Kernel: Implement a naive version of virtconsole by memcpying to physical page

This patch allocates a physical page for each of the virtqueues and
memcpys to it when receiving a buffer to get a physical, aligned
contiguous buffer as required by the virtio specification.

Co-authored-by: Sahan <sahan.h.fernando@gmail.com>

Kernel/CMakeLists.txt

@@ -220,6 +220,9 @@ set(KERNEL_SOURCES
     TimerQueue.cpp
     UBSanitizer.cpp
     UserOrKernelBuffer.cpp
+    VirtIO/VirtIO.cpp
+    VirtIO/VirtIOConsole.cpp
+    VirtIO/VirtIOQueue.cpp
     VM/AnonymousVMObject.cpp
     VM/ContiguousVMObject.cpp
     VM/InodeVMObject.cpp

Kernel/VirtIO/VirtIO.cpp

@@ -217,6 +217,10 @@ bool VirtIODevice::accept_device_features(u64 device_features, u64 accepted_feat
         accepted_features &= ~(VIRTIO_F_RING_PACKED);
     }
 
+    if (is_feature_set(device_features, VIRTIO_F_IN_ORDER)) {
+        accepted_features |= VIRTIO_F_IN_ORDER;
+    }
+
     dbgln_if(VIRTIO_DEBUG, "{}: Device features: {}", m_class_name, device_features);
     dbgln_if(VIRTIO_DEBUG, "{}: Accepted features: {}", m_class_name, accepted_features);
 
@@ -342,7 +346,7 @@ bool VirtIODevice::finish_init()
 void VirtIODevice::supply_buffer_and_notify(u16 queue_index, const u8* buffer, u32 len, BufferType buffer_type)
 {
     VERIFY(queue_index < m_queue_count);
-    if (get_queue(queue_index).supply_buffer(buffer, len, buffer_type))
+    if (get_queue(queue_index).supply_buffer({}, buffer, len, buffer_type))
         notify_queue(queue_index);
 }
 
@@ -356,7 +360,6 @@ u8 VirtIODevice::isr_status()
 void VirtIODevice::handle_irq(const RegisterState&)
 {
     u8 isr_type = isr_status();
-    dbgln_if(VIRTIO_DEBUG, "{}: Handling interrupt with status: {}", m_class_name, isr_type);
     if (isr_type & DEVICE_CONFIG_INTERRUPT) {
         if (!handle_device_config_change()) {
             set_status_bit(DEVICE_STATUS_FAILED);
@@ -369,6 +372,8 @@ void VirtIODevice::handle_irq(const RegisterState&)
                 return;
         }
     }
+    if (isr_type & ~(QUEUE_INTERRUPT | DEVICE_CONFIG_INTERRUPT))
+        dbgln("{}: Handling interrupt with unknown type: {}", m_class_name, isr_type);
 }
 
 }

Kernel/VirtIO/VirtIO.h

@@ -56,6 +56,7 @@ namespace Kernel {
 
 #define VIRTIO_F_VERSION_1 ((u64)1 << 32)
 #define VIRTIO_F_RING_PACKED ((u64)1 << 34)
+#define VIRTIO_F_IN_ORDER ((u64)1 << 35)
 
 #define VIRTIO_PCI_CAP_COMMON_CFG 1
 #define VIRTIO_PCI_CAP_NOTIFY_CFG 2

Kernel/VirtIO/VirtIOConsole.cpp

@@ -61,9 +61,14 @@ VirtIOConsole::VirtIOConsole(PCI::Address address)
             get_queue(RECEIVEQ).on_data_available = [&]() {
                 dbgln("VirtIOConsole: receive_queue on_data_available");
             };
+            m_receive_region = MM.allocate_contiguous_kernel_region(PAGE_SIZE, "VirtIOConsole Receive", Region::Access::Read | Region::Access::Write);
+            if (m_receive_region) {
+                supply_buffer_and_notify(RECEIVEQ, m_receive_region->physical_page(0)->paddr().as_ptr(), m_receive_region->size(), BufferType::DeviceWritable);
+            }
             get_queue(TRANSMITQ).on_data_available = [&]() {
                 dbgln("VirtIOConsole: send_queue on_data_available");
             };
+            m_transmit_region = MM.allocate_contiguous_kernel_region(PAGE_SIZE, "VirtIOConsole Transmit", Region::Access::Read | Region::Access::Write);
             dbgln("TODO: Populate receive queue with a receive buffer");
         }
     }
@@ -101,17 +106,14 @@ KResultOr<size_t> VirtIOConsole::write(FileDescription&, u64, const UserOrKernel
 {
     if (!size)
         return 0;
+    VERIFY(size <= PAGE_SIZE);
 
-    dbgln("VirtIOConsole: Write with size {}, kernel: {}", size, data.is_kernel_buffer());
+    if (!data.read(m_transmit_region->vaddr().as_ptr(), size)) {
+        return Kernel::KResult((ErrnoCode)-EFAULT);
+    }
+    supply_buffer_and_notify(TRANSMITQ, m_transmit_region->physical_page(0)->paddr().as_ptr(), size, BufferType::DeviceReadable);
 
-    ssize_t nread = data.read_buffered<256>(size, [&](const u8* bytes, size_t bytes_count) {
+    return size;
-        supply_buffer_and_notify(TRANSMITQ, bytes, bytes_count, BufferType::DeviceReadable);
-        return (ssize_t)bytes_count;
-    });
-
-    if (nread < 0)
-        return Kernel::KResult((ErrnoCode)-nread);
-    return (size_t)nread;
 }
 
 }

Kernel/VirtIO/VirtIOConsole.h

@@ -59,8 +59,8 @@ private:
     virtual bool handle_device_config_change() override;
     virtual String device_name() const override { return String::formatted("hvc{}", minor()); }
 
-    VirtIOQueue* m_receive_queue { nullptr };
+    OwnPtr<Region> m_receive_region;
-    VirtIOQueue* m_send_queue { nullptr };
+    OwnPtr<Region> m_transmit_region;
 };
 
 }

Kernel/VirtIO/VirtIOQueue.cpp

@@ -64,15 +64,15 @@ void VirtIOQueue::disable_interrupts()
     m_driver->flags = 1;
 }
 
-bool VirtIOQueue::supply_buffer(const u8* buffer, u32 len, BufferType buffer_type)
+bool VirtIOQueue::supply_buffer(Badge<VirtIODevice>, const u8* buffer, u32 length, BufferType buffer_type)
 {
-    VERIFY(buffer && len > 0);
+    VERIFY(buffer && length > 0);
     VERIFY(m_free_buffers > 0);
 
     auto descriptor_index = m_free_head;
     m_descriptors[descriptor_index].flags = static_cast<u16>(buffer_type);
     m_descriptors[descriptor_index].address = reinterpret_cast<u64>(buffer);
-    m_descriptors[descriptor_index].length = len;
+    m_descriptors[descriptor_index].length = length;
 
     m_free_buffers--;
     m_free_head = (m_free_head + 1) % m_queue_size;

Kernel/VirtIO/VirtIOQueue.h

@@ -26,6 +26,7 @@
 
 #pragma once
 
+#include <AK/Badge.h>
 #include <Kernel/SpinLock.h>
 #include <Kernel/VM/MemoryManager.h>
 
@@ -36,6 +37,8 @@ enum class BufferType {
     DeviceWritable = 2
 };
 
+class VirtIODevice;
+
 class VirtIOQueue {
 public:
     VirtIOQueue(u16 queue_size, u16 notify_offset);
@@ -51,7 +54,7 @@ public:
     PhysicalAddress driver_area() const { return to_physical(m_driver.ptr()); }
     PhysicalAddress device_area() const { return to_physical(m_device.ptr()); }
 
-    bool supply_buffer(const u8* buffer, u32 len, BufferType);
+    bool supply_buffer(Badge<VirtIODevice>, const u8* buffer, u32 length, BufferType);
     bool new_data_available() const;
 
     bool handle_interrupt();

Meta/run.sh

@@ -53,7 +53,10 @@ $SERENITY_EXTRA_QEMU_ARGS
 -drive file=${SERENITY_DISK_IMAGE},format=raw,index=0,media=disk
 -device ich9-ahci
 -usb
--debugcon stdio
+-device virtio-serial
+-chardev stdio,id=stdout,mux=on
+-device virtconsole,chardev=stdout
+-device isa-debugcon,chardev=stdout
 -soundhw pcspk
 -device sb16
 "