[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: Why guest physical addresses are not the same as the corresponding h
From: |
harry harry |
Subject: |
Re: Why guest physical addresses are not the same as the corresponding host virtual addresses in QEMU/KVM? Thanks! |
Date: |
Tue, 13 Oct 2020 00:30:39 -0400 |
Hi Sean,
Thank you very much for your thorough explanations. Please see my
inline replies as follows. Thanks!
On Mon, Oct 12, 2020 at 12:54 PM Sean Christopherson
<sean.j.christopherson@intel.com> wrote:
>
> No, the guest physical address spaces is not intrinsically tied to the host
> virtual address spaces. The fact that GPAs and HVAs are related in KVM is a
> property KVM's architecture. EPT/NPT has absolutely nothing to do with HVAs.
>
> As Maxim pointed out, KVM links a guest's physical address space, i.e. GPAs,
> to
> the host's virtual address space, i.e. HVAs, via memslots. For all intents
> and
> purposes, this is an extra layer of address translation that is purely
> software
> defined. The memslots allow KVM to retrieve the HPA for a given GPA when
> servicing a shadow page fault (a.k.a. EPT violation).
>
> When EPT is enabled, a shadow page fault due to an unmapped GPA will look
> like:
>
> GVA -> [guest page tables] -> GPA -> EPT Violation VM-Exit
>
> The above walk of the guest page tables is done in hardware. KVM then does
> the
> following walks in software to retrieve the desired HPA:
>
> GPA -> [memslots] -> HVA -> [host page tables] -> HPA
Do you mean that GPAs are different from their corresponding HVAs when
KVM does the walks (as you said above) in software?
Thanks,
Harry
- Why guest physical addresses are not the same as the corresponding host virtual addresses in QEMU/KVM? Thanks!, harry harry, 2020/10/11
- Re: Why guest physical addresses are not the same as the corresponding host virtual addresses in QEMU/KVM? Thanks!, Maxim Levitsky, 2020/10/11
- Re: Why guest physical addresses are not the same as the corresponding host virtual addresses in QEMU/KVM? Thanks!, harry harry, 2020/10/11
- Re: Why guest physical addresses are not the same as the corresponding host virtual addresses in QEMU/KVM? Thanks!, Sean Christopherson, 2020/10/12
- Re: Why guest physical addresses are not the same as the corresponding host virtual addresses in QEMU/KVM? Thanks!,
harry harry <=
- Re: Why guest physical addresses are not the same as the corresponding host virtual addresses in QEMU/KVM? Thanks!, Sean Christopherson, 2020/10/13
- Re: Why guest physical addresses are not the same as the corresponding host virtual addresses in QEMU/KVM? Thanks!, harry harry, 2020/10/13
- Re: Why guest physical addresses are not the same as the corresponding host virtual addresses in QEMU/KVM? Thanks!, harry harry, 2020/10/13
- Re: Why guest physical addresses are not the same as the corresponding host virtual addresses in QEMU/KVM? Thanks!, Paolo Bonzini, 2020/10/13
- Re: Why guest physical addresses are not the same as the corresponding host virtual addresses in QEMU/KVM? Thanks!, harry harry, 2020/10/13
- Re: Why guest physical addresses are not the same as the corresponding host virtual addresses in QEMU/KVM? Thanks!, Paolo Bonzini, 2020/10/14
- Re: Why guest physical addresses are not the same as the corresponding host virtual addresses in QEMU/KVM? Thanks!, Maxim Levitsky, 2020/10/14
- Re: Why guest physical addresses are not the same as the corresponding host virtual addresses in QEMU/KVM? Thanks!, harry harry, 2020/10/14
- Re: Why guest physical addresses are not the same as the corresponding host virtual addresses in QEMU/KVM? Thanks!, Sean Christopherson, 2020/10/13
- Re: Why guest physical addresses are not the same as the corresponding host virtual addresses in QEMU/KVM? Thanks!, harry harry, 2020/10/13