KVM: selftests: Add operand to vmsave/vmload/vmrun in svm.c

Building the KVM selftests with LLVM's integrated assembler fails with:

$ CFLAGS=-fintegrated-as make -C tools/testing/selftests/kvm CC=clang
lib/x86_64/svm.c:77:16: error: too few operands for instruction
asm volatile ("vmsave\n\t" : : "a" (vmcb_gpa) : "memory");
^
<inline asm>:1:2: note: instantiated into assembly here
vmsave
^
lib/x86_64/svm.c:134:3: error: too few operands for instruction
"vmload\n\t"
^
<inline asm>:1:2: note: instantiated into assembly here
vmload
^
This is because LLVM IAS does not currently support calling vmsave,
vmload, or vmload without an explicit %rax operand.

Add an explicit operand to vmsave, vmload, and vmrum in svm.c. Fixing
this was suggested by Sean Christopherson.

Tested: building without this error in clang 11. The following patch
(not queued yet) needs to be applied to solve the other remaining error:
"selftests: kvm: remove reassignment of non-absolute variables".

Suggested-by: Sean Christopherson <[e-mail]>
Link: https://lore.kernel.org/kvm/[e-mail]/
Reviewed-by: Jim Mattson <[e-mail]>
Signed-off-by: Ricardo Koller <[e-mail]>
Message-Id: <[e-mail]>
Signed-off-by: Paolo Bonzini <[e-mail]>

tools/testing/selftests/kvm/lib/x86_64/svm.c

···
 	wrmsr(MSR_VM_HSAVE_PA, svm->save_area_gpa);
 
 	memset(vmcb, 0, sizeof(*vmcb));
-	asm volatile ("vmsave\n\t" : : "a" (vmcb_gpa) : "memory");
+	asm volatile ("vmsave %0\n\t" : : "a" (vmcb_gpa) : "memory");
 	vmcb_set_seg(&save->es, get_es(), 0, -1U, data_seg_attr);
 	vmcb_set_seg(&save->cs, get_cs(), 0, -1U, code_seg_attr);
 	vmcb_set_seg(&save->ss, get_ss(), 0, -1U, data_seg_attr);
···
 void run_guest(struct vmcb *vmcb, uint64_t vmcb_gpa)
 {
 	asm volatile (
-		"vmload\n\t"
+		"vmload %[vmcb_gpa]\n\t"
 		"mov rflags, %%r15\n\t"	// rflags
 		"mov %%r15, 0x170(%[vmcb])\n\t"
 		"mov guest_regs, %%r15\n\t"	// rax
 		"mov %%r15, 0x1f8(%[vmcb])\n\t"
 		LOAD_GPR_C
-		"vmrun\n\t"
+		"vmrun %[vmcb_gpa]\n\t"
 		SAVE_GPR_C
 		"mov 0x170(%[vmcb]), %%r15\n\t"	// rflags
 		"mov %%r15, rflags\n\t"
 		"mov 0x1f8(%[vmcb]), %%r15\n\t"	// rax
 		"mov %%r15, guest_regs\n\t"
-		"vmsave\n\t"
+		"vmsave %[vmcb_gpa]\n\t"
 		: : [vmcb] "r" (vmcb), [vmcb_gpa] "a" (vmcb_gpa)
 		: "r15", "memory");
 }