x86/virt/tdx: Drop the outdated requirement that TDX be enabled in IRQ context

Remove TDX's outdated requirement that per-CPU enabling be done via IPI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
Tested-by: Chao Gao <chao.gao@intel.com>
Reviewed-by: Dan Williams <dan.j.williams@intel.com>
Tested-by: Sagi Shahar <sagis@google.com>
Link: https://patch.msgid.link/20260214012702.2368778-11-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
index f81b562733efe22322f6b2801407b4d1e3c7536d..60e7ba8836753f8809eabfb5de6124b2121211dd 100644 (file)
--- a/arch/x86/kvm/vmx/tdx.c
+++ b/arch/x86/kvm/vmx/tdx.c
@@ -3293,17 +3293,10 @@ 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 8b8e165a2001ab55ab4a6d9903bc7754162d0e80..61cece496bdb498f816b9872f99e2245071ef60b 100644 (file)
--- a/arch/x86/virt/vmx/tdx/tdx.c
+++ b/arch/x86/virt/vmx/tdx/tdx.c
@@ -106,8 +106,7 @@ static __always_inline int sc_retry_prerr(sc_func_t func,
 
 /*
  * Do the module global initialization once and return its result.
- * It can be done on any cpu.  It's always called with interrupts
- * disabled.
+ * It can be done on any cpu, and from task or IRQ context.
  */
 static int try_init_module_global(void)
 {
@@ -116,8 +115,6 @@ static int try_init_module_global(void)
        static bool sysinit_done;
        static int sysinit_ret;
 
-       lockdep_assert_irqs_disabled();
-
        raw_spin_lock(&sysinit_lock);
 
        if (sysinit_done)
@@ -148,8 +145,6 @@ out:
  * 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 +155,6 @@ 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;