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Tsirkin" , Jason Wang Cc: Xuan Zhuo , =?UTF-8?q?Eugenio=20P=C3=A9rez?= , virtualization@lists.linux.dev, Andrew Stellman Subject: [PATCH 1/4] virtio-mmio: wait for status readback after reset Date: Tue, 7 Apr 2026 08:39:01 -0400 Message-ID: <20260407123904.6390-2-astellman@stellman-greene.com> X-Mailer: git-send-email 2.50.1 In-Reply-To: <20260407123904.6390-1-astellman@stellman-greene.com> References: <20260407123904.6390-1-astellman@stellman-greene.com> Precedence: bulk X-Mailing-List: virtualization@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit The virtio specification requires that after writing 0 to the status register, the driver must wait until the device has actually completed the reset (status reads back as 0) before proceeding. vm_reset() writes 0 but returns immediately without confirming the device has reset. Add a poll loop matching the pattern already used in virtio-pci's vp_reset(), which calls msleep(1) in a loop until the status register reads 0. Signed-off-by: Andrew Stellman --- drivers/virtio/virtio_mmio.c | 3 +++ 1 file changed, 3 insertions(+) diff --git a/drivers/virtio/virtio_mmio.c b/drivers/virtio/virtio_mmio.c index 595c227..a477977 100644 --- a/drivers/virtio/virtio_mmio.c +++ b/drivers/virtio/virtio_mmio.c @@ -56,6 +56,7 @@ #include #include +#include #include #include #include @@ -254,6 +255,8 @@ static void vm_reset(struct virtio_device *vdev) /* 0 status means a reset. */ writel(0, vm_dev->base + VIRTIO_MMIO_STATUS); + while (readl(vm_dev->base + VIRTIO_MMIO_STATUS)) + msleep(1); } -- 2.34.1