From: Steven Price <steven.price@arm.com>
To: Marc Zyngier <maz@kernel.org>, Will Deacon <will@kernel.org>,
linux-arm-kernel@lists.infradead.org,
kvmarm@lists.cs.columbia.edu
Cc: linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
Catalin Marinas <catalin.marinas@arm.com>,
linux-doc@vger.kernel.org, Russell King <linux@armlinux.org.uk>,
Steven Price <steven.price@arm.com>,
Paolo Bonzini <pbonzini@redhat.com>
Subject: [PATCH v4 01/10] KVM: arm64: Document PV-time interface
Date: Fri, 30 Aug 2019 09:42:46 +0100 [thread overview]
Message-ID: <20190830084255.55113-2-steven.price@arm.com> (raw)
In-Reply-To: <20190830084255.55113-1-steven.price@arm.com>
Introduce a paravirtualization interface for KVM/arm64 based on the
"Arm Paravirtualized Time for Arm-Base Systems" specification DEN 0057A.
This only adds the details about "Stolen Time" as the details of "Live
Physical Time" have not been fully agreed.
User space can specify a reserved area of memory for the guest and
inform KVM to populate the memory with information on time that the host
kernel has stolen from the guest.
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: Steven Price <steven.price@arm.com>
---
Documentation/virt/kvm/arm/pvtime.txt | 64 +++++++++++++++++++++++++
Documentation/virt/kvm/devices/vcpu.txt | 14 ++++++
2 files changed, 78 insertions(+)
create mode 100644 Documentation/virt/kvm/arm/pvtime.txt
diff --git a/Documentation/virt/kvm/arm/pvtime.txt b/Documentation/virt/kvm/arm/pvtime.txt
new file mode 100644
index 000000000000..dda3f0f855b9
--- /dev/null
+++ b/Documentation/virt/kvm/arm/pvtime.txt
@@ -0,0 +1,64 @@
+Paravirtualized time support for arm64
+======================================
+
+Arm specification DEN0057/A defined a standard for paravirtualised time
+support for AArch64 guests:
+
+https://developer.arm.com/docs/den0057/a
+
+KVM/arm64 implements the stolen time part of this specification by providing
+some hypervisor service calls to support a paravirtualized guest obtaining a
+view of the amount of time stolen from its execution.
+
+Two new SMCCC compatible hypercalls are defined:
+
+PV_FEATURES 0xC5000020
+PV_TIME_ST 0xC5000022
+
+These are only available in the SMC64/HVC64 calling convention as
+paravirtualized time is not available to 32 bit Arm guests. The existence of
+the PV_FEATURES hypercall should be probed using the SMCCC 1.1 ARCH_FEATURES
+mechanism before calling it.
+
+PV_FEATURES
+ Function ID: (uint32) : 0xC5000020
+ PV_func_id: (uint32) : Either PV_TIME_LPT or PV_TIME_ST
+ Return value: (int32) : NOT_SUPPORTED (-1) or SUCCESS (0) if the relevant
+ PV-time feature is supported by the hypervisor.
+
+PV_TIME_ST
+ Function ID: (uint32) : 0xC5000022
+ Return value: (int64) : IPA of the stolen time data structure for this
+ VCPU. On failure:
+ NOT_SUPPORTED (-1)
+
+The IPA returned by PV_TIME_ST should be mapped by the guest as normal memory
+with inner and outer write back caching attributes, in the inner shareable
+domain. A total of 16 bytes from the IPA returned are guaranteed to be
+meaningfully filled by the hypervisor (see structure below).
+
+PV_TIME_ST returns the structure for the calling VCPU.
+
+Stolen Time
+-----------
+
+The structure pointed to by the PV_TIME_ST hypercall is as follows:
+
+ Field | Byte Length | Byte Offset | Description
+ ----------- | ----------- | ----------- | --------------------------
+ Revision | 4 | 0 | Must be 0 for version 0.1
+ Attributes | 4 | 4 | Must be 0
+ Stolen time | 8 | 8 | Stolen time in unsigned
+ | | | nanoseconds indicating how
+ | | | much time this VCPU thread
+ | | | was involuntarily not
+ | | | running on a physical CPU.
+
+The structure will be updated by the hypervisor prior to scheduling a VCPU. It
+will be present within a reserved region of the normal memory given to the
+guest. The guest should not attempt to write into this memory. There is a
+structure per VCPU of the guest.
+
+For the user space interface see Documentation/virt/kvm/devices/vcpu.txt
+section "3. GROUP: KVM_ARM_VCPU_PVTIME_CTRL".
+
diff --git a/Documentation/virt/kvm/devices/vcpu.txt b/Documentation/virt/kvm/devices/vcpu.txt
index 2b5dab16c4f2..896777f76f36 100644
--- a/Documentation/virt/kvm/devices/vcpu.txt
+++ b/Documentation/virt/kvm/devices/vcpu.txt
@@ -60,3 +60,17 @@ time to use the number provided for a given timer, overwriting any previously
configured values on other VCPUs. Userspace should configure the interrupt
numbers on at least one VCPU after creating all VCPUs and before running any
VCPUs.
+
+3. GROUP: KVM_ARM_VCPU_PVTIME_CTRL
+Architectures: ARM64
+
+3.1 ATTRIBUTE: KVM_ARM_VCPU_PVTIME_SET_IPA
+Parameters: 64-bit base address
+Returns: -ENXIO: Stolen time not implemented
+ -EEXIST: Base address already set for this VCPU
+ -EINVAL: Base address not 64 byte aligned
+
+Specifies the base address of the stolen time structure for this VCPU. The
+base address must be 64 byte aligned and exist within a valid guest memory
+region. See Documentation/virt/kvm/arm/pvtime.txt for more information
+including the layout of the stolen time structure.
--
2.20.1
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next prev parent reply other threads:[~2019-08-30 8:43 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-30 8:42 [PATCH v4 00/10] arm64: Stolen time support Steven Price
2019-08-30 8:42 ` Steven Price [this message]
2019-08-30 14:47 ` [PATCH v4 01/10] KVM: arm64: Document PV-time interface Andrew Jones
2019-08-30 15:25 ` Steven Price
2019-09-02 12:52 ` Andrew Jones
2019-09-04 13:55 ` Steven Price
2019-09-04 14:22 ` Andrew Jones
2019-09-04 15:07 ` Steven Price
2019-08-30 8:42 ` [PATCH v4 02/10] KVM: arm/arm64: Factor out hypercall handling from PSCI code Steven Price
2019-09-02 7:06 ` kbuild test robot
2019-09-04 15:05 ` Steven Price
2019-09-02 13:07 ` kbuild test robot
2019-08-30 8:42 ` [PATCH v4 03/10] KVM: arm64: Implement PV_FEATURES call Steven Price
2019-08-30 8:42 ` [PATCH v4 04/10] KVM: Implement kvm_put_guest() Steven Price
2019-08-30 8:42 ` [PATCH v4 05/10] KVM: arm64: Support stolen time reporting via shared structure Steven Price
2019-08-30 9:42 ` Christoffer Dall
2019-08-30 9:52 ` Steven Price
2019-09-03 9:14 ` Zenghui Yu
2019-09-04 15:53 ` Steven Price
2019-08-30 8:42 ` [PATCH v4 06/10] KVM: Allow kvm_device_ops to be const Steven Price
2019-08-30 8:42 ` [PATCH v4 07/10] KVM: arm64: Provide VCPU attributes for stolen time Steven Price
2019-08-30 10:02 ` Marc Zyngier
2019-08-30 15:04 ` Steven Price
2019-08-30 8:42 ` [PATCH v4 08/10] arm/arm64: Provide a wrapper for SMCCC 1.1 calls Steven Price
2019-08-30 8:42 ` [PATCH v4 09/10] arm/arm64: Make use of the SMCCC 1.1 wrapper Steven Price
2019-08-30 8:42 ` [PATCH v4 10/10] arm64: Retrieve stolen time as paravirtualized guest Steven Price
2019-09-03 8:47 ` Andrew Jones
2019-09-04 16:01 ` Steven Price
2019-09-03 8:03 ` [PATCH v4 00/10] arm64: Stolen time support Andrew Jones
2019-09-03 8:49 ` Andrew Jones
2019-09-04 16:02 ` Steven Price
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