[PATCH v2 2/3] KVM: TDX: Do not retry locally when the retry is caused by invalid memslot

Yan Zhao
2025-08-22T07:06:06Z

From: Sean Christopherson <seanjc@google.com>

Avoid local retries within the TDX EPT violation handler if a retry is
triggered by faulting in an invalid memslot, indicating that the memslot is
undergoing a removal process.

This prevents the slot removal process from being blocked while waiting for
the VMExit handler to release the SRCU lock.

Opportunistically, export symbol kvm_vcpu_gfn_to_memslot() to allow for
per-vCPU acceleration of gfn_to_memslot translation.

[Yan: Wrote patch log, comment, fixed a minor error, function export]

Reported-by: Reinette Chatre <reinette.chatre@intel.com>
Closes: https://lore.kernel.org/all/20250519023737.30360-1-yan.y.zhao@intel.com
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Yan Zhao <yan.y.zhao@intel.com>
---
arch/x86/kvm/vmx/tdx.c | 11 +++++++++++
virt/kvm/kvm_main.c | 1 +
2 files changed, 12 insertions(+)

diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c
index 6784aaaced87..de2c4bb36069 100644
--- a/arch/x86/kvm/vmx/tdx.c
+++ b/arch/x86/kvm/vmx/tdx.c
@@ -1992,6 +1992,11 @@ static int tdx_handle_ept_violation(struct kvm_vcpu *vcpu)
* blocked by TDs, false positives are inevitable i.e., KVM may re-enter
* the guest even if the IRQ/NMI can't be delivered.
*
+ * Breaking out of the local retries if a retry is caused by faulting
+ * in an invalid memslot (indicating the slot is under removal), so that
+ * the slot removal will not be blocked due to waiting for releasing
+ * SRCU lock in the VMExit handler.
+ *
* Note: even without breaking out of local retries, zero-step
* mitigation may still occur due to
* - invoking of TDH.VP.ENTER after KVM_EXIT_MEMORY_FAULT,
@@ -2002,6 +2007,8 @@ static int tdx_handle_ept_violation(struct kvm_vcpu *vcpu)
* handle retries locally in their EPT violation handlers.
*/
while (1) {
+ struct kvm_memory_slot *slot;
+
ret = __vmx_handle_ept_violation(vcpu, gpa, exit_qual);

if (ret != RET_PF_RETRY || !local_retry)
@@ -2015,6 +2022,10 @@ static int tdx_handle_ept_violation(struct kvm_vcpu *vcpu)
break;
}

+ slot = kvm_vcpu_gfn_to_memslot(vcpu, gpa_to_gfn(gpa));
+ if (slot && slot->flags & KVM_MEMSLOT_INVALID)
+ break;
+
cond_resched();
}
return ret;
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 6c07dd423458..f769d1dccc21 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -2661,6 +2661,7 @@ struct kvm_memory_slot *kvm_vcpu_gfn_to_memslot(struct kvm_vcpu *vcpu, gfn_t gfn

return NULL;
}
+EXPORT_SYMBOL_GPL(kvm_vcpu_gfn_to_memslot);

bool kvm_is_visible_gfn(struct kvm *kvm, gfn_t gfn)
{
--
2.43.2