Date:   Tue, 30 Apr 2019 21:31:47 +0200
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Konrad Rzeszutek Wilk <konrad.wilk@...cle.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>,
        "rkrcmar@...hat.com" <rkrcmar@...hat.com>,
        "x86@...nel.org" <x86@...nel.org>
Subject: Re: [PATCH v6 00/14] KVM/X86: Introduce a new guest mapping interface

On 29/04/19 15:58, Konrad Rzeszutek Wilk wrote:
> On Mon, Mar 18, 2019 at 07:16:28PM +0000, Raslan, KarimAllah wrote:
>> On Mon, 2019-03-18 at 10:22 -0400, Konrad Rzeszutek Wilk wrote:
>>> On Mon, Mar 18, 2019 at 01:10:24PM +0000, Raslan, KarimAllah wrote:
>>>>
>>>> I guess this patch series missed the 5.1 merge window? :)
>>>
>>> Were there any outstanding fixes that had to be addressed?
>>
>> Not as far as I can remember. This version addressed all requests raised in 
>> 'v5'.
> 
> Paolo,
> 
> Are there any concerns in pulling this patchset in?

No, it should be in 5.2.

Paolo

> 
> Thank you!
>>
>>>
>>>>
>>>>
>>>> On Thu, 2019-01-31 at 21:24 +0100, KarimAllah Ahmed wrote:
>>>>>
>>>>> Guest memory can either be directly managed by the kernel (i.e. have a "struct
>>>>> page") or they can simply live outside kernel control (i.e. do not have a
>>>>> "struct page"). KVM mostly support these two modes, except in a few places
>>>>> where the code seems to assume that guest memory must have a "struct page".
>>>>>
>>>>> This patchset introduces a new mapping interface to map guest memory into host
>>>>> kernel memory which also supports PFN-based memory (i.e. memory without 'struct
>>>>> page'). It also converts all offending code to this interface or simply
>>>>> read/write directly from guest memory. Patch 2 is additionally fixing an
>>>>> incorrect page release and marking the page as dirty (i.e. as a side-effect of
>>>>> using the helper function to write).
>>>>>
>>>>> As far as I can see all offending code is now fixed except the APIC-access page
>>>>> which I will handle in a seperate series along with dropping
>>>>> kvm_vcpu_gfn_to_page and kvm_vcpu_gpa_to_page from the internal KVM API.
>>>>>
>>>>> The current implementation of the new API uses memremap to map memory that does
>>>>> not have a "struct page". This proves to be very slow for high frequency
>>>>> mappings. Since this does not affect the normal use-case where a "struct page"
>>>>> is available, the performance of this API will be handled by a seperate patch
>>>>> series.
>>>>>
>>>>> So the simple way to use memory outside kernel control is:
>>>>>
>>>>> 1- Pass 'mem=' in the kernel command-line to limit the amount of memory managed 
>>>>>    by the kernel.
>>>>> 2- Map this physical memory you want to give to the guest with:
>>>>>    mmap("/dev/mem", physical_address_offset, ..)
>>>>> 3- Use the user-space virtual address as the "userspace_addr" field in
>>>>>    KVM_SET_USER_MEMORY_REGION ioctl.
>>>>>
>>>>> v5 -> v6:
>>>>> - Added one extra patch to ensure that support for this mem= case is complete
>>>>>   for x86.
>>>>> - Added a helper function to check if the mapping is mapped or not.
>>>>> - Added more comments on the struct.
>>>>> - Setting ->page to NULL on unmap and to a poison ptr if unused during map
>>>>> - Checking for map ptr before using it.
>>>>> - Change kvm_vcpu_unmap to also mark page dirty for LM. That requires
>>>>>   passing the vCPU pointer again to this function.
>>>>>
>>>>> v4 -> v5:
>>>>> - Introduce a new parameter 'dirty' into kvm_vcpu_unmap
>>>>> - A horrible rebase due to nested.c :)
>>>>> - Dropped a couple of hyperv patches as the code was fixed already as a
>>>>>   side-effect of another patch.
>>>>> - Added a new trivial cleanup patch.
>>>>>
>>>>> v3 -> v4:
>>>>> - Rebase
>>>>> - Add a new patch to also fix the newly introduced enlightned VMCS.
>>>>>
>>>>> v2 -> v3:
>>>>> - Rebase
>>>>> - Add a new patch to also fix the newly introduced shadow VMCS.
>>>>>
>>>>> Filippo Sironi (1):
>>>>>   X86/KVM: Handle PFNs outside of kernel reach when touching GPTEs
>>>>>
>>>>> KarimAllah Ahmed (13):
>>>>>   X86/nVMX: handle_vmon: Read 4 bytes from guest memory
>>>>>   X86/nVMX: Update the PML table without mapping and unmapping the page
>>>>>   KVM: Introduce a new guest mapping API
>>>>>   X86/nVMX: handle_vmptrld: Use kvm_vcpu_map when copying VMCS12 from
>>>>>     guest memory
>>>>>   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/nSVM: Use the new mapping API for mapping guest memory
>>>>>   KVM/nVMX: Use kvm_vcpu_map for accessing the shadow VMCS
>>>>>   KVM/nVMX: Use kvm_vcpu_map for accessing the enlightened VMCS
>>>>>   KVM/nVMX: Use page_address_valid in a few more locations
>>>>>   kvm, x86: Properly check whether a pfn is an MMIO or not
>>>>>
>>>>>  arch/x86/include/asm/e820/api.h |   1 +
>>>>>  arch/x86/kernel/e820.c          |  18 ++++-
>>>>>  arch/x86/kvm/mmu.c              |   5 +-
>>>>>  arch/x86/kvm/paging_tmpl.h      |  38 +++++++---
>>>>>  arch/x86/kvm/svm.c              |  97 ++++++++++++------------
>>>>>  arch/x86/kvm/vmx/nested.c       | 160 +++++++++++++++-------------------------
>>>>>  arch/x86/kvm/vmx/vmx.c          |  19 ++---
>>>>>  arch/x86/kvm/vmx/vmx.h          |   9 ++-
>>>>>  arch/x86/kvm/x86.c              |  14 ++--
>>>>>  include/linux/kvm_host.h        |  28 +++++++
>>>>>  virt/kvm/kvm_main.c             |  64 ++++++++++++++++
>>>>>  11 files changed, 267 insertions(+), 186 deletions(-)
>>>>>
>>>>
>>>>
>>>>
>>>> Amazon Development Center Germany GmbH
>>>> Krausenstr. 38
>>>> 10117 Berlin
>>>> Geschaeftsfuehrer: Christian Schlaeger, Ralf Herbrich
>>>> Ust-ID: DE 289 237 879
>>>> Eingetragen am Amtsgericht Charlottenburg HRB 149173 B
>>>>
>>
>>
>>
>> Amazon Development Center Germany GmbH
>> Krausenstr. 38
>> 10117 Berlin
>> Geschaeftsfuehrer: Christian Schlaeger, Ralf Herbrich
>> Ust-ID: DE 289 237 879
>> Eingetragen am Amtsgericht Charlottenburg HRB 149173 B
>>

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