[PATCH 4.19 44/72] KVM: x86/mmu: Allocate PAE root array when using SVMs 32-bit NPT

Greg Kroah-Hartman
2019-07-02T08:07:05Z

From: Sean Christopherson <sean.j.christopherson@intel.com>

commit b6b80c78af838bef17501416d5d383fedab0010a upstream.

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@vger.kernel.org
Reported-by: Jiri Palecek <jpalecek@web.de>
Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Cc: Jiri Palecek <jpalecek@web.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/x86/kvm/mmu.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)

--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -5386,7 +5386,16 @@ static int alloc_mmu_pages(struct kvm_vc
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;

/*