linux-kernel - Re: [PATCH v6 0/6] kvm, mem-hotplug: Do not pin ept identity pagetable and apic access page.

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Date:	Tue, 16 Sep 2014 13:44:42 +0200
From:	Paolo Bonzini <pbonzini@...hat.com>
To:	Tang Chen <tangchen@...fujitsu.com>, gleb@...nel.org,
	mtosatti@...hat.com, nadav.amit@...il.com, jan.kiszka@....de
CC:	kvm@...r.kernel.org, laijs@...fujitsu.com,
	isimatu.yasuaki@...fujitsu.com, guz.fnst@...fujitsu.com,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 0/6] kvm, mem-hotplug: Do not pin ept identity pagetable
 and apic access page.

Il 16/09/2014 12:41, Tang Chen ha scritto:
> ept identity pagetable and apic access page in kvm are pinned in memory.
> As a result, they cannot be migrated/hot-removed.
> 
> But actually they don't need to be pinned in memory.
> 
> [For ept identity page]
> Just do not pin it. When it is migrated, guest will be able to find the
> new page in the next ept violation.
> 
> [For apic access page]
> The hpa of apic access page is stored in VMCS APIC_ACCESS_ADDR pointer.
> When apic access page is migrated, we update VMCS APIC_ACCESS_ADDR pointer
> for each vcpu in addition.
> 
> NOTE: Tested with -cpu xxx,-x2apic option.
>       But since nested vm pins some other pages in memory, if user uses nested
>       vm, memory hot-remove will not work.
> 
> Change log v5 -> v6:
> 1. Patch 1/6 has been applied by Paolo Bonzini <pbonzini@...hat.com>, just resend it.
> 2. Simplify comment in alloc_identity_pagetable() and add a BUG_ON() in patch 2/6.
> 3. Move err initialization forward in patch 3/6.
> 4. Rename vcpu_reload_apic_access_page() to kvm_vcpu_reload_apic_access_page() and 
>    use it instead of kvm_reload_apic_access_page() in nested_vmx_vmexit() in patch 5/6.
> 5. Reuse kvm_vcpu_reload_apic_access_page() in prepare_vmcs02() and vmx_vcpu_reset() in patch 6/6.
> 6. Remove original patch 7 since we are not able to handle the situation in nested vm.

I'll push 1-3 soon to kvm/queue.  I think v7 will be good. :)

Paolo
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