[PATCH 4/6] Add GHCB allocations and helpers

[Peter Gonda <pgonda@google.com>]

Add GHCB management functionality similar to the ucall management.
Allows for selftest vCPUs to acquire GHCBs for their usage.

Cc: Vishal Annapurve <vannapurve@google.com>
Cc: Ackerley Tng <ackerleytng@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: Sean Christopherson <seanjc@google.com>
Cc: Carlos Bilbao <carlos.bilbao@amd.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Michael Roth <michael.roth@amd.com>
Cc: kvm@vger.kernel.org
Cc: linux-kselftest@vger.kernel.org
Signed-off-by: Peter Gonda <pgonda@google.com>
---
 .../selftests/kvm/include/x86_64/sev.h        |  2 +
 .../selftests/kvm/lib/x86_64/processor.c      |  8 ++
 tools/testing/selftests/kvm/lib/x86_64/sev.c  | 77 +++++++++++++++++++
 3 files changed, 87 insertions(+)

diff --git a/tools/testing/selftests/kvm/include/x86_64/sev.h b/tools/testing/selftests/kvm/include/x86_64/sev.h
index 8a1bf88474c9..bfd481707f67 100644
--- a/tools/testing/selftests/kvm/include/x86_64/sev.h
+++ b/tools/testing/selftests/kvm/include/x86_64/sev.h
@@ -27,6 +27,8 @@ enum sev_guest_state {
 
 #define GHCB_MSR_TERM_REQ	0x100
 
+int ghcb_nr_pages_required(uint64_t page_size);
+
 void sev_vm_launch(struct kvm_vm *vm, uint32_t policy);
 void sev_vm_launch_measure(struct kvm_vm *vm, uint8_t *measurement);
 void sev_vm_launch_finish(struct kvm_vm *vm);
diff --git a/tools/testing/selftests/kvm/lib/x86_64/processor.c b/tools/testing/selftests/kvm/lib/x86_64/processor.c
index 49288fe10cd3..fd94a1bd82c9 100644
--- a/tools/testing/selftests/kvm/lib/x86_64/processor.c
+++ b/tools/testing/selftests/kvm/lib/x86_64/processor.c
@@ -584,6 +584,14 @@ void kvm_arch_vm_post_create(struct kvm_vm *vm)
 		sev_es_vm_init(vm);
 }
 
+int kvm_arch_vm_additional_pages_required(struct vm_shape shape, uint64_t page_size)
+{
+	if (shape.subtype == VM_SUBTYPE_SEV_ES)
+		return  ghcb_nr_pages_required(page_size);
+
+	return 0;
+}
+
 void vcpu_arch_set_entry_point(struct kvm_vcpu *vcpu, void *guest_code)
 {
 	struct kvm_regs regs;
diff --git a/tools/testing/selftests/kvm/lib/x86_64/sev.c b/tools/testing/selftests/kvm/lib/x86_64/sev.c
index e248d3364b9c..27ae1d3b1355 100644
--- a/tools/testing/selftests/kvm/lib/x86_64/sev.c
+++ b/tools/testing/selftests/kvm/lib/x86_64/sev.c
@@ -4,6 +4,80 @@
 #include <stdbool.h>
 
 #include "sev.h"
+#include "linux/bitmap.h"
+#include "svm.h"
+#include "svm_util.h"
+
+struct ghcb_entry {
+	struct ghcb ghcb;
+
+	/* Guest physical address of this GHCB. */
+	void *gpa;
+
+	/* Host virtual address of this struct. */
+	struct ghcb_entry *hva;
+};
+
+struct ghcb_header {
+	struct ghcb_entry ghcbs[KVM_MAX_VCPUS];
+	DECLARE_BITMAP(in_use, KVM_MAX_VCPUS);
+};
+
+static struct ghcb_header *ghcb_pool;
+
+int ghcb_nr_pages_required(uint64_t page_size)
+{
+	return align_up(sizeof(struct ghcb_header), page_size) / page_size;
+}
+
+void ghcb_init(struct kvm_vm *vm)
+{
+	struct ghcb_header *hdr;
+	struct ghcb_entry *entry;
+	vm_vaddr_t vaddr;
+	int i;
+
+	vaddr = vm_vaddr_alloc_shared(vm, sizeof(*hdr), KVM_UTIL_MIN_VADDR,
+				      MEM_REGION_DATA);
+	hdr = (struct ghcb_header *)addr_gva2hva(vm, vaddr);
+	memset(hdr, 0, sizeof(*hdr));
+
+	for (i = 0; i < KVM_MAX_VCPUS; ++i) {
+		entry = &hdr->ghcbs[i];
+		entry->hva = entry;
+		entry->gpa = addr_hva2gpa(vm, &entry->ghcb);
+	}
+
+	write_guest_global(vm, ghcb_pool, (struct ghcb_header *)vaddr);
+}
+
+static struct ghcb_entry *ghcb_alloc(void)
+{
+	return &ghcb_pool->ghcbs[0];
+	struct ghcb_entry *entry;
+	int i;
+
+	if (!ghcb_pool)
+		goto ucall_failed;
+
+	for (i = 0; i < KVM_MAX_VCPUS; ++i) {
+		if (!test_and_set_bit(i, ghcb_pool->in_use)) {
+			entry = &ghcb_pool->ghcbs[i];
+			memset(&entry->ghcb, 0, sizeof(entry->ghcb));
+			return entry;
+		}
+	}
+
+ucall_failed:
+	return NULL;
+}
+
+static void ghcb_free(struct ghcb_entry *entry)
+{
+	/* Beware, here be pointer arithmetic.  */
+	clear_bit(entry - ghcb_pool->ghcbs, ghcb_pool->in_use);
+}
+
 
 /*
  * sparsebit_next_clear() can return 0 if [x, 2**64-1] are all set, and the
@@ -44,6 +118,9 @@ void sev_vm_launch(struct kvm_vm *vm, uint32_t policy)
 	struct kvm_sev_guest_status status;
 	int ctr;
 
+	if (policy & SEV_POLICY_ES)
+		ghcb_init(vm);
+
 	vm_sev_ioctl(vm, KVM_SEV_LAUNCH_START, &launch_start);
 	vm_sev_ioctl(vm, KVM_SEV_GUEST_STATUS, &status);
 
-- 
2.44.0.478.gd926399ef9-goog