xen/mmu: Use Xen specific TLB flush instead of the generic one.
As Mukesh explained it, the MMUEXT_TLB_FLUSH_ALL allows the hypervisor to do a TLB flush on all active vCPUs. If instead we were using the generic one (which ends up being xen_flush_tlb) we end up making the MMUEXT_TLB_FLUSH_LOCAL hypercall. But before we make that hypercall the kernel will IPI all of the vCPUs (even those that were asleep from the hypervisor perspective). The end result is that we needlessly wake them up and do a TLB flush when we can just let the hypervisor do it correctly. This patch gives around 50% speed improvement when migrating idle guest's from one host to another. Oracle-bug: 14630170 CC: email@example.com Tested-by: Jingjie Jiang <firstname.lastname@example.org> Suggested-by: Mukesh Rathor <email@example.com> Signed-off-by: Konrad Rzeszutek Wilk <firstname.lastname@example.org>
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