From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9ED10C77B75 for ; Mon, 22 May 2023 19:50:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235376AbjEVTu3 (ORCPT ); Mon, 22 May 2023 15:50:29 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44324 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235486AbjEVTuF (ORCPT ); Mon, 22 May 2023 15:50:05 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DDE5E9C for ; Mon, 22 May 2023 12:50:04 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 7B4BF62A7A for ; Mon, 22 May 2023 19:50:04 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8F9BBC4339B; Mon, 22 May 2023 19:50:03 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1684785003; bh=7sWHbjLpTk9hTUbwz1b/qNIcH8+0wYvTN+Z5BoxoFVk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=v/ZeVzhgF/oPmQdvJ0VQS5rpqVR+w4UZ7ebgkHDPOZJehHhTPy+7UMWocg5IDzovo 8AVK/TvZMm3q/OMAcdz3XopXGh04YrdKN3ZyJhmMBZp+kN1YhFZ9B0jwYnyzdWy14q MkHINZfPjfEabUZ8q4StB9gwLui6YcMN5hYlHOg8= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, John Starks , Michael Kelley , "Martin K. Petersen" , Sasha Levin Subject: [PATCH 6.3 276/364] scsi: storvsc: Dont pass unused PFNs to Hyper-V host Date: Mon, 22 May 2023 20:09:41 +0100 Message-Id: <20230522190419.621484695@linuxfoundation.org> X-Mailer: git-send-email 2.40.1 In-Reply-To: <20230522190412.801391872@linuxfoundation.org> References: <20230522190412.801391872@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Michael Kelley [ Upstream commit 4e81a6cba517cb33584308a331f14f5e3fec369b ] In a SCSI request, storvsc pre-allocates space for up to MAX_PAGE_BUFFER_COUNT physical frame numbers to be passed to Hyper-V. If the size of the I/O request requires more PFNs, a separate memory area of exactly the correct size is dynamically allocated. But when the pre-allocated area is used, current code always passes MAX_PAGE_BUFFER_COUNT PFNs to Hyper-V, even if fewer are needed. While this doesn't break anything because the additional PFNs are always zero, more bytes than necessary are copied into the VMBus channel ring buffer. This takes CPU cycles and wastes space in the ring buffer. For a typical 4 Kbyte I/O that requires only a single PFN, 248 unnecessary bytes are copied. Fix this by setting the payload_sz based on the actual number of PFNs required, not the size of the pre-allocated space. Reported-by: John Starks Fixes: 8f43710543ef ("scsi: storvsc: Support PAGE_SIZE larger than 4K") Signed-off-by: Michael Kelley Link: https://lore.kernel.org/r/1684171241-16209-1-git-send-email-mikelley@microsoft.com Signed-off-by: Martin K. Petersen Signed-off-by: Sasha Levin --- drivers/scsi/storvsc_drv.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/drivers/scsi/storvsc_drv.c b/drivers/scsi/storvsc_drv.c index d9ce379c4d2e8..e6bc622954cfa 100644 --- a/drivers/scsi/storvsc_drv.c +++ b/drivers/scsi/storvsc_drv.c @@ -1780,7 +1780,7 @@ static int storvsc_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *scmnd) length = scsi_bufflen(scmnd); payload = (struct vmbus_packet_mpb_array *)&cmd_request->mpb; - payload_sz = sizeof(cmd_request->mpb); + payload_sz = 0; if (scsi_sg_count(scmnd)) { unsigned long offset_in_hvpg = offset_in_hvpage(sgl->offset); @@ -1789,10 +1789,10 @@ static int storvsc_queuecommand(struct Scsi_Host *host, struct scsi_cmnd *scmnd) unsigned long hvpfn, hvpfns_to_add; int j, i = 0, sg_count; - if (hvpg_count > MAX_PAGE_BUFFER_COUNT) { + payload_sz = (hvpg_count * sizeof(u64) + + sizeof(struct vmbus_packet_mpb_array)); - payload_sz = (hvpg_count * sizeof(u64) + - sizeof(struct vmbus_packet_mpb_array)); + if (hvpg_count > MAX_PAGE_BUFFER_COUNT) { payload = kzalloc(payload_sz, GFP_ATOMIC); if (!payload) return SCSI_MLQUEUE_DEVICE_BUSY; -- 2.39.2