Patch "KVM: x86/mmu: Avoid indirect call for get_cr3" has been added to the 6.3-stable tree

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This is a note to let you know that I've just added the patch titled

    KVM: x86/mmu: Avoid indirect call for get_cr3

to the 6.3-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     kvm-x86-mmu-avoid-indirect-call-for-get_cr3.patch
and it can be found in the queue-6.3 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 486a413cb7ee0c99d3a559cbad97cae281706ad9
Author: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Date:   Fri May 12 15:20:20 2023 +0200

    KVM: x86/mmu: Avoid indirect call for get_cr3
    
    [ 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@xxxxxxxxxx>
    Signed-off-by: Mathias Krause <minipli@xxxxxxxxxxxxxx>
    Link: https://lore.kernel.org/r/20230322013731.102955-2-minipli@xxxxxxxxxxxxxx
    Signed-off-by: Sean Christopherson <seanjc@xxxxxxxxxx>
    Signed-off-by: Mathias Krause <minipli@xxxxxxxxxxxxxx>  # backport to v6.3.x
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index c8ebe542c565f..18c0deeaa2ec4 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -242,6 +242,20 @@ static struct kvm_mmu_role_regs vcpu_to_role_regs(struct kvm_vcpu *vcpu)
 	return regs;
 }
 
+static unsigned long get_guest_cr3(struct kvm_vcpu *vcpu)
+{
+	return kvm_read_cr3(vcpu);
+}
+
+static inline unsigned long kvm_mmu_get_guest_pgd(struct kvm_vcpu *vcpu,
+						  struct kvm_mmu *mmu)
+{
+	if (IS_ENABLED(CONFIG_RETPOLINE) && mmu->get_guest_pgd == get_guest_cr3)
+		return kvm_read_cr3(vcpu);
+
+	return mmu->get_guest_pgd(vcpu);
+}
+
 static inline bool kvm_available_flush_tlb_with_range(void)
 {
 	return kvm_x86_ops.tlb_remote_flush_with_range;
@@ -3731,7 +3745,7 @@ static int mmu_alloc_shadow_roots(struct kvm_vcpu *vcpu)
 	int quadrant, i, r;
 	hpa_t root;
 
-	root_pgd = mmu->get_guest_pgd(vcpu);
+	root_pgd = kvm_mmu_get_guest_pgd(vcpu, mmu);
 	root_gfn = root_pgd >> PAGE_SHIFT;
 
 	if (mmu_check_root(vcpu, root_gfn))
@@ -4181,7 +4195,7 @@ static bool kvm_arch_setup_async_pf(struct kvm_vcpu *vcpu, gpa_t cr2_or_gpa,
 	arch.token = alloc_apf_token(vcpu);
 	arch.gfn = gfn;
 	arch.direct_map = vcpu->arch.mmu->root_role.direct;
-	arch.cr3 = vcpu->arch.mmu->get_guest_pgd(vcpu);
+	arch.cr3 = kvm_mmu_get_guest_pgd(vcpu, vcpu->arch.mmu);
 
 	return kvm_setup_async_pf(vcpu, cr2_or_gpa,
 				  kvm_vcpu_gfn_to_hva(vcpu, gfn), &arch);
@@ -4200,7 +4214,7 @@ void kvm_arch_async_page_ready(struct kvm_vcpu *vcpu, struct kvm_async_pf *work)
 		return;
 
 	if (!vcpu->arch.mmu->root_role.direct &&
-	      work->arch.cr3 != vcpu->arch.mmu->get_guest_pgd(vcpu))
+	      work->arch.cr3 != kvm_mmu_get_guest_pgd(vcpu, vcpu->arch.mmu))
 		return;
 
 	kvm_mmu_do_page_fault(vcpu, work->cr2_or_gpa, 0, true);
@@ -4604,11 +4618,6 @@ void kvm_mmu_new_pgd(struct kvm_vcpu *vcpu, gpa_t new_pgd)
 }
 EXPORT_SYMBOL_GPL(kvm_mmu_new_pgd);
 
-static unsigned long get_cr3(struct kvm_vcpu *vcpu)
-{
-	return kvm_read_cr3(vcpu);
-}
-
 static bool sync_mmio_spte(struct kvm_vcpu *vcpu, u64 *sptep, gfn_t gfn,
 			   unsigned int access)
 {
@@ -5159,7 +5168,7 @@ static void init_kvm_tdp_mmu(struct kvm_vcpu *vcpu,
 	context->page_fault = kvm_tdp_page_fault;
 	context->sync_page = nonpaging_sync_page;
 	context->invlpg = NULL;
-	context->get_guest_pgd = get_cr3;
+	context->get_guest_pgd = get_guest_cr3;
 	context->get_pdptr = kvm_pdptr_read;
 	context->inject_page_fault = kvm_inject_page_fault;
 
@@ -5309,7 +5318,7 @@ static void init_kvm_softmmu(struct kvm_vcpu *vcpu,
 
 	kvm_init_shadow_mmu(vcpu, cpu_role);
 
-	context->get_guest_pgd     = get_cr3;
+	context->get_guest_pgd     = get_guest_cr3;
 	context->get_pdptr         = kvm_pdptr_read;
 	context->inject_page_fault = kvm_inject_page_fault;
 }
@@ -5323,7 +5332,7 @@ static void init_kvm_nested_mmu(struct kvm_vcpu *vcpu,
 		return;
 
 	g_context->cpu_role.as_u64   = new_mode.as_u64;
-	g_context->get_guest_pgd     = get_cr3;
+	g_context->get_guest_pgd     = 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/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h
index 57f0b75c80f9d..2ea2861bbb3c1 100644
--- a/arch/x86/kvm/mmu/paging_tmpl.h
+++ b/arch/x86/kvm/mmu/paging_tmpl.h
@@ -324,7 +324,7 @@ static int FNAME(walk_addr_generic)(struct guest_walker *walker,
 	trace_kvm_mmu_pagetable_walk(addr, access);
 retry_walk:
 	walker->level = mmu->cpu_role.base.level;
-	pte           = mmu->get_guest_pgd(vcpu);
+	pte           = kvm_mmu_get_guest_pgd(vcpu, mmu);
 	have_ad       = PT_HAVE_ACCESSED_DIRTY(mmu);
 
 #if PTTYPE == 64



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