From patchwork Wed Jul 31 05:57:55 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: WangYuli X-Patchwork-Id: 13748087 Received: from smtpbgsg2.qq.com (smtpbgsg2.qq.com [54.254.200.128]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 32CB519478 for ; Wed, 31 Jul 2024 05:59:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=54.254.200.128 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722405562; cv=none; b=h+Mc2sp126qHuT+B5NFjN1+qy1zRHrPQljDWoNBui29uFsi5AsuOqvZIqCSblX2amrFruBHREqBg9ygExtRdFKdCIt5KO5ROMcVElTqZ1iMdk8+PQxkI9OYAPkLLf+KABdUKSBcv7qBIZlIMFHiqbKLet/1/+A15bazcPV3XqVc= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1722405562; c=relaxed/simple; bh=fw8pV2E6JodKBn5rCcZhCplE6uJAE3CqlzItsieqkQY=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=Bmgc98aPr+meLVBXMWrK2UgxayfUgnm6J6TsgFk68WHXoF0bNO3tb+hAxHs8ZvUSt0esC6vqYMjOWAEx1VkvjTSk211JTqLEzcqzb6qeBCFS4k2qWF1YqTGtQTRKFKJp90OfJcM59ng0ivDUaKjNrG04wmG1LXbHnNomeygL4X4= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=uniontech.com; spf=pass smtp.mailfrom=uniontech.com; arc=none smtp.client-ip=54.254.200.128 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=uniontech.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=uniontech.com X-QQ-mid: bizesmtpsz5t1722405490tkcp2mr X-QQ-Originating-IP: H58t0EWCHvpjS6Y/q97tg7C/r3E8tCwlmahWgIbr3bo= Received: from localhost.localdomain ( [113.57.152.160]) by bizesmtp.qq.com (ESMTP) with id ; Wed, 31 Jul 2024 13:58:08 +0800 (CST) X-QQ-SSF: 0000000000000000000000000000000 X-QQ-GoodBg: 1 X-BIZMAIL-ID: 8111145318027343872 From: WangYuli To: pbonzini@redhat.com, corbet@lwn.net, zhaotianrui@loongson.cn, maobibo@loongson.cn, chenhuacai@kernel.org Cc: kernel@xen0n.name, kvm@vger.kernel.org, loongarch@lists.linux.dev, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, guanwentao@uniontech.com, Xianglai Li , WangYuli Subject: [PATCH] Loongarch: KVM: Add KVM hypercalls documentation for LoongArch Date: Wed, 31 Jul 2024 13:57:55 +0800 Message-ID: <04DAF94279B88A3F+20240731055755.84082-1-wangyuli@uniontech.com> X-Mailer: git-send-email 2.43.4 Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-QQ-SENDSIZE: 520 Feedback-ID: bizesmtpsz:uniontech.com:qybglogicsvrgz:qybglogicsvrgz8a-1 From: Bibo Mao Add documentation topic for using pv_virt when running as a guest on KVM hypervisor. Signed-off-by: Bibo Mao Signed-off-by: Xianglai Li Signed-off-by: WangYuli --- Documentation/virt/kvm/index.rst | 1 + .../virt/kvm/loongarch/hypercalls.rst | 79 +++++++++++++++++++ Documentation/virt/kvm/loongarch/index.rst | 10 +++ MAINTAINERS | 1 + 4 files changed, 91 insertions(+) create mode 100644 Documentation/virt/kvm/loongarch/hypercalls.rst create mode 100644 Documentation/virt/kvm/loongarch/index.rst diff --git a/Documentation/virt/kvm/index.rst b/Documentation/virt/kvm/index.rst index ad13ec55ddfe..9ca5a45c2140 100644 --- a/Documentation/virt/kvm/index.rst +++ b/Documentation/virt/kvm/index.rst @@ -14,6 +14,7 @@ KVM s390/index ppc-pv x86/index + loongarch/index locking vcpu-requests diff --git a/Documentation/virt/kvm/loongarch/hypercalls.rst b/Documentation/virt/kvm/loongarch/hypercalls.rst new file mode 100644 index 000000000000..1679e48d67d2 --- /dev/null +++ b/Documentation/virt/kvm/loongarch/hypercalls.rst @@ -0,0 +1,79 @@ +.. SPDX-License-Identifier: GPL-2.0 + +=================================== +The LoongArch paravirtual interface +=================================== + +KVM hypercalls use the HVCL instruction with code 0x100, and the hypercall +number is put in a0 and up to five arguments may be placed in a1-a5, the +return value is placed in v0 (alias with a0). + +The code for that interface can be found in arch/loongarch/kvm/* + +Querying for existence +====================== + +To find out if we're running on KVM or not, cpucfg can be used with index +CPUCFG_KVM_BASE (0x40000000), cpucfg range between 0x40000000 - 0x400000FF +is marked as a specially reserved range. All existing and future processors +will not implement any features in this range. + +When Linux is running on KVM, cpucfg with index CPUCFG_KVM_BASE (0x40000000) +returns magic string "KVM\0" + +Once you determined you're running under a PV capable KVM, you can now use +hypercalls as described below. + +KVM hypercall ABI +================= + +Hypercall ABI on KVM is simple, only one scratch register a0 (v0) and at most +five generic registers used as input parameter. FP register and vector register +is not used for input register and should not be modified during hypercall. +Hypercall function can be inlined since there is only one scratch register. + +The parameters are as follows: + + ======== ================ ================ + Register IN OUT + ======== ================ ================ + a0 function number Return code + a1 1st parameter - + a2 2nd parameter - + a3 3rd parameter - + a4 4th parameter - + a5 5th parameter - + ======== ================ ================ + +Return codes can be as follows: + + ==== ========================= + Code Meaning + ==== ========================= + 0 Success + -1 Hypercall not implemented + -2 Hypercall parameter error + ==== ========================= + +KVM Hypercalls Documentation +============================ + +The template for each hypercall is: +1. Hypercall name +2. Purpose + +1. KVM_HCALL_FUNC_PV_IPI +------------------------ + +:Purpose: Send IPIs to multiple vCPUs. + +- a0: KVM_HCALL_FUNC_PV_IPI +- a1: lower part of the bitmap of destination physical CPUIDs +- a2: higher part of the bitmap of destination physical CPUIDs +- a3: the lowest physical CPUID in bitmap + +The hypercall lets a guest send multicast IPIs, with at most 128 +destinations per hypercall. The destinations are represented by a bitmap +contained in the first two arguments (a1 and a2). Bit 0 of a1 corresponds +to the physical CPUID in the third argument (a3), bit 1 corresponds to the +physical ID a3+1, and so on. diff --git a/Documentation/virt/kvm/loongarch/index.rst b/Documentation/virt/kvm/loongarch/index.rst new file mode 100644 index 000000000000..83387b4c5345 --- /dev/null +++ b/Documentation/virt/kvm/loongarch/index.rst @@ -0,0 +1,10 @@ +.. SPDX-License-Identifier: GPL-2.0 + +========================= +KVM for LoongArch systems +========================= + +.. toctree:: + :maxdepth: 2 + + hypercalls.rst diff --git a/MAINTAINERS b/MAINTAINERS index 958e935449e5..8aa5d92b12ee 100644 --- a/MAINTAINERS +++ b/MAINTAINERS @@ -12073,6 +12073,7 @@ L: kvm@vger.kernel.org L: loongarch@lists.linux.dev S: Maintained T: git git://git.kernel.org/pub/scm/virt/kvm/kvm.git +F: Documentation/virt/kvm/loongarch/ F: arch/loongarch/include/asm/kvm* F: arch/loongarch/include/uapi/asm/kvm* F: arch/loongarch/kvm/