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KVM: SVM: Add register operand to vmsave call in sev_es_vcpu_load

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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@gmail.com>
Message-Id: <20201219063711.3526947-1-natechancellor@gmail.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Nathan Chancellor 2020-12-18 23:37:11 -07:00 committed by Paolo Bonzini
parent bc351f0726
commit f65cf84ee7
1 changed files with 1 additions and 1 deletions
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2
arch/x86/kvm/svm/sev.c
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@ -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 * of which one step is to perform a VMLOAD. Since hardware does not
* perform a VMSAVE on VMRUN, the host savearea must be updated. * 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 %0") : : "a" (__sme_page_pa(sd->save_area)) : "memory");
/* /*
* Certain MSRs are restored on VMEXIT, only save ones that aren't * Certain MSRs are restored on VMEXIT, only save ones that aren't