tools/lguest: insert driver references from the 1.0 spec (4.1 Virtio Over PCI)

As a demonstration, the lguest launcher is pretty strict, trying to
catch badly behaved drivers.  Document this precisely.

A good implementation would *NOT* crash the guest when these happened!

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

1 files changed, 57 insertions, 2 deletions

diff --git a/tools/lguest/lguest.c b/tools/lguest/lguest.c
index 10a72b810127..80dc6346030e 100644
--- a/tools/lguest/lguest.c
+++ b/tools/lguest/lguest.c
@@ -1211,7 +1211,12 @@ static bool valid_bar_access(struct device *d,
             && cfg_access->cap.length != 4)
                 return false;
 
-        /* Offset must be multiple of length */
+        /*
+         * 4.1.4.7.2:
+         *
+         *  The driver MUST NOT write a cap.offset which is not a multiple of
+         *  cap.length (ie. all accesses MUST be aligned).
+         */
         if (cfg_access->cap.offset % cfg_access->cap.length != 0)
                 return false;
 
@@ -1342,7 +1347,13 @@ static bool pci_data_iowrite(u16 port, u32 mask, u32 val)
                 return true;
         }
 
-        /* Complain about other writes. */
+        /*
+         * 4.1.4.1:
+         *
+         *  The driver MUST NOT write into any field of the capability
+         *  structure, with the exception of those with cap_type
+         *  VIRTIO_PCI_CAP_PCI_CFG...
+         */
         return false;
 }
 
@@ -1789,6 +1800,12 @@ static void emulate_mmio_write(struct device *d, u32 off, u32 val, u32 mask)
                 restore_vq_config(&d->mmio->cfg, vq);
                 goto write_through16;
         case offsetof(struct virtio_pci_mmio, cfg.queue_size):
+                /*
+                 * 4.1.4.3.2:
+                 *
+                 *  The driver MUST NOT write a value which is not a power of 2
+                 *  to queue_size.
+                 */
                 if (val & (val-1))
                         errx(1, "%s: invalid queue size %u\n", d->name, val);
                 if (d->mmio->cfg.queue_enable)
@@ -1799,11 +1816,22 @@ static void emulate_mmio_write(struct device *d, u32 off, u32 val, u32 mask)
                 errx(1, "%s: attempt to set MSIX vector to %u",
                      d->name, val);
         case offsetof(struct virtio_pci_mmio, cfg.queue_enable):
+                /*
+                 * 4.1.4.3.2:
+                 *
+                 *  The driver MUST NOT write a 0 to queue_enable.
+                 */
                 if (val != 1)
                         errx(1, "%s: setting queue_enable to %u", d->name, val);
                 d->mmio->cfg.queue_enable = val;
                 save_vq_config(&d->mmio->cfg,
                                vq_by_num(d, d->mmio->cfg.queue_select));
+                /*
+                 * 4.1.4.3.2:
+                 *
+                 *  The driver MUST configure the other virtqueue fields before
+                 *  enabling the virtqueue with queue_enable.
+                 */
                 enable_virtqueue(d, vq_by_num(d, d->mmio->cfg.queue_select));
                 goto write_through16;
         case offsetof(struct virtio_pci_mmio, cfg.queue_notify_off):
@@ -1814,6 +1842,12 @@ static void emulate_mmio_write(struct device *d, u32 off, u32 val, u32 mask)
         case offsetof(struct virtio_pci_mmio, cfg.queue_avail_hi):
         case offsetof(struct virtio_pci_mmio, cfg.queue_used_lo):
         case offsetof(struct virtio_pci_mmio, cfg.queue_used_hi):
+                /*
+                 * 4.1.4.3.2:
+                 *
+                 *  The driver MUST configure the other virtqueue fields before
+                 *  enabling the virtqueue with queue_enable.
+                 */
                 if (d->mmio->cfg.queue_enable)
                         errx(1, "%s: changing queue on live device",
                              d->name);
@@ -1837,9 +1871,23 @@ static void emulate_mmio_write(struct device *d, u32 off, u32 val, u32 mask)
                 }
                 /* Fall through... */
         default:
+                /*
+                 * 4.1.4.3.2:
+                 *
+                 *   The driver MUST NOT write to device_feature, num_queues,
+                 *   config_generation or queue_notify_off.
+                 */
                 errx(1, "%s: Unexpected write to offset %u", d->name, off);
         }
 
+
+        /*
+         * 4.1.3.1:
+         *
+         *  The driver MUST access each field using the “natural” access
+         *  method, i.e. 32-bit accesses for 32-bit fields, 16-bit accesses for
+         *  16-bit fields and 8-bit accesses for 8-bit fields.
+         */
 write_through32:
         if (mask != 0xFFFFFFFF) {
                 errx(1, "%s: non-32-bit write to offset %u (%#x)",
@@ -1923,6 +1971,13 @@ static u32 emulate_mmio_read(struct device *d, u32 off, u32 mask)
                         goto read_through8;
         }
 
+        /*
+         * 4.1.3.1:
+         *
+         *  The driver MUST access each field using the “natural” access
+         *  method, i.e. 32-bit accesses for 32-bit fields, 16-bit accesses for
+         *  16-bit fields and 8-bit accesses for 8-bit fields.
+         */
 read_through32:
         if (mask != 0xFFFFFFFF)
                 errx(1, "%s: non-32-bit read to offset %u (%#x)",