From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-132.freemail.mail.aliyun.com (out30-132.freemail.mail.aliyun.com [115.124.30.132]) (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 BD06621ADB7; Thu, 5 Feb 2026 01:28:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.132 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770254903; cv=none; b=JRsI8LTPV/BnTX7REVF5LDryAuol4sXq1askbQ7SZ4xokZfVnxRK+bn14aWNwC/Zzs4ivi7nHuxyiSTOmCHmCYXPR4my82IstNLHT6Q6QiBMjG7zeKHsmHonI8m7Z5D3+Xwg6PhWo9fHBAuMYU3EH6dMUyP3RikOb5Cbd0awF/I= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1770254903; c=relaxed/simple; bh=U6I0qix+enFlE4sbK3k8XgOzt02MZF0j3tf/bMnHaig=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=iNV74Df9Qg+u4SBjFnMRfDGQm+gpoDmgWaBx0xaT91GVulXvn0iXhcxUahjmoBblYeMRmBevC/ggPdWZg9UE70zIcJgDxTO08b1G6wEEKP8EGExLhfpejS/lcz6P6FULduKi/X90UpXvqkRD3ErA8nJwDkRmIxCyHN8pGurTbMU= 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=kQJPMdJM; arc=none smtp.client-ip=115.124.30.132 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="kQJPMdJM" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1770254893; h=From:To:Subject:Date:Message-Id:MIME-Version; bh=ch2lw3Gkx/tmSQGhjBy06LxNeqZ/lvoi8ni6rWgh66M=; b=kQJPMdJMKpKWi43ymOHB+IBcV8DKgbFDhzi3mgC4TI4159ZhTTeD4tz/b1imKgGkzbhe0O5kaVqnwemoqw7YVE57HNRAWQ4HHy1iuLtfR9KJeOIreYm+lhTDQKgj+ois6e1Cinetkll/nW/rmyeQKVYg6FG1q9in+UMH3BELMRE= Received: from localhost.localdomain(mailfrom:fangyu.yu@linux.alibaba.com fp:SMTPD_---0WyZ3nte_1770254889 cluster:ay36) by smtp.aliyun-inc.com; Thu, 05 Feb 2026 09:28:11 +0800 From: fangyu.yu@linux.alibaba.com To: andrew.jones@oss.qualcomm.com Cc: 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 Subject: Re: Re: [PATCH v5 3/3] RISC-V: KVM: add KVM_CAP_RISCV_SET_HGATP_MODE Date: Thu, 5 Feb 2026 09:28:08 +0800 Message-Id: <20260205012808.98973-1-fangyu.yu@linux.alibaba.com> X-Mailer: git-send-email 2.39.3 (Apple Git-146) In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-doc@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 | 19 +++++++++++++++++-- >> include/uapi/linux/kvm.h | 1 + >> 3 files changed, 45 insertions(+), 2 deletions(-) >> >> diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst >> index 01a3abef8abb..62dc120857c1 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 >> +: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. >> + > >Currently the documentation for KVM_SET_ONE_REG has this for EBUSY > > EBUSY (riscv) changing register value not allowed after the vcpu > has run at least once > >I suggest we update the KVM_SET_ONE_REG EBUSY description to say > >(riscv) changing register value not allowed. This may occur after the vcpu >has run at least once or when other setup has completed which depends on >the value of the register. Thanks for the suggestion. In this series the HGATP mode is configured via KVM_ENABLE_CAP at the VM level (kvm_vm_ioctl_enable_cap), not via KVM_SET_ONE_REG. Updating the KVM_SET_ONE_REG -EBUSY description might be misleading since it is vCPU one-reg specific and not directly related to this series. >> +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. >> + >> +If this capability is not enabled, KVM will select the default HGATP mode >> +automatically. The default is the highest HGATP.MODE value supported by >> +hardware. >> + >> +``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. Supported-mode bitmask use HGATP.MODE >> +encodings as defined by the RISC-V privileged specification, such as Sv39x4 >> +corresponds to HGATP.MODE=8, so userspace should test bitmask & BIT(8). >> + >> 8. Other capabilities. >> ====================== >> >> diff --git a/arch/riscv/kvm/vm.c b/arch/riscv/kvm/vm.c >> index 4b2156df40fc..7d1e1d257df5 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 +215,24 @@ 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: >> + if (!kvm_riscv_hgatp_mode_is_valid(cap->args[0])) >> + return -EINVAL; >> + >> + if (kvm->created_vcpus || !kvm_are_all_memslots_empty(kvm)) >> + return -EBUSY; >> +#ifdef CONFIG_64BIT >> + kvm->arch.kvm_riscv_gstage_pgd_levels = >> + 3 + cap->args[0] - HGATP_MODE_SV39X4; >> +#endif > > 'if (IS_ENABLED(CONFIG_64BIT))' is preferred to the #ifdef. > >> + 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