On 19/12/2019 11:45, yezengruan wrote:
Hi Steve,
On 2019/12/17 22:21, Steven Price wrote:
quoted
On Tue, Dec 17, 2019 at 01:55:45PM +0000, yezengruan@huawei.com wrote:
quoted
From: Zengruan Ye <redacted>
Introduce a paravirtualization interface for KVM/arm64 to obtain the vcpu
is currently running or not.
A hypercall interface is provided for the guest to interrogate the
hypervisor's support for this interface and the location of the shared
memory structures.
Signed-off-by: Zengruan Ye <redacted>
---
Documentation/virt/kvm/arm/pvlock.rst | 31 +++++++++++++++++++++++++++
1 file changed, 31 insertions(+)
create mode 100644 Documentation/virt/kvm/arm/pvlock.rst
diff --git a/Documentation/virt/kvm/arm/pvlock.rst b/Documentation/virt/kvm/arm/pvlock.rst
new file mode 100644
index 000000000000..eec0c36edf17
--- /dev/null
+++ b/Documentation/virt/kvm/arm/pvlock.rst
@@ -0,0 +1,31 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+Paravirtualized lock support for arm64
+======================================
+
+KVM/arm64 provids some hypervisor service calls to support a paravirtualized
+guest obtaining the vcpu is currently running or not.
+
+Two new SMCCC compatible hypercalls are defined:
+
+* PV_LOCK_FEATURES: 0xC5000040
+* PV_LOCK_PREEMPTED: 0xC5000041
These values are in the "Standard Hypervisor Service Calls" section of
SMCCC - so is there a document that describes this features such that
other OSes or hypervisors can implement it? I'm also not entirely sure
of the process of ensuring that the IDs picked are non-conflicting.
Otherwise if this is a KVM specific interface this should probably
belong within the "Vendor Specific Hypervisor Service Calls" section
along with some probing that the hypervisor is actually KVM. Although I
don't see anything KVM specific.
Thanks for pointing it out to me! Actually, I also don't see any documents
or KVM specific that describes this features. The values in the "Vendor
Specific Hypervisor Service Calls" section may be more appropriate, such as
the following
* PV_LOCK_FEATURES: 0xC6000020
* PV_LOCK_PREEMPTED: 0xC6000021
Please let me know if you have any suggestions.
I don't have strong feelings on whether this should be KVM-specific or
generic. I'm not familiar with whether there are competing solutions to
this problem - it's obviously ideal if all hypervisors can make use of
the same interface if possible, but maybe that ship has sailed already?
However if this going to be KVM-specific then you'll need to add the
probing logic for checking whether the hypervisor is KVM or not. Will
has a couple of patches on a branch which do this [1] and [2]. Then you
can use kvm_arm_hyp_services_available() as the first step to probe
whether the hypervisor is KVM.
[1]
https://git.kernel.org/pub/scm/linux/kernel/git/will/linux.git/commit/?h=kvm/hvc&id=464f5a1741e5959c3e4d2be1966ae0093b4dce06
[2]
https://git.kernel.org/pub/scm/linux/kernel/git/will/linux.git/commit/?h=kvm/hvc&id=6597490e005d0eeca8ed8c1c1d7b4318ee014681
Steve
quoted
quoted
+
+The existence of the PV_LOCK hypercall should be probed using the SMCCC 1.1
+ARCH_FEATURES mechanism before calling it.
+
+PV_LOCK_FEATURES
+ ============= ======== ==========
+ Function ID: (uint32) 0xC5000040
+ PV_call_id: (uint32) The function to query for support.
+ Return value: (int64) NOT_SUPPORTED (-1) or SUCCESS (0) if the relevant
+ PV-lock feature is supported by the hypervisor.
+ ============= ======== ==========
+
+PV_LOCK_PREEMPTED
+ ============= ======== ==========
+ Function ID: (uint32) 0xC5000041
+ Return value: (int64) NOT_SUPPORTED (-1) or SUCCESS (0) if the IPA of
+ this vcpu's pv data structure is configured by
+ the hypervisor.
+ ============= ======== ==========
quoted
From the code it looks like there's another argument for this SMC - the
physical address (or IPA) of a struct pvlock_vcpu_state. This structure
also needs to be described as it is part of the ABI.
Will update.
quoted
Steve
.
Thanks,
Zengruan
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel