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Tue, 21 Oct 2025 09:56:20 -0700 (PDT) Date: Tue, 21 Oct 2025 09:56:19 -0700 In-Reply-To: Mime-Version: 1.0 References: <20251017003244.186495-1-seanjc@google.com> <20251017003244.186495-24-seanjc@google.com> Message-ID: Subject: Re: [PATCH v3 23/25] KVM: TDX: Use guard() to acquire kvm->lock in tdx_vm_ioctl() From: Sean Christopherson To: Rick P Edgecombe Cc: "chenhuacai@kernel.org" , "frankja@linux.ibm.com" , "maz@kernel.org" , "borntraeger@linux.ibm.com" , "pjw@kernel.org" , "aou@eecs.berkeley.edu" , "kas@kernel.org" , "maobibo@loongson.cn" , "pbonzini@redhat.com" , "maddy@linux.ibm.com" , "palmer@dabbelt.com" , "imbrenda@linux.ibm.com" , "zhaotianrui@loongson.cn" , "anup@brainfault.org" , "oliver.upton@linux.dev" , "kvm@vger.kernel.org" , "linux-coco@lists.linux.dev" , Kai Huang , Yan Y Zhao , "michael.roth@amd.com" , "linux-kernel@vger.kernel.org" , Ira Weiny , "loongarch@lists.linux.dev" , "binbin.wu@linux.intel.com" , "ackerleytng@google.com" , "kvmarm@lists.linux.dev" , Vishal Annapurve , "kvm-riscv@lists.infradead.org" , "linuxppc-dev@lists.ozlabs.org" , "linux-arm-kernel@lists.infradead.org" , "linux-mips@vger.kernel.org" , "linux-riscv@lists.infradead.org" , "x86@kernel.org" X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20251021_095622_937878_8ACFDE47 X-CRM114-Status: GOOD ( 10.17 ) X-BeenThere: kvm-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kvm-riscv" Errors-To: kvm-riscv-bounces+kvm-riscv=archiver.kernel.org@lists.infradead.org On Tue, Oct 21, 2025, Rick P Edgecombe wrote: > On Thu, 2025-10-16 at 17:32 -0700, Sean Christopherson wrote: > > Use guard() in tdx_vm_ioctl() to tidy up the code a small amount, but more > > importantly to minimize the diff of a future change, which will use > > guard-like semantics to acquire and release multiple locks. > > > > No functional change intended. > > There is a tiny functional change. In the default case it no longer re-copies > the struct back to userspace. No? The default case doesn't copy the struct back even before this patch, it explicitly skips the copy_to_user(). mutex_lock(&kvm->lock); switch (tdx_cmd.id) { case KVM_TDX_CAPABILITIES: r = tdx_get_capabilities(&tdx_cmd); break; case KVM_TDX_INIT_VM: r = tdx_td_init(kvm, &tdx_cmd); break; case KVM_TDX_FINALIZE_VM: r = tdx_td_finalize(kvm, &tdx_cmd); break; default: r = -EINVAL; goto out; <==================== } if (copy_to_user(argp, &tdx_cmd, sizeof(struct kvm_tdx_cmd))) r = -EFAULT; out: mutex_unlock(&kvm->lock); return r; -- kvm-riscv mailing list kvm-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kvm-riscv From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f201.google.com (mail-pl1-f201.google.com [209.85.214.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id F0E223446BF for ; Tue, 21 Oct 2025 16:56:21 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; 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Tue, 21 Oct 2025 09:56:20 -0700 (PDT) Date: Tue, 21 Oct 2025 09:56:19 -0700 In-Reply-To: Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20251017003244.186495-1-seanjc@google.com> <20251017003244.186495-24-seanjc@google.com> Message-ID: Subject: Re: [PATCH v3 23/25] KVM: TDX: Use guard() to acquire kvm->lock in tdx_vm_ioctl() From: Sean Christopherson To: Rick P Edgecombe Cc: "chenhuacai@kernel.org" , "frankja@linux.ibm.com" , "maz@kernel.org" , "borntraeger@linux.ibm.com" , "pjw@kernel.org" , "aou@eecs.berkeley.edu" , "kas@kernel.org" , "maobibo@loongson.cn" , "pbonzini@redhat.com" , "maddy@linux.ibm.com" , "palmer@dabbelt.com" , "imbrenda@linux.ibm.com" , "zhaotianrui@loongson.cn" , "anup@brainfault.org" , "oliver.upton@linux.dev" , "kvm@vger.kernel.org" , "linux-coco@lists.linux.dev" , Kai Huang , Yan Y Zhao , "michael.roth@amd.com" , "linux-kernel@vger.kernel.org" , Ira Weiny , "loongarch@lists.linux.dev" , "binbin.wu@linux.intel.com" , "ackerleytng@google.com" , "kvmarm@lists.linux.dev" , Vishal Annapurve , "kvm-riscv@lists.infradead.org" , "linuxppc-dev@lists.ozlabs.org" , "linux-arm-kernel@lists.infradead.org" , "linux-mips@vger.kernel.org" , "linux-riscv@lists.infradead.org" , "x86@kernel.org" Content-Type: text/plain; charset="us-ascii" On Tue, Oct 21, 2025, Rick P Edgecombe wrote: > On Thu, 2025-10-16 at 17:32 -0700, Sean Christopherson wrote: > > Use guard() in tdx_vm_ioctl() to tidy up the code a small amount, but more > > importantly to minimize the diff of a future change, which will use > > guard-like semantics to acquire and release multiple locks. > > > > No functional change intended. > > There is a tiny functional change. In the default case it no longer re-copies > the struct back to userspace. No? The default case doesn't copy the struct back even before this patch, it explicitly skips the copy_to_user(). mutex_lock(&kvm->lock); switch (tdx_cmd.id) { case KVM_TDX_CAPABILITIES: r = tdx_get_capabilities(&tdx_cmd); break; case KVM_TDX_INIT_VM: r = tdx_td_init(kvm, &tdx_cmd); break; case KVM_TDX_FINALIZE_VM: r = tdx_td_finalize(kvm, &tdx_cmd); break; default: r = -EINVAL; goto out; <==================== } if (copy_to_user(argp, &tdx_cmd, sizeof(struct kvm_tdx_cmd))) r = -EFAULT; out: mutex_unlock(&kvm->lock); return r; From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id ABB48CCD184 for ; Tue, 21 Oct 2025 16:56:42 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; 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Tue, 21 Oct 2025 09:56:20 -0700 (PDT) Date: Tue, 21 Oct 2025 09:56:19 -0700 In-Reply-To: Mime-Version: 1.0 References: <20251017003244.186495-1-seanjc@google.com> <20251017003244.186495-24-seanjc@google.com> Message-ID: Subject: Re: [PATCH v3 23/25] KVM: TDX: Use guard() to acquire kvm->lock in tdx_vm_ioctl() From: Sean Christopherson To: Rick P Edgecombe Cc: "chenhuacai@kernel.org" , "frankja@linux.ibm.com" , "maz@kernel.org" , "borntraeger@linux.ibm.com" , "pjw@kernel.org" , "aou@eecs.berkeley.edu" , "kas@kernel.org" , "maobibo@loongson.cn" , "pbonzini@redhat.com" , "maddy@linux.ibm.com" , "palmer@dabbelt.com" , "imbrenda@linux.ibm.com" , "zhaotianrui@loongson.cn" , "anup@brainfault.org" , "oliver.upton@linux.dev" , "kvm@vger.kernel.org" , "linux-coco@lists.linux.dev" , Kai Huang , Yan Y Zhao , "michael.roth@amd.com" , "linux-kernel@vger.kernel.org" , Ira Weiny , "loongarch@lists.linux.dev" , "binbin.wu@linux.intel.com" , "ackerleytng@google.com" , "kvmarm@lists.linux.dev" , Vishal Annapurve , "kvm-riscv@lists.infradead.org" , "linuxppc-dev@lists.ozlabs.org" , "linux-arm-kernel@lists.infradead.org" , "linux-mips@vger.kernel.org" , "linux-riscv@lists.infradead.org" , "x86@kernel.org" X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20251021_095622_937867_BE74457C X-CRM114-Status: GOOD ( 10.17 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org On Tue, Oct 21, 2025, Rick P Edgecombe wrote: > On Thu, 2025-10-16 at 17:32 -0700, Sean Christopherson wrote: > > Use guard() in tdx_vm_ioctl() to tidy up the code a small amount, but more > > importantly to minimize the diff of a future change, which will use > > guard-like semantics to acquire and release multiple locks. > > > > No functional change intended. > > There is a tiny functional change. In the default case it no longer re-copies > the struct back to userspace. No? The default case doesn't copy the struct back even before this patch, it explicitly skips the copy_to_user(). mutex_lock(&kvm->lock); switch (tdx_cmd.id) { case KVM_TDX_CAPABILITIES: r = tdx_get_capabilities(&tdx_cmd); break; case KVM_TDX_INIT_VM: r = tdx_td_init(kvm, &tdx_cmd); break; case KVM_TDX_FINALIZE_VM: r = tdx_td_finalize(kvm, &tdx_cmd); break; default: r = -EINVAL; goto out; <==================== } if (copy_to_user(argp, &tdx_cmd, sizeof(struct kvm_tdx_cmd))) r = -EFAULT; out: mutex_unlock(&kvm->lock); return r; _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv