[v3] KVM: x86/mmu: TDX post-populate cleanups

[PATCH v3 23/25] KVM: TDX: Use guard() to acquire kvm->lock in tdx_vm_ioctl()

Posted by Sean Christopherson 3 months, 3 weeks ago

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.

Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 arch/x86/kvm/vmx/tdx.c | 9 +++------
 1 file changed, 3 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
index 1de5f17a7989..84b5fe654c99 100644
--- a/arch/x86/kvm/vmx/tdx.c
+++ b/arch/x86/kvm/vmx/tdx.c
@@ -2781,7 +2781,7 @@ int tdx_vm_ioctl(struct kvm *kvm, void __user *argp)
 	if (r)
 		return r;
 
-	mutex_lock(&kvm->lock);
+	guard(mutex)(&kvm->lock);
 
 	switch (tdx_cmd.id) {
 	case KVM_TDX_CAPABILITIES:
@@ -2794,15 +2794,12 @@ int tdx_vm_ioctl(struct kvm *kvm, void __user *argp)
 		r = tdx_td_finalize(kvm, &tdx_cmd);
 		break;
 	default:
-		r = -EINVAL;
-		goto out;
+		return -EINVAL;
 	}
 
 	if (copy_to_user(argp, &tdx_cmd, sizeof(struct kvm_tdx_cmd)))
-		r = -EFAULT;
+		return -EFAULT;
 
-out:
-	mutex_unlock(&kvm->lock);
 	return r;
 }
 
-- 
2.51.0.858.gf9c4a03a3a-goog

Re: [PATCH v3 23/25] KVM: TDX: Use guard() to acquire kvm->lock in tdx_vm_ioctl()

Posted by Huang, Kai 3 months, 2 weeks ago

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.
> 
> Signed-off-by: Sean Christopherson <seanjc@google.com>

Reviewed-by: Kai Huang <kai.huang@intel.com>

Re: [PATCH v3 23/25] KVM: TDX: Use guard() to acquire kvm->lock in tdx_vm_ioctl()

Posted by Edgecombe, Rick P 3 months, 2 weeks ago

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.

> 
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> ---

Reviewed-by: Rick Edgecombe <rick.p.edgecombe@intel.com>

Re: [PATCH v3 23/25] KVM: TDX: Use guard() to acquire kvm->lock in tdx_vm_ioctl()

Posted by Sean Christopherson 3 months, 2 weeks ago

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;

Re: [PATCH v3 23/25] KVM: TDX: Use guard() to acquire kvm->lock in tdx_vm_ioctl()

Posted by Edgecombe, Rick P 3 months, 2 weeks ago

On Tue, 2025-10-21 at 09:56 -0700, Sean Christopherson wrote:
> No?  The default case doesn't copy the struct back even before this patch, it
> explicitly skips the copy_to_user().

Err, right. sorry.