linux-kernel - Re: [PATCH v3 0/5] KVM: MMU: 5 level EPT/shadow support

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Message-ID: <d8c1a2b8-8770-c0af-4c90-280f5e267ce9@redhat.com>
Date:   Thu, 24 Aug 2017 15:47:33 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Yu Zhang <yu.c.zhang@...ux.intel.com>, kvm@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, rkrcmar@...hat.com,
        tglx@...utronix.de, mingo@...hat.com, hpa@...or.com,
        xiaoguangrong@...cent.com, joro@...tes.org
Subject: Re: [PATCH v3 0/5] KVM: MMU: 5 level EPT/shadow support

On 24/08/2017 14:27, Yu Zhang wrote:
> Intel's existing processors limit the maximum linear address width to
> 48 bits, and the maximum physical address width to 46 bits. And the
> upcoming processors will extend maximum linear address width to 57 bits
> and maximum physical address width can go upto 52 bits in practical.
> 
> With linear address width greater than 48, a new paging mode in IA-32e
> is introduced - 5 level paging(also known as LA57). And to support VMs 
> with this feature, KVM MMU code need to be extended. 
> 
> And to achieve this, this patchset:
> 1> leverages 2 qemu parameters: +la57 and phys-bits to expose wider linear
> address width and physical address width to the VM; 
> 2> extends shadow logic to construct 5 level shadow page for VMs running
> in LA57 mode;
> 3> extends ept logic to construct 5 level ept table for VMs whose maximum
> physical width exceeds 48 bits.
> 
> Changes in v3: 
> - Address comments from Paolo Bonzini: do not fall into check_cpuid_limit()
>   in kvm_cpuid() for em_movbe() and check_fxsr();
> - Address comments from Paolo Bonzini: change parameter 'check_limit' of
>   kvm_cpuid() to bool type;
> - Address comments from Paolo Bonzini: set maxphyaddr to 36, for guest cr3
>   reserved bits check if cpuid.0x80000008 is not available;
> - Address comments from Paolo Bonzini: replace the hardcoded value 48 as
>   va_bits in __linearize();
> - Rebase change: add new eptp definition VMX_EPTP_PWL_5, instead of use bit
>   shifts(in line with previous commit bb97a01).
> 
> Changes in v2: 
> - Address comments from Paolo Bonzini and Jim Mattson: add a new patch to let
>   kvm_cpuid() return false when cpuid entry is not found; 
> - Address comments from Paolo Bonzini: fix a typo in check_cr_write() and use
>   62 as the upper limit when checking reserved bits for a physical address;
> - Address comments from Paolo Bonzini: move definition of PT64_ROOT_MAX_LEVEL
>   into kvm_host.h;
> - Address comments from Paolo Bonzini: add checking for shadow_root_level in
>   mmu_free_roots(); 
> - Address comments from Paolo Bonzini: set root_level & shadow_root_level both
>   to PT64_ROOT_4LEVEL for shadow ept situation.
> 
> 
> Yu Zhang (5):
>   KVM: x86: Add return value to kvm_cpuid().
>   KVM: MMU: check guest CR3 reserved bits based on its physical address
>     width.
>   KVM: MMU: Rename PT64_ROOT_LEVEL to PT64_ROOT_4LEVEL.
>   KVM: MMU: Add 5 level EPT & Shadow page table support.
>   KVM: MMU: Expose the LA57 feature to VM.
> 
>  arch/x86/include/asm/kvm_emulate.h |  4 +--
>  arch/x86/include/asm/kvm_host.h    | 31 ++++++--------------
>  arch/x86/include/asm/vmx.h         |  2 ++
>  arch/x86/kvm/cpuid.c               | 38 +++++++++++++++++-------
>  arch/x86/kvm/cpuid.h               |  3 +-
>  arch/x86/kvm/emulate.c             | 42 +++++++++++++++++----------
>  arch/x86/kvm/kvm_cache_regs.h      |  2 +-
>  arch/x86/kvm/mmu.c                 | 59 ++++++++++++++++++++++++--------------
>  arch/x86/kvm/mmu.h                 |  6 +++-
>  arch/x86/kvm/mmu_audit.c           |  4 +--
>  arch/x86/kvm/svm.c                 |  8 +++---
>  arch/x86/kvm/trace.h               | 11 ++++---
>  arch/x86/kvm/vmx.c                 | 29 ++++++++++++-------
>  arch/x86/kvm/x86.c                 | 21 ++++++++------
>  arch/x86/kvm/x86.h                 | 44 ++++++++++++++++++++++++++++
>  15 files changed, 201 insertions(+), 103 deletions(-)
> 

Applied to kvm/queue.  The only change I made is to make
kvm_mmu_reset_context unconditional in patch 4, because changing
MAXPHYADDR invalidates the MMU's bitmasks for reserved bits.

Thanks,

Paolo