Kernel/PCI: Split host bridge code from the Access singleton

Two classes are added - HostBridge and MemoryBackedHostBridge, which
both derive from HostController class. This allows the kernel to map
different busses from different PCI domains in the same time. Each
HostController implementation doesn't take the Address object to address
PCI devices but instead we take distinct numbers of the PCI bus, device
and function as it allows us to specify arbitrary PCI domains in the
Address structure and still to get the correct PCI devices. This also
matches the hardware behavior of PCI domains - the host bridge merely
takes memory operations or IO operations and translates them to
addressing of three components - PCI bus, device and function.

These changes also greatly simplify how enumeration of Host Bridges work
now - scanning of the hardware depends on what the Host bridges can do
for us, so in case we have multiple host bridges that expose a memory
mapped region or IO ports to access PCI configuration space, we simply
let the code of the host bridge to figure out how to fetch data for us.

Another semantical change is that a PCI domain structure is no longer
attached to a PhysicalAddress, so even in the case that the machine
doesn't implement PCI domains, we still treat that machine to contain 1
PCI domain to treat that one host bridge in the same way, like with a
machine with one or more PCI domains.

Kernel/Bus/PCI/Controller/MemoryBackedHostBridge.cpp

@@ -0,0 +1,94 @@
+/*
+ * Copyright (c) 2022, Liav A. <liavalb@hotmail.co.il>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <AK/ByteReader.h>
+#include <Kernel/Arch/x86/IO.h>
+#include <Kernel/Bus/PCI/Access.h>
+#include <Kernel/Bus/PCI/Controller/MemoryBackedHostBridge.h>
+
+namespace Kernel::PCI {
+
+NonnullOwnPtr<MemoryBackedHostBridge> MemoryBackedHostBridge::must_create(Domain const& domain, PhysicalAddress start_address)
+{
+    return adopt_own_if_nonnull(new (nothrow) MemoryBackedHostBridge(domain, start_address)).release_nonnull();
+}
+
+MemoryBackedHostBridge::MemoryBackedHostBridge(PCI::Domain const& domain, PhysicalAddress start_address)
+    : HostBridge(domain)
+    , m_start_address(start_address)
+{
+}
+
+u8 MemoryBackedHostBridge::read8_field(BusNumber bus, DeviceNumber device, FunctionNumber function, u32 field)
+{
+    VERIFY(Access::the().access_lock().is_locked());
+    VERIFY(field <= 0xfff);
+    return *((volatile u8*)(get_device_configuration_memory_mapped_space(bus, device, function).get() + (field & 0xfff)));
+}
+u16 MemoryBackedHostBridge::read16_field(BusNumber bus, DeviceNumber device, FunctionNumber function, u32 field)
+{
+    VERIFY(Access::the().access_lock().is_locked());
+    VERIFY(field < 0xfff);
+    u16 data = 0;
+    ByteReader::load<u16>(get_device_configuration_memory_mapped_space(bus, device, function).offset(field & 0xfff).as_ptr(), data);
+    return data;
+}
+u32 MemoryBackedHostBridge::read32_field(BusNumber bus, DeviceNumber device, FunctionNumber function, u32 field)
+{
+    VERIFY(Access::the().access_lock().is_locked());
+    VERIFY(field <= 0xffc);
+    u32 data = 0;
+    ByteReader::load<u32>(get_device_configuration_memory_mapped_space(bus, device, function).offset(field & 0xfff).as_ptr(), data);
+    return data;
+}
+void MemoryBackedHostBridge::write8_field(BusNumber bus, DeviceNumber device, FunctionNumber function, u32 field, u8 value)
+{
+    VERIFY(Access::the().access_lock().is_locked());
+    VERIFY(field <= 0xfff);
+    *((volatile u8*)(get_device_configuration_memory_mapped_space(bus, device, function).get() + (field & 0xfff))) = value;
+}
+void MemoryBackedHostBridge::write16_field(BusNumber bus, DeviceNumber device, FunctionNumber function, u32 field, u16 value)
+{
+    VERIFY(Access::the().access_lock().is_locked());
+    VERIFY(field < 0xfff);
+    ByteReader::store<u16>(get_device_configuration_memory_mapped_space(bus, device, function).offset(field & 0xfff).as_ptr(), value);
+}
+void MemoryBackedHostBridge::write32_field(BusNumber bus, DeviceNumber device, FunctionNumber function, u32 field, u32 value)
+{
+    VERIFY(Access::the().access_lock().is_locked());
+    VERIFY(field <= 0xffc);
+    ByteReader::store<u32>(get_device_configuration_memory_mapped_space(bus, device, function).offset(field & 0xfff).as_ptr(), value);
+}
+
+void MemoryBackedHostBridge::map_bus_region(BusNumber bus)
+{
+    VERIFY(Access::the().access_lock().is_locked());
+    if (m_mapped_bus == bus && m_mapped_bus_region)
+        return;
+    auto bus_base_address = determine_memory_mapped_bus_base_address(bus);
+    auto region_or_error = MM.allocate_kernel_region(bus_base_address, memory_range_per_bus, "PCI ECAM", Memory::Region::Access::ReadWrite);
+    // FIXME: Find a way to propagate error from here.
+    if (region_or_error.is_error())
+        VERIFY_NOT_REACHED();
+    m_mapped_bus_region = region_or_error.release_value();
+    m_mapped_bus = bus;
+    dbgln_if(PCI_DEBUG, "PCI: New PCI ECAM Mapped region for bus {} @ {} {}", bus, m_mapped_bus_region->vaddr(), m_mapped_bus_region->physical_page(0)->paddr());
+}
+
+VirtualAddress MemoryBackedHostBridge::get_device_configuration_memory_mapped_space(BusNumber bus, DeviceNumber device, FunctionNumber function)
+{
+    VERIFY(Access::the().access_lock().is_locked());
+    map_bus_region(bus);
+    return m_mapped_bus_region->vaddr().offset(mmio_device_space_size * function.value() + (mmio_device_space_size * to_underlying(Limits::MaxFunctionsPerDevice)) * device.value());
+}
+
+PhysicalAddress MemoryBackedHostBridge::determine_memory_mapped_bus_base_address(BusNumber bus) const
+{
+    auto start_bus = min(bus.value(), m_domain.start_bus());
+    return m_start_address.offset(memory_range_per_bus * (bus.value() - start_bus));
+}
+
+}