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

[Quan Xu]

On 2017/12/12 02:08, Jim Mattson wrote:
> Removing these two lines from the initialization of
> field_to_offset_table[] means that vmcs_field_to_offset() will return
> -ENOENT for IO_BITMAP_A or IO_BITMAP_B. Hence, handle_vmread and
> handle_vmwrite will incorrectly report these fields as unsupported
> VMCS components if an L1 hypervisor tries to access them.

I will fix in v2.

Quan
Alibaba Cloud



> On Sun, Dec 10, 2017 at 9:37 PM, Quan Xu <quan.xu0@xxxxxxxxx> wrote:
> > 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?
> >
> > Alibaba Cloud
> > Quan