[pve-devel] [PATCH v2 qemu] add two more stable patches

Fabian Ebner f.ebner at proxmox.com
Tue Jul 19 10:19:31 CEST 2022


For the io_uring patch, it's not very clear which configurations can
trigger it, but it should be rather uncommon. See qemu commit
be6a166fde652589761cf70471bcde623e9bd72a for a bit more information.

Signed-off-by: Fabian Ebner <f.ebner at proxmox.com>
---

Changes from v1:
    * Cherry-pick io_uring patch instead of taking it from mail (was
      applied upstream in the meantime).
    * Include patch for e1000 issue.

 ...20-io_uring-fix-short-read-slow-path.patch | 49 +++++++++++
 ...criptor-status-in-a-separate-operati.patch | 82 +++++++++++++++++++
 debian/patches/series                         |  2 +
 3 files changed, 133 insertions(+)
 create mode 100644 debian/patches/extra/0020-io_uring-fix-short-read-slow-path.patch
 create mode 100644 debian/patches/extra/0021-e1000-set-RX-descriptor-status-in-a-separate-operati.patch

diff --git a/debian/patches/extra/0020-io_uring-fix-short-read-slow-path.patch b/debian/patches/extra/0020-io_uring-fix-short-read-slow-path.patch
new file mode 100644
index 0000000..88cf137
--- /dev/null
+++ b/debian/patches/extra/0020-io_uring-fix-short-read-slow-path.patch
@@ -0,0 +1,49 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Dominique Martinet <dominique.martinet at atmark-techno.com>
+Date: Thu, 30 Jun 2022 10:01:37 +0900
+Subject: [PATCH] io_uring: fix short read slow path
+
+sqeq.off here is the offset to read within the disk image, so obviously
+not 'nread' (the amount we just read), but as the author meant to write
+its current value incremented by the amount we just read.
+
+Normally recent versions of linux will not issue short reads,
+but it can happen so we should fix this.
+
+This lead to weird image corruptions when short read happened
+
+Fixes: 6663a0a33764 ("block/io_uring: implements interfaces for io_uring")
+Link: https://lkml.kernel.org/r/YrrFGO4A1jS0GI0G@atmark-techno.com
+Signed-off-by: Dominique Martinet <dominique.martinet at atmark-techno.com>
+Message-Id: <20220630010137.2518851-1-dominique.martinet at atmark-techno.com>
+Reviewed-by: Hanna Reitz <hreitz at redhat.com>
+Reviewed-by: Stefano Garzarella <sgarzare at redhat.com>
+Signed-off-by: Stefan Hajnoczi <stefanha at redhat.com>
+(cherry-picked from commit c06fc7ce147e57ab493bad9263f1601b8298484b)
+Signed-off-by: Fabian Ebner <f.ebner at proxmox.com>
+---
+ block/io_uring.c | 4 ++--
+ 1 file changed, 2 insertions(+), 2 deletions(-)
+
+diff --git a/block/io_uring.c b/block/io_uring.c
+index 782afdb433..e451e55de0 100644
+--- a/block/io_uring.c
++++ b/block/io_uring.c
+@@ -89,7 +89,7 @@ static void luring_resubmit_short_read(LuringState *s, LuringAIOCB *luringcb,
+     trace_luring_resubmit_short_read(s, luringcb, nread);
+ 
+     /* Update read position */
+-    luringcb->total_read = nread;
++    luringcb->total_read += nread;
+     remaining = luringcb->qiov->size - luringcb->total_read;
+ 
+     /* Shorten qiov */
+@@ -103,7 +103,7 @@ static void luring_resubmit_short_read(LuringState *s, LuringAIOCB *luringcb,
+                       remaining);
+ 
+     /* Update sqe */
+-    luringcb->sqeq.off = nread;
++    luringcb->sqeq.off += nread;
+     luringcb->sqeq.addr = (__u64)(uintptr_t)luringcb->resubmit_qiov.iov;
+     luringcb->sqeq.len = luringcb->resubmit_qiov.niov;
+ 
diff --git a/debian/patches/extra/0021-e1000-set-RX-descriptor-status-in-a-separate-operati.patch b/debian/patches/extra/0021-e1000-set-RX-descriptor-status-in-a-separate-operati.patch
new file mode 100644
index 0000000..ee66fba
--- /dev/null
+++ b/debian/patches/extra/0021-e1000-set-RX-descriptor-status-in-a-separate-operati.patch
@@ -0,0 +1,82 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Ding Hui <dinghui at sangfor.com.cn>
+Date: Wed, 29 Jun 2022 17:40:26 +0800
+Subject: [PATCH] e1000: set RX descriptor status in a separate operation
+
+The code of setting RX descriptor status field maybe work fine in
+previously, however with the update of glibc version, it shows two
+issues when guest using dpdk receive packets:
+
+  1. The dpdk has a certain probability getting wrong buffer_addr
+
+     this impact may be not obvious, such as lost a packet once in
+     a while
+
+  2. The dpdk may consume a packet twice when scan the RX desc queue
+     over again
+
+     this impact will lead a infinite wait in Qemu, since the RDT
+     (tail pointer) be inscreased to equal to RDH by unexpected,
+     which regard as the RX desc queue is full
+
+Write a whole of RX desc with DD flag on is not quite correct, because
+when the underlying implementation of memcpy using XMM registers to
+copy e1000_rx_desc (when AVX or something else CPU feature is usable),
+the bytes order of desc writing to memory is indeterminacy
+
+We can use full-scale test case to reproduce the issue-2 by
+https://github.com/BASM/qemu_dpdk_e1000_test (thanks to Leonid Myravjev)
+
+I also write a POC test case at https://github.com/cdkey/e1000_poc
+which can reproduce both of them, and easy to verify the patch effect.
+
+The hw watchpoint also shows that, when Qemu using XMM related instructions
+writing 16 bytes e1000_rx_desc, concurrent with DPDK using movb
+writing 1 byte status, the final result of writing to memory will be one
+of them, if it made by Qemu which DD flag is on, DPDK will consume it
+again.
+
+Setting DD status in a separate operation, can prevent the impact of
+disorder memory writing by memcpy, also avoid unexpected data when
+concurrent writing status by qemu and guest dpdk.
+
+Links: https://lore.kernel.org/qemu-devel/20200102110504.GG121208@stefanha-x1.localdomain/T/
+
+Reported-by: Leonid Myravjev <asm at asm.pp.ru>
+Cc: Stefan Hajnoczi <stefanha at gmail.com>
+Cc: Paolo Bonzini <pbonzini at redhat.com>
+Cc: Michael S. Tsirkin <mst at redhat.com>
+Cc: qemu-stable at nongnu.org
+Tested-by: Jing Zhang <zhangjing at sangfor.com.cn>
+Reviewed-by: Frank Lee <lifan38153 at sangfor.com.cn>
+Signed-off-by: Ding Hui <dinghui at sangfor.com.cn>
+Signed-off-by: Jason Wang <jasowang at redhat.com>
+(cherry-picked from commit 034d00d4858161e1d4cff82d8d230bce874a04d3)
+Signed-off-by: Fabian Ebner <f.ebner at proxmox.com>
+---
+ hw/net/e1000.c | 5 ++++-
+ 1 file changed, 4 insertions(+), 1 deletion(-)
+
+diff --git a/hw/net/e1000.c b/hw/net/e1000.c
+index f5bc81296d..e26e0a64c1 100644
+--- a/hw/net/e1000.c
++++ b/hw/net/e1000.c
+@@ -979,7 +979,7 @@ e1000_receive_iov(NetClientState *nc, const struct iovec *iov, int iovcnt)
+         base = rx_desc_base(s) + sizeof(desc) * s->mac_reg[RDH];
+         pci_dma_read(d, base, &desc, sizeof(desc));
+         desc.special = vlan_special;
+-        desc.status |= (vlan_status | E1000_RXD_STAT_DD);
++        desc.status &= ~E1000_RXD_STAT_DD;
+         if (desc.buffer_addr) {
+             if (desc_offset < size) {
+                 size_t iov_copy;
+@@ -1013,6 +1013,9 @@ e1000_receive_iov(NetClientState *nc, const struct iovec *iov, int iovcnt)
+             DBGOUT(RX, "Null RX descriptor!!\n");
+         }
+         pci_dma_write(d, base, &desc, sizeof(desc));
++        desc.status |= (vlan_status | E1000_RXD_STAT_DD);
++        pci_dma_write(d, base + offsetof(struct e1000_rx_desc, status),
++                      &desc.status, sizeof(desc.status));
+ 
+         if (++s->mac_reg[RDH] * sizeof(desc) >= s->mac_reg[RDLEN])
+             s->mac_reg[RDH] = 0;
diff --git a/debian/patches/series b/debian/patches/series
index 3850a52..b65e7f1 100644
--- a/debian/patches/series
+++ b/debian/patches/series
@@ -17,6 +17,8 @@ extra/0016-vdpa-Fix-bad-index-calculus-at-vhost_vdpa_get_vring_.patch
 extra/0017-vdpa-Fix-index-calculus-at-vhost_vdpa_svqs_start.patch
 extra/0018-hw-virtio-Replace-g_memdup-by-g_memdup2.patch
 extra/0019-vhost-Fix-element-in-vhost_svq_add-failure.patch
+extra/0020-io_uring-fix-short-read-slow-path.patch
+extra/0021-e1000-set-RX-descriptor-status-in-a-separate-operati.patch
 bitmap-mirror/0001-drive-mirror-add-support-for-sync-bitmap-mode-never.patch
 bitmap-mirror/0002-drive-mirror-add-support-for-conditional-and-always-.patch
 bitmap-mirror/0003-mirror-add-check-for-bitmap-mode-without-bitmap.patch
-- 
2.30.2





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