1 files changed, 34 insertions, 0 deletions

diff --git a/gitlab/issues/target_missing/host_missing/accel_missing/1342.toml b/gitlab/issues/target_missing/host_missing/accel_missing/1342.toml
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index 00000000..5a1845dc
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@@ -0,0 +1,34 @@
+id = 1342
+title = "Default machine setting of force-legacy=true causes problems for any modern VirtIO device using MMIO"
+state = "opened"
+created_at = "2022-11-25T16:31:04.271Z"
+closed_at = "n/a"
+labels = ["Documentation", "device:virtio", "kind::Bug"]
+url = "https://gitlab.com/qemu-project/qemu/-/issues/1342"
+host-os = "Linux"
+host-arch = "All"
+qemu-version = "7.2-rc2 and before"
+guest-os = "Linux"
+guest-arch = "All"
+description = """The default causes problems if you enable any non-legacy VirtIO device which has the VIRTIO_F_VERSION_1 feature bit will not properly read all feature bits. This is because reading VIRTIO_MMIO_VERSION returns VIRT_VERSION_LEGACY which in turn results in the driver not reading all feature bits, e.g. the qtest access:
+
+```
+static uint64_t qvirtio_mmio_get_features(QVirtioDevice *d)
+{
+    QVirtioMMIODevice *dev = container_of(d, QVirtioMMIODevice, vdev);
+    uint64_t lo;
+    uint64_t hi = 0;
+
+    qtest_writel(dev->qts, dev->addr + QVIRTIO_MMIO_HOST_FEATURES_SEL, 0);
+    lo = qtest_readl(dev->qts, dev->addr + QVIRTIO_MMIO_HOST_FEATURES);
+
+    if (dev->version >= 2) {
+        qtest_writel(dev->qts, dev->addr + QVIRTIO_MMIO_HOST_FEATURES_SEL, 1);
+        hi = qtest_readl(dev->qts, dev->addr + QVIRTIO_MMIO_HOST_FEATURES);
+    }
+
+    return (hi << 32) | lo;
+}
+```"""
+reproduce = "n/a"
+additional = """"""