Many code patterns and hardware procedures rely on reliable delay in the
microseconds granularity, and since they are using such delays which are
valid cases, but should not rely on x86 specific code, we allow to
determine in compile time the proper platform-specific code to use to
invoke such delays.
I believe this to be safe, as the main thing that LockRefPtr provides
over RefPtr is safe copying from a shared LockRefPtr instance. I've
inspected the uses of RefPtr<PhysicalPage> and it seems they're all
guarded by external locking. Some of it is less obvious, but this is
an area where we're making continuous headway.
Until now, our kernel has reimplemented a number of AK classes to
provide automatic internal locking:
- RefPtr
- NonnullRefPtr
- WeakPtr
- Weakable
This patch renames the Kernel classes so that they can coexist with
the original AK classes:
- RefPtr => LockRefPtr
- NonnullRefPtr => NonnullLockRefPtr
- WeakPtr => LockWeakPtr
- Weakable => LockWeakable
The goal here is to eventually get rid of the Lock* classes in favor of
using external locking.
The underlying driver does not need to recalculate the buffer size as
it is passed in the AsyncBlockDevice struct anyway. This also helps in
removing any assumptions of the underlying block size of the device.
Add polling support to NVMe so that it does not use interrupt to
complete a IO but instead actively polls for completion. This probably
is not very efficient in terms of CPU usage but it does not use
interrupts to complete a IO which is beneficial at the moment as there
is no MSI(X) support and it can reduce the latency of an IO in a very
fast NVMe device.
The NVMeQueue class has been made the base class for NVMeInterruptQueue
and NVMePollQueue. The factory function `NVMeQueue::try_create` will
return the appropriate queue to the controller based on the polling
boot parameter.
The polling mode can be enabled by adding an extra boot parameter:
`nvme_poll`.
There was a bug while calculating the next index in submit_sync_sqe
function. Use the NVMeQueue's class variable m_qdepth instead of the
hardcoded IO_QUEUE_SIZE.
Instead, try to allocate the DMA buffer before trying to construct the
NVMeQueue. This allows us to fail early if we can't allocate the DMA
buffer before allocating and creating the heavier NVMeQueue object.
Only a generic struct definition was present for NVMeSubmission. To
improve type safety and clarity, added an union of NVMeSubmission
structs that are applicable to the command being submitted.
We need to use the volatile keyword when mapping the device registers,
or the compiler may optimize access, which lead to this QEMU error:
pci_nvme_ub_mmiord_toosmall in nvme_mmio_read: MMIO read smaller than
32-bits, offset=0x0
Add a basic NVMe driver support to serenity
based on NVMe spec 1.4.
The driver can support multiple NVMe drives (subsystems).
But in a NVMe drive, the driver can support one controller
with multiple namespaces.
Each core will get a separate NVMe Queue.
As the system lacks MSI support, PIN based interrupts are
used for IO.
Tested the NVMe support by replacing IDE driver
with the NVMe driver :^)
