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SubjectRe: [PATCH] iommu/vt-d: Fix a bug in intel_iommu_iova_to_phys() for huge page
From
Date
Hi,

On 2020/2/20 2:51, Yonghyun Hwang wrote:
> Hello Lu and Moritz,
>
> I think it's better to keep "if (level > 1)" because
> level_to_offset_bits() returns (unsigned int) -1 * LEVEL_STRIDE if level
> becomes 0.

@level will never be 0 in this case.

Best regards,
baolu

>
> static inline unsigned int level_to_offset_bits(int level)
> {
>   return (level - 1) * LEVEL_STRIDE;
> }
>
> On Tue, Feb 18, 2020 at 8:42 PM Moritz Fischer <mdf@kernel.org
> <mailto:mdf@kernel.org>> wrote:
>
> Hi Baolu, Yonghyun
>
> On Wed, Feb 19, 2020 at 11:15:36AM +0800, Lu Baolu wrote:
> > Hi Yonghyun,
> >
> > Thanks for the patch.
> >
> > On 2020/2/19 6:23, Yonghyun Hwang wrote:
> > > intel_iommu_iova_to_phys() has a bug when it translates an IOVA
> for a huge
> > > page onto its corresponding physical address. This commit fixes
> the bug by
> > > accomodating the level of page entry for the IOVA and adds
> IOVA's lower
> > > address to the physical address. >
> > > Signed-off-by: Yonghyun Hwang <yonghyun@google.com
> <mailto:yonghyun@google.com>>
> > > ---
> > >   drivers/iommu/intel-iommu.c | 11 +++++++++--
> > >   1 file changed, 9 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/iommu/intel-iommu.c
> b/drivers/iommu/intel-iommu.c
> > > index 0c8d81f56a30..ed6e69adb578 100644
> > > --- a/drivers/iommu/intel-iommu.c
> > > +++ b/drivers/iommu/intel-iommu.c
> > > @@ -5555,13 +5555,20 @@ static phys_addr_t
> intel_iommu_iova_to_phys(struct iommu_domain *domain,
> > >     struct dma_pte *pte;
> > >     int level = 0;
> > >     u64 phys = 0;
> > > +   const unsigned long pfn = iova >> VTD_PAGE_SHIFT;
> >
> > Why do you need a "const unsigned long" here?
>
>
>
> It's because pfn_to_dma_pte() takes pfn for its second parameter as
> "unsigned int" type and pfn is not changed in intel_iommu_iova_to_phys().
>
> >
> > >     if (dmar_domain->flags & DOMAIN_FLAG_LOSE_CHILDREN)
> > >             return 0;
> > > -   pte = pfn_to_dma_pte(dmar_domain, iova >> VTD_PAGE_SHIFT,
> &level);
> > > -   if (pte)
> > > +   pte = pfn_to_dma_pte(dmar_domain, pfn, &level);
> > > +   if (pte) {
> > >             phys = dma_pte_addr(pte);
> > > +           if (level > 1)
> > > +                   phys += (pfn &
> > > +                           ((1UL <<
> level_to_offset_bits(level)) - 1))
> > > +                           << VTD_PAGE_SHIFT;
> > > +           phys += iova & (VTD_PAGE_SIZE - 1);
> >
> > How about
>
> >
> > diff --git a/drivers/iommu/intel-iommu.c
> b/drivers/iommu/intel-iommu.c
> > index 9dc37672bf89..bd17c2510bb2 100644
> > --- a/drivers/iommu/intel-iommu.c
> > +++ b/drivers/iommu/intel-iommu.c
> > @@ -5693,8 +5693,14 @@ static phys_addr_t
> intel_iommu_iova_to_phys(struct
> > iommu_domain *domain,
> >         u64 phys = 0;
> >
> >         pte = pfn_to_dma_pte(dmar_domain, iova >> VTD_PAGE_SHIFT,
> &level);
> > -       if (pte)
> > +       if (pte) {
> > +               unsigned long offset_mask;
> > +
> > +               offset_mask = BIT_MASK(level_to_offset_bits(level) +
> > +                                      VTD_PAGE_SHIFT) - 1;
> >                 phys = dma_pte_addr(pte);
> > +               phys += iova & (bitmask - 1);
> Did you mean:
>
> phys += iova & (offset_mask - 1);
>
> > +       }
>
> At that point why not define a helper:
>
> static inline unsigned long offset_mask(int level)
> {
>         return BIT_MASK(level_to_offset_bits(level) +
> VTD_PAGE_SHIFT) - 1;
> }
>
> At which point the above would reduce to:
>
> if (pte)
>         phys = dma_pte_addr(pte) + iova & offset_mask(level) - 1;
>
>
>
> Let me introduce the helper function and upstream the patch again. Thank
> you Lu and Moritz.
>
>
> I might've fatfingered something here, but you get the idea :)
>
> Cheers,
> Moritz
>
>
> On Tue, Feb 18, 2020 at 8:42 PM Moritz Fischer <mdf@kernel.org
> <mailto:mdf@kernel.org>> wrote:
>
> Hi Baolu, Yonghyun
>
> On Wed, Feb 19, 2020 at 11:15:36AM +0800, Lu Baolu wrote:
> > Hi Yonghyun,
> >
> > Thanks for the patch.
> >
> > On 2020/2/19 6:23, Yonghyun Hwang wrote:
> > > intel_iommu_iova_to_phys() has a bug when it translates an IOVA
> for a huge
> > > page onto its corresponding physical address. This commit fixes
> the bug by
> > > accomodating the level of page entry for the IOVA and adds
> IOVA's lower
> > > address to the physical address. >
> > > Signed-off-by: Yonghyun Hwang <yonghyun@google.com
> <mailto:yonghyun@google.com>>
> > > ---
> > >   drivers/iommu/intel-iommu.c | 11 +++++++++--
> > >   1 file changed, 9 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/iommu/intel-iommu.c
> b/drivers/iommu/intel-iommu.c
> > > index 0c8d81f56a30..ed6e69adb578 100644
> > > --- a/drivers/iommu/intel-iommu.c
> > > +++ b/drivers/iommu/intel-iommu.c
> > > @@ -5555,13 +5555,20 @@ static phys_addr_t
> intel_iommu_iova_to_phys(struct iommu_domain *domain,
> > >     struct dma_pte *pte;
> > >     int level = 0;
> > >     u64 phys = 0;
> > > +   const unsigned long pfn = iova >> VTD_PAGE_SHIFT;
> >
> > Why do you need a "const unsigned long" here?
> >
> > >     if (dmar_domain->flags & DOMAIN_FLAG_LOSE_CHILDREN)
> > >             return 0;
> > > -   pte = pfn_to_dma_pte(dmar_domain, iova >> VTD_PAGE_SHIFT,
> &level);
> > > -   if (pte)
> > > +   pte = pfn_to_dma_pte(dmar_domain, pfn, &level);
> > > +   if (pte) {
> > >             phys = dma_pte_addr(pte);
> > > +           if (level > 1)
> > > +                   phys += (pfn &
> > > +                           ((1UL <<
> level_to_offset_bits(level)) - 1))
> > > +                           << VTD_PAGE_SHIFT;
> > > +           phys += iova & (VTD_PAGE_SIZE - 1);
> >
> > How about
>
> >
> > diff --git a/drivers/iommu/intel-iommu.c
> b/drivers/iommu/intel-iommu.c
> > index 9dc37672bf89..bd17c2510bb2 100644
> > --- a/drivers/iommu/intel-iommu.c
> > +++ b/drivers/iommu/intel-iommu.c
> > @@ -5693,8 +5693,14 @@ static phys_addr_t
> intel_iommu_iova_to_phys(struct
> > iommu_domain *domain,
> >         u64 phys = 0;
> >
> >         pte = pfn_to_dma_pte(dmar_domain, iova >> VTD_PAGE_SHIFT,
> &level);
> > -       if (pte)
> > +       if (pte) {
> > +               unsigned long offset_mask;
> > +
> > +               offset_mask = BIT_MASK(level_to_offset_bits(level) +
> > +                                      VTD_PAGE_SHIFT) - 1;
> >                 phys = dma_pte_addr(pte);
> > +               phys += iova & (bitmask - 1);
> Did you mean:
>
> phys += iova & (offset_mask - 1);
>
> > +       }
>
> At that point why not define a helper:
>
> static inline unsigned long offset_mask(int level)
> {
>         return BIT_MASK(level_to_offset_bits(level) +
> VTD_PAGE_SHIFT) - 1;
> }
>
> At which point the above would reduce to:
>
> if (pte)
>         phys = dma_pte_addr(pte) + iova & offset_mask(level) - 1;
>
> I might've fatfingered something here, but you get the idea :)
>
> Cheers,
> Moritz
>

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