From nobody Tue Feb 10 16:21:46 2026 Delivered-To: importer@patchew.org Authentication-Results: mx.zohomail.com; spf=pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org Return-Path: Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) by mx.zohomail.com with SMTPS id 1763782128144651.3683796215608; Fri, 21 Nov 2025 19:28:48 -0800 (PST) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1vMd6S-0004KL-Qs; Fri, 21 Nov 2025 21:11:57 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1vMcjt-0000fc-3T; Fri, 21 Nov 2025 20:48:37 -0500 Received: from isrv.corpit.ru ([212.248.84.144]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1vMchq-0004oj-IV; Fri, 21 Nov 2025 20:48:32 -0500 Received: from tsrv.corpit.ru (tsrv.tls.msk.ru [192.168.177.2]) by isrv.corpit.ru (Postfix) with ESMTP id 9971E16CA6E; Fri, 21 Nov 2025 21:44:26 +0300 (MSK) Received: from think4mjt.tls.msk.ru (mjtthink.wg.tls.msk.ru [192.168.177.146]) by tsrv.corpit.ru (Postfix) with ESMTP id 54F0E321CAA; Fri, 21 Nov 2025 21:44:35 +0300 (MSK) From: Michael Tokarev To: qemu-devel@nongnu.org Cc: qemu-stable@nongnu.org, Peter Maydell , Akihiko Odaki , Jason Wang , Michael Tokarev Subject: [Stable-10.0.7 51/81] hw/net/e1000e_core: Don't advance desc_offset for NULL buffer RX descriptors Date: Fri, 21 Nov 2025 21:43:50 +0300 Message-ID: <20251121184424.1137669-51-mjt@tls.msk.ru> X-Mailer: git-send-email 2.47.3 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Received-SPF: pass (zohomail.com: domain of gnu.org designates 209.51.188.17 as permitted sender) client-ip=209.51.188.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Received-SPF: pass client-ip=212.248.84.144; envelope-from=mjt@tls.msk.ru; helo=isrv.corpit.ru X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: qemu-devel-bounces+importer=patchew.org@nongnu.org X-ZM-MESSAGEID: 1763782129180018900 Content-Type: text/plain; charset="utf-8" From: Peter Maydell In e1000e_write_packet_to_guest() we don't write data for RX descriptors where the buffer address is NULL (as required by the i82574 datasheet section 7.1.7.2). However, when we do this we still update desc_offset by the amount of data we would have written to the RX descriptor if it had a valid buffer pointer, resulting in our dropping that data entirely. The data sheet is not 100% clear on the subject, but this seems unlikely to be the correct behaviour. Rearrange the null-descriptor logic so that we don't treat these do-nothing descriptors as if we'd really written the data. This both fixes a bug and also is a prerequisite to cleaning up the size calculation logic in the next patch. (Cc to stable largely because it will be needed for the next patch, which fixes a more serious bug.) Cc: qemu-stable@nongnu.org Signed-off-by: Peter Maydell Reviewed-by: Akihiko Odaki Signed-off-by: Jason Wang (cherry picked from commit 6da0c9828194eb21e54fe4264cd29a1b85a29f33) Signed-off-by: Michael Tokarev diff --git a/hw/net/e1000e_core.c b/hw/net/e1000e_core.c index 06657bb3ac..8e93bd3d81 100644 --- a/hw/net/e1000e_core.c +++ b/hw/net/e1000e_core.c @@ -1481,7 +1481,6 @@ e1000e_write_packet_to_guest(E1000ECore *core, struct= NetRxPkt *pkt, PCIDevice *d =3D core->owner; dma_addr_t base; union e1000_rx_desc_union desc; - size_t desc_size; size_t desc_offset =3D 0; size_t iov_ofs =3D 0; =20 @@ -1500,12 +1499,6 @@ e1000e_write_packet_to_guest(E1000ECore *core, struc= t NetRxPkt *pkt, E1000EBAState bastate =3D { { 0 } }; bool is_last =3D false; =20 - desc_size =3D total_size - desc_offset; - - if (desc_size > core->rx_desc_buf_size) { - desc_size =3D core->rx_desc_buf_size; - } - if (e1000e_ring_empty(core, rxi)) { return; } @@ -1519,6 +1512,12 @@ e1000e_write_packet_to_guest(E1000ECore *core, struc= t NetRxPkt *pkt, e1000e_read_rx_descr(core, &desc, ba); =20 if (ba[0]) { + size_t desc_size =3D total_size - desc_offset; + + if (desc_size > core->rx_desc_buf_size) { + desc_size =3D core->rx_desc_buf_size; + } + if (desc_offset < size) { static const uint32_t fcs_pad; size_t iov_copy; @@ -1582,13 +1581,13 @@ e1000e_write_packet_to_guest(E1000ECore *core, stru= ct NetRxPkt *pkt, (const char *) &fcs_pad, e1000x_fcs_len(core->ma= c)); } } + desc_offset +=3D desc_size; + if (desc_offset >=3D total_size) { + is_last =3D true; + } } else { /* as per intel docs; skip descriptors with null buf addr= */ trace_e1000e_rx_null_descriptor(); } - desc_offset +=3D desc_size; - if (desc_offset >=3D total_size) { - is_last =3D true; - } =20 e1000e_write_rx_descr(core, &desc, is_last ? core->rx_pkt : NULL, rss_info, do_ps ? ps_hdr_len : 0, &bastate.writ= ten); --=20 2.47.3