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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: X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list 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;