From: Paolo Bonzini <pbonzini@redhat.com>
To: Nathan Chancellor <natechancellor@gmail.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>,
Sean Christopherson <seanjc@google.com>,
Vitaly Kuznetsov <vkuznets@redhat.com>,
Wanpeng Li <wanpengli@tencent.com>,
Jim Mattson <jmattson@google.com>, Joerg Roedel <joro@8bytes.org>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
x86@kernel.org, kvm@vger.kernel.org,
linux-kernel@vger.kernel.org, clang-built-linux@googlegroups.com,
Nick Desaulniers <ndesaulniers@google.com>,
Sami Tolvanen <samitolvanen@google.com>
Subject: Re: [PATCH] KVM: SVM: Add register operand to vmsave call in sev_es_vcpu_load
Date: Mon, 21 Dec 2020 19:12:33 +0100 [thread overview]
Message-ID: <f6d61324-4243-e5ed-9450-6ee8f9b1f44b@redhat.com> (raw)
In-Reply-To: <20201219063711.3526947-1-natechancellor@gmail.com>
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@gmail.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
>
Queued, thanks.
Paolo
prev parent reply other threads:[~2020-12-21 18:14 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-19 6:37 [PATCH] KVM: SVM: Add register operand to vmsave call in sev_es_vcpu_load Nathan Chancellor
2020-12-21 17:48 ` Sean Christopherson
2020-12-21 18:10 ` Sean Christopherson
2020-12-21 18:12 ` Paolo Bonzini [this message]
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