Commit 0efe5dc1 authored by Sean Christopherson's avatar Sean Christopherson
Browse files

x86/virt/tdx: Drop the outdated requirement that TDX be enabled in IRQ context 

Remove TDX's outdated requirement that per-CPU enabling be done via IPI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


Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
parent 8528a7f9

arch/x86/kvm/vmx/tdx.c

+1 −8
Original line number Diff line number Diff line
@@ -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)

arch/x86/virt/vmx/tdx/tdx.c

+1 −8
Original line number Diff line number Diff line
@@ -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 @@ 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 +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;