KVM: x86/mmu: Allocate PAE root array when using SVM's 32-bit NPT (b6b80c78) · Commits · 戴 / test

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: ("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>

arch/x86/kvm/mmu.c

+10 −6

Original line number	Diff line number	Diff line
		@@ -5602,14 +5602,18 @@ static int alloc_mmu_pages(struct kvm_vcpu *vcpu)
		struct page *page;
		int i;

		if (tdp_enabled)
		return 0;

		/*
		* When emulating 32-bit mode, cr3 is only 32 bits even on x86_64.
		* Therefore we need to allocate shadow page tables in the first
		* 4GB of memory, which happens to fit the DMA32 zone.
		* 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;

		page = alloc_page(GFP_KERNEL_ACCOUNT \| __GFP_DMA32);
		if (!page)
		return -ENOMEM;

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