Re: [Xen-devel] [PATCH 0/9] x86/vvmx: Read instruction operands correctly on VM exit

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

> From: Andrew Cooper [mailto:andrew.cooper3@xxxxxxxxxx]
> Sent: Friday, October 27, 2017 1:59 AM
> 
> On 26/10/17 18:03, Euan Harris wrote:
> > decode_vmx_inst() does not read instruction operands correctly on VM
> exit:
> >
> >  * It incorrectly uses vmx_inst_info's address_size field to calculate
> >    the sizes of the exit-causing instruction's operands.  The sizes of
> >    the operands are specified in the SDM and might depend on whether
> the
> >    guest is running in 32-bit or 64-bit mode, but they have nothing to do
> >    with the address_size field.
> >
> >  * It includes its own segmentation logic, duplicating code elsewhere.
> >    This segmentation logic is also incorrect and will raise #GP fault
> >    rather than a #SS fault in response to an invalid memory access
> >    through the stack segment.
> >
> > Patches 1-6 (up to 'Remove operand decoding from decode_vmx_inst()')
> > refactor decode_vmx_inst() in preparation for fixing the bugs mentioned
> > above.  They remove unnecessary code and extract the logic for reading
> > operands from decode_vmx_inst() into a new operand_read() function.
> > These patches should not cause any functional changes.
> >
> > Patch 7 ('Use correct sizes when reading operands') replaces the incorrect
> > operand size calculations based on address_size with the correct sizes
> > from the SDM.
> >
> > Patches 8 and 9 add new hvm_copy_{to,from}_guest_virt() helpers and
> use
> > them to read memory operands in place of the incorrect segmentation
> > logic in decode_vmx_inst().
> >
> > Euan Harris (9):
> >   x86/vvmx: Remove enum vmx_regs_enc
> >   x86/vvmx: Unify operands in struct vmx_inst_decoded
> >   x86/vvmx: Extract operand reading logic into operand_read()
> >   x86/vvmx: Remove unnecessary VMX operand reads
> >   x86/vvmx: Replace direct calls to reg_read() with operand_read()
> >   x86/vvmx: Remove operand reading from decode_vmx_inst()
> >   x86/vvmx: Use correct sizes when reading operands
> >   x86/hvm: Add hvm_copy_{to,from}_guest_virt() helpers
> >   x86/vvmx: Use hvm_copy_{to,from}_guest_virt() to read operands
> 
> All Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>.  I've
> noticed a few trivial style issues which can be fixed up on commit if
> there are no other issues.
> 

Acked-by: Kevin Tian <kevin.tian@xxxxxxxxx>
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