[RFC 00/11] Hyper-V: Support PAGE_SIZE larger than 4K

[Boqun Feng <boqun.feng@gmail.com>]

This patchset add the necessary changes to support guests whose page
size is larger than 4K.

Hyper-V always uses 4K as the page size and expects the same page size
when communicating with guests. That is, all the "pfn"s in the
hypervisor-guest communication protocol are the page numbers in the unit
of HV_HYP_PAGE_SIZE rather than PAGE_SIZE. To support guests with larger
page size, we need to convert between these two page sizes correctly in
the hypervisor-guest communication, which is basically what this
patchset does.

In this conversion, one challenge is how to handle the ringbuffer. A
ringbuffer has two parts: a header and a data part, both of which want
to be PAGE_SIZE aligned in the guest, because we use the "double
mapping" trick to map the data part twice in the guest virtual address
space for faster wrap-around and ease to process data in place. However,
the Hyper-V hypervisor always treats the ringbuffer headers as 4k pages.
To overcome this gap, we enlarge the hv_ring_buffer structure to be
always PAGE_SIZE aligned, and introduce the gpadl type concept to allow
vmbus_establish_gpadl() to handle ringbuffer cases specially. Note that
gpadl type is only meaningful to the guest, there is no such concept in
Hyper-V hypervisor.

This patchset consists of 11 patches:

Patch 1~4: Introduce the types of gpadl, so that we can handle
	   ringbuffer when PAGE_SIZE != HV_HYP_PAGE_SIZE, and also fix
	   a few places where we should use HV_HYP_PAGE_SIZE other than
	   PAGE_SIZE.

Patch 5~6: Add a few helper functions to help calculate the hvpfn (page
	   number in the unit of HV_HYP_PAGE_SIZE) and other related
	   data. So that we can use them in the code of drivers.

Patch 7~11: Use the helpers and change the driver code accordingly to
	    make net/input/util/storage driver work with PAGE_SIZE !=
	    HV_HYP_PAGE_SIZE

I've done some tests with PAGE_SIZE=64k and PAGE_SIZE=16k configurations
on ARM64 guests (with Michael's patchset[1] for ARM64 Hyper-V guest
support), nothing major breaks yet ;-) (I could observe an error caused
by unaligned firmware data, but it's better to have it fixed in the
Hyper-V).

Looking forwards to comments and suggestions!

Regards,
Boqun

[1]: https://lore.kernel.org/lkml/1584200119-18594-1-git-send-email-mikelley@microsoft.com/

Boqun Feng (11):
  Drivers: hv: vmbus: Always use HV_HYP_PAGE_SIZE for gpadl
  Drivers: hv: vmbus: Move __vmbus_open()
  Drivers: hv: vmbus: Introduce types of GPADL
  Drivers: hv: Use HV_HYP_PAGE in hv_synic_enable_regs()
  Drivers: hv: vmbus: Move virt_to_hvpfn() to hyperv header
  hv: hyperv.h: Introduce some hvpfn helper functions
  hv_netvsc: Use HV_HYP_PAGE_SIZE for Hyper-V communication
  Input: hyperv-keyboard: Make ringbuffer at least take two pages
  HID: hyperv: Make ringbuffer at least take two pages
  Driver: hv: util: Make ringbuffer at least take two pages
  scsi: storvsc: Support PAGE_SIZE larger than 4K

 drivers/hid/hid-hyperv.c              |   4 +-
 drivers/hv/channel.c                  | 452 +++++++++++++++-----------
 drivers/hv/hv.c                       |   4 +-
 drivers/hv/hv_util.c                  |  16 +-
 drivers/input/serio/hyperv-keyboard.c |   4 +-
 drivers/net/hyperv/netvsc.c           |   2 +-
 drivers/net/hyperv/netvsc_drv.c       |  46 +--
 drivers/net/hyperv/rndis_filter.c     |  12 +-
 drivers/scsi/storvsc_drv.c            |  27 +-
 include/linux/hyperv.h                |  63 +++-
 10 files changed, 400 insertions(+), 230 deletions(-)

-- 
2.27.0