Commit 7c548038 authored by Yan Zhao's avatar Yan Zhao Committed by Paolo Bonzini
Browse files

KVM: x86/mmu: Return RET_PF* instead of 1 in kvm_mmu_page_fault() 



Return RET_PF* (excluding RET_PF_EMULATE/RET_PF_CONTINUE/RET_PF_INVALID)
instead of 1 in kvm_mmu_page_fault().

The callers of kvm_mmu_page_fault() are KVM page fault handlers (i.e.,
npf_interception(), handle_ept_misconfig(), __vmx_handle_ept_violation(),
kvm_handle_page_fault()). They either check if the return value is > 0 (as
in npf_interception()) or pass it further to vcpu_run() to decide whether
to break out of the kernel loop and return to the user when r <= 0.
Therefore, returning any positive value is equivalent to returning 1.

Warn if r == RET_PF_CONTINUE (which should not be a valid value) to ensure
a positive return value.

This is a preparation to allow TDX's EPT violation handler to check the
RET_PF* value and retry internally for RET_PF_RETRY.

No functional changes are intended.

Signed-off-by: default avatarYan Zhao <yan.y.zhao@intel.com>
Message-ID: <20250113021138.18875-1-yan.y.zhao@intel.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 2c3412e9

arch/x86/kvm/mmu/mmu.c

+9 −1
Original line number Diff line number Diff line
@@ -6111,8 +6111,16 @@ int noinline kvm_mmu_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa, u64 err 
	else if (r == RET_PF_SPURIOUS)

		vcpu->stat.pf_spurious++;



	/*

	 * None of handle_mmio_page_fault(), kvm_mmu_do_page_fault(), or

	 * kvm_mmu_write_protect_fault() return RET_PF_CONTINUE.

	 * kvm_mmu_do_page_fault() only uses RET_PF_CONTINUE internally to

	 * indicate continuing the page fault handling until to the final

	 * page table mapping phase.

	 */

	WARN_ON_ONCE(r == RET_PF_CONTINUE);

	if (r != RET_PF_EMULATE)

		return 1;

		return r;



emulate:

	return x86_emulate_instruction(vcpu, cr2_or_gpa, emulation_type, insn,

arch/x86/kvm/mmu/mmu_internal.h

+9 −3
Original line number Diff line number Diff line
@@ -315,9 +315,7 @@ int kvm_tdp_page_fault(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault); 
 * tracepoints via TRACE_DEFINE_ENUM() in mmutrace.h

 *

 * Note, all values must be greater than or equal to zero so as not to encroach

 * on -errno return values.  Somewhat arbitrarily use '0' for CONTINUE, which

 * will allow for efficient machine code when checking for CONTINUE, e.g.

 * "TEST %rax, %rax, JNZ", as all "stop!" values are non-zero.

 * on -errno return values.

 */

enum {

	RET_PF_CONTINUE = 0,
@@ -329,6 +327,14 @@ enum { 
	RET_PF_SPURIOUS,

};



/*

 * Define RET_PF_CONTINUE as 0 to allow for

 * - efficient machine code when checking for CONTINUE, e.g.

 *   "TEST %rax, %rax, JNZ", as all "stop!" values are non-zero,

 * - kvm_mmu_do_page_fault() to return other RET_PF_* as a positive value.

 */

static_assert(RET_PF_CONTINUE == 0);



static inline void kvm_mmu_prepare_memory_fault_exit(struct kvm_vcpu *vcpu,

						     struct kvm_page_fault *fault)

{