Re: [PATCH v4 3/4] intel_iommu: fix type of the mask field in VTDIOTLBPageInvInfo

[Michael S. Tsirkin]

On Mon, Jul 08, 2024 at 03:12:27PM +0800, Yi Liu wrote:
> On 2024/7/5 19:01, CLEMENT MATHIEU--DRIF wrote:
> > From: Clément Mathieu--Drif <clement.mathieu--drif@eviden.com>
> > 
> > The mask we are trying to store into VTDIOTLBPageInvInfo.mask might not
> > fit in an uint8_t. Use uint64_t to avoid overflows
> 
> Per the below code, it can overflow as am can be larger than 8 according
> to the CH 6.5.2.3 IOTLB Invalidate.

I don't understand what you are saying. What can overflow?
Are you suggesting text for commit log here?

> And you may want a fix tag as well.

why not.

> info.mask = ~((1 << am) - 1);
> 
> CH 6.5.2.3 IOTLB Invalidate
> 
> Address Mask (AM): For page-selective-within-domain invalidations, the
> Address Mask specifies
> the number of low order bits of the ADDR field that must be masked for the
> invalidation operation.
> This field enables software to request invalidation of contiguous mappings
> for size-aligned
> regions. Refer to Table 19 for encodings of this field. When invalidating a
> large-page translation,
> software must use the appropriate Address Mask value (0 for 4KByte page, 9
> for 2-MByte page,
> and 18 for 1-GByte page). Hardware implementations report the maximum
> supported address
> mask value through the Capability register
> 
> > Signed-off-by: Clément Mathieu--Drif <clement.mathieu--drif@eviden.com>
> > ---
> >   hw/i386/intel_iommu_internal.h | 2 +-
> >   1 file changed, 1 insertion(+), 1 deletion(-)
> > 
> > diff --git a/hw/i386/intel_iommu_internal.h b/hw/i386/intel_iommu_internal.h
> > index faea23e8d6..5f32c36943 100644
> > --- a/hw/i386/intel_iommu_internal.h
> > +++ b/hw/i386/intel_iommu_internal.h
> > @@ -436,7 +436,7 @@ struct VTDIOTLBPageInvInfo {
> >       uint16_t domain_id;
> >       uint32_t pasid;
> >       uint64_t addr;
> > -    uint8_t mask;
> > +    uint64_t mask;
> >   };
> >   typedef struct VTDIOTLBPageInvInfo VTDIOTLBPageInvInfo;
> 
> -- 
> Regards,
> Yi Liu