From: Steven Price <steven.price@arm.com>
To: unlisted-recipients:; (no To-header on input)
Cc: "Steven Price" <steven.price@arm.com>,
"Catalin Marinas" <catalin.marinas@arm.com>,
"Marc Zyngier" <maz@kernel.org>,
"Paolo Bonzini" <pbonzini@redhat.com>,
"Radim Krčmář" <rkrcmar@redhat.com>,
"Russell King" <linux@armlinux.org.uk>,
"Will Deacon" <will@kernel.org>,
"James Morse" <james.morse@arm.com>,
"Julien Thierry" <julien.thierry.kdev@gmail.com>,
"Suzuki K Pouloze" <suzuki.poulose@arm.com>,
kvm@vger.kernel.org, kvmarm@lists.cs.columbia.edu,
linux-arm-kernel@lists.infradead.org, linux-doc@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: [PATCH 1/9] KVM: arm64: Document PV-time interface
Date: Fri, 2 Aug 2019 15:50:09 +0100 [thread overview]
Message-ID: <20190802145017.42543-2-steven.price@arm.com> (raw)
In-Reply-To: <20190802145017.42543-1-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/virtual/kvm/arm/pvtime.txt | 107 +++++++++++++++++++++++
1 file changed, 107 insertions(+)
create mode 100644 Documentation/virtual/kvm/arm/pvtime.txt
diff --git a/Documentation/virtual/kvm/arm/pvtime.txt b/Documentation/virtual/kvm/arm/pvtime.txt
new file mode 100644
index 000000000000..e6ae9799e1d5
--- /dev/null
+++ b/Documentation/virtual/kvm/arm/pvtime.txt
@@ -0,0 +1,107 @@
+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.
+
+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
+ (V)CPU. On failure:
+ NOT_SUPPORTED (-1)
+
+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 periodically as time is stolen
+from the 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 by VCPU of the guest.
+
+User space interface
+====================
+
+User space can request that KVM provide the paravirtualized time interface to
+a guest by creating a KVM_DEV_TYPE_ARM_PV_TIME device, for example:
+
+ struct kvm_create_device pvtime_device = {
+ .type = KVM_DEV_TYPE_ARM_PV_TIME,
+ .attr = 0,
+ .flags = 0,
+ };
+
+ pvtime_fd = ioctl(vm_fd, KVM_CREATE_DEVICE, &pvtime_device);
+
+The guest IPA of the structures must be given to KVM. This is the base address
+of an array of stolen time structures (one for each VCPU). For example:
+
+ struct kvm_device_attr st_base = {
+ .group = KVM_DEV_ARM_PV_TIME_PADDR,
+ .attr = KVM_DEV_ARM_PV_TIME_ST,
+ .addr = (u64)(unsigned long)&st_paddr
+ };
+
+ ioctl(pvtime_fd, KVM_SET_DEVICE_ATTR, &st_base);
+
+For migration (or save/restore) of a guest it is necessary to save the contents
+of the shared page(s) and later restore them. KVM_DEV_ARM_PV_TIME_STATE_SIZE
+provides the size of this data and KVM_DEV_ARM_PV_TIME_STATE allows the state
+to be read/written.
+
+It is also necessary for the physical address to be set identically when
+restoring.
+
+ void *save_state(int fd, u64 attr, u32 *size) {
+ struct kvm_device_attr get_size = {
+ .group = KVM_DEV_ARM_PV_TIME_STATE_SIZE,
+ .attr = attr,
+ .addr = (u64)(unsigned long)size
+ };
+
+ ioctl(fd, KVM_GET_DEVICE_ATTR, get_size);
+
+ void *buffer = malloc(*size);
+
+ struct kvm_device_attr get_state = {
+ .group = KVM_DEV_ARM_PV_TIME_STATE,
+ .attr = attr,
+ .addr = (u64)(unsigned long)size
+ };
+
+ ioctl(fd, KVM_GET_DEVICE_ATTR, buffer);
+ }
+
+ void *st_state = save_state(pvtime_fd, KVM_DEV_ARM_PV_TIME_ST, &st_size);
+
--
2.20.1
next prev parent reply other threads:[~2019-08-02 14:51 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-02 14:50 [PATCH 0/9] arm64: Stolen time support Steven Price
2019-08-02 14:50 ` Steven Price [this message]
2019-08-03 11:13 ` [PATCH 1/9] KVM: arm64: Document PV-time interface Marc Zyngier
2019-08-05 13:06 ` Steven Price
2019-08-05 3:23 ` Zenghui Yu
2019-08-05 13:06 ` Steven Price
2019-08-05 16:40 ` Christophe de Dinechin
2019-08-07 13:21 ` Steven Price
[not found] ` <9F77FA64-C71B-4025-A58D-3AC07E6688DE@dinechin.org>
2019-08-07 15:26 ` Steven Price
2019-08-02 14:50 ` [PATCH 2/9] KVM: arm/arm64: Factor out hypercall handling from PSCI code Steven Price
2019-08-02 14:50 ` [PATCH 3/9] KVM: arm64: Implement PV_FEATURES call Steven Price
2019-08-03 11:21 ` Marc Zyngier
2019-08-05 13:14 ` Steven Price
2019-08-02 14:50 ` [PATCH 4/9] KVM: arm64: Support stolen time reporting via shared structure Steven Price
2019-08-03 11:55 ` Marc Zyngier
2019-08-05 14:09 ` Steven Price
2019-08-03 17:58 ` Marc Zyngier
2019-08-03 18:13 ` Marc Zyngier
2019-08-05 14:18 ` Steven Price
2019-08-02 14:50 ` [PATCH 5/9] KVM: Allow kvm_device_ops to be const Steven Price
2019-08-02 14:50 ` [PATCH 6/9] KVM: arm64: Provide a PV_TIME device to user space Steven Price
2019-08-03 12:51 ` Marc Zyngier
2019-08-03 17:34 ` Marc Zyngier
2019-08-07 13:39 ` Steven Price
2019-08-07 13:51 ` Marc Zyngier
2019-08-05 16:10 ` Steven Price
2019-08-05 16:28 ` Marc Zyngier
2019-08-02 14:50 ` [PATCH 7/9] arm/arm64: Provide a wrapper for SMCCC 1.1 calls Steven Price
2019-08-05 10:03 ` Will Deacon
2019-08-02 14:50 ` [PATCH 8/9] arm/arm64: Make use of the SMCCC 1.1 wrapper Steven Price
2019-08-02 14:50 ` [PATCH 9/9] arm64: Retrieve stolen time as paravirtualized guest Steven Price
2019-08-04 9:53 ` Marc Zyngier
2019-08-08 15:29 ` Steven Price
2019-08-08 15:49 ` Marc Zyngier
2019-08-09 13:51 ` Zenghui Yu
2019-08-12 10:39 ` Steven Price
2019-08-13 6:06 ` Zenghui Yu
2019-08-03 18:05 ` [PATCH 0/9] arm64: Stolen time support Marc Zyngier
2019-08-05 13:06 ` Steven Price
2019-08-05 13:26 ` Marc Zyngier
2019-08-14 13:02 ` Alexander Graf
[not found] ` <8636i3omnd.wl-maz@kernel.org>
2019-08-14 14:52 ` [UNVERIFIED SENDER] " Alexander Graf
2019-08-16 10:23 ` Steven Price
2020-07-21 3:26 ` zhukeqian
2020-07-27 10:48 ` Steven Price
2020-07-29 2:57 ` zhukeqian
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