KVM: x86/mmu: Declare flush_remote_tlbs{_range}() hooks iff HYPERV!=n

[PATCH] KVM: x86/mmu: Declare flush_remote_tlbs{_range}() hooks iff HYPERV!=n

Posted by Sean Christopherson 2 years, 1 month ago

Declare the kvm_x86_ops hooks used to wire up paravirt TLB flushes when
running under Hyper-V if and only if CONFIG_HYPERV!=n.  Wrapping yet more
code with IS_ENABLED(CONFIG_HYPERV) eliminates a handful of conditional
branches, and makes it super obvious why the hooks *might* be valid.

Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
---
 arch/x86/include/asm/kvm-x86-ops.h |  2 ++
 arch/x86/include/asm/kvm_host.h    | 12 ++++++++++++
 arch/x86/kvm/mmu/mmu.c             | 12 ++++--------
 3 files changed, 18 insertions(+), 8 deletions(-)

diff --git a/arch/x86/include/asm/kvm-x86-ops.h b/arch/x86/include/asm/kvm-x86-ops.h
index 26b628d84594..f482216bbdb8 100644
--- a/arch/x86/include/asm/kvm-x86-ops.h
+++ b/arch/x86/include/asm/kvm-x86-ops.h
@@ -55,8 +55,10 @@ KVM_X86_OP(set_rflags)
 KVM_X86_OP(get_if_flag)
 KVM_X86_OP(flush_tlb_all)
 KVM_X86_OP(flush_tlb_current)
+#if IS_ENABLED(CONFIG_HYPERV)
 KVM_X86_OP_OPTIONAL(flush_remote_tlbs)
 KVM_X86_OP_OPTIONAL(flush_remote_tlbs_range)
+#endif
 KVM_X86_OP(flush_tlb_gva)
 KVM_X86_OP(flush_tlb_guest)
 KVM_X86_OP(vcpu_pre_run)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 7c228ae05df0..f0d1ac871465 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1614,9 +1614,11 @@ struct kvm_x86_ops {
 
 	void (*flush_tlb_all)(struct kvm_vcpu *vcpu);
 	void (*flush_tlb_current)(struct kvm_vcpu *vcpu);
+#if IS_ENABLED(CONFIG_HYPERV)
 	int  (*flush_remote_tlbs)(struct kvm *kvm);
 	int  (*flush_remote_tlbs_range)(struct kvm *kvm, gfn_t gfn,
 					gfn_t nr_pages);
+#endif
 
 	/*
 	 * Flush any TLB entries associated with the given GVA.
@@ -1825,6 +1827,7 @@ static inline struct kvm *kvm_arch_alloc_vm(void)
 #define __KVM_HAVE_ARCH_VM_FREE
 void kvm_arch_free_vm(struct kvm *kvm);
 
+#if IS_ENABLED(CONFIG_HYPERV)
 #define __KVM_HAVE_ARCH_FLUSH_REMOTE_TLBS
 static inline int kvm_arch_flush_remote_tlbs(struct kvm *kvm)
 {
@@ -1836,6 +1839,15 @@ static inline int kvm_arch_flush_remote_tlbs(struct kvm *kvm)
 }
 
 #define __KVM_HAVE_ARCH_FLUSH_REMOTE_TLBS_RANGE
+static inline int kvm_arch_flush_remote_tlbs_range(struct kvm *kvm, gfn_t gfn,
+						   u64 nr_pages)
+{
+	if (!kvm_x86_ops.flush_remote_tlbs_range)
+		return -EOPNOTSUPP;
+
+	return static_call(kvm_x86_flush_remote_tlbs_range)(kvm, gfn, nr_pages);
+}
+#endif /* CONFIG_HYPERV */
 
 #define kvm_arch_pmi_in_guest(vcpu) \
 	((vcpu) && (vcpu)->arch.handling_intr_from_guest)
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 5d3dc7119e57..0702f5234d69 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -271,15 +271,11 @@ static inline unsigned long kvm_mmu_get_guest_pgd(struct kvm_vcpu *vcpu,
 
 static inline bool kvm_available_flush_remote_tlbs_range(void)
 {
+#if IS_ENABLED(CONFIG_HYPERV)
 	return kvm_x86_ops.flush_remote_tlbs_range;
-}
-
-int kvm_arch_flush_remote_tlbs_range(struct kvm *kvm, gfn_t gfn, u64 nr_pages)
-{
-	if (!kvm_x86_ops.flush_remote_tlbs_range)
-		return -EOPNOTSUPP;
-
-	return static_call(kvm_x86_flush_remote_tlbs_range)(kvm, gfn, nr_pages);
+#else
+	return false;
+#endif
 }
 
 static gfn_t kvm_mmu_page_get_gfn(struct kvm_mmu_page *sp, int index);

base-commit: 437bba5ad2bba00c2056c896753a32edf80860cc
-- 
2.42.0.655.g421f12c284-goog

Re: [PATCH] KVM: x86/mmu: Declare flush_remote_tlbs{_range}() hooks iff HYPERV!=n

Posted by Sean Christopherson 2 years ago

On Wed, 18 Oct 2023 12:23:25 -0700, Sean Christopherson wrote:
> Declare the kvm_x86_ops hooks used to wire up paravirt TLB flushes when
> running under Hyper-V if and only if CONFIG_HYPERV!=n.  Wrapping yet more
> code with IS_ENABLED(CONFIG_HYPERV) eliminates a handful of conditional
> branches, and makes it super obvious why the hooks *might* be valid.
> 
> 

Applied to kvm-x86 hyperv, thanks!

[1/1] KVM: x86/mmu: Declare flush_remote_tlbs{_range}() hooks iff HYPERV!=n
      https://github.com/kvm-x86/linux/commit/0277022a77a5

--
https://github.com/kvm-x86/linux/tree/next

Re: [PATCH] KVM: x86/mmu: Declare flush_remote_tlbs{_range}() hooks iff HYPERV!=n

Posted by Vitaly Kuznetsov 2 years, 1 month ago

Sean Christopherson <seanjc@google.com> writes:

> Declare the kvm_x86_ops hooks used to wire up paravirt TLB flushes when
> running under Hyper-V if and only if CONFIG_HYPERV!=n.  Wrapping yet more
> code with IS_ENABLED(CONFIG_HYPERV) eliminates a handful of conditional
> branches, and makes it super obvious why the hooks *might* be valid.
>
> Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
> Signed-off-by: Sean Christopherson <seanjc@google.com>
> ---
>  arch/x86/include/asm/kvm-x86-ops.h |  2 ++
>  arch/x86/include/asm/kvm_host.h    | 12 ++++++++++++
>  arch/x86/kvm/mmu/mmu.c             | 12 ++++--------
>  3 files changed, 18 insertions(+), 8 deletions(-)
>
> diff --git a/arch/x86/include/asm/kvm-x86-ops.h b/arch/x86/include/asm/kvm-x86-ops.h
> index 26b628d84594..f482216bbdb8 100644
> --- a/arch/x86/include/asm/kvm-x86-ops.h
> +++ b/arch/x86/include/asm/kvm-x86-ops.h
> @@ -55,8 +55,10 @@ KVM_X86_OP(set_rflags)
>  KVM_X86_OP(get_if_flag)
>  KVM_X86_OP(flush_tlb_all)
>  KVM_X86_OP(flush_tlb_current)
> +#if IS_ENABLED(CONFIG_HYPERV)
>  KVM_X86_OP_OPTIONAL(flush_remote_tlbs)
>  KVM_X86_OP_OPTIONAL(flush_remote_tlbs_range)
> +#endif
>  KVM_X86_OP(flush_tlb_gva)
>  KVM_X86_OP(flush_tlb_guest)
>  KVM_X86_OP(vcpu_pre_run)
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index 7c228ae05df0..f0d1ac871465 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -1614,9 +1614,11 @@ struct kvm_x86_ops {
>  
>  	void (*flush_tlb_all)(struct kvm_vcpu *vcpu);
>  	void (*flush_tlb_current)(struct kvm_vcpu *vcpu);
> +#if IS_ENABLED(CONFIG_HYPERV)
>  	int  (*flush_remote_tlbs)(struct kvm *kvm);
>  	int  (*flush_remote_tlbs_range)(struct kvm *kvm, gfn_t gfn,
>  					gfn_t nr_pages);
> +#endif
>  
>  	/*
>  	 * Flush any TLB entries associated with the given GVA.
> @@ -1825,6 +1827,7 @@ static inline struct kvm *kvm_arch_alloc_vm(void)
>  #define __KVM_HAVE_ARCH_VM_FREE
>  void kvm_arch_free_vm(struct kvm *kvm);
>  
> +#if IS_ENABLED(CONFIG_HYPERV)
>  #define __KVM_HAVE_ARCH_FLUSH_REMOTE_TLBS
>  static inline int kvm_arch_flush_remote_tlbs(struct kvm *kvm)
>  {
> @@ -1836,6 +1839,15 @@ static inline int kvm_arch_flush_remote_tlbs(struct kvm *kvm)
>  }
>  
>  #define __KVM_HAVE_ARCH_FLUSH_REMOTE_TLBS_RANGE
> +static inline int kvm_arch_flush_remote_tlbs_range(struct kvm *kvm, gfn_t gfn,
> +						   u64 nr_pages)
> +{
> +	if (!kvm_x86_ops.flush_remote_tlbs_range)
> +		return -EOPNOTSUPP;
> +
> +	return static_call(kvm_x86_flush_remote_tlbs_range)(kvm, gfn, nr_pages);
> +}
> +#endif /* CONFIG_HYPERV */
>  
>  #define kvm_arch_pmi_in_guest(vcpu) \
>  	((vcpu) && (vcpu)->arch.handling_intr_from_guest)
> diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
> index 5d3dc7119e57..0702f5234d69 100644
> --- a/arch/x86/kvm/mmu/mmu.c
> +++ b/arch/x86/kvm/mmu/mmu.c
> @@ -271,15 +271,11 @@ static inline unsigned long kvm_mmu_get_guest_pgd(struct kvm_vcpu *vcpu,
>  
>  static inline bool kvm_available_flush_remote_tlbs_range(void)
>  {
> +#if IS_ENABLED(CONFIG_HYPERV)
>  	return kvm_x86_ops.flush_remote_tlbs_range;
> -}
> -
> -int kvm_arch_flush_remote_tlbs_range(struct kvm *kvm, gfn_t gfn, u64 nr_pages)
> -{
> -	if (!kvm_x86_ops.flush_remote_tlbs_range)
> -		return -EOPNOTSUPP;
> -
> -	return static_call(kvm_x86_flush_remote_tlbs_range)(kvm, gfn, nr_pages);
> +#else
> +	return false;
> +#endif
>  }
>  
>  static gfn_t kvm_mmu_page_get_gfn(struct kvm_mmu_page *sp, int index);
>
> base-commit: 437bba5ad2bba00c2056c896753a32edf80860cc

Makes sense,

Reviewed-by: Vitaly Kuznetsov <vkuznets@redhat.com>

I can take it to my CONFIG_KVM_HYPERV series but it doesn't seem to
intersect with it so I guess there's no need for that.

-- 
Vitaly

Re: [PATCH] KVM: x86/mmu: Declare flush_remote_tlbs{_range}() hooks iff HYPERV!=n

Posted by Sean Christopherson 2 years, 1 month ago

On Thu, Oct 19, 2023, Vitaly Kuznetsov wrote:
> I can take it to my CONFIG_KVM_HYPERV series but it doesn't seem to
> intersect with it so I guess there's no need for that.

Yeah, I checked before sending (I've had this patch lying around for quite some
time).  I was quite surprised that there wasn't any overlap.