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

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