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Message-ID: <9e3f1bb8-bbfd-174c-b7a7-617dea7c2c9a@linux.intel.com>
Date: Thu, 20 Feb 2020 07:32:54 +0800
From: Lu Baolu <baolu.lu@...ux.intel.com>
To: Yonghyun Hwang <yonghyun@...gle.com>,
Moritz Fischer <mdf@...nel.org>
Cc: David Woodhouse <dwmw2@...radead.org>,
Joerg Roedel <joro@...tes.org>,
iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
Havard Skinnemoen <hskinnemoen@...gle.com>,
Deepa Dinamani <deepadinamani@...gle.com>,
Moritz Fischer <moritzf@...gle.com>
Subject: Re: [PATCH] iommu/vt-d: Fix a bug in intel_iommu_iova_to_phys() for
huge page
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@...nel.org
> <mailto:mdf@...nel.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@...gle.com
> <mailto:yonghyun@...gle.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@...nel.org
> <mailto:mdf@...nel.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@...gle.com
> <mailto:yonghyun@...gle.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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