Re: [RFC PATCH v2 51/69] KVM: x86/mmu: Allow per-VM override of the TDP max page level

From: Paolo Bonzini
Date: Tue Jul 06 2021 - 10:59:10 EST


On 03/07/21 00:04, isaku.yamahata@xxxxxxxxx wrote:
From: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>

TODO: This is tentative patch. Support large page and delete this patch.

Allow TDX to effectively disable large pages, as SEPT will initially
support only 4k pages.

Signed-off-by: Sean Christopherson <sean.j.christopherson@xxxxxxxxx>
Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
---
arch/x86/include/asm/kvm_host.h | 1 +
arch/x86/kvm/mmu/mmu.c | 4 +++-
2 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 9631b985ebdc..a47e17892258 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -989,6 +989,7 @@ 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/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 82db62753acb..4ee6d7803f18 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -4084,7 +4084,7 @@ int kvm_tdp_page_fault(struct kvm_vcpu *vcpu, gpa_t gpa, u32 error_code,
kvm_pfn_t pfn;
int max_level;
- for (max_level = KVM_MAX_HUGEPAGE_LEVEL;
+ for (max_level = vcpu->kvm->arch.tdp_max_page_level;
max_level > PG_LEVEL_4K;
max_level--) {
int page_num = KVM_PAGES_PER_HPAGE(max_level);
@@ -5802,6 +5802,8 @@ 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)


Seems good enough for now.

Reviewed-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>

Paolo