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[PATCH] x86: limit issuing of IBPB during context switch
- To: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Mon, 25 Jul 2022 14:09:12 +0200
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- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>
- Delivery-date: Mon, 25 Jul 2022 12:09:19 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
When the outgoing vCPU had IBPB issued upon entering Xen there's no
need for a 2nd barrier during context switch.
Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -2098,7 +2098,8 @@ void context_switch(struct vcpu *prev, s
ctxt_switch_levelling(next);
- if ( opt_ibpb_ctxt_switch && !is_idle_domain(nextd) )
+ if ( opt_ibpb_ctxt_switch && !is_idle_domain(nextd) &&
+ !(prevd->arch.spec_ctrl_flags & SCF_entry_ibpb) )
{
static DEFINE_PER_CPU(unsigned int, last);
unsigned int *last_id = &this_cpu(last);
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