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Date: Wed, 29 Jun 2022 03:17:44 -0700
From: Isaku Yamahata <isaku.yamahata@...il.com>
To: Sagi Shahar <sagis@...gle.com>
Cc: "Yamahata, Isaku" <isaku.yamahata@...el.com>, kvm@...r.kernel.org,
linux-kernel@...r.kernel.org, isaku.yamahata@...il.com,
Paolo Bonzini <pbonzini@...hat.com>,
Erdem Aktas <erdemaktas@...gle.com>,
Sean Christopherson <seanjc@...gle.com>
Subject: Re: [RFC PATCH v6 093/104] KVM: TDX: Handle TDX PV MMIO hypercall
On Tue, Jun 14, 2022 at 11:08:16AM -0700,
Sagi Shahar <sagis@...gle.com> wrote:
> On Thu, May 5, 2022 at 11:16 AM <isaku.yamahata@...el.com> wrote:
> >
> > From: Sean Christopherson <sean.j.christopherson@...el.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@...el.com>
> > Signed-off-by: Isaku Yamahata <isaku.yamahata@...el.com>
> > Reviewed-by: Paolo Bonzini <pbonzini@...hat.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 ee0cf5336ade..6ab4a52fc9e9 100644
> > --- a/arch/x86/kvm/vmx/tdx.c
> > +++ b/arch/x86/kvm/vmx/tdx.c
> > @@ -1057,6 +1057,118 @@ 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;
> > +
> > + WARN_ON(vcpu->mmio_needed != 1);
> > + 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;
> > +
> > + WARN_ON(vcpu->mmio_needed);
> > +
> > + 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. */
> > + gpa = gpa & ~gfn_to_gpa(kvm_gfn_shared_mask(vcpu->kvm));
> > +
> > + if (size > 8u || ((gpa + size - 1) ^ gpa) & PAGE_MASK)
> > + 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)) {
> > + 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, TDG_VP_VMCALL_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, TDG_VP_VMCALL_SUCCESS);
>
> We should return an error code here.
Yes, I'll fix it as follows. Thanks for catching it.
error:
- tdvmcall_set_return_code(vcpu, TDG_VP_VMCALL_SUCCESS);
+ tdvmcall_set_return_code(vcpu, TDG_VP_VMCALL_INVALID_OPERAND);
return 1;
}
--
Isaku Yamahata <isaku.yamahata@...il.com>
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