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Message-ID: <8326ebac-ea35-3e26-ae6a-e57b73e07783@redhat.com>
Date: Wed, 18 Jul 2018 13:59:06 +0200
From: Paolo Bonzini <pbonzini@...hat.com>
To: Tianyu Lan <Tianyu.Lan@...rosoft.com>
Cc: KY Srinivasan <kys@...rosoft.com>,
Haiyang Zhang <haiyangz@...rosoft.com>,
Stephen Hemminger <sthemmin@...rosoft.com>,
"tglx@...utronix.de" <tglx@...utronix.de>,
"mingo@...hat.com" <mingo@...hat.com>,
"hpa@...or.com" <hpa@...or.com>, "x86@...nel.org" <x86@...nel.org>,
"rkrcmar@...hat.com" <rkrcmar@...hat.com>,
"devel@...uxdriverproject.org" <devel@...uxdriverproject.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"kvm@...r.kernel.org" <kvm@...r.kernel.org>,
"Michael Kelley (EOSG)" <Michael.H.Kelley@...rosoft.com>,
"vkuznets@...hat.com" <vkuznets@...hat.com>
Subject: Re: [PATCH V2 3/5] KVM/VMX: Add identical ept table pointer check
On 09/07/2018 11:02, Tianyu Lan wrote:
> +static void check_ept_pointer(struct kvm_vcpu *vcpu, u64 eptp)
> +{
> + struct kvm *kvm = vcpu->kvm;
> + u64 tmp_eptp = INVALID_PAGE;
> + int i;
> +
> + if (!kvm_x86_ops->tlb_remote_flush)
> + return;
> +
> + spin_lock(&to_kvm_vmx(kvm)->ept_pointer_lock);
> + to_vmx(vcpu)->ept_pointer = eptp;
> +
> + kvm_for_each_vcpu(i, vcpu, kvm) {
> + if (!VALID_PAGE(tmp_eptp)) {
> + tmp_eptp = to_vmx(vcpu)->ept_pointer;
> + } else if (tmp_eptp != to_vmx(vcpu)->ept_pointer) {
> + to_kvm_vmx(kvm)->ept_pointers_match = false;
> + spin_unlock(&to_kvm_vmx(kvm)->ept_pointer_lock);
> + return;
> + }
> + }
> +
> + to_kvm_vmx(kvm)->ept_pointers_match = true;
> + spin_unlock(&to_kvm_vmx(kvm)->ept_pointer_lock);
> +}
> +
Is there any reason to do the check here, rather than the first time the
TLB flush is invoked? You could:
- have a tristate (true, false, check) value for ept_pointers_match
- reset it to "check" in vmx_set_cr3
- set it to either true or false in tlb_remote_flush if it is check, and
do the hypercall if it is true.
Paolo
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