Re: [PATCH] hw/i386/intel_iommu: Block CFI when necessary

[Yuke Peng <pykfirst@gmail.com>]

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On Wed, Jun 26, 2024 at 2:15 PM cmd <clement.mathieudrif.etu@gmail.com>
wrote:

> Hi,
>
> On 25/06/2024 13:28, Yuke Peng wrote:
> > According to Intel VT-d specification 5.1.4, CFI must be blocked when
> > Extended Interrupt Mode is enabled or Compatibility format interrupts
> > are disabled.
> >
> > Signed-off-by: Yuke Peng <pykfirst@gmail.com>
> > ---
> >   hw/i386/intel_iommu.c         | 28 ++++++++++++++++++++++++++++
> >   hw/i386/trace-events          |  1 +
> >   include/hw/i386/intel_iommu.h |  1 +
> >   3 files changed, 30 insertions(+)
> >
> > diff --git a/hw/i386/intel_iommu.c b/hw/i386/intel_iommu.c
> > index 5085a6fee3..dfa2f979e7 100644
> > --- a/hw/i386/intel_iommu.c
> > +++ b/hw/i386/intel_iommu.c
> > @@ -2410,6 +2410,22 @@ static void vtd_handle_gcmd_ire(IntelIOMMUState
> *s, bool en)
> >       }
> >   }
> >
> > +/* Handle Compatibility Format Interrupts Enable/Disable */
> > +static void vtd_handle_gcmd_cfi(IntelIOMMUState *s, bool en)
> > +{
> > +    trace_vtd_cfi_enable(en);
> > +
> > +    if (en) {
> > +        s->cfi_enabled = true;
> > +        /* Ok - report back to driver */
> > +        vtd_set_clear_mask_long(s, DMAR_GSTS_REG, 0, VTD_GSTS_CFIS);
> > +    } else {
> > +        s->cfi_enabled = false;
> > +        /* Ok - report back to driver */
> > +        vtd_set_clear_mask_long(s, DMAR_GSTS_REG, VTD_GSTS_CFIS, 0);
> > +    }
> You have the same comment in both branches of the if statement, couldn't
> we put it between 'trace' and 'if'?
>

The reason I put the comment within the branches is that the function
'vtd_handle_gcmd_cfi'  is similar to the function 'vtd_handle_gcmd_ire'
and  'vtd_handle_gcmd_te'. So for consistency, I also put comments
within the branches instead of in front of 'if'. Besides, I think the
comments
only explain the statement 'vtd_set_clear_mask_long'.

The 'vtd_handle_gcmd_ire' function:

> /* Handle Interrupt Remap Enable/Disable */
> static void vtd_handle_gcmd_ire(IntelIOMMUState *s, bool en)
> {
>     trace_vtd_ir_enable(en);
>
>     if (en) {
>         s->intr_enabled = true;
>         /* Ok - report back to driver */
>         vtd_set_clear_mask_long(s, DMAR_GSTS_REG, 0, VTD_GSTS_IRES);
>     } else {
>         s->intr_enabled = false;
>         /* Ok - report back to driver */
>         vtd_set_clear_mask_long(s, DMAR_GSTS_REG, VTD_GSTS_IRES, 0);
>     }
> }

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