| Message ID | 20230330154918.4014761-2-oliver.upton@linux.dev (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2,01/13] KVM: x86: Redefine 'longmode' as a flag for KVM_EXIT_HYPERCALL | expand |
On Thu, Mar 30, 2023, Oliver Upton wrote: > The 'longmode' field is a bit annoying as it blows an entire __u32 to > represent a boolean value. Since other architectures are looking to add > support for KVM_EXIT_HYPERCALL, now is probably a good time to clean it > up. > > Redefine the field (and the remaining padding) as a set of flags. > Preserve the existing ABI by using bit 0 to indicate if the guest was in > long mode and requiring that the remaining 31 bits must be zero. > > Cc: Paolo Bonzini <pbonzini@redhat.com> > Cc: Sean Christopherson <seanjc@google.com> > Signed-off-by: Oliver Upton <oliver.upton@linux.dev> > --- Acked-by: Sean Christopherson <seanjc@google.com> > Documentation/virt/kvm/api.rst | 3 +-- > arch/x86/include/asm/kvm_host.h | 7 +++++++ > arch/x86/include/uapi/asm/kvm.h | 3 +++ > arch/x86/kvm/x86.c | 6 +++++- > include/uapi/linux/kvm.h | 9 +++++++-- > 5 files changed, 23 insertions(+), 5 deletions(-) > > diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst > index 62de0768d6aa..9b01e3d0e757 100644 > --- a/Documentation/virt/kvm/api.rst > +++ b/Documentation/virt/kvm/api.rst > @@ -6218,8 +6218,7 @@ to the byte array. > __u64 nr; > __u64 args[6]; > __u64 ret; > - __u32 longmode; > - __u32 pad; > + __u64 flags; > } hypercall; > > Unused. This was once used for 'hypercall to userspace'. To implement Note to self, this needs to be updated as "hypercall" is longer unused.
diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst index 62de0768d6aa..9b01e3d0e757 100644 --- a/Documentation/virt/kvm/api.rst +++ b/Documentation/virt/kvm/api.rst @@ -6218,8 +6218,7 @@ to the byte array. __u64 nr; __u64 args[6]; __u64 ret; - __u32 longmode; - __u32 pad; + __u64 flags; } hypercall; Unused. This was once used for 'hypercall to userspace'. To implement diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h index 808c292ad3f4..15bda40517ff 100644 --- a/arch/x86/include/asm/kvm_host.h +++ b/arch/x86/include/asm/kvm_host.h @@ -2204,4 +2204,11 @@ int memslot_rmap_alloc(struct kvm_memory_slot *slot, unsigned long npages); KVM_X86_QUIRK_FIX_HYPERCALL_INSN | \ KVM_X86_QUIRK_MWAIT_NEVER_UD_FAULTS) +/* + * KVM previously used a u32 field in kvm_run to indicate the hypercall was + * initiated from long mode. KVM now sets bit 0 to indicate long mode, but the + * remaining 31 lower bits must be 0 to preserve ABI. + */ +#define KVM_EXIT_HYPERCALL_MBZ GENMASK_ULL(31, 1) + #endif /* _ASM_X86_KVM_HOST_H */ diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h index 7f467fe05d42..1a6a1f987949 100644 --- a/arch/x86/include/uapi/asm/kvm.h +++ b/arch/x86/include/uapi/asm/kvm.h @@ -559,4 +559,7 @@ struct kvm_pmu_event_filter { #define KVM_VCPU_TSC_CTRL 0 /* control group for the timestamp counter (TSC) */ #define KVM_VCPU_TSC_OFFSET 0 /* attribute for the TSC offset */ +/* x86-specific KVM_EXIT_HYPERCALL flags. */ +#define KVM_EXIT_HYPERCALL_LONG_MODE BIT(0) + #endif /* _ASM_X86_KVM_H */ diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index 7713420abab0..27a1d5c1a018 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -9803,7 +9803,11 @@ int kvm_emulate_hypercall(struct kvm_vcpu *vcpu) vcpu->run->hypercall.args[0] = gpa; vcpu->run->hypercall.args[1] = npages; vcpu->run->hypercall.args[2] = attrs; - vcpu->run->hypercall.longmode = op_64_bit; + vcpu->run->hypercall.flags = 0; + if (op_64_bit) + 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; return 0; } diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h index d77aef872a0a..dd42d7dfb86c 100644 --- a/include/uapi/linux/kvm.h +++ b/include/uapi/linux/kvm.h @@ -341,8 +341,13 @@ struct kvm_run { __u64 nr; __u64 args[6]; __u64 ret; - __u32 longmode; - __u32 pad; + + union { +#ifndef __KERNEL__ + __u32 longmode; +#endif + __u64 flags; + }; } hypercall; /* KVM_EXIT_TPR_ACCESS */ struct {
The 'longmode' field is a bit annoying as it blows an entire __u32 to represent a boolean value. Since other architectures are looking to add support for KVM_EXIT_HYPERCALL, now is probably a good time to clean it up. Redefine the field (and the remaining padding) as a set of flags. Preserve the existing ABI by using bit 0 to indicate if the guest was in long mode and requiring that the remaining 31 bits must be zero. Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Sean Christopherson <seanjc@google.com> Signed-off-by: Oliver Upton <oliver.upton@linux.dev> --- Documentation/virt/kvm/api.rst | 3 +-- arch/x86/include/asm/kvm_host.h | 7 +++++++ arch/x86/include/uapi/asm/kvm.h | 3 +++ arch/x86/kvm/x86.c | 6 +++++- include/uapi/linux/kvm.h | 9 +++++++-- 5 files changed, 23 insertions(+), 5 deletions(-)