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Date: Thu, 10 Aug 2017 20:56:46 +0200 From: Peter Zijlstra <peterz@...radead.org> To: sixiao@...rosoft.com, haiyangz@...rosoft.com, Jork.Loeser@...rosoft.com, sthemmin@...rosoft.com, torvalds@...ux-foundation.org, luto@...nel.org, hpa@...or.com, vkuznets@...hat.com, linux-kernel@...r.kernel.org, rostedt@...dmis.org, andy.shevchenko@...il.com, tglx@...utronix.de, kys@...rosoft.com, mingo@...nel.org Cc: linux-tip-commits@...r.kernel.org Subject: Re: [tip:x86/platform] x86/hyper-v: Use hypercall for remote TLB flush On Thu, Aug 10, 2017 at 11:21:49AM -0700, tip-bot for Vitaly Kuznetsov wrote: > Commit-ID: 2ffd9e33ce4af4e8cfa3e17bf493defe8474e2eb > Gitweb: http://git.kernel.org/tip/2ffd9e33ce4af4e8cfa3e17bf493defe8474e2eb > Author: Vitaly Kuznetsov <vkuznets@...hat.com> > AuthorDate: Wed, 2 Aug 2017 18:09:19 +0200 > Committer: Ingo Molnar <mingo@...nel.org> > CommitDate: Thu, 10 Aug 2017 20:16:44 +0200 > > x86/hyper-v: Use hypercall for remote TLB flush > > Hyper-V host can suggest us to use hypercall for doing remote TLB flush, > this is supposed to work faster than IPIs. > > Implementation details: to do HvFlushVirtualAddress{Space,List} hypercalls > we need to put the input somewhere in memory and we don't really want to > have memory allocation on each call so we pre-allocate per cpu memory areas > on boot. > > pv_ops patching is happening very early so we need to separate > hyperv_setup_mmu_ops() and hyper_alloc_mmu(). > > It is possible and easy to implement local TLB flushing too and there is > even a hint for that. However, I don't see a room for optimization on the > host side as both hypercall and native tlb flush will result in vmexit. The > hint is also not set on modern Hyper-V versions. Hold on.. if we don't IPI for TLB invalidation. What serializes our software page table walkers like fast_gup() ?
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