diff mbox series

[v2,1/5] x86/shim: map and unmap page tables in replace_va_mapping

Message ID 7638095024ec3379a8d9ddadfe47e36da168e4dd.1586352238.git.hongyxia@amazon.com (mailing list archive)
State Superseded
Headers show
Series use new API for Xen page tables | expand

Commit Message

Hongyan Xia April 8, 2020, 1:36 p.m. UTC 
From: Wei Liu <wei.liu2@citrix.com>

Also, introduce lYe_from_lXe() macros which do not rely on the direct
map when walking page tables. Unfortunately, they cannot be inline
functions due to the header dependency on domain_page.h, so keep them as
macros just like map_lYt_from_lXe().

Signed-off-by: Wei Liu <wei.liu2@citrix.com>
Signed-off-by: Hongyan Xia <hongyxia@amazon.com>

---
Changed in v2:
- unmap as early as possible instead of unmapping all at the end.
- use lYe_from_lXe() macros and lift them from a later patch to this
  patch.
- const qualify pointers in new macros.
---
 xen/arch/x86/pv/shim.c     |  9 +++++----
 xen/include/asm-x86/page.h | 13 +++++++++++++
 2 files changed, 18 insertions(+), 4 deletions(-)

Comments

Jan Beulich April 9, 2020, 9:42 a.m. UTC | #1 
On 08.04.2020 15:36, Hongyan Xia wrote:
> --- a/xen/arch/x86/pv/shim.c
> +++ b/xen/arch/x86/pv/shim.c
> @@ -168,16 +168,17 @@ const struct platform_bad_page *__init pv_shim_reserved_pages(unsigned int *size
>  static void __init replace_va_mapping(struct domain *d, l4_pgentry_t *l4start,
>                                        unsigned long va, mfn_t mfn)
>  {
> -    l4_pgentry_t *pl4e = l4start + l4_table_offset(va);
> -    l3_pgentry_t *pl3e = l4e_to_l3e(*pl4e) + l3_table_offset(va);
> -    l2_pgentry_t *pl2e = l3e_to_l2e(*pl3e) + l2_table_offset(va);
> -    l1_pgentry_t *pl1e = l2e_to_l1e(*pl2e) + l1_table_offset(va);
> +    l4_pgentry_t l4e = l4start[l4_table_offset(va)];
> +    l3_pgentry_t l3e = l3e_from_l4e(l4e, l3_table_offset(va));
> +    l2_pgentry_t l2e = l2e_from_l3e(l3e, l2_table_offset(va));
> +    l1_pgentry_t *pl1e = map_l1t_from_l2e(l2e) + l1_table_offset(va);
>      struct page_info *page = mfn_to_page(l1e_get_mfn(*pl1e));
>  
>      put_page_and_type(page);
>  
>      *pl1e = l1e_from_mfn(mfn, (!is_pv_32bit_domain(d) ? L1_PROT
>                                                        : COMPAT_L1_PROT));
> +    UNMAP_DOMAIN_PAGE(pl1e);
>  }

As said before, here and below I think it should be unmap_domain_page().

> --- a/xen/include/asm-x86/page.h
> +++ b/xen/include/asm-x86/page.h
> @@ -196,6 +196,19 @@ static inline l4_pgentry_t l4e_from_paddr(paddr_t pa, unsigned int flags)
>  #define map_l2t_from_l3e(x)        (l2_pgentry_t *)map_domain_page(l3e_get_mfn(x))
>  #define map_l3t_from_l4e(x)        (l3_pgentry_t *)map_domain_page(l4e_get_mfn(x))
>  
> +/* Unlike lYe_to_lXe(), lXe_from_lYe() do not rely on the direct map. */
> +#define l2e_from_l3e(l3e, offset) ({                        \
> +        const l2_pgentry_t *l2t = map_l2t_from_l3e(l3e);    \
> +        l2_pgentry_t l2e = l2t[offset];                     \
> +        UNMAP_DOMAIN_PAGE(l2t);                             \
> +        l2e; })
> +
> +#define l3e_from_l4e(l4e, offset) ({                        \
> +        const l3_pgentry_t *l3t = map_l3t_from_l4e(l4e);    \
> +        l3_pgentry_t l3e = l3t[offset];                     \
> +        UNMAP_DOMAIN_PAGE(l3t);                             \
> +        l3e; })

I think l1e_from_l2e() should be introduced at the same time, even
if for now it's unused. I also think, like we do elsewhere, that
macro-local variables would better have _ suffixes, to avoid
possible variable aliasing issues.

Jan
Hongyan Xia April 14, 2020, 4:53 p.m. UTC | #2 
On Thu, 2020-04-09 at 11:42 +0200, Jan Beulich wrote:
> On 08.04.2020 15:36, Hongyan Xia wrote:
> > --- a/xen/arch/x86/pv/shim.c
> > +++ b/xen/arch/x86/pv/shim.c
> > @@ -168,16 +168,17 @@ const struct platform_bad_page *__init
> > pv_shim_reserved_pages(unsigned int *size
> >  static void __init replace_va_mapping(struct domain *d,
> > l4_pgentry_t *l4start,
> >                                        unsigned long va, mfn_t mfn)
> >  {
> > -    l4_pgentry_t *pl4e = l4start + l4_table_offset(va);
> > -    l3_pgentry_t *pl3e = l4e_to_l3e(*pl4e) + l3_table_offset(va);
> > -    l2_pgentry_t *pl2e = l3e_to_l2e(*pl3e) + l2_table_offset(va);
> > -    l1_pgentry_t *pl1e = l2e_to_l1e(*pl2e) + l1_table_offset(va);
> > +    l4_pgentry_t l4e = l4start[l4_table_offset(va)];
> > +    l3_pgentry_t l3e = l3e_from_l4e(l4e, l3_table_offset(va));
> > +    l2_pgentry_t l2e = l2e_from_l3e(l3e, l2_table_offset(va));
> > +    l1_pgentry_t *pl1e = map_l1t_from_l2e(l2e) +
> > l1_table_offset(va);
> >      struct page_info *page = mfn_to_page(l1e_get_mfn(*pl1e));
> >  
> >      put_page_and_type(page);
> >  
> >      *pl1e = l1e_from_mfn(mfn, (!is_pv_32bit_domain(d) ? L1_PROT
> >                                                        :
> > COMPAT_L1_PROT));
> > +    UNMAP_DOMAIN_PAGE(pl1e);
> >  }
> 
> As said before, here and below I think it should be
> unmap_domain_page().
> 
> > --- a/xen/include/asm-x86/page.h
> > +++ b/xen/include/asm-x86/page.h
> > @@ -196,6 +196,19 @@ static inline l4_pgentry_t
> > l4e_from_paddr(paddr_t pa, unsigned int flags)
> >  #define map_l2t_from_l3e(x)        (l2_pgentry_t
> > *)map_domain_page(l3e_get_mfn(x))
> >  #define map_l3t_from_l4e(x)        (l3_pgentry_t
> > *)map_domain_page(l4e_get_mfn(x))
> >  
> > +/* Unlike lYe_to_lXe(), lXe_from_lYe() do not rely on the direct
> > map. */
> > +#define l2e_from_l3e(l3e, offset) ({                        \
> > +        const l2_pgentry_t *l2t = map_l2t_from_l3e(l3e);    \
> > +        l2_pgentry_t l2e = l2t[offset];                     \
> > +        UNMAP_DOMAIN_PAGE(l2t);                             \
> > +        l2e; })
> > +
> > +#define l3e_from_l4e(l4e, offset) ({                        \
> > +        const l3_pgentry_t *l3t = map_l3t_from_l4e(l4e);    \
> > +        l3_pgentry_t l3e = l3t[offset];                     \
> > +        UNMAP_DOMAIN_PAGE(l3t);                             \
> > +        l3e; })
> 
> I think l1e_from_l2e() should be introduced at the same time, even
> if for now it's unused. I also think, like we do elsewhere, that
> macro-local variables would better have _ suffixes, to avoid
> possible variable aliasing issues.

Shall I address the comments and send a new rev now, or is this small
series still being reviewed?

Hongyan
Jan Beulich April 15, 2020, 6:13 a.m. UTC | #3 
On 14.04.2020 18:53, Hongyan Xia wrote:
> On Thu, 2020-04-09 at 11:42 +0200, Jan Beulich wrote:
>> On 08.04.2020 15:36, Hongyan Xia wrote:
>>> --- a/xen/arch/x86/pv/shim.c
>>> +++ b/xen/arch/x86/pv/shim.c
>>> @@ -168,16 +168,17 @@ const struct platform_bad_page *__init
>>> pv_shim_reserved_pages(unsigned int *size
>>>  static void __init replace_va_mapping(struct domain *d,
>>> l4_pgentry_t *l4start,
>>>                                        unsigned long va, mfn_t mfn)
>>>  {
>>> -    l4_pgentry_t *pl4e = l4start + l4_table_offset(va);
>>> -    l3_pgentry_t *pl3e = l4e_to_l3e(*pl4e) + l3_table_offset(va);
>>> -    l2_pgentry_t *pl2e = l3e_to_l2e(*pl3e) + l2_table_offset(va);
>>> -    l1_pgentry_t *pl1e = l2e_to_l1e(*pl2e) + l1_table_offset(va);
>>> +    l4_pgentry_t l4e = l4start[l4_table_offset(va)];
>>> +    l3_pgentry_t l3e = l3e_from_l4e(l4e, l3_table_offset(va));
>>> +    l2_pgentry_t l2e = l2e_from_l3e(l3e, l2_table_offset(va));
>>> +    l1_pgentry_t *pl1e = map_l1t_from_l2e(l2e) +
>>> l1_table_offset(va);
>>>      struct page_info *page = mfn_to_page(l1e_get_mfn(*pl1e));
>>>  
>>>      put_page_and_type(page);
>>>  
>>>      *pl1e = l1e_from_mfn(mfn, (!is_pv_32bit_domain(d) ? L1_PROT
>>>                                                        :
>>> COMPAT_L1_PROT));
>>> +    UNMAP_DOMAIN_PAGE(pl1e);
>>>  }
>>
>> As said before, here and below I think it should be
>> unmap_domain_page().
>>
>>> --- a/xen/include/asm-x86/page.h
>>> +++ b/xen/include/asm-x86/page.h
>>> @@ -196,6 +196,19 @@ static inline l4_pgentry_t
>>> l4e_from_paddr(paddr_t pa, unsigned int flags)
>>>  #define map_l2t_from_l3e(x)        (l2_pgentry_t
>>> *)map_domain_page(l3e_get_mfn(x))
>>>  #define map_l3t_from_l4e(x)        (l3_pgentry_t
>>> *)map_domain_page(l4e_get_mfn(x))
>>>  
>>> +/* Unlike lYe_to_lXe(), lXe_from_lYe() do not rely on the direct
>>> map. */
>>> +#define l2e_from_l3e(l3e, offset) ({                        \
>>> +        const l2_pgentry_t *l2t = map_l2t_from_l3e(l3e);    \
>>> +        l2_pgentry_t l2e = l2t[offset];                     \
>>> +        UNMAP_DOMAIN_PAGE(l2t);                             \
>>> +        l2e; })
>>> +
>>> +#define l3e_from_l4e(l4e, offset) ({                        \
>>> +        const l3_pgentry_t *l3t = map_l3t_from_l4e(l4e);    \
>>> +        l3_pgentry_t l3e = l3t[offset];                     \
>>> +        UNMAP_DOMAIN_PAGE(l3t);                             \
>>> +        l3e; })
>>
>> I think l1e_from_l2e() should be introduced at the same time, even
>> if for now it's unused. I also think, like we do elsewhere, that
>> macro-local variables would better have _ suffixes, to avoid
>> possible variable aliasing issues.
> 
> Shall I address the comments and send a new rev now, or is this small
> series still being reviewed?

I didn't get to look at patches 2 thru 5 yet, if this (partly)
answers the question.

Jan
diff mbox series

Patch

diff --git a/xen/arch/x86/pv/shim.c b/xen/arch/x86/pv/shim.c
index ed2ece8a8a..28d2076065 100644
--- a/xen/arch/x86/pv/shim.c
+++ b/xen/arch/x86/pv/shim.c
@@ -168,16 +168,17 @@  const struct platform_bad_page *__init pv_shim_reserved_pages(unsigned int *size
 static void __init replace_va_mapping(struct domain *d, l4_pgentry_t *l4start,
                                       unsigned long va, mfn_t mfn)
 {
-    l4_pgentry_t *pl4e = l4start + l4_table_offset(va);
-    l3_pgentry_t *pl3e = l4e_to_l3e(*pl4e) + l3_table_offset(va);
-    l2_pgentry_t *pl2e = l3e_to_l2e(*pl3e) + l2_table_offset(va);
-    l1_pgentry_t *pl1e = l2e_to_l1e(*pl2e) + l1_table_offset(va);
+    l4_pgentry_t l4e = l4start[l4_table_offset(va)];
+    l3_pgentry_t l3e = l3e_from_l4e(l4e, l3_table_offset(va));
+    l2_pgentry_t l2e = l2e_from_l3e(l3e, l2_table_offset(va));
+    l1_pgentry_t *pl1e = map_l1t_from_l2e(l2e) + l1_table_offset(va);
     struct page_info *page = mfn_to_page(l1e_get_mfn(*pl1e));
 
     put_page_and_type(page);
 
     *pl1e = l1e_from_mfn(mfn, (!is_pv_32bit_domain(d) ? L1_PROT
                                                       : COMPAT_L1_PROT));
+    UNMAP_DOMAIN_PAGE(pl1e);
 }
 
 static void evtchn_reserve(struct domain *d, unsigned int port)
diff --git a/xen/include/asm-x86/page.h b/xen/include/asm-x86/page.h
index c98d8f5ede..1e16f3980d 100644
--- a/xen/include/asm-x86/page.h
+++ b/xen/include/asm-x86/page.h
@@ -196,6 +196,19 @@  static inline l4_pgentry_t l4e_from_paddr(paddr_t pa, unsigned int flags)
 #define map_l2t_from_l3e(x)        (l2_pgentry_t *)map_domain_page(l3e_get_mfn(x))
 #define map_l3t_from_l4e(x)        (l3_pgentry_t *)map_domain_page(l4e_get_mfn(x))
 
+/* Unlike lYe_to_lXe(), lXe_from_lYe() do not rely on the direct map. */
+#define l2e_from_l3e(l3e, offset) ({                        \
+        const l2_pgentry_t *l2t = map_l2t_from_l3e(l3e);    \
+        l2_pgentry_t l2e = l2t[offset];                     \
+        UNMAP_DOMAIN_PAGE(l2t);                             \
+        l2e; })
+
+#define l3e_from_l4e(l4e, offset) ({                        \
+        const l3_pgentry_t *l3t = map_l3t_from_l4e(l4e);    \
+        l3_pgentry_t l3e = l3t[offset];                     \
+        UNMAP_DOMAIN_PAGE(l3t);                             \
+        l3e; })
+
 /* Given a virtual address, get an entry offset into a page table. */
 #define l1_table_offset(a)         \
     (((a) >> L1_PAGETABLE_SHIFT) & (L1_PAGETABLE_ENTRIES - 1))