A series of hcalls have been added to the PAPR which allow a regular
guest partition to create and manage guest partitions of its own. KVM
already had an interface that allowed this on powernv platforms. This
existing interface will now be called "nestedv1". The newly added PAPR
interface will be called "nestedv2". PHYP will support the nestedv2
interface. At this time the host side of the nestedv2 interface has not
been implemented on powernv but there is no technical reason why it
could not be added.
The nestedv1 interface is still supported.
Add support to KVM to utilize these hcalls to enable running nested
guests as a pseries guest on PHYP.
Overview of the new hcall usage:
- L1 and L0 negotiate capabilities with
H_GUEST_{G,S}ET_CAPABILITIES()
- L1 requests the L0 create a L2 with
H_GUEST_CREATE() and receives a handle to use in future hcalls
- L1 requests the L0 create a L2 vCPU with
H_GUEST_CREATE_VCPU()
- L1 sets up the L2 using H_GUEST_SET and the
H_GUEST_VCPU_RUN input buffer
- L1 requests the L0 runs the L2 vCPU using H_GUEST_VCPU_RUN()
- L2 returns to L1 with an exit reason and L1 reads the
H_GUEST_VCPU_RUN output buffer populated by the L0
- L1 handles the exit using H_GET_STATE if necessary
- L1 reruns L2 vCPU with H_GUEST_VCPU_RUN
- L1 frees the L2 in the L0 with H_GUEST_DELETE()
Support for the new API is determined by trying
H_GUEST_GET_CAPABILITIES. On a successful return, use the nestedv2
interface.
Use the vcpu register state setters for tracking modified guest state
elements and copy the thread wide values into the H_GUEST_VCPU_RUN input
buffer immediately before running a L2. The guest wide
elements can not be added to the input buffer so send them with a
separate H_GUEST_SET call if necessary.
Make the vcpu register getter load the corresponding value from the real
host with H_GUEST_GET. To avoid unnecessarily calling H_GUEST_GET, track
which values have already been loaded between H_GUEST_VCPU_RUN calls. If
an element is present in the H_GUEST_VCPU_RUN output buffer it also does
not need to be loaded again.
Tested-by: Sachin Sant <sachinp@linux.ibm.com>
Signed-off-by: Vaibhav Jain <vaibhav@linux.ibm.com>
Signed-off-by: Gautam Menghani <gautam@linux.ibm.com>
Signed-off-by: Kautuk Consul <kconsul@linux.vnet.ibm.com>
Signed-off-by: Amit Machhiwal <amachhiw@linux.vnet.ibm.com>
Signed-off-by: Jordan Niethe <jniethe5@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230914030600.16993-11-jniethe5@gmail.com
The PAPR "Nestedv2" guest API introduces the concept of a Guest State
Buffer for communication about L2 guests between L1 and L0 hosts.
In the new API, the L0 manages the L2 on behalf of the L1. This means
that if the L1 needs to change L2 state (e.g. GPRs, SPRs, partition
table...), it must request the L0 perform the modification. If the
nested host needs to read L2 state likewise this request must
go through the L0.
The Guest State Buffer is a Type-Length-Value style data format defined
in the PAPR which assigns all relevant partition state a unique
identity. Unlike a typical TLV format the length is redundant as the
length of each identity is fixed but is included for checking
correctness.
A guest state buffer consists of an element count followed by a stream
of elements, where elements are composed of an ID number, data length,
then the data:
Header:
<---4 bytes--->
+----------------+-----
| Element Count | Elements...
+----------------+-----
Element:
<----2 bytes---> <-2 bytes-> <-Length bytes->
+----------------+-----------+----------------+
| Guest State ID | Length | Data |
+----------------+-----------+----------------+
Guest State IDs have other attributes defined in the PAPR such as
whether they are per thread or per guest, or read-only.
Introduce a library for using guest state buffers. This includes support
for actions such as creating buffers, adding elements to buffers,
reading the value of elements and parsing buffers. This will be used
later by the nestedv2 guest support.
Signed-off-by: Jordan Niethe <jniethe5@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20230914030600.16993-9-jniethe5@gmail.com
