[PATCH v3 10/16] x86/virt/tdx: Drop the outdated requirement that TDX be enabled in IRQ context

[Sean Christopherson <seanjc@google.com>]

Remove TDX's outdated requirement that per-CPU enabling be done via IPI
function call, which was a stale artifact leftover from early versions of
the TDX enablement series.  The requirement that IRQs be disabled should
have been dropped as part of the revamped series that relied on a the KVM
rework to enable VMX at module load.

In other words, the kernel's "requirement" was never a requirement at all,
but instead a reflection of how KVM enabled VMX (via IPI callback) when
the TDX subsystem code was merged.

Note, accessing per-CPU information is safe even without disabling IRQs,
as tdx_online_cpu() is invoked via a cpuhp callback, i.e. from a per-CPU
thread.

Link: https://lore.kernel.org/all/ZyJOiPQnBz31qLZ7@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 arch/x86/kvm/vmx/tdx.c      | 9 +--------
 arch/x86/virt/vmx/tdx/tdx.c | 4 ----
 2 files changed, 1 insertion(+), 12 deletions(-)

diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
index 0c790eb0bfa6..582469118b79 100644
--- a/arch/x86/kvm/vmx/tdx.c
+++ b/arch/x86/kvm/vmx/tdx.c
@@ -3294,17 +3294,10 @@ int tdx_gmem_max_mapping_level(struct kvm *kvm, kvm_pfn_t pfn, bool is_private)
 
 static int tdx_online_cpu(unsigned int cpu)
 {
-	unsigned long flags;
-	int r;
-
 	/* Sanity check CPU is already in post-VMXON */
 	WARN_ON_ONCE(!(cr4_read_shadow() & X86_CR4_VMXE));
 
-	local_irq_save(flags);
-	r = tdx_cpu_enable();
-	local_irq_restore(flags);
-
-	return r;
+	return tdx_cpu_enable();
 }
 
 static int tdx_offline_cpu(unsigned int cpu)
diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
index 5ce4ebe99774..dfd82fac0498 100644
--- a/arch/x86/virt/vmx/tdx/tdx.c
+++ b/arch/x86/virt/vmx/tdx/tdx.c
@@ -148,8 +148,6 @@ static int try_init_module_global(void)
  * global initialization SEAMCALL if not done) on local cpu to make this
  * cpu be ready to run any other SEAMCALLs.
  *
- * Always call this function via IPI function calls.
- *
  * Return 0 on success, otherwise errors.
  */
 int tdx_cpu_enable(void)
@@ -160,8 +158,6 @@ int tdx_cpu_enable(void)
 	if (!boot_cpu_has(X86_FEATURE_TDX_HOST_PLATFORM))
 		return -ENODEV;
 
-	lockdep_assert_irqs_disabled();
-
 	if (__this_cpu_read(tdx_lp_initialized))
 		return 0;
 
-- 
2.53.0.310.g728cabbaf7-goog