On 15/08/18 07:09, Jan Beulich wrote: > Use EFLAGS.IF for all ordinary purposes; there's in particular no need > to unduly defer NMI/#MC. Clear/set GIF solely around VMRUN itself. This > has the additional advantage that svm_stgi_label now indeed marks the > only place where GIF gets set. > > A note regarding the main STI(s) placement: Quite counterintuitively the > host's EFLAGS.IF continues to have a meaning while the guest runs; see > PM Vol 2 section "Physical (INTR) Interrupt Masking in EFLAGS". Hence we > need to set the flag for the duration of time being in guest context. > However, SPEC_CTRL_ENTRY_FROM_HVM wants to be carried out with EFLAGS.IF > clear. > > Suggested-by: Andrew Cooper <andrew.coop...@citrix.com> > Signed-off-by: Jan Beulich <jbeul...@suse.com> > --- > v2: Add CLI after VMRUN. Adjust description. > > --- a/xen/arch/x86/hvm/svm/entry.S > +++ b/xen/arch/x86/hvm/svm/entry.S > @@ -43,7 +43,7 @@ ENTRY(svm_asm_do_resume) > lea irq_stat+IRQSTAT_softirq_pending(%rip),%rdx > xor %ecx,%ecx > shl $IRQSTAT_shift,%eax > - CLGI > + cli > cmp %ecx,(%rdx,%rax,1) > jne .Lsvm_process_softirqs > > @@ -57,7 +57,7 @@ UNLIKELY_START(ne, nsvm_hap) > * Someone shot down our nested p2m table; go round again > * and nsvm_vcpu_switch() will fix it for us. > */ > - STGI > + sti > jmp .Lsvm_do_resume > __UNLIKELY_END(nsvm_hap) > > @@ -87,7 +87,12 @@ __UNLIKELY_END(nsvm_hap) > pop %rsi > pop %rdi > > + CLGI > + sti > VMRUN > + cli > + STGI > +GLOBAL(svm_stgi_label) > > SAVE_ALL > > @@ -96,13 +101,12 @@ __UNLIKELY_END(nsvm_hap) > SPEC_CTRL_ENTRY_FROM_HVM /* Req: b=curr %rsp=regs/cpuinfo, Clob: > acd */ > /* WARNING! `ret`, `call *`, `jmp *` not safe before this point. */ > > - STGI > -GLOBAL(svm_stgi_label) > + sti
Nack. As indicated in v1, moving this breaks SPEC_CTRL_ENTRY_FROM_HVM (Even if there is an unexpected bug on the VT-x side of things which needs fixing differently). Furthermore, to fix LBR handling, the first thing I'd have to do is revert this, so please leave it as it is. ~Andrew > mov %rsp,%rdi > call svm_vmexit_handler > jmp .Lsvm_do_resume > > .Lsvm_process_softirqs: > - STGI > + sti > call do_softirq > jmp .Lsvm_do_resume > > > > _______________________________________________ Xen-devel mailing list Xen-devel@lists.xenproject.org https://lists.xenproject.org/mailman/listinfo/xen-devel
