[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] Ping: [PATCH 4/4] x86/PV: remove unnecessary toggle_guest_pt() overhead
>>> On 13.03.19 at 13:39, wrote: > While the mere updating of ->pv_cr3 and ->root_pgt_changed aren't overly > expensive (but still needed only for the toggle_guest_mode() path), the > effect of the latter on the exit-to-guest path is not insignificant. > Move the logic into toggle_guest_mode(). > > Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx> I think I did address the one concern you had. Jan > --- a/xen/arch/x86/pv/domain.c > +++ b/xen/arch/x86/pv/domain.c > @@ -349,18 +349,10 @@ bool __init xpti_pcid_enabled(void) > > static void _toggle_guest_pt(struct vcpu *v) > { > - const struct domain *d = v->domain; > - struct cpu_info *cpu_info = get_cpu_info(); > unsigned long cr3; > > v->arch.flags ^= TF_kernel_mode; > update_cr3(v); > - if ( d->arch.pv.xpti ) > - { > - cpu_info->root_pgt_changed = true; > - cpu_info->pv_cr3 = __pa(this_cpu(root_pgt)) | > - (d->arch.pv.pcid ? get_pcid_bits(v, true) : 0); > - } > > /* > * Don't flush user global mappings from the TLB. Don't tick TLB clock. > @@ -368,15 +360,11 @@ static void _toggle_guest_pt(struct vcpu > * In shadow mode, though, update_cr3() may need to be accompanied by a > * TLB flush (for just the incoming PCID), as the top level page table > may > * have changed behind our backs. To be on the safe side, suppress the > - * no-flush unconditionally in this case. The XPTI CR3 write, if > enabled, > - * will then need to be a flushing one too. > + * no-flush unconditionally in this case. > */ > cr3 = v->arch.cr3; > - if ( shadow_mode_enabled(d) ) > - { > + if ( shadow_mode_enabled(v->domain) ) > cr3 &= ~X86_CR3_NOFLUSH; > - cpu_info->pv_cr3 &= ~X86_CR3_NOFLUSH; > - } > write_cr3(cr3); > > if ( !(v->arch.flags & TF_kernel_mode) ) > @@ -392,6 +380,8 @@ static void _toggle_guest_pt(struct vcpu > > void toggle_guest_mode(struct vcpu *v) > { > + const struct domain *d = v->domain; > + > ASSERT(!is_pv_32bit_vcpu(v)); > > /* %fs/%gs bases can only be stale if WR{FS,GS}BASE are usable. */ > @@ -405,6 +395,21 @@ void toggle_guest_mode(struct vcpu *v) > asm volatile ( "swapgs" ); > > _toggle_guest_pt(v); > + > + if ( d->arch.pv.xpti ) > + { > + struct cpu_info *cpu_info = get_cpu_info(); > + > + cpu_info->root_pgt_changed = true; > + cpu_info->pv_cr3 = __pa(this_cpu(root_pgt)) | > + (d->arch.pv.pcid ? get_pcid_bits(v, true) : 0); > + /* > + * As in _toggle_guest_pt() the XPTI CR3 write needs to be a TLB- > + * flushing one too for shadow mode guests. > + */ > + if ( shadow_mode_enabled(d) ) > + cpu_info->pv_cr3 &= ~X86_CR3_NOFLUSH; > + } > } > > void toggle_guest_pt(struct vcpu *v) > > > > _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxxx https://lists.xenproject.org/mailman/listinfo/xen-devel
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