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From: Paolo Bonzini <pbonzini@redhat.com>
To: Yang Weijiang <weijiang.yang@intel.com>
Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org,
	sean.j.christopherson@intel.com, mst@redhat.com,
	rkrcmar@redhat.com, jmattson@google.com, yu.c.zhang@intel.com,
	alazar@bitdefender.com
Subject: Re: [PATCH RESEND v4 8/9] KVM: MMU: Enable Lazy mode SPPT setup
Date: Mon, 9 Sep 2019 19:10:22 +0200
Message-ID: <6cdea038-8d6f-6d75-47b2-bb23ff1c9f15@redhat.com> (raw)
In-Reply-To: <20190904134925.GA25149@local-michael-cet-test.sh.intel.com>

On 04/09/19 15:49, Yang Weijiang wrote:
>>> This would not enable SPP if the guest is backed by huge pages.
>>> Instead, either the PT_PAGE_TABLE_LEVEL level must be forced for all
>>> pages covered by SPP ranges, or (better) kvm_enable_spp_protection must
>>> be able to cover multiple pages at once.
>>>
>>> Paolo
>> OK, I'll figure out how to make it, thanks!
> Hi, Paolo,
> Regarding this change, I have some concerns, splitting EPT huge page
> entries(e.g., 1GB page)will take long time compared with normal EPT page
> fault processing, especially for multiple vcpus/pages,so the in-flight time increases,
> but HW walks EPT for translations in the meantime, would it bring any side effect? 
> or there's a way to mitigate it?

Sub-page permissions are only defined on EPT PTEs, not on large pages.
Therefore, in order to allow subpage permissions the EPT page tables
must already be split.

Paolo

  reply index

Thread overview: 40+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-14  7:03 [PATCH RESEND v4 0/9] Enable Sub-page Write Protection Support Yang Weijiang
2019-08-14  7:03 ` [PATCH RESEND v4 1/9] Documentation: Introduce EPT based Subpage Protection Yang Weijiang
2019-08-14  7:03 ` [PATCH RESEND v4 2/9] KVM: VMX: Add control flags for SPP enabling Yang Weijiang
2019-08-14  7:03 ` [PATCH RESEND v4 3/9] KVM: VMX: Implement functions for SPPT paging setup Yang Weijiang
2019-08-14  7:03 ` [PATCH RESEND v4 4/9] KVM: VMX: Introduce SPP access bitmap and operation functions Yang Weijiang
2019-08-14  7:03 ` [PATCH RESEND v4 5/9] KVM: VMX: Add init/set/get functions for SPP Yang Weijiang
2019-08-14 12:43   ` Vitaly Kuznetsov
2019-08-14 14:34     ` Yang Weijiang
2019-08-15 13:43     ` Yang Weijiang
2019-08-15 14:03       ` Vitaly Kuznetsov
2019-08-19 14:06         ` Yang Weijiang
2019-08-15 16:25       ` Jim Mattson
2019-08-15 16:38         ` Sean Christopherson
2019-08-16 13:31           ` Yang Weijiang
2019-08-16 18:19             ` Jim Mattson
2019-08-19  2:08               ` Yang Weijiang
2019-08-19 15:15                 ` Paolo Bonzini
2019-08-20 12:33                   ` Yang Weijiang
2019-08-19 15:05   ` Paolo Bonzini
2019-08-20 12:36     ` Yang Weijiang
2019-08-19 15:13   ` Paolo Bonzini
2019-08-20 13:09     ` Yang Weijiang
2019-08-14  7:04 ` [PATCH RESEND v4 6/9] KVM: VMX: Introduce SPP user-space IOCTLs Yang Weijiang
2019-08-14  7:04 ` [PATCH RESEND v4 7/9] KVM: VMX: Handle SPP induced vmexit and page fault Yang Weijiang
2019-08-19 14:43   ` Paolo Bonzini
2019-08-19 15:04     ` Paolo Bonzini
2019-08-20 13:44       ` Yang Weijiang
2019-08-22 13:17         ` Yang Weijiang
2019-08-22 16:38           ` Paolo Bonzini
2019-08-23  0:26             ` Yang Weijiang
2019-08-14  7:04 ` [PATCH RESEND v4 8/9] KVM: MMU: Enable Lazy mode SPPT setup Yang Weijiang
2019-08-19 14:46   ` Paolo Bonzini
2019-08-20 13:12     ` Yang Weijiang
2019-09-04 13:49       ` Yang Weijiang
2019-09-09 17:10         ` Paolo Bonzini [this message]
2019-09-11  0:23           ` Yang Weijiang
2019-08-14  7:04 ` [PATCH RESEND v4 9/9] KVM: MMU: Handle host memory remapping and reclaim Yang Weijiang
2019-08-14 12:36 ` [PATCH RESEND v4 0/9] Enable Sub-page Write Protection Support Paolo Bonzini
2019-08-14 14:02   ` Yang Weijiang
2019-08-14 14:06     ` Paolo Bonzini

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