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Subject[PATCH v3 00/11] Hyper-V: Support PAGE_SIZE larger than 4K
Date
This patchset add the necessary changes to support guests whose page
size is larger than 4K. And the main architecture which we develop this
for is ARM64 (also it's the architecture that I use to test this
feature). Now as the patchset has been deeply reviewed, I change it from
"RFC" to "PATCH", and also add ARM64 people Cced for broader insights
(although the code is arch-independent).

Previous version:
v1: https://lore.kernel.org/lkml/20200721014135.84140-1-boqun.feng@gmail.com/
v2: https://lore.kernel.org/lkml/20200902030107.33380-1-boqun.feng@gmail.com

Changes since v2:

* Use a simpler and straight-forwards method to set up the payload
array for storvsc thanks to the inspiration from Michael Kelley.

* Some typo fixes as per suggestion from Michael Kelley.

* Fixes compiler warnings due to the different types of two
operands for max().


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), everything worked fine ;-) (I could observe an error caused
by unaligned firmware data, but it's better to have it fixed in the
Hyper-V). I also have done a build and boot test on x86, everything
worked well.

Looking forwards to comments and suggestions!

Regards,
Boqun

[1]: https://lore.kernel.org/lkml/1598287583-71762-1-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 | 461 ++++++++++++++++----------
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 | 13 +-
drivers/scsi/storvsc_drv.c | 54 ++-
include/linux/hyperv.h | 64 +++-
10 files changed, 441 insertions(+), 227 deletions(-)

--
2.28.0

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