[RFC PATCH v5 37/45] KVM: x86/tdp_mmu: Alloc external_spt page for mirror page table splitting

[Sean Christopherson]

From: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>

Enhance tdp_mmu_alloc_sp_for_split() to allocate a page table page for the
external page table for splitting the mirror page table.

Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
Co-developed-by: Yan Zhao <yan.y.zhao@xxxxxxxxx>
Signed-off-by: Yan Zhao <yan.y.zhao@xxxxxxxxx>
[sean: use kvm_x86_ops.alloc_external_sp()]
Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
---
 arch/x86/kvm/mmu/tdp_mmu.c | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/mmu/tdp_mmu.c b/arch/x86/kvm/mmu/tdp_mmu.c
index 3b0da898824a..4f5b80f0ca03 100644
--- a/arch/x86/kvm/mmu/tdp_mmu.c
+++ b/arch/x86/kvm/mmu/tdp_mmu.c
@@ -1447,7 +1447,7 @@ bool kvm_tdp_mmu_wrprot_slot(struct kvm *kvm,
 	return spte_set;
 }
 
-static struct kvm_mmu_page *tdp_mmu_alloc_sp_for_split(void)
+static struct kvm_mmu_page *tdp_mmu_alloc_sp_for_split(struct tdp_iter *iter)
 {
 	struct kvm_mmu_page *sp;
 
@@ -1461,6 +1461,15 @@ static struct kvm_mmu_page *tdp_mmu_alloc_sp_for_split(void)
 		return NULL;
 	}
 
+	if (is_mirror_sptep(iter->sptep)) {
+		sp->external_spt = (void *)kvm_x86_call(alloc_external_sp)(GFP_KERNEL_ACCOUNT);
+		if (!sp->external_spt) {
+			free_page((unsigned long)sp->spt);
+			kmem_cache_free(mmu_page_header_cache, sp);
+			return NULL;
+		}
+	}
+
 	return sp;
 }
 
@@ -1540,7 +1549,7 @@ static int tdp_mmu_split_huge_pages_root(struct kvm *kvm,
 			else
 				write_unlock(&kvm->mmu_lock);
 
-			sp = tdp_mmu_alloc_sp_for_split();
+			sp = tdp_mmu_alloc_sp_for_split(&iter);
 
 			if (shared)
 				read_lock(&kvm->mmu_lock);
-- 
2.53.0.rc1.217.geba53bf80e-goog