Re: [PATCH v4 2/6] KVM: x86: Add a helper to check for user interception of KVM hypercalls

Tom Lendacky
2024-12-02T18:58:04Z

On 11/27/24 18:43, Sean Christopherson wrote:
> From: Binbin Wu <binbin.wu@linux.intel.com>
>
> Add and use user_exit_on_hypercall() to check if userspace wants to handle
> a KVM hypercall instead of open-coding the logic everywhere.
>
> No functional change intended.
>
> Signed-off-by: Binbin Wu <binbin.wu@linux.intel.com>
> Reviewed-by: Isaku Yamahata <isaku.yamahata@intel.com>
> Reviewed-by: Kai Huang <kai.huang@intel.com>
> Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
> [sean: squash into one patch, keep explicit KVM_HC_MAP_GPA_RANGE check]
> Signed-off-by: Sean Christopherson <seanjc@google.com>

Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>

> ---
> arch/x86/kvm/svm/sev.c | 4 ++--
> arch/x86/kvm/x86.c | 2 +-
> arch/x86/kvm/x86.h | 5 +++++
> 3 files changed, 8 insertions(+), 3 deletions(-)
>
> diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
> index 72674b8825c4..6ac6312c4d57 100644
> --- a/arch/x86/kvm/svm/sev.c
> +++ b/arch/x86/kvm/svm/sev.c
> @@ -3640,7 +3640,7 @@ static int snp_begin_psc_msr(struct vcpu_svm *svm, u64 ghcb_msr)
> return 1; /* resume guest */
> }
>
> - if (!(vcpu->kvm->arch.hypercall_exit_enabled & (1 << KVM_HC_MAP_GPA_RANGE))) {
> + if (!user_exit_on_hypercall(vcpu->kvm, KVM_HC_MAP_GPA_RANGE)) {
> set_ghcb_msr(svm, GHCB_MSR_PSC_RESP_ERROR);
> return 1; /* resume guest */
> }
> @@ -3723,7 +3723,7 @@ static int snp_begin_psc(struct vcpu_svm *svm, struct psc_buffer *psc)
> bool huge;
> u64 gfn;
>
> - if (!(vcpu->kvm->arch.hypercall_exit_enabled & (1 << KVM_HC_MAP_GPA_RANGE))) {
> + if (!user_exit_on_hypercall(vcpu->kvm, KVM_HC_MAP_GPA_RANGE)) {
> snp_complete_psc(svm, VMGEXIT_PSC_ERROR_GENERIC);
> return 1;
> }
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 0b2fe4aa04a2..13fe5d6eb8f3 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -10041,7 +10041,7 @@ unsigned long __kvm_emulate_hypercall(struct kvm_vcpu *vcpu, unsigned long nr,
> u64 gpa = a0, npages = a1, attrs = a2;
>
> ret = -KVM_ENOSYS;
> - if (!(vcpu->kvm->arch.hypercall_exit_enabled & (1 << KVM_HC_MAP_GPA_RANGE)))
> + if (!user_exit_on_hypercall(vcpu->kvm, KVM_HC_MAP_GPA_RANGE))
> break;
>
> if (!PAGE_ALIGNED(gpa) || !npages ||
> diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
> index ec623d23d13d..45dd53284dbd 100644
> --- a/arch/x86/kvm/x86.h
> +++ b/arch/x86/kvm/x86.h
> @@ -612,4 +612,9 @@ int kvm_sev_es_string_io(struct kvm_vcpu *vcpu, unsigned int size,
> unsigned int port, void *data, unsigned int count,
> int in);
>
> +static inline bool user_exit_on_hypercall(struct kvm *kvm, unsigned long hc_nr)
> +{
> + return kvm->arch.hypercall_exit_enabled & BIT(hc_nr);
> +}
> +
> #endif