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FAILED: patch "[PATCH] KVM: x86/mmu: Allocate PAE root array when using SVM's 32-bit" failed to apply to 4.19-stable tree

PATCH In review [email protected] 3 participants 3 messages Jun 23, 2019 – Jun 25, 2019

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#0 lore raw

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 <[email protected]>.

thanks,

greg k-h

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

From b6b80c78af838bef17501416d5d383fedab0010a Mon Sep 17 00:00:00 2001
From: Sean Christopherson <[email protected]>
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 [email protected]
Reported-by Jiri Palecek <[email protected]>
Signed-off-by Sean Christopherson <[email protected]>
Signed-off-by Paolo Bonzini <[email protected]>
arch/x86/kvm/mmu.c +10 -6
index 1e9ba81accba..d3c3d5e5ffd4 100644
@@ -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;
#1 lore raw

PATCH 1/1 KVM: x86/mmu: Allocate PAE root array when using SVM's 32-bit NPT

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 [email protected]
Reported-by Jiri Palecek <[email protected]>
Signed-off-by Sean Christopherson <[email protected]>
Signed-off-by Paolo Bonzini <[email protected]>
---
 arch/x86/kvm/mmu.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)
arch/x86/kvm/mmu.c +10 -1
index 779ed52047d1..e0f982e35c96 100644
@@ -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

maintainer
#2 lore raw

Re: [PATCH] KVM: x86/mmu: Allocate PAE root array when using SVM's 32-bit NPT

Quoted 11 lines · Jiri Palecek

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 [email protected]
Reported-by Jiri Palecek <[email protected]>
Signed-off-by Sean Christopherson <[email protected]>
Signed-off-by Paolo Bonzini <[email protected]>

Could you add your signed-off-by please?

--
Thanks,
Sasha