KVM: SVM: Support MMIO for an SEV-ES guest

For an SEV-ES guest, MMIO is performed to a shared (un-encrypted) page
so that both the hypervisor and guest can read or write to it and each
see the contents.

The GHCB specification provides software-defined VMGEXIT exit codes to
indicate a request for an MMIO read or an MMIO write. Add support to
recognize the MMIO requests and invoke SEV-ES specific routines that
can complete the MMIO operation. These routines use common KVM support
to complete the MMIO operation.

Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com>
Message-Id: <af8de55127d5bcc3253d9b6084a0144c12307d4d.1607620209.git.thomas.lendacky@amd.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 123 insertions, 0 deletions

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 02c6fb166fc3..fd4c47b7c71c 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -11292,6 +11292,129 @@ int kvm_handle_invpcid(struct kvm_vcpu *vcpu, unsigned long type, gva_t gva)
 }
 EXPORT_SYMBOL_GPL(kvm_handle_invpcid);
 
+static int complete_sev_es_emulated_mmio(struct kvm_vcpu *vcpu)
+{
+	struct kvm_run *run = vcpu->run;
+	struct kvm_mmio_fragment *frag;
+	unsigned int len;
+
+	BUG_ON(!vcpu->mmio_needed);
+
+	/* Complete previous fragment */
+	frag = &vcpu->mmio_fragments[vcpu->mmio_cur_fragment];
+	len = min(8u, frag->len);
+	if (!vcpu->mmio_is_write)
+		memcpy(frag->data, run->mmio.data, len);
+
+	if (frag->len <= 8) {
+		/* Switch to the next fragment. */
+		frag++;
+		vcpu->mmio_cur_fragment++;
+	} else {
+		/* Go forward to the next mmio piece. */
+		frag->data += len;
+		frag->gpa += len;
+		frag->len -= len;
+	}
+
+	if (vcpu->mmio_cur_fragment >= vcpu->mmio_nr_fragments) {
+		vcpu->mmio_needed = 0;
+
+		// VMG change, at this point, we're always done
+		// RIP has already been advanced
+		return 1;
+	}
+
+	// More MMIO is needed
+	run->mmio.phys_addr = frag->gpa;
+	run->mmio.len = min(8u, frag->len);
+	run->mmio.is_write = vcpu->mmio_is_write;
+	if (run->mmio.is_write)
+		memcpy(run->mmio.data, frag->data, min(8u, frag->len));
+	run->exit_reason = KVM_EXIT_MMIO;
+
+	vcpu->arch.complete_userspace_io = complete_sev_es_emulated_mmio;
+
+	return 0;
+}
+
+int kvm_sev_es_mmio_write(struct kvm_vcpu *vcpu, gpa_t gpa, unsigned int bytes,
+			  void *data)
+{
+	int handled;
+	struct kvm_mmio_fragment *frag;
+
+	if (!data)
+		return -EINVAL;
+
+	handled = write_emultor.read_write_mmio(vcpu, gpa, bytes, data);
+	if (handled == bytes)
+		return 1;
+
+	bytes -= handled;
+	gpa += handled;
+	data += handled;
+
+	/*TODO: Check if need to increment number of frags */
+	frag = vcpu->mmio_fragments;
+	vcpu->mmio_nr_fragments = 1;
+	frag->len = bytes;
+	frag->gpa = gpa;
+	frag->data = data;
+
+	vcpu->mmio_needed = 1;
+	vcpu->mmio_cur_fragment = 0;
+
+	vcpu->run->mmio.phys_addr = gpa;
+	vcpu->run->mmio.len = min(8u, frag->len);
+	vcpu->run->mmio.is_write = 1;
+	memcpy(vcpu->run->mmio.data, frag->data, min(8u, frag->len));
+	vcpu->run->exit_reason = KVM_EXIT_MMIO;
+
+	vcpu->arch.complete_userspace_io = complete_sev_es_emulated_mmio;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(kvm_sev_es_mmio_write);
+
+int kvm_sev_es_mmio_read(struct kvm_vcpu *vcpu, gpa_t gpa, unsigned int bytes,
+			 void *data)
+{
+	int handled;
+	struct kvm_mmio_fragment *frag;
+
+	if (!data)
+		return -EINVAL;
+
+	handled = read_emultor.read_write_mmio(vcpu, gpa, bytes, data);
+	if (handled == bytes)
+		return 1;
+
+	bytes -= handled;
+	gpa += handled;
+	data += handled;
+
+	/*TODO: Check if need to increment number of frags */
+	frag = vcpu->mmio_fragments;
+	vcpu->mmio_nr_fragments = 1;
+	frag->len = bytes;
+	frag->gpa = gpa;
+	frag->data = data;
+
+	vcpu->mmio_needed = 1;
+	vcpu->mmio_cur_fragment = 0;
+
+	vcpu->run->mmio.phys_addr = gpa;
+	vcpu->run->mmio.len = min(8u, frag->len);
+	vcpu->run->mmio.is_write = 0;
+	vcpu->run->exit_reason = KVM_EXIT_MMIO;
+
+	vcpu->arch.complete_userspace_io = complete_sev_es_emulated_mmio;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(kvm_sev_es_mmio_read);
+
 EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_exit);
 EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_fast_mmio);
 EXPORT_TRACEPOINT_SYMBOL_GPL(kvm_inj_virq);