The patch below does not apply to the 4.19-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From b6b80c78af838bef17501416d5d383fedab0010a Mon Sep 17 00:00:00 2001

From: Sean Christopherson sean.j.christopherson@intel.com Date: Thu, 13 Jun 2019 10:22:23 -0700 Subject: [PATCH] KVM: x86/mmu: Allocate PAE root array when using SVM's 32-bit NPT

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

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index 1e9ba81accba..d3c3d5e5ffd4 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -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;