Re: [PATCH] kvm: VMX: do not use vm-exit instruction length for fast MMIO

From	David Hildenbrand <david@redhat.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH] kvm: VMX: do not use vm-exit instruction length for fast MMIO
Date	2017-08-18 14:50 +0200
Message-ID	<ufOSS-3M9-25@gated-at.bofh.it> (permalink)
References	<uf6Ia-7Ci-15@gated-at.bofh.it> <ufO6t-3bH-3@gated-at.bofh.it> <ufOJc-3Ie-13@gated-at.bofh.it>
Organization	Red Hat GmbH

Show all headers | View raw

On 18.08.2017 14:35, Paolo Bonzini wrote:
> On 18/08/2017 13:57, David Hildenbrand wrote:
>> What about a hack:
>>
>> 1. clear instruction length when entering
>> 2. check if instruction length is set when trying to forward the RIP
>> 2a. if set, use it
>> 2b. if not set, compute it
> 
> It's undefined, so we don't know that the instruction length remains
> zero (also, on older processors and possibly some nested setups the
> field is read-only).

Oh I see, too bad :(

> 
> Testing the hypervisor bit is the first line of action.
> 
> Paolo


-- 

Thanks,

David

Back to linux.kernel | Previous | Next — Previous in thread | Find similar | Unroll thread

Thread

[PATCH] kvm: VMX: do not use vm-exit instruction length for fast MMIO Paolo Bonzini <pbonzini@redhat.com> - 2017-08-16 15:40 +0200
  Re: [PATCH] kvm: VMX: do not use vm-exit instruction length for fast  MMIO "Michael S. Tsirkin" <mst@redhat.com> - 2017-08-16 16:20 +0200
    Re: [PATCH] kvm: VMX: do not use vm-exit instruction length for fast  MMIO Radim Krčmář <rkrcmar@redhat.com> - 2017-08-16 19:00 +0200
      Re: [PATCH] kvm: VMX: do not use vm-exit instruction length for fast  MMIO "Michael S. Tsirkin" <mst@redhat.com> - 2017-08-16 19:10 +0200
      Re: [PATCH] kvm: VMX: do not use vm-exit instruction length for fast  MMIO Yang Zhang <yang.zhang.wz@gmail.com> - 2017-08-17 10:10 +0200
        Re: [PATCH] kvm: VMX: do not use vm-exit instruction length for fast MMIO Wanpeng Li <kernellwp@gmail.com> - 2017-08-17 10:30 +0200
          Re: [PATCH] kvm: VMX: do not use vm-exit instruction length for fast MMIO Wanpeng Li <kernellwp@gmail.com> - 2017-08-17 10:40 +0200
            Re: [PATCH] kvm: VMX: do not use vm-exit instruction length for fast  MMIO Yang Zhang <yang.zhang.wz@gmail.com> - 2017-08-17 10:50 +0200
              Re: [PATCH] kvm: VMX: do not use vm-exit instruction length for fast MMIO Wanpeng Li <kernellwp@gmail.com> - 2017-08-17 11:00 +0200
                Re: [PATCH] kvm: VMX: do not use vm-exit instruction length for fast  MMIO Yang Zhang <yang.zhang.wz@gmail.com> - 2017-08-18 05:40 +0200
    Re: [PATCH] kvm: VMX: do not use vm-exit instruction length for fast  MMIO Jason Wang <jasowang@redhat.com> - 2017-08-18 10:50 +0200
      Re: [PATCH] kvm: VMX: do not use vm-exit instruction length for fast  MMIO Radim Krčmář <rkrcmar@redhat.com> - 2017-08-21 18:10 +0200
  Re: [PATCH] kvm: VMX: do not use vm-exit instruction length for fast  MMIO David Hildenbrand <david@redhat.com> - 2017-08-18 14:00 +0200
    Re: [PATCH] kvm: VMX: do not use vm-exit instruction length for fast  MMIO Paolo Bonzini <pbonzini@redhat.com> - 2017-08-18 14:40 +0200
      Re: [PATCH] kvm: VMX: do not use vm-exit instruction length for fast  MMIO David Hildenbrand <david@redhat.com> - 2017-08-18 14:50 +0200

csiph-web