db5f1f1fb8
[ Upstream commit b5ff74c1ef50fe08e384026875fec660fadfaedd ] For a physical PCI device that is passed through to a Hyper-V guest VM, current code specifies the VMBus ring buffer size as 4 pages. But this is an inappropriate dependency, since the amount of ring buffer space needed is unrelated to PAGE_SIZE. For example, on x86 the ring buffer size ends up as 16 Kbytes, while on ARM64 with 64 Kbyte pages, the ring size bloats to 256 Kbytes. The ring buffer for PCI pass-thru devices is used for only a few messages during device setup and removal, so any space above a few Kbytes is wasted. Fix this by declaring the ring buffer size to be a fixed 16 Kbytes. Furthermore, use the VMBUS_RING_SIZE() macro so that the ring buffer header is properly accounted for, and so the size is rounded up to a page boundary, using the page size for which the kernel is built. While w/64 Kbyte pages this results in a 64 Kbyte ring buffer header plus a 64 Kbyte ring buffer, that's the smallest possible with that page size. It's still 128 Kbytes better than the current code. Link: https://lore.kernel.org/linux-pci/20240216202240.251818-1-mhklinux@outlook.com Signed-off-by: Michael Kelley <mhklinux@outlook.com> Signed-off-by: Krzysztof Wilczyński <kwilczynski@kernel.org> Reviewed-by: Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@linux.intel.com> Reviewed-by: Ilpo Jarvinen <ilpo.jarvinen@linux.intel.com> Reviewed-by: Long Li <longli@microsoft.com> Cc: <stable@vger.kernel.org> # 5.15.x Signed-off-by: Sasha Levin <sashal@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.