linux-kernel - Re: [PATCH 00/10] KVM/X86: Handle guest memory that does not have a struct page

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Date:   Fri, 2 Mar 2018 18:40:43 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Jim Mattson <jmattson@...gle.com>,
        "Raslan, KarimAllah" <karahmed@...zon.de>
Cc:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>, "hpa@...or.com" <hpa@...or.com>,
        "rkrcmar@...hat.com" <rkrcmar@...hat.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "mingo@...hat.com" <mingo@...hat.com>
Subject: Re: [PATCH 00/10] KVM/X86: Handle guest memory that does not have a
 struct page

On 01/03/2018 18:51, Jim Mattson wrote:
> No complaints here!

It seems sane here too, I'll review the individual patches as soon as
possible.

Thanks,

Paolo

> On Thu, Mar 1, 2018 at 7:24 AM, Raslan, KarimAllah <karahmed@...zon.de> wrote:
>> Jim/Paolo/Radim,
>>
>> Any complains about the current API? (introduced in 4/10)
>>
>> I have more patches on top and I would like to ensure that this is
>> agreed upon at least before sending more revisions/patches.
>>
>> Also 1, 2, and 3 should be a bit straight forward and does not use
>> this API.
>>
>> Thanks.
>>
>> On Wed, 2018-02-21 at 18:47 +0100, KarimAllah Ahmed wrote:
>>> For the most part, KVM can handle guest memory that does not have a struct
>>> page (i.e. not directly managed by the kernel). However, There are a few places
>>> in the code, specially in the nested code, that does not support that.
>>>
>>> Patch 1, 2, and 3 avoid the mapping and unmapping all together and just
>>> directly use kvm_guest_read and kvm_guest_write.
>>>
>>> Patch 4 introduces a new guest mapping interface that encapsulate all the
>>> bioler plate code that is needed to map and unmap guest memory. It also
>>> supports guest memory without "struct page".
>>>
>>> Patch 5, 6, 7, 8, 9, and 10 switch most of the offending code in VMX and hyperv
>>> to use the new guest mapping API.
>>>
>>> This patch series is the first set of fixes. Handling SVM and APIC-access page
>>> will be handled in a different patch series.
>>>
>>> KarimAllah Ahmed (10):
>>>   X86/nVMX: handle_vmon: Read 4 bytes from guest memory instead of
>>>     map->read->unmap sequence
>>>   X86/nVMX: handle_vmptrld: Copy the VMCS12 directly from guest memory
>>>     instead of map->copy->unmap sequence.
>>>   X86/nVMX: Update the PML table without mapping and unmapping the page
>>>   KVM: Introduce a new guest mapping API
>>>   KVM/nVMX: Use kvm_vcpu_map when mapping the L1 MSR bitmap
>>>   KVM/nVMX: Use kvm_vcpu_map when mapping the virtual APIC page
>>>   KVM/nVMX: Use kvm_vcpu_map when mapping the posted interrupt
>>>     descriptor table
>>>   KVM/X86: Use kvm_vcpu_map in emulator_cmpxchg_emulated
>>>   KVM/X86: hyperv: Use kvm_vcpu_map in synic_clear_sint_msg_pending
>>>   KVM/X86: hyperv: Use kvm_vcpu_map in synic_deliver_msg
>>>
>>>  arch/x86/kvm/hyperv.c    |  28 ++++-----
>>>  arch/x86/kvm/vmx.c       | 144 +++++++++++++++--------------------------------
>>>  arch/x86/kvm/x86.c       |  13 ++---
>>>  include/linux/kvm_host.h |  15 +++++
>>>  virt/kvm/kvm_main.c      |  50 ++++++++++++++++
>>>  5 files changed, 129 insertions(+), 121 deletions(-)
>>>
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