linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Lu Baolu <baolu.lu@linux.intel.com>
To: Yonghyun Hwang <yonghyun@google.com>, Moritz Fischer <mdf@kernel.org>
Cc: David Woodhouse <dwmw2@infradead.org>,
	Joerg Roedel <joro@8bytes.org>,
	iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
	Havard Skinnemoen <hskinnemoen@google.com>,
	Deepa Dinamani <deepadinamani@google.com>,
	Moritz Fischer <moritzf@google.com>
Subject: Re: [PATCH] iommu/vt-d: Fix a bug in intel_iommu_iova_to_phys() for huge page
Date: Thu, 20 Feb 2020 07:32:54 +0800	[thread overview]
Message-ID: <9e3f1bb8-bbfd-174c-b7a7-617dea7c2c9a@linux.intel.com> (raw)
In-Reply-To: <CAEauFbw_FGWuQJMpr7PgyyCAefKChXoszKAz-ykBKgxFc-aa4g@mail.gmail.com>

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
> 

  parent reply	other threads:[~2020-02-19 23:33 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-02-18 22:23 [PATCH] iommu/vt-d: Fix a bug in intel_iommu_iova_to_phys() for huge page Yonghyun Hwang
2020-02-19  3:15 ` Lu Baolu
2020-02-19  4:42   ` Moritz Fischer
     [not found]     ` <CAEauFbw_FGWuQJMpr7PgyyCAefKChXoszKAz-ykBKgxFc-aa4g@mail.gmail.com>
2020-02-19 23:32       ` Lu Baolu [this message]
2020-02-20  0:12         ` Yonghyun Hwang
2020-02-20  2:35           ` Lu Baolu
2020-02-19 19:32 Yonghyun Hwang

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=9e3f1bb8-bbfd-174c-b7a7-617dea7c2c9a@linux.intel.com \
    --to=baolu.lu@linux.intel.com \
    --cc=deepadinamani@google.com \
    --cc=dwmw2@infradead.org \
    --cc=hskinnemoen@google.com \
    --cc=iommu@lists.linux-foundation.org \
    --cc=joro@8bytes.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mdf@kernel.org \
    --cc=moritzf@google.com \
    --cc=yonghyun@google.com \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).