From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out30-98.freemail.mail.aliyun.com (out30-98.freemail.mail.aliyun.com [115.124.30.98]) (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 988CD2264B0; Fri, 16 Jan 2026 14:30:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=115.124.30.98 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768573805; cv=none; b=MIlBkcEPnXuH92WBbwGeDyYSUhErQMfUlYqP9saJecajV2nbVJAykWhWezVCyOYHeXzJrcoCk73iBeLauRWFbfItHn5yZcQWJ9N4Un1t0DjW55nBDaUWst2c+e60th/ndO29Mlkr8URQn4AcvumR2qwjlacp/eDZ60h4s7Qe4t8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768573805; c=relaxed/simple; bh=Ze8/tNVvQO7baDWI7fWfu7Bet/8G2e9QTRDyHU8fgn0=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version; b=NSM5MQeTbf+AEptH2MEbTLq8R2gf2OeJvMZHcU+ZwqEggr4fOqAgrEyENOINKGXTWUcxcTe5IvWw/VmuLw2/aAmq8yBK6QFsnEaKQ/w38H3+jNy4FQFoiDOT9QkzOxLFvSZSxr+4jQINchk3zNQuvb7SibdLs5i27F0H/7zuIz4= 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=WWkresjD; arc=none smtp.client-ip=115.124.30.98 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="WWkresjD" DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.alibaba.com; s=default; t=1768573794; h=From:To:Subject:Date:Message-Id:MIME-Version; bh=XnMbHiZD4Q8ihaJAYTR3qJJVShDyzERVKVSspF7MbMc=; b=WWkresjDY+kOIakHS+Ll9HuhWEMGMZq2hM/VOE18HFCgxoe24Zv+S/wQa8f9+vz1gYn0hjIxfx2HPn7WNf/U3oJQHLn40KaYy+eovkYiRS7bXzmmdOUwYxmpa9QiGPz7VgoQkx3neJtlI+/tGwRwPBO5Ulsdbk6vkTAJrW6glMU= Received: from localhost.localdomain(mailfrom:fangyu.yu@linux.alibaba.com fp:SMTPD_---0WxARSAt_1768573791 cluster:ay36) by smtp.aliyun-inc.com; Fri, 16 Jan 2026 22:29:53 +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, rkrcmar@ventanamicro.com Subject: Re: Re: [PATCH v2] RISC-V: KVM: add KVM_CAP_RISCV_SET_HGATP_MODE Date: Fri, 16 Jan 2026 22:29:47 +0800 Message-Id: <20260116142947.30520-1-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-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit >> From: Fangyu Yu >> >> This capability allows userspace to explicitly select the HGATP mode >> for the VM. The selected mode must be less than or equal to the max >> HGATP mode supported by the hardware. This capability must be enabled >> before creating any vCPUs, and can only be set once per VM. >> >> Signed-off-by: Fangyu Yu >> --- >> Documentation/virt/kvm/api.rst | 14 ++++++++++++++ >> arch/riscv/kvm/vm.c | 26 ++++++++++++++++++++++++-- >> include/uapi/linux/kvm.h | 1 + >> 3 files changed, 39 insertions(+), 2 deletions(-) >> >> diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst >> index 01a3abef8abb..9e17788e3a9d 100644 >> --- a/Documentation/virt/kvm/api.rst >> +++ b/Documentation/virt/kvm/api.rst >> @@ -8765,6 +8765,20 @@ 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 arg[0] is outside the range of hgatp >> + modes supported by the hardware. >> + >> +This capability allows userspace to explicitly select the HGATP mode for >> +the VM. The selected mode must be less than or equal to the maximum HGATP >> +mode supported by the hardware. This capability must be enabled before >> +creating any vCPUs, and can only be set once per VM. > >I think I would prefer a KVM_CAP_RISCV_SET_MAX_GPA type of capability. The >reason is because, while one of the results of the max-gpa being set will >be to set hgatp, there may be other reasons to track the guest's maximum >physical address too and kvm userspace shouldn't need to think about each >individually. That makes sense, thanks. >> + >> 8. Other capabilities. >> ====================== >> >> diff --git a/arch/riscv/kvm/vm.c b/arch/riscv/kvm/vm.c >> index 4b2156df40fc..e9275023a73a 100644 >> --- a/arch/riscv/kvm/vm.c >> +++ b/arch/riscv/kvm/vm.c >> @@ -202,6 +202,13 @@ 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: >> +#ifdef CONFIG_64BIT >> + r = 1; >> +#else/* CONFIG_32BIT */ >> + r = 0; >> +#endif > > r = IS_ENABLED(CONFIG_64BIT) ? 1 : 0; Ack. >> + break; >> default: >> r = 0; >> break; >> @@ -212,12 +219,27 @@ 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; > >add blank line Ack, will add a blank line after the flags check. > >> 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 (cap->args[0] < HGATP_MODE_SV39X4 || >> + cap->args[0] > kvm_riscv_gstage_max_mode) >> + return -EINVAL; >> + if (kvm->arch.gstage_mode_initialized) >> + return 0; > >I think we want to return -EBUSY here and it should be documented where it >already states "...can only be set once per VM" Agreed. >> + kvm->arch.gstage_mode_initialized = true; > >In the previous patch I thought we were missing this, but I see now it >means "user initialized". Let's rename it as such, > > gstage_mode_user_initialized Agreed. >> + kvm->arch.kvm_riscv_gstage_mode = cap->args[0]; >> + kvm->arch.kvm_riscv_gstage_pgd_levels = 3 + >> + kvm->arch.kvm_riscv_gstage_mode - HGATP_MODE_SV39X4; >> + kvm_info("using SV%lluX4 G-stage page table format\n", >> + 39 + (cap->args[0] - HGATP_MODE_SV39X4) * 9); >> +#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