| Message ID | 20170905090306.gz52hlo7s2ybogoy@hirez.programming.kicks-ass.net (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 05/09/17 11:03, Peter Zijlstra wrote: > On Tue, Sep 05, 2017 at 10:52:06AM +0200, Juergen Gross wrote: >>> Hmm, that might work. Could we somehow nop that call when >>> !X86_FEATURE_HYPERVISOR?, that saves native from having to do the call >>> and would be a win for everyone. >> >> So in fact we want a "always false" shortcut for bare metal and for any >> virtualization environment selecting bare metal behavior. >> >> I'll have a try. > > Right, so for native I think you can do this: > > > diff --git a/arch/x86/kernel/paravirt_patch_64.c b/arch/x86/kernel/paravirt_patch_64.c > index 11aaf1eaa0e4..4e9839001291 100644 > --- a/arch/x86/kernel/paravirt_patch_64.c > +++ b/arch/x86/kernel/paravirt_patch_64.c > @@ -21,6 +21,7 @@ DEF_NATIVE(, mov64, "mov %rdi, %rax"); > #if defined(CONFIG_PARAVIRT_SPINLOCKS) > DEF_NATIVE(pv_lock_ops, queued_spin_unlock, "movb $0, (%rdi)"); > DEF_NATIVE(pv_lock_ops, vcpu_is_preempted, "xor %rax, %rax"); > +DEF_NATIVE(pv_lock_ops, virt_spin_lock, "xor %rax, %rax"); > #endif > > unsigned paravirt_patch_ident_32(void *insnbuf, unsigned len) > @@ -77,6 +78,13 @@ unsigned native_patch(u8 type, u16 clobbers, void *ibuf, > goto patch_site; > } > goto patch_default; > + case PARAVIRT_PATCH(pv_lock_ops.virt_spin_lock): > + if (!this_cpu_has(X86_FEATURE_HYPERVISOR)) { > + start = start_pv_lock_ops_virt_spin_lock; > + end = end_pv_lock_ops_virt_spin_lock; > + goto patch_side; > + } > + goto patch_default; I'd rather add a test to paravirt_patch_default() similar to the _paravirt_ident_* cases for catching the Xen (and possibly KVM) cases, too. I just need to add _paravirt_zero_[32|64] functions I can use for bare metal and the nopvspin cases. Juergen
diff --git a/arch/x86/kernel/paravirt_patch_64.c b/arch/x86/kernel/paravirt_patch_64.c index 11aaf1eaa0e4..4e9839001291 100644 --- a/arch/x86/kernel/paravirt_patch_64.c +++ b/arch/x86/kernel/paravirt_patch_64.c @@ -21,6 +21,7 @@ DEF_NATIVE(, mov64, "mov %rdi, %rax"); #if defined(CONFIG_PARAVIRT_SPINLOCKS) DEF_NATIVE(pv_lock_ops, queued_spin_unlock, "movb $0, (%rdi)"); DEF_NATIVE(pv_lock_ops, vcpu_is_preempted, "xor %rax, %rax"); +DEF_NATIVE(pv_lock_ops, virt_spin_lock, "xor %rax, %rax"); #endif unsigned paravirt_patch_ident_32(void *insnbuf, unsigned len) @@ -77,6 +78,13 @@ unsigned native_patch(u8 type, u16 clobbers, void *ibuf, goto patch_site; } goto patch_default; + case PARAVIRT_PATCH(pv_lock_ops.virt_spin_lock): + if (!this_cpu_has(X86_FEATURE_HYPERVISOR)) { + start = start_pv_lock_ops_virt_spin_lock; + end = end_pv_lock_ops_virt_spin_lock; + goto patch_side; + } + goto patch_default; #endif default: