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Kernel: Implement ScatterList for handling scattered DMA pages

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This class is used in the AHCI code to handle a big request of
read/write to the disk. If we happen to encounter such request,
we will get the needed amount of physical pages from the
already-allocated physical pages in AHCIPort, and with that we
will create a ScatterList that will create a Region that maps
all of these pages in a contiguous virtual memory range.

Then, we could easily copy to/from this range, before and after
calling the operation on the StorageDevice as needed with
read or write operations.
This commit is contained in:
Liav A 2021-02-26 14:38:17 +02:00 • committed by Andreas Kling
parent ecb169b61e
commit 17e7cdc6cc
2 changed files with 84 additions and 16 deletions
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20
Kernel/Storage/AHCIPort.h
View file

@ -37,6 +37,7 @@
#include <Kernel/Storage/AHCI.h>
#include <Kernel/Storage/AHCIPortHandler.h>
#include <Kernel/Storage/StorageDevice.h>
#include <Kernel/VM/AnonymousVMObject.h>
#include <Kernel/VM/PhysicalPage.h>
#include <Kernel/WaitQueue.h>
@ -50,6 +51,21 @@ class AHCIPort : public RefCounted<AHCIPort> {
friend class AHCIPortHandler;
friend class SATADiskDevice;
private:
class ScatterList : public RefCounted<ScatterList> {
public:
static NonnullRefPtr<ScatterList> create(AsyncBlockDeviceRequest&, NonnullRefPtrVector<PhysicalPage> allocated_pages, size_t device_block_size);
const VMObject& vmobject() const { return m_vm_object; }
VirtualAddress dma_region() const { return m_dma_region->vaddr(); }
size_t scatters_count() const { return m_vm_object->physical_pages().size(); }
private:
ScatterList(AsyncBlockDeviceRequest&, NonnullRefPtrVector<PhysicalPage> allocated_pages, size_t device_block_size);
NonnullRefPtr<AnonymousVMObject> m_vm_object;
size_t m_device_block_size;
OwnPtr<Region> m_dma_region;
};
public:
UNMAP_AFTER_INIT static NonnullRefPtr<AHCIPort> create(const AHCIPortHandler&, volatile AHCI::PortRegisters&, u32 port_index);
@ -83,6 +99,8 @@ private:
void start_request(AsyncBlockDeviceRequest&);
void complete_current_request(AsyncDeviceRequest::RequestResult);
bool access_device(AsyncBlockDeviceRequest::RequestType, u64 lba, u8 block_count);
size_t calculate_descriptors_count(size_t block_count) const;
[[nodiscard]] Optional<AsyncDeviceRequest::RequestResult> prepare_and_set_scatter_list(AsyncBlockDeviceRequest& request);
ALWAYS_INLINE bool is_interrupts_enabled() const;
@ -127,6 +145,8 @@ private:
NonnullRefPtr<AHCIPortHandler> m_parent_handler;
AHCI::PortInterruptStatusBitField m_interrupt_status;
AHCI::PortInterruptEnableBitField m_interrupt_enable;
RefPtr<AHCIPort::ScatterList> m_current_scatter_list;
bool m_disabled_by_firmware { false };
};
}