Add a testcase to exercise KVM_CAP_X86_VMWARE_HYPERCALL and validate
that KVM exits to userspace on hypercalls and registers are correctly
preserved.

Signed-off-by: Zack Rusin <zack.ru...@broadcom.com>
Cc: Doug Covelli <doug.cove...@broadcom.com>
Cc: Paolo Bonzini <pbonz...@redhat.com>
Cc: Shuah Khan <sh...@kernel.org>
Cc: Sean Christopherson <sea...@google.com>
Cc: Namhyung Kim <namhy...@kernel.org>
Cc: Joel Stanley <j...@jms.id.au>
Cc: Zack Rusin <zack.ru...@broadcom.com>
Cc: Isaku Yamahata <isaku.yamah...@intel.com>
Cc: Arnaldo Carvalho de Melo <a...@redhat.com>
Cc: linux-kernel@vger.kernel.org
Cc: k...@vger.kernel.org
Cc: linux-kselft...@vger.kernel.org
---
 tools/include/uapi/linux/kvm.h                |   3 +
 tools/testing/selftests/kvm/Makefile.kvm      |   1 +
 .../selftests/kvm/x86/vmware_hypercall_test.c | 121 ++++++++++++++++++
 3 files changed, 125 insertions(+)
 create mode 100644 tools/testing/selftests/kvm/x86/vmware_hypercall_test.c

diff --git a/tools/include/uapi/linux/kvm.h b/tools/include/uapi/linux/kvm.h
index 502ea63b5d2e..3b3ad1827245 100644
--- a/tools/include/uapi/linux/kvm.h
+++ b/tools/include/uapi/linux/kvm.h
@@ -933,6 +933,9 @@ struct kvm_enable_cap {
 #define KVM_CAP_PRE_FAULT_MEMORY 236
 #define KVM_CAP_X86_APIC_BUS_CYCLES_NS 237
 #define KVM_CAP_X86_GUEST_MODE 238
+#define KVM_CAP_X86_VMWARE_BACKDOOR 239
+#define KVM_CAP_X86_VMWARE_HYPERCALL 240
+#define KVM_CAP_X86_VMWARE_NESTED_BACKDOOR_L0 241
 
 struct kvm_irq_routing_irqchip {
        __u32 irqchip;
diff --git a/tools/testing/selftests/kvm/Makefile.kvm 
b/tools/testing/selftests/kvm/Makefile.kvm
index 4277b983cace..9eea93b330e4 100644
--- a/tools/testing/selftests/kvm/Makefile.kvm
+++ b/tools/testing/selftests/kvm/Makefile.kvm
@@ -90,6 +90,7 @@ TEST_GEN_PROGS_x86 += x86/sync_regs_test
 TEST_GEN_PROGS_x86 += x86/ucna_injection_test
 TEST_GEN_PROGS_x86 += x86/userspace_io_test
 TEST_GEN_PROGS_x86 += x86/userspace_msr_exit_test
+TEST_GEN_PROGS_x86 += x86/vmware_hypercall_test
 TEST_GEN_PROGS_x86 += x86/vmx_apic_access_test
 TEST_GEN_PROGS_x86 += x86/vmx_close_while_nested_test
 TEST_GEN_PROGS_x86 += x86/vmx_dirty_log_test
diff --git a/tools/testing/selftests/kvm/x86/vmware_hypercall_test.c 
b/tools/testing/selftests/kvm/x86/vmware_hypercall_test.c
new file mode 100644
index 000000000000..8daca272933c
--- /dev/null
+++ b/tools/testing/selftests/kvm/x86/vmware_hypercall_test.c
@@ -0,0 +1,121 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * vmware_hypercall_test
+ *
+ * Copyright (c) 2025 Broadcom. All Rights Reserved. The term
+ * “Broadcom” refers to Broadcom Inc. and/or its subsidiaries.
+ *
+ * Based on:
+ *    xen_vmcall_test.c
+ *
+ *    Copyright © 2020 Amazon.com, Inc. or its affiliates.
+ *
+ * VMware hypercall testing
+ */
+
+#include "test_util.h"
+#include "kvm_util.h"
+#include "processor.h"
+
+#define ARGVALUE(x) (0xdeadbeef5a5a0000UL + (x))
+#define RETVALUE(x) (0xcafef00dfbfbffffUL + (x))
+
+static void guest_code(void)
+{
+       uint64_t error_code;
+       uint8_t vector;
+
+       unsigned long rax = ARGVALUE(1);
+       unsigned long rbx = ARGVALUE(2);
+       unsigned long rcx = ARGVALUE(3);
+       unsigned long rdx = ARGVALUE(4);
+       unsigned long rsi = ARGVALUE(5);
+       unsigned long rdi = ARGVALUE(6);
+       register unsigned long rbp __asm__("rbp") = ARGVALUE(7);
+
+       asm volatile(KVM_ASM_SAFE("vmcall")
+                    : "=a"(rax),  "=b"(rbx), "=c"(rcx), "=d"(rdx),
+                      "=S"(rsi), "=D"(rdi),
+                      KVM_ASM_SAFE_OUTPUTS(vector, error_code)
+                    : "a"(rax), "b"(rbx), "c"(rcx), "d"(rdx),
+                      "S"(rsi), "D"(rdi), "r"(rbp)
+                    : KVM_ASM_SAFE_CLOBBERS);
+       GUEST_ASSERT_EQ(rax, RETVALUE(11));
+       GUEST_ASSERT_EQ(rbx, RETVALUE(12));
+       GUEST_ASSERT_EQ(rcx, RETVALUE(13));
+       GUEST_ASSERT_EQ(rdx, RETVALUE(14));
+       GUEST_ASSERT_EQ(rsi, RETVALUE(15));
+       GUEST_ASSERT_EQ(rdi, RETVALUE(16));
+       GUEST_ASSERT_EQ(vector, 12);
+       GUEST_ASSERT_EQ(error_code, 14);
+       GUEST_DONE();
+}
+
+int main(int argc, char *argv[])
+{
+       struct kvm_vcpu *vcpu;
+       struct kvm_vm *vm;
+
+       if (!kvm_check_cap(KVM_CAP_X86_VMWARE_HYPERCALL)) {
+               print_skip("KVM_CAP_X86_VMWARE_HYPERCALL not available");
+               exit(KSFT_SKIP);
+       }
+
+       vm = vm_create_with_one_vcpu(&vcpu, guest_code);
+
+       vm_enable_cap(vm, KVM_CAP_X86_VMWARE_HYPERCALL, 1);
+
+       for (;;) {
+               struct kvm_run *run = vcpu->run;
+               struct ucall uc;
+
+               vcpu_run(vcpu);
+
+               if (run->exit_reason == KVM_EXIT_VMWARE) {
+                       struct kvm_regs regs;
+
+                       TEST_ASSERT_EQ(run->vmware.type, KVM_EXIT_VMWARE_HCALL);
+                       TEST_ASSERT_EQ(run->vmware.hcall.longmode, 1);
+                       TEST_ASSERT_EQ(run->vmware.hcall.cpl, 0);
+                       TEST_ASSERT_EQ(run->vmware.hcall.rax, ARGVALUE(1));
+                       TEST_ASSERT_EQ(run->vmware.hcall.rbx, ARGVALUE(2));
+                       TEST_ASSERT_EQ(run->vmware.hcall.rcx, ARGVALUE(3));
+                       TEST_ASSERT_EQ(run->vmware.hcall.rdx, ARGVALUE(4));
+                       TEST_ASSERT_EQ(run->vmware.hcall.rsi, ARGVALUE(5));
+                       TEST_ASSERT_EQ(run->vmware.hcall.rdi, ARGVALUE(6));
+                       TEST_ASSERT_EQ(run->vmware.hcall.rbp, ARGVALUE(7));
+
+                       run->vmware.hcall.exception.inject = 1;
+                       run->vmware.hcall.exception.vector = 12;
+                       run->vmware.hcall.exception.error_code = 14;
+                       run->vmware.hcall.exception.address = 0;
+
+                       run->vmware.hcall.result = RETVALUE(11);
+                       vcpu_regs_get(vcpu, &regs);
+                       regs.rbx = RETVALUE(12);
+                       regs.rcx = RETVALUE(13);
+                       regs.rdx = RETVALUE(14);
+                       regs.rsi = RETVALUE(15);
+                       regs.rdi = RETVALUE(16);
+                       vcpu_regs_set(vcpu, &regs);
+                       continue;
+               }
+
+               TEST_ASSERT_KVM_EXIT_REASON(vcpu, KVM_EXIT_IO);
+
+               switch (get_ucall(vcpu, &uc)) {
+               case UCALL_ABORT:
+                       REPORT_GUEST_ASSERT(uc);
+                       /* NOT REACHED */
+               case UCALL_SYNC:
+                       break;
+               case UCALL_DONE:
+                       goto done;
+               default:
+                       TEST_FAIL("Unknown ucall 0x%lx.", uc.cmd);
+               }
+       }
+done:
+       kvm_vm_free(vm);
+       return 0;
+}
-- 
2.48.1


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