Re: [PATCH 15/15] Drivers: hv: Add modules to expose /dev/mshv to VMMs running on Hyper-V

From: Nuno Das Neves <nunodasneves@linux.microsoft.com>
To: Wei Liu <wei.liu@kernel.org>
Cc: linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org,
	x86@kernel.org, linux-arm-kernel@lists.infradead.org,
	linux-arch@vger.kernel.org, mikelley@microsoft.com,
	kys@microsoft.com, haiyangz@microsoft.com, decui@microsoft.com,
	ssengar@linux.microsoft.com, mukeshrathor@microsoft.com,
	stanislav.kinsburskiy@gmail.com, jinankjain@linux.microsoft.com,
	apais@linux.microsoft.com, Tianyu.Lan@microsoft.com,
	vkuznets@redhat.com, tglx@linutronix.de, mingo@redhat.com,
	bp@alien8.de, dave.hansen@linux.intel.com, hpa@zytor.com,
	will@kernel.org, catalin.marinas@arm.com
Subject: Re: [PATCH 15/15] Drivers: hv: Add modules to expose /dev/mshv to VMMs running on Hyper-V
Date: Thu, 17 Aug 2023 10:57:01 -0700	[thread overview]
Message-ID: <e8d95099-0477-4930-8a87-d4abacd1587f@linux.microsoft.com> (raw)
In-Reply-To: <ZMsBjAmPdqZdNPEF@liuwe-devbox-debian-v2>

On 8/2/2023 6:23 PM, Wei Liu wrote:
> On Thu, Jul 27, 2023 at 12:54:50PM -0700, Nuno Das Neves wrote:
>> Add mshv, mshv_root, and mshv_vtl modules.
>> - mshv provides /dev/mshv and common code, and is the parent module
>> - mshv_root provides APIs for creating and managing child partitions
>> - mshv_vtl provides VTL (Virtual Trust Level) support for VMMs
> 
> Please provide a slightly more detailed description of what these
> modules do. This is huge patch after all. People doing code archaeology
> will appreciate a better commit message.
> 
> For example (please correct if I'm wrong):
> 
> Module mshv provides /dev/mshv and common code, and is the parent module
> to the other two modules. At its core, it implements an eventfd frame
> work, and defines some helper functions for the other modules.
> 
> Module mshv_root provides APIs for creating and managing child
> partitions. It defines abstractions for vcpus, partitions and other
> things related to running a guest inside the kernel. It also exposes
> user space interfaces for the VMMs.
> 
> Module mshv_vtl provides VTL (Virtual Trust Level) support for VMMs. It
> allows the VMM to run in a higher trust level than the guest but still
> within the same context as the guest. This is a useful feature for in
> guest emulation for better isolation and performance.
> 

Thanks - I will provide some more detail, including what you described.

I will make a couple of changes - the eventfd framework is in mshv_root,
not mshv. I will amend the mshv_vtl part a little for clarity.

>>
>> Signed-off-by: Nuno Das Neves <nunodasneves@linux.microsoft.com>
>> ---
>>  drivers/hv/Kconfig             |   54 +
>>  drivers/hv/Makefile            |   21 +
>>  drivers/hv/hv_call.c           |  119 ++
>>  drivers/hv/mshv.h              |  156 +++
>>  drivers/hv/mshv_eventfd.c      |  758 ++++++++++++
>>  drivers/hv/mshv_eventfd.h      |   80 ++
>>  drivers/hv/mshv_main.c         |  208 ++++
>>  drivers/hv/mshv_msi.c          |  129 +++
>>  drivers/hv/mshv_portid_table.c |   84 ++
>>  drivers/hv/mshv_root.h         |  194 ++++
>>  drivers/hv/mshv_root_hv_call.c | 1064 +++++++++++++++++
>>  drivers/hv/mshv_root_main.c    | 1964 ++++++++++++++++++++++++++++++++
>>  drivers/hv/mshv_synic.c        |  689 +++++++++++
>>  drivers/hv/mshv_vtl.h          |   52 +
>>  drivers/hv/mshv_vtl_main.c     | 1541 +++++++++++++++++++++++++
>>  drivers/hv/xfer_to_guest.c     |   28 +
>>  include/uapi/linux/mshv.h      |  298 +++++
>>  17 files changed, 7439 insertions(+)
>>  create mode 100644 drivers/hv/hv_call.c
>>  create mode 100644 drivers/hv/mshv.h
>>  create mode 100644 drivers/hv/mshv_eventfd.c
>>  create mode 100644 drivers/hv/mshv_eventfd.h
>>  create mode 100644 drivers/hv/mshv_main.c
>>  create mode 100644 drivers/hv/mshv_msi.c
>>  create mode 100644 drivers/hv/mshv_portid_table.c
>>  create mode 100644 drivers/hv/mshv_root.h
>>  create mode 100644 drivers/hv/mshv_root_hv_call.c
>>  create mode 100644 drivers/hv/mshv_root_main.c
>>  create mode 100644 drivers/hv/mshv_synic.c
>>  create mode 100644 drivers/hv/mshv_vtl.h
>>  create mode 100644 drivers/hv/mshv_vtl_main.c
>>  create mode 100644 drivers/hv/xfer_to_guest.c
>>  create mode 100644 include/uapi/linux/mshv.h
>>
>> diff --git a/drivers/hv/Kconfig b/drivers/hv/Kconfig
>> index 00242107d62e..b150d686e902 100644
>> --- a/drivers/hv/Kconfig
>> +++ b/drivers/hv/Kconfig
>> @@ -54,4 +54,58 @@ config HYPERV_BALLOON
>>  	help
>>  	  Select this option to enable Hyper-V Balloon driver.
>>  
>> +config MSHV
>> +	tristate "Microsoft Hypervisor root partition interfaces: /dev/mshv"
>> +	depends on X86_64 && HYPERV
>> +	select EVENTFD
>> +	select MSHV_VFIO
> 
> This is not needed yet, right? I think this is just dead code right now.
> 
> It can be introduced when we start upstreaming the VFIO bits.
> 

Right. Removed, along with config MSHV_VFIO below.

>> +	select MSHV_XFER_TO_GUEST_WORK
>> +	help
>> +	  Select this option to enable core functionality for managing guest
>> +	  virtual machines running under the Microsoft Hypervisor.
>> +
>> +	  The interfaces are provided via a device named /dev/mshv.
>> +
>> +	  To compile this as a module, choose M here.
>> +
>> +	  If unsure, say N.
>> +
>> +config MSHV_ROOT
>> +	tristate "Microsoft Hyper-V root partition APIs driver"
>> +	depends on MSHV
>> +	help
>> +	  Select this option to provide /dev/mshv interfaces specific to
>> +	  running as the root partition on Microsoft Hypervisor.
>> +
>> +	  To compile this as a module, choose M here.
>> +
>> +	  If unsure, say N.
>> +
>> +config MSHV_VTL
>> +	tristate "Microsoft Hyper-V VTL driver"
>> +	depends on MSHV
>> +	select HYPERV_VTL_MODE
>> +	select TRANSPARENT_HUGEPAGE
>> +	help
>> +	  Select this option to enable Hyper-V VTL driver.
>> +	  Virtual Secure Mode (VSM) is a set of hypervisor capabilities and
>> +	  enlightenments offered to host and guest partitions which enables
>> +	  the creation and management of new security boundaries within
>> +	  operating system software.
>> +
>> +	  VSM achieves and maintains isolation through Virtual Trust Levels
>> +	  (VTLs). Virtual Trust Levels are hierarchical, with higher levels
>> +	  being more privileged than lower levels. VTL0 is the least privileged
>> +	  level, and currently only other level supported is VTL2.
>> +
>> +	  To compile this as a module, choose M here.
>> +
>> +	  If unsure, say N.
> 
> The changes to the function which indicates if output pages are needed
> should be in this patch.
> 

Yes - I will add it in this patch.

>> +
>> +config MSHV_VFIO
>> +	bool
>> +
>> +config MSHV_XFER_TO_GUEST_WORK
>> +	bool
>> +
>>  endmenu
>> diff --git a/drivers/hv/Makefile b/drivers/hv/Makefile
>> index d76df5c8c2a9..113c79cfadb9 100644
>> --- a/drivers/hv/Makefile
>> +++ b/drivers/hv/Makefile
>> @@ -2,10 +2,31 @@
>>  obj-$(CONFIG_HYPERV)		+= hv_vmbus.o
>>  obj-$(CONFIG_HYPERV_UTILS)	+= hv_utils.o
>>  obj-$(CONFIG_HYPERV_BALLOON)	+= hv_balloon.o
>> +obj-$(CONFIG_DXGKRNL)		+= dxgkrnl/
> 
> This is not yet upstreamed. It shouldn't be here. Does this not break
> the build for you?
> 
Oops! Nope, it doesn't seem to break the build... Anyway, removed.

> The rest is basically a copy of what was posted many moons before plus
> some VTL stuff, and new code for the root scheduler and async hypercall
> support. I've probably gone through some versions of this code already,
> so I only skim the code.
> 
> Since this is a Microsoft only driver, I don't expect to get much review
> from the community -- the last few rounds were quiet. I will however let
> this patch series float for a while before taking any further actions
> just in case.
> 
> If people are interested in specific bits of the code in the driver,
> please let Nuno and I know.
> 
> Thanks,
> Wei.

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