linux-kernel - [RFC PATCH v5 038/104] KVM: x86/mmu: Allow per-VM override of the TDP max page level

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Date:   Fri,  4 Mar 2022 11:48:54 -0800
From:   isaku.yamahata@...el.com
To:     kvm@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     isaku.yamahata@...el.com, isaku.yamahata@...il.com,
        Paolo Bonzini <pbonzini@...hat.com>,
        Jim Mattson <jmattson@...gle.com>, erdemaktas@...gle.com,
        Connor Kuehl <ckuehl@...hat.com>,
        Sean Christopherson <seanjc@...gle.com>
Subject: [RFC PATCH v5 038/104] KVM: x86/mmu: Allow per-VM override of the TDP max page level

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

In the existing x86 KVM MMU code, there is already max_level member in
struct kvm_page_fault with KVM_MAX_HUGEPAGE_LEVEL initial value.  The KVM
page fault handler denies page size larger than max_level.

Add per-VM member to indicate the allowed maximum page size with
KVM_MAX_HUGEPAGE_LEVEL as default value and initialize max_level in struct
kvm_page_fault with it.

For the guest TD, the set per-VM value for allows maximum page size to 4K
page size.  Then only allowed page size is 4K.  It means large page is
disabled.

Signed-off-by: Sean Christopherson <sean.j.christopherson@...el.com>
Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
---
 arch/x86/include/asm/kvm_host.h | 1 +
 arch/x86/kvm/mmu.h              | 2 +-
 arch/x86/kvm/mmu/mmu.c          | 2 ++
 3 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index d8b78d6abc10..d33d79f2af2d 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1053,6 +1053,7 @@ struct kvm_arch {
 	unsigned long n_requested_mmu_pages;
 	unsigned long n_max_mmu_pages;
 	unsigned int indirect_shadow_pages;
+	int tdp_max_page_level;
 	u8 mmu_valid_gen;
 	struct hlist_head mmu_page_hash[KVM_NUM_MMU_PAGES];
 	struct list_head active_mmu_pages;
diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
index 0ae91b8b25df..650989c37f2e 100644
--- a/arch/x86/kvm/mmu.h
+++ b/arch/x86/kvm/mmu.h
@@ -192,7 +192,7 @@ static inline int kvm_mmu_do_page_fault(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
 		.is_tdp = likely(vcpu->arch.mmu->page_fault == kvm_tdp_page_fault),
 		.nx_huge_page_workaround_enabled = is_nx_huge_page_enabled(),
 
-		.max_level = KVM_MAX_HUGEPAGE_LEVEL,
+		.max_level = vcpu->kvm->arch.tdp_max_page_level,
 		.req_level = PG_LEVEL_4K,
 		.goal_level = PG_LEVEL_4K,
 	};
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index a474f2e76d78..e9212394a530 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -5782,6 +5782,8 @@ void kvm_mmu_init_vm(struct kvm *kvm)
 	node->track_write = kvm_mmu_pte_write;
 	node->track_flush_slot = kvm_mmu_invalidate_zap_pages_in_memslot;
 	kvm_page_track_register_notifier(kvm, node);
+
+	kvm->arch.tdp_max_page_level = KVM_MAX_HUGEPAGE_LEVEL;
 }
 
 void kvm_mmu_uninit_vm(struct kvm *kvm)
-- 
2.25.1