Re: [Xen-devel] [PATCH 16/17] xen/mm: Convert {s, g}et_gpfn_from_mfn() to use typesafe MFN

From: Hongyan Xia <hx242@xen.org>
To: julien@xen.org, xen-devel@lists.xenproject.org
Cc: "Stefano Stabellini" <sstabellini@kernel.org>,
	"Wei Liu" <wl@xen.org>,
	"Andrew Cooper" <andrew.cooper3@citrix.com>,
	"Ian Jackson" <ian.jackson@eu.citrix.com>,
	"George Dunlap" <george.dunlap@citrix.com>,
	"Julien Grall" <julien.grall@arm.com>,
	"Tamas K Lengyel" <tamas@tklengyel.com>,
	"Jan Beulich" <jbeulich@suse.com>,
	"Volodymyr Babchuk" <Volodymyr_Babchuk@epam.com>,
	"Roger Pau Monné" <roger.pau@citrix.com>
Subject: Re: [Xen-devel] [PATCH 16/17] xen/mm: Convert {s, g}et_gpfn_from_mfn() to use typesafe MFN
Date: Mon, 23 Mar 2020 12:11:58 +0000	[thread overview]
Message-ID: <7017afd81363e61996b8645fce566679fc500ab3.camel@xen.org> (raw)
In-Reply-To: <20200322161418.31606-17-julien@xen.org>

On Sun, 2020-03-22 at 16:14 +0000, julien@xen.org wrote:
> From: Julien Grall <julien.grall@arm.com>
> 
> The first parameter of {s,g}et_gpfn_from_mfn() is an MFN, so it can
> be
> switched to use the typesafe.
> 
> At the same time, replace gpfn with pfn in the helpers as they all
> deal
> with PFN and also turn the macros to static inline.
> 
> Note that the return of the getter and the 2nd parameter of the
> setter
> have not been converted to use typesafe PFN because it was requiring
> more changes than expected.
> 
> Signed-off-by: Julien Grall <julien.grall@arm.com>
> 
> ---
>     This was originally sent as part of "xen/arm: Properly disable
> M2P
>     on Arm" [1].
> 
>     Changes since the original version:
>         - mfn_to_gmfn() is still present for now so update it
>         - Remove stray +
>         - Avoid churn in set_pfn_from_mfn() by inverting mfn and mfn_
>         - Remove tags
>         - Fix build in mem_sharing
> 
>     [1] <20190603160350.29806-1-julien.grall@arm.com>
> ---
>  xen/arch/x86/cpu/mcheck/mcaction.c |  2 +-
>  xen/arch/x86/mm.c                  | 14 +++----
>  xen/arch/x86/mm/mem_sharing.c      | 20 ++++-----
>  xen/arch/x86/mm/p2m-pod.c          |  4 +-
>  xen/arch/x86/mm/p2m-pt.c           | 35 ++++++++--------
>  xen/arch/x86/mm/p2m.c              | 66 +++++++++++++++-------------
> --
>  xen/arch/x86/mm/paging.c           |  4 +-
>  xen/arch/x86/pv/dom0_build.c       |  6 +--
>  xen/arch/x86/x86_64/traps.c        |  8 ++--
>  xen/common/page_alloc.c            |  2 +-
>  xen/include/asm-arm/mm.h           |  2 +-
>  xen/include/asm-x86/grant_table.h  |  2 +-
>  xen/include/asm-x86/mm.h           | 12 ++++--
>  xen/include/asm-x86/p2m.h          |  2 +-
>  14 files changed, 93 insertions(+), 86 deletions(-)
> 
> 

[...]

> diff --git a/xen/include/asm-arm/mm.h b/xen/include/asm-arm/mm.h
> index abf4cc23e4..11614f9107 100644
> --- a/xen/include/asm-arm/mm.h
> +++ b/xen/include/asm-arm/mm.h
> @@ -319,7 +319,7 @@ struct page_info *get_page_from_gva(struct vcpu
> *v, vaddr_t va,
>  #define SHARED_M2P(_e)           ((_e) == SHARED_M2P_ENTRY)
>  
>  /* Xen always owns P2M on ARM */
> -#define set_gpfn_from_mfn(mfn, pfn) do { (void) (mfn), (void)(pfn);
> } while (0)
> +static inline void set_pfn_from_mfn(mfn_t mfn, unsigned long pfn) {}
>  #define mfn_to_gmfn(_d, mfn)  (mfn) 

I do not have a setup to compile and test code for Arm, but wouldn't
the compiler complain about unused arguments here? The marco version
explicitly silenced compiler complaints.

> diff --git a/xen/include/asm-x86/grant_table.h b/xen/include/asm-
> x86/grant_table.h
> index 5871238f6d..b6a09c4c6c 100644
> --- a/xen/include/asm-x86/grant_table.h
> +++ b/xen/include/asm-x86/grant_table.h
> @@ -41,7 +41,7 @@ static inline int
> replace_grant_host_mapping(uint64_t addr, mfn_t frame,
>  #define gnttab_get_frame_gfn(gt, st, idx)
> ({                             \
>      mfn_t mfn_ = (st) ? gnttab_status_mfn(gt,
> idx)                       \
>                        : gnttab_shared_mfn(gt,
> idx);                      \
> -    unsigned long gpfn_ =
> get_gpfn_from_mfn(mfn_x(mfn_));                \
> +    unsigned long gpfn_ =
> get_pfn_from_mfn(mfn_);                        \
>      VALID_M2P(gpfn_) ? _gfn(gpfn_) :
> INVALID_GFN;                        \
>  })
>  
> diff --git a/xen/include/asm-x86/mm.h b/xen/include/asm-x86/mm.h
> index 53f2ed7c7d..2a4f42e78f 100644
> --- a/xen/include/asm-x86/mm.h
> +++ b/xen/include/asm-x86/mm.h
> @@ -500,9 +500,10 @@ extern paddr_t mem_hotplug;
>   */
>  extern bool machine_to_phys_mapping_valid;
>  
> -static inline void set_gpfn_from_mfn(unsigned long mfn, unsigned
> long pfn)
> +static inline void set_pfn_from_mfn(mfn_t mfn_, unsigned long pfn)
>  {
> -    const struct domain *d = page_get_owner(mfn_to_page(_mfn(mfn)));
> +    const unsigned long mfn = mfn_x(mfn_);
> +    const struct domain *d = page_get_owner(mfn_to_page(mfn_));
>      unsigned long entry = (d && (d == dom_cow)) ? SHARED_M2P_ENTRY :
> pfn;
>  
>      if ( !machine_to_phys_mapping_valid )
> @@ -515,11 +516,14 @@ static inline void set_gpfn_from_mfn(unsigned
> long mfn, unsigned long pfn)
>  
>  extern struct rangeset *mmio_ro_ranges;
>  
> -#define get_gpfn_from_mfn(mfn)      (machine_to_phys_mapping[(mfn)])
> +static inline unsigned long get_pfn_from_mfn(mfn_t mfn)
> +{
> +    return machine_to_phys_mapping[mfn_x(mfn)];
> +}

Any specific reason this (and some other macros) are turned into static
inline? I don't have a problem with them being inline functions but
just wondering if there is a reason to do so.

>  #define mfn_to_gmfn(_d, mfn)                            \
>      ( (paging_mode_translate(_d))                       \
> -      ? get_gpfn_from_mfn(mfn)                          \
> +      ? get_pfn_from_mfn(_mfn(mfn))                     \
>        : (mfn) )
>  
>  #define compat_pfn_to_cr3(pfn) (((unsigned)(pfn) << 12) |
> ((unsigned)(pfn) >> 20))
> diff --git a/xen/include/asm-x86/p2m.h b/xen/include/asm-x86/p2m.h
> index a2c6049834..39dae242b0 100644
> --- a/xen/include/asm-x86/p2m.h
> +++ b/xen/include/asm-x86/p2m.h
> @@ -505,7 +505,7 @@ static inline struct page_info
> *get_page_from_gfn(
>  static inline gfn_t mfn_to_gfn(const struct domain *d, mfn_t mfn)
>  {
>      if ( paging_mode_translate(d) )
> -        return _gfn(get_gpfn_from_mfn(mfn_x(mfn)));
> +        return _gfn(get_pfn_from_mfn(mfn));
>      else
>          return _gfn(mfn_x(mfn));
>  }

Apart from the two comments above, looks good to me.

Reviewed-by: Hongyan Xia <hongyxia@amazon.com>

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