diff mbox series

[5.4,1/3] KVM: x86/mmu: Avoid indirect call for get_cr3

Message ID 20230508154943.30113-2-minipli@grsecurity.net (mailing list archive)
State New, archived
Headers show
Series KVM CR0.WP series backport | expand

Commit Message

Mathias Krause May 8, 2023, 3:49 p.m. UTC 
From: Paolo Bonzini <pbonzini@redhat.com>

[ Upstream commit 2fdcc1b324189b5fb20655baebd40cd82e2bdf0c ]

Most of the time, calls to get_guest_pgd result in calling
kvm_read_cr3 (the exception is only nested TDP).  Hardcode
the default instead of using the get_cr3 function, avoiding
a retpoline if they are enabled.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Mathias Krause <minipli@grsecurity.net>
Link: https://lore.kernel.org/r/20230322013731.102955-2-minipli@grsecurity.net
Signed-off-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Mathias Krause <minipli@grsecurity.net>	# backport to v5.4.x
---
 arch/x86/kvm/mmu.c         | 14 +++++++-------
 arch/x86/kvm/mmu.h         | 11 +++++++++++
 arch/x86/kvm/paging_tmpl.h |  2 +-
 arch/x86/kvm/x86.c         |  2 +-
 4 files changed, 20 insertions(+), 9 deletions(-)
diff mbox series

Patch

diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 015da62e4ad7..a6efd71a0a6e 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -3815,7 +3815,7 @@  static int mmu_alloc_direct_roots(struct kvm_vcpu *vcpu)
 		vcpu->arch.mmu->root_hpa = __pa(vcpu->arch.mmu->pae_root);
 	} else
 		BUG();
-	vcpu->arch.mmu->root_cr3 = vcpu->arch.mmu->get_cr3(vcpu);
+	vcpu->arch.mmu->root_cr3 = kvm_mmu_get_guest_cr3(vcpu, vcpu->arch.mmu);
 
 	return 0;
 }
@@ -3827,7 +3827,7 @@  static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
 	gfn_t root_gfn, root_cr3;
 	int i;
 
-	root_cr3 = vcpu->arch.mmu->get_cr3(vcpu);
+	root_cr3 = kvm_mmu_get_guest_cr3(vcpu, vcpu->arch.mmu);
 	root_gfn = root_cr3 >> PAGE_SHIFT;
 
 	if (mmu_check_root(vcpu, root_gfn))
@@ -4191,7 +4191,7 @@  static int kvm_arch_setup_async_pf(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
 	arch.token = (vcpu->arch.apf.id++ << 12) | vcpu->vcpu_id;
 	arch.gfn = gfn;
 	arch.direct_map = vcpu->arch.mmu->direct_map;
-	arch.cr3 = vcpu->arch.mmu->get_cr3(vcpu);
+	arch.cr3 = kvm_mmu_get_guest_cr3(vcpu, vcpu->arch.mmu);
 
 	return kvm_setup_async_pf(vcpu, cr2_or_gpa,
 				  kvm_vcpu_gfn_to_hva(vcpu, gfn), &arch);
@@ -4453,7 +4453,7 @@  void kvm_mmu_new_cr3(struct kvm_vcpu *vcpu, gpa_t new_cr3, bool skip_tlb_flush)
 }
 EXPORT_SYMBOL_GPL(kvm_mmu_new_cr3);
 
-static unsigned long get_cr3(struct kvm_vcpu *vcpu)
+unsigned long get_guest_cr3(struct kvm_vcpu *vcpu)
 {
 	return kvm_read_cr3(vcpu);
 }
@@ -5040,7 +5040,7 @@  static void init_kvm_tdp_mmu(struct kvm_vcpu *vcpu)
 	context->shadow_root_level = kvm_x86_ops->get_tdp_level(vcpu);
 	context->direct_map = true;
 	context->set_cr3 = kvm_x86_ops->set_tdp_cr3;
-	context->get_cr3 = get_cr3;
+	context->get_cr3 = get_guest_cr3;
 	context->get_pdptr = kvm_pdptr_read;
 	context->inject_page_fault = kvm_inject_page_fault;
 
@@ -5187,7 +5187,7 @@  static void init_kvm_softmmu(struct kvm_vcpu *vcpu)
 
 	kvm_init_shadow_mmu(vcpu);
 	context->set_cr3           = kvm_x86_ops->set_cr3;
-	context->get_cr3           = get_cr3;
+	context->get_cr3           = get_guest_cr3;
 	context->get_pdptr         = kvm_pdptr_read;
 	context->inject_page_fault = kvm_inject_page_fault;
 }
@@ -5202,7 +5202,7 @@  static void init_kvm_nested_mmu(struct kvm_vcpu *vcpu)
 		return;
 
 	g_context->mmu_role.as_u64 = new_role.as_u64;
-	g_context->get_cr3           = get_cr3;
+	g_context->get_cr3           = get_guest_cr3;
 	g_context->get_pdptr         = kvm_pdptr_read;
 	g_context->inject_page_fault = kvm_inject_page_fault;
 
diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
index ea9945a05b83..a53b223a245a 100644
--- a/arch/x86/kvm/mmu.h
+++ b/arch/x86/kvm/mmu.h
@@ -102,6 +102,17 @@  static inline void kvm_mmu_load_cr3(struct kvm_vcpu *vcpu)
 					      kvm_get_active_pcid(vcpu));
 }
 
+unsigned long get_guest_cr3(struct kvm_vcpu *vcpu);
+
+static inline unsigned long kvm_mmu_get_guest_cr3(struct kvm_vcpu *vcpu,
+						  struct kvm_mmu *mmu)
+{
+	if (IS_ENABLED(CONFIG_RETPOLINE) && mmu->get_cr3 == get_guest_cr3)
+		return kvm_read_cr3(vcpu);
+
+	return mmu->get_cr3(vcpu);
+}
+
 /*
  * Currently, we have two sorts of write-protection, a) the first one
  * write-protects guest page to sync the guest modification, b) another one is
diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index 1a1d2b5e7b35..b61ab1cdeab1 100644
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -315,7 +315,7 @@  static int FNAME(walk_addr_generic)(struct guest_walker *walker,
 	trace_kvm_mmu_pagetable_walk(addr, access);
 retry_walk:
 	walker->level = mmu->root_level;
-	pte           = mmu->get_cr3(vcpu);
+	pte           = kvm_mmu_get_guest_cr3(vcpu, mmu);
 	have_ad       = PT_HAVE_ACCESSED_DIRTY(mmu);
 
 #if PTTYPE == 64
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index f5e9590a8f31..f073c56b9301 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -10130,7 +10130,7 @@  void kvm_arch_async_page_ready(struct kvm_vcpu *vcpu, struct kvm_async_pf *work)
 		return;
 
 	if (!vcpu->arch.mmu->direct_map &&
-	      work->arch.cr3 != vcpu->arch.mmu->get_cr3(vcpu))
+	      work->arch.cr3 != kvm_mmu_get_guest_cr3(vcpu, vcpu->arch.mmu))
 		return;
 
 	vcpu->arch.mmu->page_fault(vcpu, work->cr2_or_gpa, 0, true);