linux-kernel - [PATCH V3 11/12] KVM: X86/MMU: Don't use mmu->pae_root when shadowing PAE NPT in 64-bit host

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Message-Id: <20220521131700.3661-12-jiangshanlai@gmail.com>
Date:   Sat, 21 May 2022 21:16:59 +0800
From:   Lai Jiangshan <jiangshanlai@...il.com>
To:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>
Cc:     Vitaly Kuznetsov <vkuznets@...hat.com>,
        Maxim Levitsky <mlevitsk@...hat.com>,
        David Matlack <dmatlack@...gle.com>,
        Lai Jiangshan <jiangshan.ljs@...group.com>
Subject: [PATCH V3 11/12] KVM: X86/MMU: Don't use mmu->pae_root when shadowing PAE NPT in 64-bit host

From: Lai Jiangshan <jiangshan.ljs@...group.com>

Allocate the tables when allocating the local shadow page.

Signed-off-by: Lai Jiangshan <jiangshan.ljs@...group.com>
---
 arch/x86/kvm/mmu/mmu.c | 17 +++++++++--------
 1 file changed, 9 insertions(+), 8 deletions(-)

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 63c2b2c6122c..73e6a8e1e1a9 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -1809,10 +1809,12 @@ static bool using_local_root_page(struct kvm_mmu *mmu)
  * 2 or 3 levels of local shadow pages on top of non-local shadow pages.
  *
  * Local shadow pages are locally allocated.  If the local shadow page's level
- * is PT32E_ROOT_LEVEL, it will use the preallocated mmu->pae_root for its
- * sp->spt.  Because sp->spt may need to be put in the 32 bits CR3 (even in
- * x86_64) or decrypted.  Using the preallocated one to handle these
- * requirements makes the allocation simpler.
+ * is PT32E_ROOT_LEVEL, and it is not shadowing nested NPT for 32-bit L1 in
+ * 64-bit L0 (or said when the shadow pagetable's level is PT32E_ROOT_LEVEL),
+ * it will use the preallocated mmu->pae_root for its sp->spt.  Because sp->spt
+ * need to be put in the 32-bit CR3 (even in 64-bit host) or decrypted.  Using
+ * the preallocated one to handle these requirements makes the allocation
+ * simpler.
  *
  * Local shadow pages are only visible to local VCPU except through
  * sp->parent_ptes rmap from their children, so they are not in the
@@ -1852,13 +1854,12 @@ kvm_mmu_alloc_local_shadow_page(struct kvm_vcpu *vcpu, union kvm_mmu_page_role r
 	sp->gfn = 0;
 	sp->role = role;
 	/*
-	 * Use the preallocated mmu->pae_root when the shadow page's
-	 * level is PT32E_ROOT_LEVEL which may need to be put in the 32 bits
+	 * Use the preallocated mmu->pae_root when the shadow pagetable's
+	 * level is PT32E_ROOT_LEVEL which need to be put in the 32 bits
 	 * CR3 (even in x86_64) or decrypted.  The preallocated one is prepared
 	 * for the requirements.
 	 */
-	if (role.level == PT32E_ROOT_LEVEL &&
-	    !WARN_ON_ONCE(!vcpu->arch.mmu->pae_root))
+	if (vcpu->arch.mmu->root_role.level == PT32E_ROOT_LEVEL)
 		sp->spt = vcpu->arch.mmu->pae_root;
 	else
 		sp->spt = kvm_mmu_memory_cache_alloc(&vcpu->arch.mmu_shadow_page_cache);
-- 
2.19.1.6.gb485710b