[PATCH v8 0/6] Enable Linux guests on Hyper-V on ARM64

Michael Kelley
2021-02-18T23:20:33Z

This series enables Linux guests running on Hyper-V on ARM64
hardware. New ARM64-specific code in arch/arm64/hyperv initializes
Hyper-V, including its interrupts and hypercall mechanism.
Existing architecture independent drivers for Hyper-V's VMbus and
synthetic devices just work when built for ARM64. Hyper-V code is
built and included in the image and modules only if CONFIG_HYPERV
is enabled.

The six patches are organized as follows:

1) Add definitions and functions for making Hyper-V hypercalls
and getting/setting virtual processor registers provided by
Hyper-V

2) Add architecture specific definitions needed by the
architecture independent Hyper-V clocksource driver in
drivers/clocksource/hyperv_timer.c. Update the clocksource
driver to be initialized on ARM64.

3) Add functions needed by the arch independent VMbus driver
for reporting a panic to Hyper-V and as stubs for the kexec
and crash handlers.

4) Add Hyper-V initialization code and utility functions that
report Hyper-v status.

5) Export screen_info so it may be used by the Hyper-V frame buffer
driver built as a module. It is already exported for x86,
powerpc, and alpha architectures.

6) Make CONFIG_HYPERV selectable on ARM64 in addition to x86/x64.

Hyper-V on ARM64 runs with a 4 Kbyte page size, but allows guests
with 4K/16K/64K page size. Linux guests with this ARM64 enablement
code work with all three supported ARM64 page sizes.

The Hyper-V vPCI driver at drivers/pci/host/pci-hyperv.c has
x86/x64-specific code and is not being built for ARM64. Fixing
this driver to enable vPCI devices on ARM64 will be done later.

In a few cases, terminology from the x86/x64 world has been carried
over into the ARM64 code ("MSR", "TSC"). Hyper-V still uses the
x86/x64 terminology and has not replaced it with something more
generic, so the code uses the Hyper-V terminology. This will be
fixed when Hyper-V updates the usage in the TLFS.

This patch set is based on the 5.11.0 code tree, plus this patch series
https://lore.kernel.org/lkml/1611779025-21503-1-git-send-email-mikelley@microsoft.com/
that refactors the boundary between arch independent and arch
dependent code for Hyper-V.

Changes in v8:
* Removed a fair amount of code based on refactoring the boundary between
arch independent and arch dependent code for Hyper-V, per comments
from Arnd Bergmann. The removed code was either duplicated on
the x86 side, or has been folded into architecture independent
code as not really being architecture dependent.
* Added config dependency on !CONFIG_CPU_BIG_ENDIAN [Arnd Bergmann]
* Reworked the approach to Hyper-V initialization. The functionality
is the same, but is now structured like the Xen code with an early
init function called in setup_arch() and an early initcall to
finish the initialization. [Arnd Bergmann]

Changes in v7:
* Separately upstreamed split of hyperv-tlfs.h into arch dependent
and independent versions. In this patch set, update the ARM64
hyperv-tlfs.h to include architecture independent definitions.
This approach eliminates a lot of lines of otherwise duplicated
code on the ARM64 side.
* Break ARM64 mshyperv.h into smaller pieces. Have an initial
baseline, and add code along with patches for a particular
functional area. [Marc Zyngier]
* In mshyperv.h, use static inline functions instead of #defines
where possible. [Arnd Bergmann]
* Use VMbus INTID obtained from ACPI DSDT instead of hardcoding.
The STIMER INTID is still hardcoded because it is needed
before Linux has initialized the ACPI subsystem, so it can't
be obtained from the DSDT. Wedging it into the GTDT seems
dubious, so was not done. [Marc Zyngier]
* Update Hyper-V page size allocation functions to use
alloc_page() if PAGE_SIZE == HV_HYP_PAGE_SIZE [Arnd
Bergmann]
* Various other minor changes based on feedback and to rebase
to latest linux-next [Marc Zyngier and Arnd Bergmann]

Changes in v6:
* Use SMCCC hypercall interface instead of direct invocation
of HVC instruction and the Hyper-V hypercall interface
[Marc Zyngier]
* Reimplemented functions to alloc/free Hyper-V size pages
using kmalloc/kfree since kmalloc now guarantees alignment of
power of 2 size allocations [Marc Zyngier]
* Export screen_info in arm64 architecture so it can be used
by the Hyper-V buffer driver built as a module
* Renamed source file arch/arm64/hyperv/hv_init.c to hv_core.c
to better reflect its content
* Fixed the bit position of certain feature flags presented by
Hyper-V to the guest. The bit positions on ARM64 don't match
the position on x86 like originally thought.
* Minor fixups to rebase to 5.6-rc5 linux-next

Changes in v5:
* Minor fixups to rebase to 5.4-rc1 linux-next

Changes in v4:
* Moved clock-related code into an architecture independent
Hyper-V clocksource driver that is already upstream. Clock
related code is removed from this patch set except for the
ARM64 specific interrupt handler. [Marc Zyngier]
* Separately upstreamed the split of mshyperv.h into arch independent
and arch dependent portions. The arch independent portion has been
removed from this patch set.
* Divided patch #2 of the series into multiple smaller patches
[Marc Zyngier]
* Changed a dozen or so smaller things based on feedback
[Marc Zyngier, Will Deacon]
* Added functions to alloc/free Hyper-V size pages for use by
drivers for Hyper-V synthetic devices when updated to not assume
guest page size and Hyper-v page size are the same

Changes in v3:
* Added initialization of hv_vp_index array like was recently
added on x86 branch [KY Srinivasan]
* Changed Hyper-V ARM64 register symbols to be all uppercase
instead of mixed case [KY Srinivasan]
* Separated mshyperv.h into two files, one architecture
independent and one architecture dependent. After this code
is upstream, will make changes to the x86 code to use the
architecture independent file and remove duplication. And
once we have a multi-architecture Hyper-V TLFS, will do a
separate patch to split hyperv-tlfs.h in the same way.
[KY Srinivasan]
* Minor tweaks to rebase to latest linux-next code

Changes in v2:
* Removed patch to implement slow_virt_to_phys() on ARM64.
Use of slow_virt_to_phys() in arch independent Hyper-V
drivers has been eliminated by commit 6ba34171bcbd
("Drivers: hv: vmbus: Remove use of slow_virt_to_phys()")
* Minor tweaks to rebase to latest linux-next code

Michael Kelley (6):
arm64: hyperv: Add Hyper-V hypercall and register access utilities
arm64: hyperv: Add Hyper-V clocksource/clockevent support
arm64: hyperv: Add kexec and panic handlers
arm64: hyperv: Initialize hypervisor on boot
arm64: efi: Export screen_info
Drivers: hv: Enable Hyper-V code to be built on ARM64

MAINTAINERS | 3 +
arch/arm64/Kbuild | 1 +
arch/arm64/hyperv/Makefile | 2 +
arch/arm64/hyperv/hv_core.c | 220 +++++++++++++++++++++++++++++++++++
arch/arm64/hyperv/mshyperv.c | 194 ++++++++++++++++++++++++++++++
arch/arm64/include/asm/hyperv-tlfs.h | 69 +++++++++++
arch/arm64/include/asm/mshyperv.h | 73 ++++++++++++
arch/arm64/kernel/efi.c | 1 +
arch/arm64/kernel/setup.c | 4 +
drivers/clocksource/hyperv_timer.c | 14 +++
drivers/hv/Kconfig | 3 +-
11 files changed, 583 insertions(+), 1 deletion(-)
create mode 100644 arch/arm64/hyperv/Makefile
create mode 100644 arch/arm64/hyperv/hv_core.c
create mode 100644 arch/arm64/hyperv/mshyperv.c
create mode 100644 arch/arm64/include/asm/hyperv-tlfs.h
create mode 100644 arch/arm64/include/asm/mshyperv.h

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1.8.3.1