Messages in this thread Patch in this message | | | Date | Thu, 18 Apr 2024 17:29:43 +0800 | Subject | Re: [PATCH v19 110/130] KVM: TDX: Handle TDX PV MMIO hypercall | From | Binbin Wu <> |
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On 2/26/2024 4:26 PM, isaku.yamahata@intel.com wrote: > From: Sean Christopherson <sean.j.christopherson@intel.com> > > Export kvm_io_bus_read and kvm_mmio tracepoint and wire up TDX PV MMIO > hypercall to the KVM backend functions. > > kvm_io_bus_read/write() searches KVM device emulated in kernel of the given > MMIO address and emulates the MMIO. As TDX PV MMIO also needs it, export > kvm_io_bus_read(). kvm_io_bus_write() is already exported. TDX PV MMIO > emulates some of MMIO itself. To add trace point consistently with x86 > kvm, export kvm_mmio tracepoint. > > Signed-off-by: Sean Christopherson <sean.j.christopherson@intel.com> > Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com> > Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> > --- > arch/x86/kvm/vmx/tdx.c | 114 +++++++++++++++++++++++++++++++++++++++++ > arch/x86/kvm/x86.c | 1 + > virt/kvm/kvm_main.c | 2 + > 3 files changed, 117 insertions(+) > > diff --git a/arch/x86/kvm/vmx/tdx.c b/arch/x86/kvm/vmx/tdx.c > index 55fc6cc6c816..389bb95d2af0 100644 > --- a/arch/x86/kvm/vmx/tdx.c > +++ b/arch/x86/kvm/vmx/tdx.c > @@ -1217,6 +1217,118 @@ static int tdx_emulate_io(struct kvm_vcpu *vcpu) > return ret; > } > > +static int tdx_complete_mmio(struct kvm_vcpu *vcpu) > +{ > + unsigned long val = 0; > + gpa_t gpa; > + int size; > + > + KVM_BUG_ON(vcpu->mmio_needed != 1, vcpu->kvm); > + vcpu->mmio_needed = 0; > + > + if (!vcpu->mmio_is_write) { > + gpa = vcpu->mmio_fragments[0].gpa; > + size = vcpu->mmio_fragments[0].len; > + > + memcpy(&val, vcpu->run->mmio.data, size); > + tdvmcall_set_return_val(vcpu, val); > + trace_kvm_mmio(KVM_TRACE_MMIO_READ, size, gpa, &val); > + } > + return 1; > +} > + > +static inline int tdx_mmio_write(struct kvm_vcpu *vcpu, gpa_t gpa, int size, > + unsigned long val) > +{ > + if (kvm_iodevice_write(vcpu, &vcpu->arch.apic->dev, gpa, size, &val) && > + kvm_io_bus_write(vcpu, KVM_MMIO_BUS, gpa, size, &val)) > + return -EOPNOTSUPP; > + > + trace_kvm_mmio(KVM_TRACE_MMIO_WRITE, size, gpa, &val); > + return 0; > +} > + > +static inline int tdx_mmio_read(struct kvm_vcpu *vcpu, gpa_t gpa, int size) > +{ > + unsigned long val; > + > + if (kvm_iodevice_read(vcpu, &vcpu->arch.apic->dev, gpa, size, &val) && > + kvm_io_bus_read(vcpu, KVM_MMIO_BUS, gpa, size, &val)) > + return -EOPNOTSUPP; > + > + tdvmcall_set_return_val(vcpu, val); > + trace_kvm_mmio(KVM_TRACE_MMIO_READ, size, gpa, &val); > + return 0; > +} > + > +static int tdx_emulate_mmio(struct kvm_vcpu *vcpu) > +{ > + struct kvm_memory_slot *slot; > + int size, write, r; > + unsigned long val; > + gpa_t gpa; > + > + KVM_BUG_ON(vcpu->mmio_needed, vcpu->kvm); > + > + size = tdvmcall_a0_read(vcpu); > + write = tdvmcall_a1_read(vcpu); > + gpa = tdvmcall_a2_read(vcpu); > + val = write ? tdvmcall_a3_read(vcpu) : 0; > + > + if (size != 1 && size != 2 && size != 4 && size != 8) > + goto error; > + if (write != 0 && write != 1) > + goto error; > + > + /* Strip the shared bit, allow MMIO with and without it set. */ Based on the discussion https://lore.kernel.org/all/ZcUO5sFEAIH68JIA@google.com/ Do we still allow the MMIO without shared bit?
> + gpa = gpa & ~gfn_to_gpa(kvm_gfn_shared_mask(vcpu->kvm)); > + > + if (size > 8u || ((gpa + size - 1) ^ gpa) & PAGE_MASK) "size > 8u" can be removed, since based on the check of size above, it can't be greater than 8.
> + goto error; > + > + slot = kvm_vcpu_gfn_to_memslot(vcpu, gpa_to_gfn(gpa)); > + if (slot && !(slot->flags & KVM_MEMSLOT_INVALID)) > + goto error; > + > + if (!kvm_io_bus_write(vcpu, KVM_FAST_MMIO_BUS, gpa, 0, NULL)) { Should this be checked for write first?
I check the handle_ept_misconfig() in VMX, it doesn't check write first neither.
Functionally, it should be OK since guest will not read the address range of fast mmio. So the read case will be filtered out by ioeventfd_write(). But it has take a long way to get to ioeventfd_write(). Isn't it more efficient to check write first?
> + trace_kvm_fast_mmio(gpa); > + return 1; > + } > + > + if (write) > + r = tdx_mmio_write(vcpu, gpa, size, val); > + else > + r = tdx_mmio_read(vcpu, gpa, size); > + if (!r) { > + /* Kernel completed device emulation. */ > + tdvmcall_set_return_code(vcpu, TDVMCALL_SUCCESS); > + return 1; > + } > + > + /* Request the device emulation to userspace device model. */ > + vcpu->mmio_needed = 1; > + vcpu->mmio_is_write = write; > + vcpu->arch.complete_userspace_io = tdx_complete_mmio; > + > + vcpu->run->mmio.phys_addr = gpa; > + vcpu->run->mmio.len = size; > + vcpu->run->mmio.is_write = write; > + vcpu->run->exit_reason = KVM_EXIT_MMIO; > + > + if (write) { > + memcpy(vcpu->run->mmio.data, &val, size); > + } else { > + vcpu->mmio_fragments[0].gpa = gpa; > + vcpu->mmio_fragments[0].len = size; > + trace_kvm_mmio(KVM_TRACE_MMIO_READ_UNSATISFIED, size, gpa, NULL); > + } > + return 0; > + > +error: > + tdvmcall_set_return_code(vcpu, TDVMCALL_INVALID_OPERAND); > + return 1; > +} > + > static int handle_tdvmcall(struct kvm_vcpu *vcpu) > { > if (tdvmcall_exit_type(vcpu)) > @@ -1229,6 +1341,8 @@ static int handle_tdvmcall(struct kvm_vcpu *vcpu) > return tdx_emulate_hlt(vcpu); > case EXIT_REASON_IO_INSTRUCTION: > return tdx_emulate_io(vcpu); > + case EXIT_REASON_EPT_VIOLATION: > + return tdx_emulate_mmio(vcpu); > default: > break; > } > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 03950368d8db..d5b18cad9dcd 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -13975,6 +13975,7 @@ EXPORT_SYMBOL_GPL(kvm_sev_es_string_io); > > EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_entry); > EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_exit); > +EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_mmio); > EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_fast_mmio); > EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_inj_virq); > EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_page_fault); > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index e27c22449d85..bc14e1f2610c 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -2689,6 +2689,7 @@ struct kvm_memory_slot *kvm_vcpu_gfn_to_memslot(struct kvm_vcpu *vcpu, gfn_t gfn > > return NULL; > } > +EXPORT_SYMBOL_GPL(kvm_vcpu_gfn_to_memslot); > > bool kvm_is_visible_gfn(struct kvm *kvm, gfn_t gfn) > { > @@ -5992,6 +5993,7 @@ int kvm_io_bus_read(struct kvm_vcpu *vcpu, enum kvm_bus bus_idx, gpa_t addr, > r = __kvm_io_bus_read(vcpu, bus, &range, val); > return r < 0 ? r : 0; > } > +EXPORT_SYMBOL_GPL(kvm_io_bus_read); > > int kvm_io_bus_register_dev(struct kvm *kvm, enum kvm_bus bus_idx, gpa_t addr, > int len, struct kvm_io_device *dev)
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