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KVM: TDX: Handle TDX PV port I/O hypercall

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Emulate port I/O requested by TDX guest via TDVMCALL with leaf
Instruction.IO (same value as EXIT_REASON_IO_INSTRUCTION) according to
TDX Guest Host Communication Interface (GHCI).

All port I/O instructions inside the TDX guest trigger the #VE exception.
On #VE triggered by I/O instructions, TDX guest can call TDVMCALL with
leaf Instruction.IO to request VMM to emulate I/O instructions.

Similar to normal port I/O emulation, try to handle the port I/O in kernel
first, if kernel can't support it, forward the request to userspace.

Note string I/O operations are not supported in TDX.  Guest should unroll
them before calling the TDVMCALL.

Suggested-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
Co-developed-by: Binbin Wu <binbin.wu@linux.intel.com>
Signed-off-by: Binbin Wu <binbin.wu@linux.intel.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20250222014225.897298-9-binbin.wu@linux.intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Isaku Yamahata 2025-02-22 09:42:24 +08:00 committed by Paolo Bonzini
parent 79462faa2b
commit 33608aaf71
1 changed files with 62 additions and 0 deletions
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62
arch/x86/kvm/vmx/tdx.c
View File

@ -808,6 +808,8 @@ int tdx_vcpu_pre_run(struct kvm_vcpu *vcpu)
static __always_inline u32 tdcall_to_vmx_exit_reason(struct kvm_vcpu *vcpu)
{
switch (tdvmcall_leaf(vcpu)) {
case EXIT_REASON_IO_INSTRUCTION:
return tdvmcall_leaf(vcpu);
default:
break;
}
@ -1130,6 +1132,64 @@ static int tdx_report_fatal_error(struct kvm_vcpu *vcpu)
return 0;
}
static int tdx_complete_pio_out(struct kvm_vcpu *vcpu)
{
vcpu->arch.pio.count = 0;
return 1;
}
static int tdx_complete_pio_in(struct kvm_vcpu *vcpu)
{
struct x86_emulate_ctxt *ctxt = vcpu->arch.emulate_ctxt;
unsigned long val = 0;
int ret;
ret = ctxt->ops->pio_in_emulated(ctxt, vcpu->arch.pio.size,
vcpu->arch.pio.port, &val, 1);
WARN_ON_ONCE(!ret);
tdvmcall_set_return_val(vcpu, val);
return 1;
}
static int tdx_emulate_io(struct kvm_vcpu *vcpu)
{
struct vcpu_tdx *tdx = to_tdx(vcpu);
struct x86_emulate_ctxt *ctxt = vcpu->arch.emulate_ctxt;
unsigned long val = 0;
unsigned int port;
u64 size, write;
int ret;
++vcpu->stat.io_exits;
size = tdx->vp_enter_args.r12;
write = tdx->vp_enter_args.r13;
port = tdx->vp_enter_args.r14;
if ((write != 0 && write != 1) || (size != 1 && size != 2 && size != 4)) {
tdvmcall_set_return_code(vcpu, TDVMCALL_STATUS_INVALID_OPERAND);
return 1;
}
if (write) {
val = tdx->vp_enter_args.r15;
ret = ctxt->ops->pio_out_emulated(ctxt, size, port, &val, 1);
} else {
ret = ctxt->ops->pio_in_emulated(ctxt, size, port, &val, 1);
}
if (!ret)
vcpu->arch.complete_userspace_io = write ? tdx_complete_pio_out :
tdx_complete_pio_in;
else if (!write)
tdvmcall_set_return_val(vcpu, val);
return ret;
}
static int handle_tdvmcall(struct kvm_vcpu *vcpu)
{
switch (tdvmcall_leaf(vcpu)) {
@ -1507,6 +1567,8 @@ int tdx_handle_exit(struct kvm_vcpu *vcpu, fastpath_t fastpath)
return handle_tdvmcall(vcpu);
case EXIT_REASON_VMCALL:
return tdx_emulate_vmcall(vcpu);
case EXIT_REASON_IO_INSTRUCTION:
return tdx_emulate_io(vcpu);
default:
break;
}