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Kernel: Implement buffer flipping for VirtIOGPU framebuffers

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This solves tearing issues and improves performance when updating the
VirtIOGPU framebuffers.
This commit is contained in:
Tom 2021-07-03 20:42:38 -06:00 committed by Andreas Kling
parent 6e792553f2
commit 7fdf902e4a
Notes: sideshowbarker 2024-07-18 10:25:51 +09:00 
Author: https://github.com/tomuta
Commit: https://github.com/SerenityOS/serenity/commit/7fdf902e4a7
Pull-request: https://github.com/SerenityOS/serenity/pull/8409
Reviewed-by: https://github.com/ccapitalK
7 changed files with 148 additions and 65 deletions
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11
Kernel/Graphics/FramebufferDevice.cpp
View File

@ -215,6 +215,17 @@ int FramebufferDevice::ioctl(FileDescription&, unsigned request, FlatPtr arg)
return -EFAULT;
return 0;
}
case FB_IOCTL_GET_BUFFER_OFFSET: {
FBBufferOffset buffer_offset;
if (!copy_from_user(&buffer_offset, (FBBufferOffset*)arg))
return -EFAULT;
if (buffer_offset.buffer_index != 0 && buffer_offset.buffer_index != 1)
return -EINVAL;
buffer_offset.offset = (size_t)buffer_offset.buffer_index * m_framebuffer_pitch * m_framebuffer_height;
if (!copy_to_user((FBBufferOffset*)arg, &buffer_offset))
return -EFAULT;
return 0;
}
case FB_IOCTL_FLUSH_BUFFERS:
return -ENOTSUP;
default:

137
Kernel/Graphics/VirtIOGPU/VirtIOFrameBufferDevice.cpp
View File

@ -15,10 +15,8 @@ VirtIOFrameBufferDevice::VirtIOFrameBufferDevice(VirtIOGPU& virtio_gpu, VirtIOGP
, m_gpu(virtio_gpu)
, m_scanout(scanout)
{
if (display_info().enabled) {
Locker locker(m_gpu.operation_lock());
if (display_info().enabled)
create_framebuffer();
}
}
VirtIOFrameBufferDevice::~VirtIOFrameBufferDevice()
@ -27,39 +25,53 @@ VirtIOFrameBufferDevice::~VirtIOFrameBufferDevice()
void VirtIOFrameBufferDevice::create_framebuffer()
{
auto& info = display_info();
size_t buffer_length = page_round_up(calculate_framebuffer_size(info.rect.width, info.rect.height));
// First delete any existing framebuffers to free the memory first
m_framebuffer = nullptr;
m_framebuffer_sink_vmobject = nullptr;
// 1. Allocate frame buffer
m_framebuffer = MM.allocate_kernel_region(buffer_length, String::formatted("VirtGPU FrameBuffer #{}", m_scanout.value()), Region::Access::Read | Region::Access::Write, AllocationStrategy::AllocateNow);
// Allocate frame buffer for both front and back
auto& info = display_info();
m_buffer_size = calculate_framebuffer_size(info.rect.width, info.rect.height);
m_framebuffer = MM.allocate_kernel_region(m_buffer_size * 2, String::formatted("VirtGPU FrameBuffer #{}", m_scanout.value()), Region::Access::Read | Region::Access::Write, AllocationStrategy::AllocateNow);
auto write_sink_page = MM.allocate_user_physical_page(MemoryManager::ShouldZeroFill::No).release_nonnull();
auto num_needed_pages = m_framebuffer->vmobject().page_count();
NonnullRefPtrVector<PhysicalPage> pages;
for (auto i = 0u; i < num_needed_pages; ++i) {
pages.append(write_sink_page);
}
m_framebuffer_sink_vmobject = AnonymousVMObject::create_with_physical_pages(move(pages));
// 2. Create BUFFER using VIRTIO_GPU_CMD_RESOURCE_CREATE_2D
if (m_resource_id.value() != 0)
m_gpu.delete_resource(m_resource_id);
m_resource_id = m_gpu.create_2d_resource(info.rect);
Locker locker(m_gpu.operation_lock());
m_current_buffer = &buffer_from_index(m_last_set_buffer_index.load());
create_buffer(m_main_buffer, 0, m_buffer_size);
create_buffer(m_back_buffer, m_buffer_size, m_buffer_size);
}
// 3. Attach backing storage using VIRTIO_GPU_CMD_RESOURCE_ATTACH_BACKING
m_gpu.ensure_backing_storage(*m_framebuffer, buffer_length, m_resource_id);
// 4. Use VIRTIO_GPU_CMD_SET_SCANOUT to link the framebuffer to a display scanout.
m_gpu.set_scanout_resource(m_scanout.value(), m_resource_id, info.rect);
// 5. Render our test pattern
draw_ntsc_test_pattern();
// 6. Use VIRTIO_GPU_CMD_TRANSFER_TO_HOST_2D to update the host resource from guest memory.
transfer_framebuffer_data_to_host(info.rect);
// 7. Use VIRTIO_GPU_CMD_RESOURCE_FLUSH to flush the updated resource to the display.
flush_displayed_image(info.rect);
void VirtIOFrameBufferDevice::create_buffer(Buffer& buffer, size_t framebuffer_offset, size_t framebuffer_size)
{
buffer.framebuffer_offset = framebuffer_offset;
buffer.framebuffer_data = m_framebuffer->vaddr().as_ptr() + framebuffer_offset;
auto& info = display_info();
// 1. Create BUFFER using VIRTIO_GPU_CMD_RESOURCE_CREATE_2D
if (buffer.resource_id.value() != 0)
m_gpu.delete_resource(buffer.resource_id);
buffer.resource_id = m_gpu.create_2d_resource(info.rect);
// 2. Attach backing storage using VIRTIO_GPU_CMD_RESOURCE_ATTACH_BACKING
m_gpu.ensure_backing_storage(*m_framebuffer, buffer.framebuffer_offset, framebuffer_size, buffer.resource_id);
// 3. Use VIRTIO_GPU_CMD_SET_SCANOUT to link the framebuffer to a display scanout.
if (&buffer == m_current_buffer)
m_gpu.set_scanout_resource(m_scanout.value(), buffer.resource_id, info.rect);
// 4. Render our test pattern
draw_ntsc_test_pattern(buffer);
// 5. Use VIRTIO_GPU_CMD_TRANSFER_TO_HOST_2D to update the host resource from guest memory.
transfer_framebuffer_data_to_host(info.rect, buffer);
// 6. Use VIRTIO_GPU_CMD_RESOURCE_FLUSH to flush the updated resource to the display.
if (&buffer == m_current_buffer)
flush_displayed_image(info.rect, buffer);
info.enabled = 1;
}
@ -74,25 +86,19 @@ VirtIOGPURespDisplayInfo::VirtIOGPUDisplayOne& VirtIOFrameBufferDevice::display_
return m_gpu.display_info(m_scanout);
}
size_t VirtIOFrameBufferDevice::size_in_bytes() const
void VirtIOFrameBufferDevice::transfer_framebuffer_data_to_host(VirtIOGPURect const& rect, Buffer& buffer)
{
auto& info = display_info();
return info.rect.width * info.rect.height * sizeof(u32);
m_gpu.transfer_framebuffer_data_to_host(m_scanout, rect, buffer.resource_id);
}
void VirtIOFrameBufferDevice::flush_dirty_window(VirtIOGPURect const& dirty_rect)
void VirtIOFrameBufferDevice::flush_dirty_window(VirtIOGPURect const& dirty_rect, Buffer& buffer)
{
m_gpu.flush_dirty_window(m_scanout, dirty_rect, m_resource_id);
m_gpu.flush_dirty_window(m_scanout, dirty_rect, buffer.resource_id);
}
void VirtIOFrameBufferDevice::transfer_framebuffer_data_to_host(VirtIOGPURect const& rect)
void VirtIOFrameBufferDevice::flush_displayed_image(VirtIOGPURect const& dirty_rect, Buffer& buffer)
{
m_gpu.transfer_framebuffer_data_to_host(m_scanout, rect, m_resource_id);
}
void VirtIOFrameBufferDevice::flush_displayed_image(VirtIOGPURect const& dirty_rect)
{
m_gpu.flush_displayed_image(dirty_rect, m_resource_id);
m_gpu.flush_displayed_image(dirty_rect, buffer.resource_id);
}
bool VirtIOFrameBufferDevice::try_to_set_resolution(size_t width, size_t height)
@ -114,13 +120,23 @@ bool VirtIOFrameBufferDevice::try_to_set_resolution(size_t width, size_t height)
return true;
}
void VirtIOFrameBufferDevice::set_buffer(int buffer_index)
{
auto& buffer = buffer_index == 0 ? m_main_buffer : m_back_buffer;
Locker locker(m_gpu.operation_lock());
if (&buffer == m_current_buffer)
return;
m_current_buffer = &buffer;
m_gpu.set_scanout_resource(m_scanout.value(), buffer.resource_id, display_info().rect);
}
int VirtIOFrameBufferDevice::ioctl(FileDescription&, unsigned request, FlatPtr arg)
{
REQUIRE_PROMISE(video);
switch (request) {
case FB_IOCTL_GET_SIZE_IN_BYTES: {
auto* out = (size_t*)arg;
size_t value = size_in_bytes();
size_t value = m_buffer_size * 2;
if (!copy_to_user(out, &value))
return -EFAULT;
return 0;
@ -147,28 +163,53 @@ int VirtIOFrameBufferDevice::ioctl(FileDescription&, unsigned request, FlatPtr a
return -EFAULT;
return 0;
}
case FB_IOCTL_SET_BUFFER: {
auto buffer_index = (int)arg;
if (!is_valid_buffer_index(buffer_index))
return -EINVAL;
if (m_last_set_buffer_index.exchange(buffer_index) != buffer_index && m_are_writes_active)
set_buffer(buffer_index);
return 0;
}
case FB_IOCTL_FLUSH_BUFFERS: {
FBFlushRects user_flush_rects;
if (!copy_from_user(&user_flush_rects, (FBFlushRects*)arg))
return -EFAULT;
if (user_flush_rects.buffer_index != 0)
if (!is_valid_buffer_index(user_flush_rects.buffer_index))
return -EINVAL;
if (Checked<unsigned>::multiplication_would_overflow(user_flush_rects.count, sizeof(FBRect)))
return -EFAULT;
if (m_are_writes_active && user_flush_rects.count > 0) {
auto& buffer = buffer_from_index(user_flush_rects.buffer_index);
Locker locker(m_gpu.operation_lock());
for (unsigned i = 0; i < user_flush_rects.count; i++) {
FBRect user_dirty_rect;
if (!copy_from_user(&user_dirty_rect, &user_flush_rects.rects[i]))
return -EFAULT;
if (m_are_writes_active) {
VirtIOGPURect dirty_rect {
.x = user_dirty_rect.x,
.y = user_dirty_rect.y,
.width = user_dirty_rect.width,
.height = user_dirty_rect.height
};
flush_dirty_window(dirty_rect);
transfer_framebuffer_data_to_host(dirty_rect, buffer);
if (&buffer == m_current_buffer) {
// Flushing directly to screen
flush_displayed_image(dirty_rect, buffer);
}
}
}
return 0;
}
case FB_IOCTL_GET_BUFFER_OFFSET: {
FBBufferOffset buffer_offset;
if (!copy_from_user(&buffer_offset, (FBBufferOffset*)arg))
return -EFAULT;
if (!is_valid_buffer_index(buffer_offset.buffer_index))
return -EINVAL;
buffer_offset.offset = (size_t)buffer_offset.buffer_index * m_buffer_size;
if (!copy_to_user((FBBufferOffset*)arg, &buffer_offset))
return -EFAULT;
return 0;
}
default:
@ -181,9 +222,9 @@ KResultOr<Region*> VirtIOFrameBufferDevice::mmap(Process& process, FileDescripti
REQUIRE_PROMISE(video);
if (!shared)
return ENODEV;
if (offset != 0)
if (offset != 0 || !m_framebuffer)
return ENXIO;
if (range.size() != page_round_up(size_in_bytes()))
if (range.size() > m_framebuffer->size())
return EOVERFLOW;
// We only allow one process to map the region
@ -217,24 +258,28 @@ void VirtIOFrameBufferDevice::deactivate_writes()
region->set_vmobject(vm_object.release_nonnull());
region->remap();
}
set_buffer(0);
clear_to_black(buffer_from_index(0));
}
void VirtIOFrameBufferDevice::activate_writes()
{
m_are_writes_active = true;
auto last_set_buffer_index = m_last_set_buffer_index.load();
if (m_userspace_mmap_region) {
auto* region = m_userspace_mmap_region.unsafe_ptr();
region->set_vmobject(m_framebuffer->vmobject());
region->remap();
}
set_buffer(last_set_buffer_index);
}
void VirtIOFrameBufferDevice::clear_to_black()
void VirtIOFrameBufferDevice::clear_to_black(Buffer& buffer)
{
auto& info = display_info();
size_t width = info.rect.width;
size_t height = info.rect.height;
u8* data = m_framebuffer->vaddr().as_ptr();
u8* data = buffer.framebuffer_data;
for (size_t i = 0; i < width * height; ++i) {
data[4 * i + 0] = 0x00;
data[4 * i + 1] = 0x00;
@ -243,7 +288,7 @@ void VirtIOFrameBufferDevice::clear_to_black()
}
}
void VirtIOFrameBufferDevice::draw_ntsc_test_pattern()
void VirtIOFrameBufferDevice::draw_ntsc_test_pattern(Buffer& buffer)
{
static constexpr u8 colors[12][4] = {
{ 0xff, 0xff, 0xff, 0xff }, // White
@ -262,7 +307,7 @@ void VirtIOFrameBufferDevice::draw_ntsc_test_pattern()
auto& info = display_info();
size_t width = info.rect.width;
size_t height = info.rect.height;
u8* data = m_framebuffer->vaddr().as_ptr();
u8* data = buffer.framebuffer_data;
// Draw NTSC test card
for (size_t y = 0; y < height; ++y) {
for (size_t x = 0; x < width; ++x) {
@ -302,7 +347,7 @@ void VirtIOFrameBufferDevice::draw_ntsc_test_pattern()
u8* VirtIOFrameBufferDevice::framebuffer_data()
{
return m_framebuffer->vaddr().as_ptr();
return m_current_buffer->framebuffer_data;
}
}

40
Kernel/Graphics/VirtIOGPU/VirtIOFrameBufferDevice.h
View File

@ -14,6 +14,13 @@
namespace Kernel::Graphics {
class VirtIOFrameBufferDevice final : public BlockDevice {
friend class VirtIOGPUConsole;
struct Buffer {
size_t framebuffer_offset { 0 };
u8* framebuffer_data { nullptr };
VirtIOGPUResourceID resource_id { 0 };
};
public:
VirtIOFrameBufferDevice(VirtIOGPU& virtio_gpu, VirtIOGPUScanoutID);
virtual ~VirtIOFrameBufferDevice() override;
@ -22,23 +29,23 @@ public:
virtual void activate_writes();
bool try_to_set_resolution(size_t width, size_t height);
void clear_to_black();
void clear_to_black(Buffer&);
size_t width() const { return display_info().rect.width; }
size_t height() const { return display_info().rect.height; }
size_t pitch() const { return display_info().rect.width * 4; }
size_t size_in_bytes() const;
static size_t calculate_framebuffer_size(size_t width, size_t height)
{
return sizeof(u32) * width * height;
// VirtIO resources can only map on page boundaries!
return page_round_up(sizeof(u32) * width * height);
}
void flush_dirty_window(VirtIOGPURect const&);
void transfer_framebuffer_data_to_host(VirtIOGPURect const&);
void flush_displayed_image(VirtIOGPURect const&);
void flush_dirty_window(VirtIOGPURect const&, Buffer&);
void transfer_framebuffer_data_to_host(VirtIOGPURect const&, Buffer&);
void flush_displayed_image(VirtIOGPURect const&, Buffer&);
void draw_ntsc_test_pattern();
void draw_ntsc_test_pattern(Buffer&);
u8* framebuffer_data();
@ -49,6 +56,8 @@ private:
VirtIOGPURespDisplayInfo::VirtIOGPUDisplayOne& display_info();
void create_framebuffer();
void create_buffer(Buffer&, size_t, size_t);
void set_buffer(int);
virtual int ioctl(FileDescription&, unsigned request, FlatPtr arg) override;
virtual KResultOr<Region*> mmap(Process&, FileDescription&, const Range&, u64 offset, int prot, bool shared) override;
@ -61,11 +70,26 @@ private:
virtual mode_t required_mode() const override { return 0666; }
virtual String device_name() const override { return String::formatted("fb{}", minor()); }
static bool is_valid_buffer_index(int buffer_index)
{
return buffer_index == 0 || buffer_index == 1;
}
Buffer& buffer_from_index(int buffer_index)
{
return buffer_index == 0 ? m_main_buffer : m_back_buffer;
}
Buffer& current_buffer() const { return *m_current_buffer; }
VirtIOGPU& m_gpu;
const VirtIOGPUScanoutID m_scanout;
VirtIOGPUResourceID m_resource_id { 0 };
Buffer* m_current_buffer { nullptr };
Atomic<int, AK::memory_order_relaxed> m_last_set_buffer_index { 0 };
Buffer m_main_buffer;
Buffer m_back_buffer;
OwnPtr<Region> m_framebuffer;
RefPtr<VMObject> m_framebuffer_sink_vmobject;
size_t m_buffer_size { 0 };
bool m_are_writes_active { true };
// FIXME: This needs to be cleaned up if the WindowServer exits while we are in a tty
WeakPtr<Region> m_userspace_mmap_region;

12
Kernel/Graphics/VirtIOGPU/VirtIOGPU.cpp
View File

@ -127,12 +127,12 @@ VirtIOGPUResourceID VirtIOGPU::create_2d_resource(VirtIOGPURect rect)
return resource_id;
}
void VirtIOGPU::ensure_backing_storage(Region& region, size_t buffer_length, VirtIOGPUResourceID resource_id)
void VirtIOGPU::ensure_backing_storage(Region& region, size_t buffer_offset, size_t buffer_length, VirtIOGPUResourceID resource_id)
{
VERIFY(m_operation_lock.is_locked());
// Allocate backing region
auto& vm_object = region.vmobject();
size_t desired_num_pages = page_round_up(buffer_length);
size_t desired_num_pages = page_round_up(buffer_offset + buffer_length);
auto& pages = vm_object.physical_pages();
for (size_t i = pages.size(); i < desired_num_pages / PAGE_SIZE; ++i) {
auto page = MM.allocate_user_physical_page();
@ -141,7 +141,11 @@ void VirtIOGPU::ensure_backing_storage(Region& region, size_t buffer_length, Vir
pages.append(move(page));
}
region.remap();
size_t num_mem_regions = vm_object.page_count();
VERIFY(buffer_offset % PAGE_SIZE == 0);
VERIFY(buffer_length % PAGE_SIZE == 0);
auto first_page_index = buffer_offset / PAGE_SIZE;
size_t num_mem_regions = buffer_length / PAGE_SIZE;
// Send request
auto& request = *reinterpret_cast<VirtIOGPUResourceAttachBacking*>(m_scratch_space->vaddr().as_ptr());
@ -152,7 +156,7 @@ void VirtIOGPU::ensure_backing_storage(Region& region, size_t buffer_length, Vir
request.resource_id = resource_id.value();
request.num_entries = num_mem_regions;
for (size_t i = 0; i < num_mem_regions; ++i) {
request.entries[i].address = region.physical_page(i)->paddr().get();
request.entries[i].address = region.physical_page(first_page_index + i)->paddr().get();
request.entries[i].length = PAGE_SIZE;
}

2
Kernel/Graphics/VirtIOGPU/VirtIOGPU.h
View File

@ -220,7 +220,7 @@ private:
void query_display_information();
VirtIOGPUResourceID create_2d_resource(VirtIOGPURect rect);
void delete_resource(VirtIOGPUResourceID resource_id);
void ensure_backing_storage(Region& region, size_t buffer_length, VirtIOGPUResourceID resource_id);
void ensure_backing_storage(Region& region, size_t buffer_offset, size_t buffer_length, VirtIOGPUResourceID resource_id);
void detach_backing_storage(VirtIOGPUResourceID resource_id);
void set_scanout_resource(VirtIOGPUScanoutID scanout, VirtIOGPUResourceID resource_id, VirtIOGPURect rect);
void transfer_framebuffer_data_to_host(VirtIOGPUScanoutID scanout, VirtIOGPURect const& rect, VirtIOGPUResourceID resource_id);

2
Kernel/Graphics/VirtIOGPU/VirtIOGPUConsole.cpp
View File

@ -66,7 +66,7 @@ void VirtIOGPUConsole::enqueue_refresh_timer()
.height = (u32)rect.height(),
};
g_io_work->queue([this, dirty_rect]() {
m_framebuffer_device->flush_dirty_window(dirty_rect);
m_framebuffer_device->flush_dirty_window(dirty_rect, m_framebuffer_device->current_buffer());
m_dirty_rect.clear();
});
}

1
Kernel/Graphics/VirtIOGPU/VirtIOGraphicsAdapter.cpp
View File

@ -40,7 +40,6 @@ void VirtIOGraphicsAdapter::enable_consoles()
dbgln_if(VIRTIO_DEBUG, "VirtIOGPU: Enabling consoles");
m_gpu_device->for_each_framebuffer([&](auto& framebuffer, auto& console) {
framebuffer.deactivate_writes();
framebuffer.clear_to_black();
console.enable();
return IterationDecision::Continue;
});