Re: [Xen-devel] [PATCH v9 06/13] xen: Add ring 3 vmware_port support

[Andrew Cooper <andrew.cooper3@xxxxxxxxxx>]

On 16/02/15 23:05, Don Slutz wrote:
> Summary is that VMware treats "in (%dx),%eax" (or "out %eax,(%dx)")
> to port 0x5658 specially.  Note: since many operations return data
> in EAX, "in (%dx),%eax" is the one to use.  The other lengths like
> "in (%dx),%al" will still do things, only AL part of EAX will be
> changed.  For "out %eax,(%dx)" of all lengths, EAX will remain
> unchanged.
>
> This instruction is allowed to be used from ring 3.  To
> support this the vmexit for GP needs to be enabled.  I have not
> fully tested that nested HVM is doing the right thing for this.
>
> The support included is enough to allow VMware tools to install in a
> HVM domU.
>
> Enable no-fault of pio in x86_emulate for VMware port
>
> Also adjust the emulation registers after doing a VMware
> backdoor operation.
>
> Add new routine hvm_emulate_one_gp() to be used by the #GP fault
> handler.
>
> Some of the best info is at:
>
> https://sites.google.com/site/chitchatvmback/backdoor
>
> Signed-off-by: Don Slutz <dslutz@xxxxxxxxxxx>
> ---
> v9:
>    Split #GP handling (or skipping of #GP) code out of previous
>    patch to help with the review process.
>    Switch to x86_emulator to handle #GP
>    I think the hvm_emulate_ops_gp() covers all needed ops.  Not able to 
> validate
>    all paths though _hvm_emulate_one().
>
>  xen/arch/x86/hvm/emulate.c             | 62 
> ++++++++++++++++++++++++++++++++--
>  xen/arch/x86/hvm/svm/svm.c             | 27 +++++++++++++++
>  xen/arch/x86/hvm/svm/vmcb.c            |  2 ++
>  xen/arch/x86/hvm/vmware/vmport.c       | 11 ++++++
>  xen/arch/x86/hvm/vmx/vmcs.c            |  2 ++
>  xen/arch/x86/hvm/vmx/vmx.c             | 38 +++++++++++++++++++++
>  xen/arch/x86/x86_emulate/x86_emulate.c | 25 +++++++++++---
>  xen/arch/x86/x86_emulate/x86_emulate.h |  8 +++++
>  xen/include/asm-x86/hvm/emulate.h      |  2 ++
>  xen/include/asm-x86/hvm/vmport.h       |  1 +
>  10 files changed, 172 insertions(+), 6 deletions(-)
>
> diff --git a/xen/arch/x86/hvm/emulate.c b/xen/arch/x86/hvm/emulate.c
> index 636c909..a6a6a5c 100644
> --- a/xen/arch/x86/hvm/emulate.c
> +++ b/xen/arch/x86/hvm/emulate.c
> @@ -22,6 +22,7 @@
>  #include <asm/hvm/trace.h>
>  #include <asm/hvm/support.h>
>  #include <asm/hvm/svm/svm.h>
> +#include <asm/hvm/vmport.h>
>  
>  static void hvmtrace_io_assist(int is_mmio, ioreq_t *p)
>  {
> @@ -776,6 +777,7 @@ static int hvmemul_read_io_discard(
>      unsigned long *val,
>      struct x86_emulate_ctxt *ctxt)
>  {
> +    ctxt->do_vmport = 0;

This looks horribly invasive.

Why are emulation changes needed?  What is wrong with the normal
handling with a registered ioport handler?

~Andrew


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