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Date: Fri, 18 Dec 2020 23:37:11 -0700 From: Nathan Chancellor <natechancellor@...il.com> To: Paolo Bonzini <pbonzini@...hat.com> Cc: Tom Lendacky <thomas.lendacky@....com>, Sean Christopherson <seanjc@...gle.com>, Vitaly Kuznetsov <vkuznets@...hat.com>, Wanpeng Li <wanpengli@...cent.com>, Jim Mattson <jmattson@...gle.com>, Joerg Roedel <joro@...tes.org>, Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>, x86@...nel.org, kvm@...r.kernel.org, linux-kernel@...r.kernel.org, clang-built-linux@...glegroups.com, Nick Desaulniers <ndesaulniers@...gle.com>, Sami Tolvanen <samitolvanen@...gle.com>, Nathan Chancellor <natechancellor@...il.com> Subject: [PATCH] KVM: SVM: Add register operand to vmsave call in sev_es_vcpu_load 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@...il.com> --- 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 -- 2.30.0.rc0
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