From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-130.freemail.mail.aliyun.com (out30-130.freemail.mail.aliyun.com [115.124.30.130]) (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 E22E83A901D; Tue, 3 Feb 2026 14:22:20 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.130 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770128544; cv=none; b=XpDK16k46z89KFWwQRwMlnLkTugZvv5TPqVzClUYi6jsVHgWOmXH8dO9+Z8H4dhx2bZivAn0Dn0mmHBQHOFdkCl2AdImVzJr6k0JYYpUbxfxUOMEQ9nptAhmdsOCVjkQPUJ8wADTs67qOdQnThUbD1RFE7XVL6GjwBZrbLZE4w4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770128544; c=relaxed/simple; bh=9OMtrySsAik6Ak+MHK9o5jJ7Q/IlwAgFk6z6a7uFFZ4=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=OnAXB/EeTAruXnYap21h8cNxCjNzfu6GiotO7oHRolOBPM/F6URxszRrAdEUDu8K4xCBW82Dy2p3Y4HkiFITSL/tCuOlDhB9t+hDglQKRL11CKwOeFRxAjPRfESf0zfuW7xyGkfJ3K728Q1U0ng9Q4s0jjo7lrhhBINuSX5M88w= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com; spf=pass smtp.mailfrom=linux.alibaba.com; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b=ACim2Y/O; arc=none smtp.client-ip=115.124.30.130 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.alibaba.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.alibaba.com header.i=@linux.alibaba.com header.b="ACim2Y/O" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1770128533; h=From:To:Subject:Date:Message-Id:MIME-Version; bh=nm8PIuhdmjvOUlssXNxbPqc5VUHCAA6PpVhh/L+a2hk=; b=ACim2Y/OATnsFtDLwuPVEACcOhSixFnmVk1rf4CKVkE8JNhW9idHDT5jlLMuIXuxInulwU5EOdig0XIymq0CIjEmmh1sjkuPMf9fQh2omHfaiG4yRyMnR8HCXUabfvPdHxl3rekqgF5SCRldQ2fl9Tty1DI4lFplwhyfJ/SJazk= Received: from localhost.localdomain(mailfrom:fangyu.yu@linux.alibaba.com fp:SMTPD_---0WyTLON._1770128530 cluster:ay36) by smtp.aliyun-inc.com; Tue, 03 Feb 2026 22:22:12 +0800 From: fangyu.yu@linux.alibaba.com To: andrew.jones@oss.qualcomm.com Cc: ajones@ventanamicro.com, alex@ghiti.fr, anup@brainfault.org, aou@eecs.berkeley.edu, atish.patra@linux.dev, corbet@lwn.net, fangyu.yu@linux.alibaba.com, guoren@kernel.org, kvm-riscv@lists.infradead.org, kvm@vger.kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-riscv@lists.infradead.org, palmer@dabbelt.com, pbonzini@redhat.com, pjw@kernel.org, radim.krcmar@oss.qualcomm.com, rkrcmar@ventanamicro.com Subject: Re: Re: [PATCH v4 3/4] RISC-V: KVM: add KVM_CAP_RISCV_SET_HGATP_MODE Date: Tue, 3 Feb 2026 22:22:10 +0800 Message-Id: <20260203142210.98862-1-fangyu.yu@linux.alibaba.com> X-Mailer: git-send-email 2.39.3 (Apple Git-146) In-Reply-To: <73zrxri5snnenmezjxrdorbcsps4dlvtrkvkq3w4ain4ggbxdl@hjw4u73msaro> References: <73zrxri5snnenmezjxrdorbcsps4dlvtrkvkq3w4ain4ggbxdl@hjw4u73msaro> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit >> From: Fangyu Yu >> >> Add a VM capability that allows userspace to select the G-stage page table >> format by setting HGATP.MODE on a per-VM basis. >> >> Userspace enables the capability via KVM_ENABLE_CAP, passing the requested >> HGATP.MODE in args[0]. The request is rejected with -EINVAL if the mode is >> not supported by the host, and with -EBUSY if the VM has already been >> committed (e.g. vCPUs have been created or any memslot is populated). >> >> KVM_CHECK_EXTENSION(KVM_CAP_RISCV_SET_HGATP_MODE) returns a bitmask of the >> HGATP.MODE formats supported by the host. >> >> Signed-off-by: Fangyu Yu >> --- >> Documentation/virt/kvm/api.rst | 27 +++++++++++++++++++++++++++ >> arch/riscv/kvm/vm.c | 20 ++++++++++++++++++-- >> include/uapi/linux/kvm.h | 1 + >> 3 files changed, 46 insertions(+), 2 deletions(-) >> >> diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst >> index 01a3abef8abb..1a0c5ddacae8 100644 >> --- a/Documentation/virt/kvm/api.rst >> +++ b/Documentation/virt/kvm/api.rst >> @@ -8765,6 +8765,33 @@ helpful if user space wants to emulate instructions which are not >> This capability can be enabled dynamically even if VCPUs were already >> created and are running. >> >> +7.47 KVM_CAP_RISCV_SET_HGATP_MODE >> +--------------------------------- >> + >> +:Architectures: riscv > >If we only want this to work for rv64, then we should write riscv64 here, >but, as I said in the last patch, I think we can just support rv32 too >by supporting its one and only mode. Agreed. I'll update the documentation to list ":Architectures: riscv" and make the capability available on both RV32 and RV64. For RV32, userspace will be able to select the single supported G-stage mode (Sv32x4) >> +:Type: VM >> +:Parameters: args[0] contains the requested HGATP mode >> +:Returns: >> + - 0 on success. >> + - -EINVAL if args[0] is outside the range of HGATP modes supported by the >> + hardware. >> + - -EBUSY if vCPUs have already been created for the VM, if the VM has any >> + non-empty memslots. >> + >> +This capability allows userspace to explicitly select the HGATP mode for >> +the VM. The selected mode must be supported by both KVM and hardware. This >> +capability must be enabled before creating any vCPUs or memslots. > >We should write what happens if the capability (setting the mode) is not >done, i.e. what's the default mode. Good point. I'll update the documentation to explicitly state the default behavior when KVM_CAP_RISCV_SET_HGATP_MODE is not used: KVM will auto-select the HGATP G-stage mode during VM initialization. In other words, userspace only needs to set the capability when it wants to override the default auto-selection. >> + >> +``KVM_CHECK_EXTENSION(KVM_CAP_RISCV_SET_HGATP_MODE)`` returns a bitmask of >> +HGATP.MODE values supported by the host. A return value of 0 indicates that >> +the capability is not supported. >> + >> +The returned bitmask uses the following bit positions:: >> + >> + bit 0: HGATP.MODE = SV39X4 >> + bit 1: HGATP.MODE = SV48X4 >> + bit 2: HGATP.MODE = SV57X4 > >Could write something along the lines of the UAPI having the bit >definitions rather than duplicating that information here. > Sure. I'll rework this section. >> + >> 8. Other capabilities. >> ====================== >> >> diff --git a/arch/riscv/kvm/vm.c b/arch/riscv/kvm/vm.c >> index 4b2156df40fc..3bbbcb6a17a6 100644 >> --- a/arch/riscv/kvm/vm.c >> +++ b/arch/riscv/kvm/vm.c >> @@ -202,6 +202,9 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) >> case KVM_CAP_VM_GPA_BITS: >> r = kvm_riscv_gstage_gpa_bits(&kvm->arch); >> break; >> + case KVM_CAP_RISCV_SET_HGATP_MODE: >> + r = kvm_riscv_get_hgatp_mode_mask(); >> + break; >> default: >> r = 0; >> break; >> @@ -212,12 +215,25 @@ int kvm_vm_ioctl_check_extension(struct kvm *kvm, long ext) >> >> int kvm_vm_ioctl_enable_cap(struct kvm *kvm, struct kvm_enable_cap *cap) >> { >> + if (cap->flags) >> + return -EINVAL; >> + >> switch (cap->cap) { >> case KVM_CAP_RISCV_MP_STATE_RESET: >> - if (cap->flags) >> - return -EINVAL; >> kvm->arch.mp_state_reset = true; >> return 0; >> + case KVM_CAP_RISCV_SET_HGATP_MODE: >> +#ifdef CONFIG_64BIT >> + if (!kvm_riscv_hgatp_mode_is_valid(cap->args[0])) >> + return -EINVAL; >> + >> + if (kvm->created_vcpus || !kvm_are_all_memslots_empty(kvm)) >> + return -EBUSY; >> + >> + kvm->arch.kvm_riscv_gstage_pgd_levels = >> + 3 + cap->args[0] - HGATP_MODE_SV39X4; >> +#endif >> + return 0; >> default: >> return -EINVAL; >> } >> diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h >> index dddb781b0507..00c02a880518 100644 >> --- a/include/uapi/linux/kvm.h >> +++ b/include/uapi/linux/kvm.h >> @@ -974,6 +974,7 @@ struct kvm_enable_cap { >> #define KVM_CAP_GUEST_MEMFD_FLAGS 244 >> #define KVM_CAP_ARM_SEA_TO_USER 245 >> #define KVM_CAP_S390_USER_OPEREXEC 246 >> +#define KVM_CAP_RISCV_SET_HGATP_MODE 247 >> >> struct kvm_irq_routing_irqchip { >> __u32 irqchip; >> -- >> 2.50.1 >> > >Thanks, >drew Thanks, Fangyu