Original commit id b6b80c78 ported to stable/linux-4.19.y.
SVM's Nested Page Tables (NPT) reuses x86 paging for the host-controlled
page walk. For 32-bit KVM, this means PAE paging is used even when TDP
is enabled, i.e. the PAE root array needs to be allocated.
Fixes: ee6268ba3a68 ("KVM: x86: Skip pae_root shadow allocation if tdp enabled")
Cc: stable@xxxxxxxxxxxxxxx
Reported-by: Jiri Palecek <jpalecek@xxxxxx>
Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
---
arch/x86/kvm/mmu.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 779ed52047d1..e0f982e35c96 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -5386,7 +5386,16 @@ static int alloc_mmu_pages(struct kvm_vcpu *vcpu)
struct page *page;
int i;
- if (tdp_enabled)
+ /*
+ * When using PAE paging, the four PDPTEs are treated as 'root' pages,
+ * while the PDP table is a per-vCPU construct that's allocated at MMU
+ * creation. When emulating 32-bit mode, cr3 is only 32 bits even on
+ * x86_64. Therefore we need to allocate the PDP table in the first
+ * 4GB of memory, which happens to fit the DMA32 zone. Except for
+ * SVM's 32-bit NPT support, TDP paging doesn't use PAE paging and can
+ * skip allocating the PDP table.
+ */
+ if (tdp_enabled && kvm_x86_ops->get_tdp_level(vcpu) > PT32E_ROOT_LEVEL)
return 0;
/*
--
2.20.1
