From e606ff3751e66f73dd7bf9c541609c848991795b Mon Sep 17 00:00:00 2001
From: Liav A <liavalb@gmail.com>
Date: Sat, 4 Sep 2021 19:10:00 +0300
Subject: [PATCH] Kernel/VirtIO: Determine VirtIO device class also with the
 PCI device ID

According to the VirtIO 1.0 specification:
"Non-transitional devices SHOULD have a PCI Device ID in the range
0x1040 to 0x107f. Non-transitional devices SHOULD have a PCI Revision ID
of 1 or higher. Non-transitional devices SHOULD have a PCI Subsystem
Device ID of 0x40 or higher."

It also says that:
"Transitional devices MUST have a PCI Revision ID of 0. Transitional
devices MUST have the PCI Subsystem Device ID matching the Virtio
Device ID, as indicated in section 5. Transitional devices MUST have the
Transitional PCI Device ID in the range 0x1000 to 0x103f."

So, for legacy devices, we know that revision ID in the PCI header won't
be 1, so we probe for PCI_SUBSYSTEM_ID value.
Instead of using the subsystem device ID, we can probe the DEVICE_ID
value directly in case it's not a legacy device.
This should cover all possibilities for identifying VirtIO devices, both
per the specification of 0.9.5, and future revisions from 1.0 onwards.
---
 Kernel/Bus/PCI/IDs.h         |  2 ++
 Kernel/Bus/VirtIO/Device.cpp | 43 +++++++++++++++++++++++++++---------
 2 files changed, 34 insertions(+), 11 deletions(-)

diff --git a/Kernel/Bus/PCI/IDs.h b/Kernel/Bus/PCI/IDs.h
index 531e2d7826a..ddad4992e86 100644
--- a/Kernel/Bus/PCI/IDs.h
+++ b/Kernel/Bus/PCI/IDs.h
@@ -19,6 +19,8 @@ enum VendorID {
 };
 
 enum DeviceID {
+    VirtIONetAdapter = 0x1000,
+    VirtIOBlockDevice = 0x1001,
     VirtIOConsole = 0x1003,
     VirtIOEntropy = 0x1005,
     VirtIOGPU = 0x1050,
diff --git a/Kernel/Bus/VirtIO/Device.cpp b/Kernel/Bus/VirtIO/Device.cpp
index fad217e65e6..fccf363607b 100644
--- a/Kernel/Bus/VirtIO/Device.cpp
+++ b/Kernel/Bus/VirtIO/Device.cpp
@@ -47,18 +47,39 @@ UNMAP_AFTER_INIT void detect()
 
 StringView determine_device_class(const PCI::Address& address)
 {
-    auto subsystem_device_id = PCI::get_subsystem_id(address);
-    switch (subsystem_device_id) {
-    case 1:
-        return "VirtIONetAdapter";
-    case 2:
-        return "VirtIOBlockDevice";
-    case 3:
-        return "VirtIOConsole";
-    case 4:
-        return "VirtIORNG";
+    if (PCI::get_revision_id(address) == 0) {
+        // Note: If the device is a legacy (or transitional) device, therefore,
+        // probe the subsystem ID in the PCI header and figure out the
+        auto subsystem_device_id = PCI::get_subsystem_id(address);
+        switch (subsystem_device_id) {
+        case 1:
+            return "VirtIONetAdapter";
+        case 2:
+            return "VirtIOBlockDevice";
+        case 3:
+            return "VirtIOConsole";
+        case 4:
+            return "VirtIORNG";
+        }
+        dbgln("VirtIO: Unknown subsystem_device_id {}", subsystem_device_id);
+        VERIFY_NOT_REACHED();
     }
-    dbgln("VirtIO: Unknown subsystem_device_id {}", subsystem_device_id);
+
+    auto id = PCI::get_id(address);
+    VERIFY(id.vendor_id == PCI::VendorID::VirtIO);
+    switch (id.device_id) {
+    case PCI::DeviceID::VirtIONetAdapter:
+        return "VirtIONetAdapter";
+    case PCI::DeviceID::VirtIOBlockDevice:
+        return "VirtIOBlockDevice";
+    case PCI::DeviceID::VirtIOConsole:
+        return "VirtIOConsole";
+    case PCI::DeviceID::VirtIOEntropy:
+        return "VirtIORNG";
+    case PCI::DeviceID::VirtIOGPU:
+        return "VirtIOGPU";
+    }
+    dbgln("VirtIO: Unknown device_id {}", id.vendor_id);
     VERIFY_NOT_REACHED();
 }