On 19/12/20 07:37, Nathan Chancellor wrote:
When using LLVM's integrated assembler (LLVM_IAS=1) while building
x86_64_defconfig + CONFIG_KVM=y + CONFIG_KVM_AMD=y, the following build
error occurs:
$ make LLVM=1 LLVM_IAS=1 arch/x86/kvm/svm/sev.o
arch/x86/kvm/svm/sev.c:2004:15: error: too few operands for instruction
asm volatile(__ex("vmsave") : : "a" (__sme_page_pa(sd->save_area)) : "memory");
^
arch/x86/kvm/svm/sev.c:28:17: note: expanded from macro '__ex'
#define __ex(x) __kvm_handle_fault_on_reboot(x)
^
./arch/x86/include/asm/kvm_host.h:1646:10: note: expanded from macro '__kvm_handle_fault_on_reboot'
"666: \n\t" \
^
<inline asm>:2:2: note: instantiated into assembly here
vmsave
^
1 error generated.
This happens because LLVM currently does not support calling vmsave
without the fixed register operand (%rax for 64-bit and %eax for
32-bit). This will be fixed in LLVM 12 but the kernel currently supports
LLVM 10.0.1 and newer so this needs to be handled.
Add the proper register using the _ASM_AX macro, which matches the
vmsave call in vmenter.S.
Fixes: 861377730aa9 ("KVM: SVM: Provide support for SEV-ES vCPU loading")
Link: https://reviews.llvm.org/D93524
Link: https://github.com/ClangBuiltLinux/linux/issues/1216
Signed-off-by: Nathan Chancellor <natechancellor@xxxxxxxxx>
---
arch/x86/kvm/svm/sev.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index e57847ff8bd2..958370758ed0 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -2001,7 +2001,7 @@ void sev_es_vcpu_load(struct vcpu_svm *svm, int cpu)
* of which one step is to perform a VMLOAD. Since hardware does not
* perform a VMSAVE on VMRUN, the host savearea must be updated.
*/
- asm volatile(__ex("vmsave") : : "a" (__sme_page_pa(sd->save_area)) : "memory");
+ asm volatile(__ex("vmsave %%"_ASM_AX) : : "a" (__sme_page_pa(sd->save_area)) : "memory");
/*
* Certain MSRs are restored on VMEXIT, only save ones that aren't
Queued, thanks.
Paolo
