On 28.01.2022 14:29, Andrew Cooper wrote: > --- a/xen/arch/x86/hvm/svm/entry.S > +++ b/xen/arch/x86/hvm/svm/entry.S > @@ -55,11 +55,12 @@ __UNLIKELY_END(nsvm_hap) > mov %rsp, %rdi > call svm_vmenter_helper > > - mov VCPU_arch_msrs(%rbx), %rax > - mov VCPUMSR_spec_ctrl_raw(%rax), %eax > + clgi > > /* WARNING! `ret`, `call *`, `jmp *` not safe beyond this point. */ > - /* SPEC_CTRL_EXIT_TO_SVM (nothing currently) */ > + /* SPEC_CTRL_EXIT_TO_SVM Req: Clob: > C */ > + ALTERNATIVE "", STR(mov %rbx, %rdi; mov %rsp, %rsi), > X86_FEATURE_SC_MSR_HVM > + ALTERNATIVE "", STR(call vmentry_spec_ctrl), X86_FEATURE_SC_MSR_HVM
Both this and ... > @@ -86,8 +86,10 @@ __UNLIKELY_END(nsvm_hap) > > GET_CURRENT(bx) > > - /* SPEC_CTRL_ENTRY_FROM_SVM Req: b=curr %rsp=regs/cpuinfo, Clob: > ac */ > + /* SPEC_CTRL_ENTRY_FROM_SVM Req: Clob: > C */ > ALTERNATIVE "", DO_OVERWRITE_RSB, X86_FEATURE_SC_RSB_HVM > + ALTERNATIVE "", STR(mov %rsp, %rdi), X86_FEATURE_SC_MSR_HVM > + ALTERNATIVE "", STR(call vmexit_spec_ctrl), X86_FEATURE_SC_MSR_HVM > /* WARNING! `ret`, `call *`, `jmp *` not safe before this point. */ ... this now effectively violate what the warning comment says, as there is a RET involved in the C call. If this is not a problem for some reason, I'd like to ask that the comments be updated accordingly. Jan
