linux-kernel - Re: [PATCH v8 0/8] kvm, mem-hotplug: Do not pin ept identity pagetable and apic access page.

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Date:	Wed, 24 Sep 2014 10:20:04 +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 v8 0/8] kvm, mem-hotplug: Do not pin ept identity pagetable
 and apic access page.

Il 24/09/2014 09:57, 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.
> 
> This patch-set is based on Linux 3.17.0-rc5.
> 
> 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 v7->v8:
> 1. Patch 1/9~3/9 were applied to kvm/queue by Paolo Bonzini <pbonzini@...hat.com>.
>    Just resend them, no changes.
> 2. Removed previous patch 4/9, which added unnecessary hook has_secondary_apic_access().
> 3. Set kvm_x86_ops->set_apic_access_page_addr to NULL when hardware had no flexpriority
>    functionality which actually exists only on x86. 
> 4. Moved declaration of kvm_arch_mmu_notifier_invalidate_page() to arch/*/include/asm/kvm_host.h.
> 5. Removed useless set_apic_access_page_addr() hook for svm.
> 
> Tang Chen (8):
>   kvm: Use APIC_DEFAULT_PHYS_BASE macro as the apic access page address.
>   kvm: Remove ept_identity_pagetable from struct kvm_arch.
>   kvm: Make init_rmode_identity_map() return 0 on success.
>   kvm, mem-hotplug: Reload L1's apic access page in vcpu_enter_guest().
>   kvm: Rename make_all_cpus_request() to kvm_make_all_cpus_request() and
>     make it non-static.
>   kvm, mem-hotplug: Reload L1's apic access page on migration when L2 is
>     running.
>   kvm, mem-hotplug: Add arch specific mmu notifier to handle apic access
>     migration.
>   kvm, mem-hotplug: Unpin and remove kvm_arch->apic_access_page.
> 
>  arch/arm/include/asm/kvm_host.h     |   5 ++
>  arch/arm64/include/asm/kvm_host.h   |   5 ++
>  arch/ia64/include/asm/kvm_host.h    |   7 ++
>  arch/mips/include/asm/kvm_host.h    |   6 ++
>  arch/powerpc/include/asm/kvm_host.h |   5 ++
>  arch/s390/include/asm/kvm_host.h    |   8 +++
>  arch/x86/include/asm/kvm_host.h     |   7 +-
>  arch/x86/kvm/svm.c                  |   3 +-
>  arch/x86/kvm/vmx.c                  | 130 ++++++++++++++++++++++++------------
>  arch/x86/kvm/x86.c                  |  45 +++++++++++--
>  include/linux/kvm_host.h            |   2 +
>  virt/kvm/kvm_main.c                 |  13 ++--
>  12 files changed, 180 insertions(+), 56 deletions(-)
> 

Thanks for your persistence!  The patches look good, I'll test them and
apply to kvm/queue.

Paolo
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