virtio: expose shared memory regions

Signed-off-by: Fotis Xenakis <[email protected]>
Message-Id: <VI1PR03MB4383690324FC94DCDD3B4F53A6F90@VI1PR03MB4383.eurprd03.prod.outlook.com>

drivers/virtio-device.hh

@@ -76,6 +76,8 @@ public:
     virtual u8 read_config(u32 offset) = 0;
     virtual void dump_config() = 0;
 
+    virtual bool get_shm(u8 id, mmioaddr_t &addr, u64 &length) = 0;
+
     virtual bool is_modern() = 0;
     virtual size_t get_vring_alignment() = 0;
 };

drivers/virtio-mmio.hh

@@ -136,6 +136,7 @@ public:
 
     bool parse_config();
 
+    virtual bool get_shm(u8 id, mmioaddr_t &addr, u64 &length) { /* TODO */ return false; }
 private:
     mmio_device_info _dev_info;
     //u64 _id;

drivers/virtio-pci-device.cc

@@ -253,6 +253,30 @@ u8 virtio_modern_pci_device::read_and_ack_isr()
     return _isr_cfg->virtio_conf_readb(0);
 }
 
+// Stores the address and length of the shared memory region identified by @id
+// in @addr and @length respectively. Returns false and doesn't modify @addr and
+// @length if no region with a matching id is found.
+bool virtio_modern_pci_device::get_shm(u8 id, mmioaddr_t &addr, u64 &length)
+{
+    auto cap = std::find_if(_shm_cfgs.cbegin(), _shm_cfgs.cend(),
+        [id, this] (const std::unique_ptr<virtio_capability>& cap) {
+            u8 cap_id = _dev->pci_readb(cap->get_cfg_offset() +
+                offsetof(virtio_pci_cap, id));
+            return cap_id == id;
+        });
+    if (cap == _shm_cfgs.cend()) {
+        return false;
+    }
+
+    auto bar = cap->get()->get_bar();
+    if (!bar->is_mmio()) {
+        return false;
+    }
+    addr = bar->get_mmio();
+    length = bar->get_size();
+    return true;
+}
+
 bool virtio_modern_pci_device::parse_pci_config()
 {
     // Check ABI version

drivers/virtio-pci-device.hh

@@ -116,6 +116,8 @@ public:
     virtual u8 read_and_ack_isr();
 
     virtual bool is_modern() { return false; }
+
+    virtual bool get_shm(u8 id, mmioaddr_t &addr, u64 &length) { return false; }
 protected:
     virtual bool parse_pci_config();
 
@@ -243,6 +245,7 @@ public:
             _bar->writel(_bar_offset + offset, val);
         };
         u32 get_cfg_offset() { return _cfg_offset; }
+        pci::bar* get_bar() { return _bar; }
 
         void print(const char *prefix) {
             virtio_d("%s bar=%d, offset=%x, size=%x", prefix, _bar_no, _bar_offset, _length);
@@ -284,6 +287,7 @@ public:
 
     virtual bool is_modern() { return true; };
 
+    virtual bool get_shm(u8 id, mmioaddr_t &addr, u64 &length);
 protected:
     virtual bool parse_pci_config();
 private: