Re: [PATCH] KVM: VMX: drop I/O permission bitmaps

[Quan Xu]

On 2017/12/09 01:31, Jim Mattson wrote:
> On Fri, Dec 8, 2017 at 2:22 AM, Quan Xu <quan.xu0@xxxxxxxxx> wrote:
> > From: Quan Xu <quan.xu0@xxxxxxxxx>
> >
> > Since KVM removes the only I/O port 0x80 bypass on Intel hosts,
> > clear CPU_BASED_USE_IO_BITMAPS and set CPU_BASED_UNCOND_IO_EXITING
> > bit. Then these I/O permission bitmaps are not used at all, so
> > drop I/O permission bitmaps.
> >
> > Signed-off-by: Jim Mattson <jmattson@xxxxxxxxxx>
> > Signed-off-by: Radim KrÄmÃÅ <rkrcmar@xxxxxxxxxx>
> > Signed-off-by: Quan Xu <quan.xu0@xxxxxxxxx>
> > ---
> >   arch/x86/kvm/vmx.c |   17 +----------------
> >   1 files changed, 1 insertions(+), 16 deletions(-)
> >
> > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> > index 2fd9a8c..3e4f760 100644
> > --- a/arch/x86/kvm/vmx.c
> > +++ b/arch/x86/kvm/vmx.c
> > @@ -771,8 +771,6 @@ enum segment_cache_field {
> >          FIELD(HOST_FS_SELECTOR, host_fs_selector),
> >          FIELD(HOST_GS_SELECTOR, host_gs_selector),
> >          FIELD(HOST_TR_SELECTOR, host_tr_selector),
> > -       FIELD64(IO_BITMAP_A, io_bitmap_a),
> > -       FIELD64(IO_BITMAP_B, io_bitmap_b),
> These two lines should stay.
Jim, could you explain why these two lines should stay?


IIUC, the main concern is from nested virtualization, which still uses 
io_bitmap_a/io_bitmap_b..
if so, we really need to further clean up these code, as

CPU_BASED_USE_IO_BITMAPS is clear, and CPU_BASED_UNCOND_IO_EXITING is set for both L0/L2. after new patches which I mentioned
in this thread.

right?

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Quan