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Mon, 07 Nov 2022 09:56:49 -0800 (PST) From: Punit Agrawal To: Usama Arif Subject: Re: [v2 1/6] KVM: arm64: Document PV-lock interface References: <20221104062105.4119003-1-usama.arif@bytedance.com> <20221104062105.4119003-2-usama.arif@bytedance.com> Date: Mon, 07 Nov 2022 17:56:49 +0000 Message-ID: <87k0463axq.fsf@stealth> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) MIME-Version: 1.0 X-Mailman-Approved-At: Thu, 10 Nov 2022 09:51:44 -0500 Cc: kvm@vger.kernel.org, linux-doc@vger.kernel.org, catalin.marinas@arm.com, linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, fam.zheng@bytedance.com, bagasdotme@gmail.com, maz@kernel.org, punit.agrawal@bytedance.com, linux@armlinux.org.uk, liangma@liangbit.com, steven.price@arm.com, will@kernel.org, kvmarm@lists.cs.columbia.edu, linux-arm-kernel@lists.infradead.org X-BeenThere: kvmarm@lists.cs.columbia.edu X-Mailman-Version: 2.1.14 Precedence: list List-Id: Where KVM/ARM decisions are made List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: kvmarm-bounces@lists.cs.columbia.edu Sender: kvmarm-bounces@lists.cs.columbia.edu Hi Usama, Usama Arif writes: > Introduce a paravirtualization interface for KVM/arm64 to obtain whether > the VCPU is currently running or not. > > The PV lock structure of the guest is allocated by user space. > > A hypercall interface is provided for the guest to interrogate the > location of the shared memory structures. > > Signed-off-by: Zengruan Ye > Signed-off-by: Usama Arif > --- > Documentation/virt/kvm/arm/index.rst | 1 + > Documentation/virt/kvm/arm/pvlock.rst | 52 +++++++++++++++++++++++++ > Documentation/virt/kvm/devices/vcpu.rst | 25 ++++++++++++ > 3 files changed, 78 insertions(+) > create mode 100644 Documentation/virt/kvm/arm/pvlock.rst > > diff --git a/Documentation/virt/kvm/arm/index.rst b/Documentation/virt/kvm/arm/index.rst > index e84848432158..b8499dc00a6a 100644 > --- a/Documentation/virt/kvm/arm/index.rst > +++ b/Documentation/virt/kvm/arm/index.rst > @@ -10,4 +10,5 @@ ARM > hyp-abi > hypercalls > pvtime > + pvlock > ptp_kvm > diff --git a/Documentation/virt/kvm/arm/pvlock.rst b/Documentation/virt/kvm/arm/pvlock.rst > new file mode 100644 > index 000000000000..d3c391b16d36 > --- /dev/null > +++ b/Documentation/virt/kvm/arm/pvlock.rst > @@ -0,0 +1,52 @@ > +.. SPDX-License-Identifier: GPL-2.0 > + > +Paravirtualized lock support for arm64 > +====================================== > + > +KVM/arm64 provides a hypervisor service call for paravirtualized guests to > +determine whether a VCPU is currently running or not. > + > +A new SMCCC compatible hypercall is defined: > + > +* ARM_SMCCC_VENDOR_HYP_KVM_PV_LOCK_FUNC_ID: 0xC6000002 > + > +ARM_SMCCC_VENDOR_HYP_KVM_PV_LOCK_FUNC_ID > + > + ============= ======== ========================================== > + Function ID: (uint32) 0xC6000002 > + Return value: (int64) IPA of the pv lock data structure for this > + VCPU. On failure: > + NOT_SUPPORTED (-1) > + ============= ======== ========================================== > + > +The IPA returned by PV_LOCK_PREEMPTED should be mapped by the guest as normal > +memory with inner and outer write back caching attributes, in the inner > +shareable domain. > + > +PV_LOCK_PREEMPTED returns the structure for the calling VCPU. > + > +PV lock state > +------------- > + > +The structure pointed to by the PV_LOCK_PREEMPTED hypercall is as follows: > + > ++-----------+-------------+-------------+---------------------------------+ > +| Field | Byte Length | Byte Offset | Description | > ++===========+=============+=============+=================================+ > +| preempted | 8 | 0 | Indicate if the VCPU that owns | > +| | | | this struct is running or not. | > +| | | | Non-zero values mean the VCPU | > +| | | | has been preempted. Zero means | > +| | | | the VCPU is not preempted. | > ++-----------+-------------+-------------+---------------------------------+ > + > +The preempted field will be updated to 1 by the hypervisor prior to scheduling > +a VCPU. When the VCPU is scheduled out, the preempted field will be updated > +to 0 by the hypervisor. The text above doesn't match the description in the table. Please update the texts to align them with the code. [...] _______________________________________________ kvmarm mailing list kvmarm@lists.cs.columbia.edu https://lists.cs.columbia.edu/mailman/listinfo/kvmarm