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[RFC,v2,00/11] Hyper-V: Support PAGE_SIZE larger than 4K

Message ID 20200902030107.33380-1-boqun.feng@gmail.com
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Series Hyper-V: Support PAGE_SIZE larger than 4K | expand

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Boqun Feng Sept. 2, 2020, 3 a.m. UTC 
This patchset add the necessary changes to support guests whose page
size is larger than 4K.

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

Changes since v1:

*	Introduce a hv_ring_gpadl_send_offset() to improve the
	readability as per suggestion from Michael.

*	Use max(..., 2 * PAGE_SIZE) instead of hard-coding size for
	inputvsc ringbuffer to align with other ringbuffer settinngs

*	Calculate the exact size of storvsc payload (other than a
	maximum size) to save memory in storvsc_queuecommand() as per
	suggestion from Michael.

*	Use "unsigned int" for loop index inside a page, so that we can
	have the compiler's help for optimization in PAGE_SIZE ==
	HV_HYP_PAGE_SIZE case as per suggestion from Michael.

*	Rebase on to v5.9-rc2 with Michael's latest core support
	patchset[1]


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). 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                  | 462 ++++++++++++++++----------
 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            |  60 +++-
 include/linux/hyperv.h                |  63 +++-
 10 files changed, 447 insertions(+), 226 deletions(-)

Comments

Jiri Kosina Sept. 2, 2020, 8:18 a.m. UTC | #1 
On Wed, 2 Sep 2020, Boqun Feng wrote:

> When PAGE_SIZE > HV_HYP_PAGE_SIZE, we need the ringbuffer size to be at
> least 2 * PAGE_SIZE: one page for the header and at least one page of
> the data part (because of the alignment requirement for double mapping).
> 
> So make sure the ringbuffer sizes to be at least 2 * PAGE_SIZE when
> using vmbus_open() to establish the vmbus connection.
> 
> Signed-off-by: Boqun Feng <boqun.feng@gmail.com>

Acked-by: Jiri Kosina <jkosina@suse.cz>