From: Pekka Enberg <penberg@kernel.org>
Date: Wed, 5 Jan 2011 16:00:52 +0000 (+0200)
Subject: kvm: Implement virtio blk device vring lookup
X-Git-Tag: next-20110824~3^2~528^2~34
X-Git-Url: https://git.karo-electronics.de/?a=commitdiff_plain;h=1a89ab75dc760350aacaeffafad24c202652b64d;p=karo-tx-linux.git

kvm: Implement virtio blk device vring lookup

This patch changes VIRTIO_PCI_QUEUE_NOTIFY handler to look up the actual I/O
request from the vring. We don't inject anything back to the guest yet.

Signed-off-by: Pekka Enberg <penberg@kernel.org>
---

diff --git a/tools/kvm/blk-virtio.c b/tools/kvm/blk-virtio.c
index 9f98805761ca..f67457a12436 100644
--- a/tools/kvm/blk-virtio.c
+++ b/tools/kvm/blk-virtio.c
@@ -4,6 +4,7 @@
 #include "kvm/virtio_blk.h"
 #include "kvm/virtio_pci.h"
 #include "kvm/ioport.h"
+#include "kvm/util.h"
 #include "kvm/kvm.h"
 #include "kvm/pci.h"
 
@@ -14,8 +15,11 @@
 #define VIRTIO_BLK_QUEUE_SIZE	16
 
 struct virt_queue {
-	uint32_t			pfn;
 	struct vring			vring;
+	uint32_t			pfn;
+	/* The next_avail_ndx field is an index to ->ring of struct vring_avail.
+	   It's where we assume the next request index is at.  */
+	uint16_t			next_avail_ndx;
 };
 
 struct device {
@@ -130,13 +134,30 @@ static bool blk_virtio_out(struct kvm *self, uint16_t port, void *data, int size
 		device.queue_selector	= ioport__read16(data);
 		break;
 	case VIRTIO_PCI_QUEUE_NOTIFY: {
+		struct virtio_blk_outhdr *req;
 		struct virt_queue *queue;
+		struct vring_desc *desc;
 		uint16_t queue_index;
+		uint16_t desc_ndx;
 
 		queue_index		= ioport__read16(data);
 
 		queue			= &device.virt_queues[queue_index];
 
+		desc_ndx		= queue->vring.avail->ring[queue->next_avail_ndx++ % queue->vring.num];
+
+		if (queue->vring.avail->idx != queue->next_avail_ndx) {
+			/*
+			 * The hypervisor and the guest disagree on next index.
+			 */
+			warning("I/O error");
+			break;
+		}
+
+		desc			= &queue->vring.desc[desc_ndx];
+
+		req			= guest_flat_to_host(self, desc->addr);
+
 		kvm__irq_line(self, VIRTIO_BLK_IRQ, 1);
 		break;
 	}