| Message ID | 20241128004344.4072099-6-seanjc@google.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | KVM: x86: Prep KVM hypercall handling for TDX | expand |
On 11/28/2024 8:43 AM, Sean Christopherson wrote: > Finish "emulation" of KVM hypercalls by function callback, even when the > hypercall is handled entirely within KVM, i.e. doesn't require an exit to > userspace, and refactor __kvm_emulate_hypercall()'s return value to *only* > communicate whether or not KVM should exit to userspace or resume the > guest. > > (Ab)Use vcpu->run->hypercall.ret to propagate the return value to the > callback, purely to avoid having to add a trampoline for every completion > callback. > > Using the function return value for KVM's control flow eliminates the > multiplexed return value, where '0' for KVM_HC_MAP_GPA_RANGE (and only > that hypercall) means "exit to userspace". > > Note, the unnecessary extra indirect call and thus potential retpoline > will be eliminated in the near future by converting the intermediate layer > to a macro. > > Suggested-by: Binbin Wu <binbin.wu@linux.intel.com> > Suggested-by: Kai Huang <kai.huang@intel.com> > Signed-off-by: Sean Christopherson <seanjc@google.com> > --- > arch/x86/kvm/x86.c | 29 ++++++++++++----------------- > arch/x86/kvm/x86.h | 10 ++++++---- > 2 files changed, 18 insertions(+), 21 deletions(-) > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 11434752b467..39be2a891ab4 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -9982,10 +9982,11 @@ static int complete_hypercall_exit(struct kvm_vcpu *vcpu) > return kvm_skip_emulated_instruction(vcpu); > } > > -unsigned long __kvm_emulate_hypercall(struct kvm_vcpu *vcpu, unsigned long nr, > - unsigned long a0, unsigned long a1, > - unsigned long a2, unsigned long a3, > - int op_64_bit, int cpl) > +int __kvm_emulate_hypercall(struct kvm_vcpu *vcpu, unsigned long nr, > + unsigned long a0, unsigned long a1, > + unsigned long a2, unsigned long a3, > + int op_64_bit, int cpl, > + int (*complete_hypercall)(struct kvm_vcpu *)) > { > unsigned long ret; > > @@ -10061,7 +10062,7 @@ unsigned long __kvm_emulate_hypercall(struct kvm_vcpu *vcpu, unsigned long nr, > vcpu->run->hypercall.flags |= KVM_EXIT_HYPERCALL_LONG_MODE; > > WARN_ON_ONCE(vcpu->run->hypercall.flags & KVM_EXIT_HYPERCALL_MBZ); > - vcpu->arch.complete_userspace_io = complete_hypercall_exit; > + vcpu->arch.complete_userspace_io = complete_hypercall; > /* stat is incremented on completion. */ > return 0; > } > @@ -10071,13 +10072,15 @@ unsigned long __kvm_emulate_hypercall(struct kvm_vcpu *vcpu, unsigned long nr, > } > > out: > - return ret; > + vcpu->run->hypercall.ret = ret; > + complete_hypercall(vcpu); > + return 1; shouldn't it be return complete_hypercall(vcpu); ? Originally, kvm_emulate_hypercall() returns kvm_skip_emulated_instruction(). Now it becomes kvm_skip_emulated_instruction(); return 1; I don't go deep to see if kvm_skip_emulated_instruction() always return 1 for this case. But logically, return complete_hypercall(vcpu); looks more reasonable. > } > EXPORT_SYMBOL_GPL(__kvm_emulate_hypercall); > > int kvm_emulate_hypercall(struct kvm_vcpu *vcpu) > { > - unsigned long nr, a0, a1, a2, a3, ret; > + unsigned long nr, a0, a1, a2, a3; > int op_64_bit; > int cpl; > > @@ -10095,16 +10098,8 @@ int kvm_emulate_hypercall(struct kvm_vcpu *vcpu) > op_64_bit = is_64_bit_hypercall(vcpu); > cpl = kvm_x86_call(get_cpl)(vcpu); > > - ret = __kvm_emulate_hypercall(vcpu, nr, a0, a1, a2, a3, op_64_bit, cpl); > - if (nr == KVM_HC_MAP_GPA_RANGE && !ret) > - /* MAP_GPA tosses the request to the user space. */ > - return 0; > - > - if (!op_64_bit) > - ret = (u32)ret; > - kvm_rax_write(vcpu, ret); > - > - return kvm_skip_emulated_instruction(vcpu); > + return __kvm_emulate_hypercall(vcpu, nr, a0, a1, a2, a3, op_64_bit, cpl, > + complete_hypercall_exit); > } > EXPORT_SYMBOL_GPL(kvm_emulate_hypercall); > > diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h > index 6db13b696468..28adc8ea04bf 100644 > --- a/arch/x86/kvm/x86.h > +++ b/arch/x86/kvm/x86.h > @@ -617,10 +617,12 @@ static inline bool user_exit_on_hypercall(struct kvm *kvm, unsigned long hc_nr) > return kvm->arch.hypercall_exit_enabled & BIT(hc_nr); > } > > -unsigned long __kvm_emulate_hypercall(struct kvm_vcpu *vcpu, unsigned long nr, > - unsigned long a0, unsigned long a1, > - unsigned long a2, unsigned long a3, > - int op_64_bit, int cpl); > +int __kvm_emulate_hypercall(struct kvm_vcpu *vcpu, unsigned long nr, > + unsigned long a0, unsigned long a1, > + unsigned long a2, unsigned long a3, > + int op_64_bit, int cpl, > + int (*complete_hypercall)(struct kvm_vcpu *)); > + > int kvm_emulate_hypercall(struct kvm_vcpu *vcpu); > > #endif
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 11434752b467..39be2a891ab4 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -9982,10 +9982,11 @@ static int complete_hypercall_exit(struct kvm_vcpu *vcpu) return kvm_skip_emulated_instruction(vcpu); } -unsigned long __kvm_emulate_hypercall(struct kvm_vcpu *vcpu, unsigned long nr, - unsigned long a0, unsigned long a1, - unsigned long a2, unsigned long a3, - int op_64_bit, int cpl) +int __kvm_emulate_hypercall(struct kvm_vcpu *vcpu, unsigned long nr, + unsigned long a0, unsigned long a1, + unsigned long a2, unsigned long a3, + int op_64_bit, int cpl, + int (*complete_hypercall)(struct kvm_vcpu *)) { unsigned long ret; @@ -10061,7 +10062,7 @@ unsigned long __kvm_emulate_hypercall(struct kvm_vcpu *vcpu, unsigned long nr, vcpu->run->hypercall.flags |= KVM_EXIT_HYPERCALL_LONG_MODE; WARN_ON_ONCE(vcpu->run->hypercall.flags & KVM_EXIT_HYPERCALL_MBZ); - vcpu->arch.complete_userspace_io = complete_hypercall_exit; + vcpu->arch.complete_userspace_io = complete_hypercall; /* stat is incremented on completion. */ return 0; } @@ -10071,13 +10072,15 @@ unsigned long __kvm_emulate_hypercall(struct kvm_vcpu *vcpu, unsigned long nr, } out: - return ret; + vcpu->run->hypercall.ret = ret; + complete_hypercall(vcpu); + return 1; } EXPORT_SYMBOL_GPL(__kvm_emulate_hypercall); int kvm_emulate_hypercall(struct kvm_vcpu *vcpu) { - unsigned long nr, a0, a1, a2, a3, ret; + unsigned long nr, a0, a1, a2, a3; int op_64_bit; int cpl; @@ -10095,16 +10098,8 @@ int kvm_emulate_hypercall(struct kvm_vcpu *vcpu) op_64_bit = is_64_bit_hypercall(vcpu); cpl = kvm_x86_call(get_cpl)(vcpu); - ret = __kvm_emulate_hypercall(vcpu, nr, a0, a1, a2, a3, op_64_bit, cpl); - if (nr == KVM_HC_MAP_GPA_RANGE && !ret) - /* MAP_GPA tosses the request to the user space. */ - return 0; - - if (!op_64_bit) - ret = (u32)ret; - kvm_rax_write(vcpu, ret); - - return kvm_skip_emulated_instruction(vcpu); + return __kvm_emulate_hypercall(vcpu, nr, a0, a1, a2, a3, op_64_bit, cpl, + complete_hypercall_exit); } EXPORT_SYMBOL_GPL(kvm_emulate_hypercall); diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h index 6db13b696468..28adc8ea04bf 100644 --- a/arch/x86/kvm/x86.h +++ b/arch/x86/kvm/x86.h @@ -617,10 +617,12 @@ static inline bool user_exit_on_hypercall(struct kvm *kvm, unsigned long hc_nr) return kvm->arch.hypercall_exit_enabled & BIT(hc_nr); } -unsigned long __kvm_emulate_hypercall(struct kvm_vcpu *vcpu, unsigned long nr, - unsigned long a0, unsigned long a1, - unsigned long a2, unsigned long a3, - int op_64_bit, int cpl); +int __kvm_emulate_hypercall(struct kvm_vcpu *vcpu, unsigned long nr, + unsigned long a0, unsigned long a1, + unsigned long a2, unsigned long a3, + int op_64_bit, int cpl, + int (*complete_hypercall)(struct kvm_vcpu *)); + int kvm_emulate_hypercall(struct kvm_vcpu *vcpu); #endif
Finish "emulation" of KVM hypercalls by function callback, even when the hypercall is handled entirely within KVM, i.e. doesn't require an exit to userspace, and refactor __kvm_emulate_hypercall()'s return value to *only* communicate whether or not KVM should exit to userspace or resume the guest. (Ab)Use vcpu->run->hypercall.ret to propagate the return value to the callback, purely to avoid having to add a trampoline for every completion callback. Using the function return value for KVM's control flow eliminates the multiplexed return value, where '0' for KVM_HC_MAP_GPA_RANGE (and only that hypercall) means "exit to userspace". Note, the unnecessary extra indirect call and thus potential retpoline will be eliminated in the near future by converting the intermediate layer to a macro. Suggested-by: Binbin Wu <binbin.wu@linux.intel.com> Suggested-by: Kai Huang <kai.huang@intel.com> Signed-off-by: Sean Christopherson <seanjc@google.com> --- arch/x86/kvm/x86.c | 29 ++++++++++++----------------- arch/x86/kvm/x86.h | 10 ++++++---- 2 files changed, 18 insertions(+), 21 deletions(-)