linux-kernel - Re: [PATCH v2 0/3] nVMX: Emulated Page Modification Logging for Nested Virtualization

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Message-ID: <ab68500a-f781-d34f-7172-fe15c558df1a@redhat.com>
Date:   Tue, 9 May 2017 17:22:22 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Bandan Das <bsd@...hat.com>, kvm@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 0/3] nVMX: Emulated Page Modification Logging for
 Nested Virtualization



On 05/05/2017 21:25, Bandan Das wrote:
> v2:
> 2/3: Clear out all bits except bit 12
> 3/3: Slightly modify an existing comment, honor L0's
> PML setting when clearing it for L1
> 
> v1:
> http://www.spinics.net/lists/kvm/msg149247.html
> 
> These patches implement PML on top of EPT A/D emulation
> (ae1e2d1082ae).
> 
> When dirty bit is being set, we write the gpa to the
> buffer provided by L1. If the index overflows, we just
> change the exit reason before running L1.

I tested this with api/dirty-log-perf, and nested PML is more than 3
times faster than pml=0.  I want to do a few more tests because I don't
see any PML full exits in the L1 trace, but it seems to be a nice
improvement!

Paolo

> Bandan Das (3):
>   kvm: x86: Add a hook for arch specific dirty logging emulation
>   nVMX: Implement emulated Page Modification Logging
>   nVMX: Advertise PML to L1 hypervisor
> 
>  arch/x86/include/asm/kvm_host.h |  2 +
>  arch/x86/kvm/mmu.c              | 15 +++++++
>  arch/x86/kvm/mmu.h              |  1 +
>  arch/x86/kvm/paging_tmpl.h      |  4 ++
>  arch/x86/kvm/vmx.c              | 97 ++++++++++++++++++++++++++++++++++++++---
>  5 files changed, 112 insertions(+), 7 deletions(-)
>