Messages in this thread | | | From | Vitaly Kuznetsov <> | Subject | Re: [PATCH] KVM/VMX: Check ept_pointer before flushing ept tlb | Date | Wed, 07 Nov 2018 11:49:05 +0100 |
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Tianyu Lan <ltykernel@gmail.com> writes:
> Hi Vitaly: > Thanks for your review. > > On 11/6/2018 11:50 PM, Vitaly Kuznetsov wrote: >> ltykernel@gmail.com writes: >> >>> From: Lan Tianyu <Tianyu.Lan@microsoft.com> >>> >>> This patch is to initialize ept_pointer to INVALID_PAGE and check it >>> before flushing ept tlb. If ept_pointer is invalidated, bypass the flush >>> request. >>> >> >> To be honest I fail to understand the reason behind the patch: instead >> of doing one unneeded flush request with ept_pointer==0 (after vCPU is >> initialized) we now do the check every time. Could you please elaborate >> on why this is needed? > > The reason to introduce the check here is to avoid flushing ept tlb > without valid ept table. When nested guest boots up and only BP is > active, we should not do flush for APs and L1 hypervisor hasn't set > valid EPT table for APs.
Yes, I understand that but I'm trying to avoid additional checks on hotpath as during normal operation EPT pointer is always set.
Could we just initialize ept_pointers_match to something like EPT_POINTERS_NOTSET and achive the same result?
-- Vitaly
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