows > guest userspace applications to share pinned memory buffers with a > VMware hypervisor-side peer using the VMCI datagram interface. > > The driver pins user pages via get_user_pages_fast(), transmits their > physical page frame numbers to the hypervisor peer over VMCI, and avoids > an intermediate copy between the guest workload VM and the hypervisor. > > The hypervisor-side peer for this interface only speaks VMCI; there is no > virtio backend implemented on the VMware host for it. The closest > existing upstream transport, vsock (virtio-vsock), provides a socket > bytestream/datagram abstraction and does not expose a way to hand a set > of pinned guest page frame numbers to the host for true zero-copy > access; it would still require copying the payload through the socket. > This driver's purpose is specifically to pin guest pages and pass their > PFNs to the host so the payload is never copied. It also supports > bundling multiple buffers in a single request, which is required for the > all-or-none semantics of page-level zero-copy transfers. > > Signed-off-by: Rishi Chhibber > --- > Changes in v3: There is no "v3" in the subject line :(