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From: Stefano Stabellini <sstabellini@kernel.org>
To: Julien Grall <julien@xen.org>
Cc: xen-devel@lists.xenproject.org, Wei.Chen@arm.com,
	Henry.Wang@arm.com,  Penny.Zheng@arm.com,
	Bertrand.Marquis@arm.com,  Julien Grall <jgrall@amazon.com>,
	 Stefano Stabellini <sstabellini@kernel.org>,
	 Volodymyr Babchuk <Volodymyr_Babchuk@epam.com>
Subject: Re: [PATCH RFCv2 02/15] xen/arm: lpae: Use the generic helpers to defined the Xen PT helpers
Date: Tue, 11 May 2021 15:26:40 -0700 (PDT)	[thread overview]
Message-ID: <alpine.DEB.2.21.2105111515470.5018@sstabellini-ThinkPad-T480s> (raw)
In-Reply-To: <20210425201318.15447-3-julien@xen.org>

On Sun, 25 Apr 2021, Julien Grall wrote:
> From: Julien Grall <jgrall@amazon.com>
> 
> Currently, Xen PT helpers are only working with 4KB page granularity
> and open-code the generic helpers. To allow more flexibility, we can
> re-use the generic helpers and pass Xen's page granularity
> (PAGE_SHIFT).
> 
> As Xen PT helpers are used in both C and assembly, we need to move
> the generic helpers definition outside of the !__ASSEMBLY__ section.
> 
> Note the aliases for each level are still kept for the time being so we
> can avoid a massive patch to change all the callers.
> 
> Signed-off-by: Julien Grall <jgrall@amazon.com>

The patch is OK as is. I have a couple of suggestions for improvement
below. If you feel like making them, good, otherwise I am also OK if you
don't want to change anything.


> ---
>     Changes in v2:
>         - New patch
> ---
>  xen/include/asm-arm/lpae.h | 71 +++++++++++++++++++++-----------------
>  1 file changed, 40 insertions(+), 31 deletions(-)
> 
> diff --git a/xen/include/asm-arm/lpae.h b/xen/include/asm-arm/lpae.h
> index 4fb9a40a4ca9..310f5225e056 100644
> --- a/xen/include/asm-arm/lpae.h
> +++ b/xen/include/asm-arm/lpae.h
> @@ -159,6 +159,17 @@ static inline bool lpae_is_superpage(lpae_t pte, unsigned int level)
>  #define lpae_get_mfn(pte)    (_mfn((pte).walk.base))
>  #define lpae_set_mfn(pte, mfn)  ((pte).walk.base = mfn_x(mfn))
>  
> +/* Generate an array @var containing the offset for each level from @addr */
> +#define DECLARE_OFFSETS(var, addr)          \
> +    const unsigned int var[4] = {           \
> +        zeroeth_table_offset(addr),         \
> +        first_table_offset(addr),           \
> +        second_table_offset(addr),          \
> +        third_table_offset(addr)            \
> +    }
> +
> +#endif /* __ASSEMBLY__ */
> +
>  /*
>   * AArch64 supports pages with different sizes (4K, 16K, and 64K).
>   * Provide a set of generic helpers that will compute various
> @@ -190,17 +201,6 @@ static inline bool lpae_is_superpage(lpae_t pte, unsigned int level)
>  #define LPAE_TABLE_INDEX_GS(gs, lvl, addr)   \
>      (((addr) >> LEVEL_SHIFT_GS(gs, lvl)) & LPAE_ENTRY_MASK_GS(gs))
>  
> -/* Generate an array @var containing the offset for each level from @addr */
> -#define DECLARE_OFFSETS(var, addr)          \
> -    const unsigned int var[4] = {           \
> -        zeroeth_table_offset(addr),         \
> -        first_table_offset(addr),           \
> -        second_table_offset(addr),          \
> -        third_table_offset(addr)            \
> -    }
> -
> -#endif /* __ASSEMBLY__ */
> -
>  /*
>   * These numbers add up to a 48-bit input address space.
>   *
> @@ -211,26 +211,35 @@ static inline bool lpae_is_superpage(lpae_t pte, unsigned int level)
>   * therefore 39-bits are sufficient.
>   */
>  
> -#define LPAE_SHIFT      9
> -#define LPAE_ENTRIES    (_AC(1,U) << LPAE_SHIFT)
> -#define LPAE_ENTRY_MASK (LPAE_ENTRIES - 1)
> -
> -#define THIRD_SHIFT    (PAGE_SHIFT)
> -#define THIRD_ORDER    (THIRD_SHIFT - PAGE_SHIFT)
> -#define THIRD_SIZE     (_AT(paddr_t, 1) << THIRD_SHIFT)
> -#define THIRD_MASK     (~(THIRD_SIZE - 1))
> -#define SECOND_SHIFT   (THIRD_SHIFT + LPAE_SHIFT)
> -#define SECOND_ORDER   (SECOND_SHIFT - PAGE_SHIFT)
> -#define SECOND_SIZE    (_AT(paddr_t, 1) << SECOND_SHIFT)
> -#define SECOND_MASK    (~(SECOND_SIZE - 1))
> -#define FIRST_SHIFT    (SECOND_SHIFT + LPAE_SHIFT)
> -#define FIRST_ORDER    (FIRST_SHIFT - PAGE_SHIFT)
> -#define FIRST_SIZE     (_AT(paddr_t, 1) << FIRST_SHIFT)
> -#define FIRST_MASK     (~(FIRST_SIZE - 1))
> -#define ZEROETH_SHIFT  (FIRST_SHIFT + LPAE_SHIFT)
> -#define ZEROETH_ORDER  (ZEROETH_SHIFT - PAGE_SHIFT)
> -#define ZEROETH_SIZE   (_AT(paddr_t, 1) << ZEROETH_SHIFT)
> -#define ZEROETH_MASK   (~(ZEROETH_SIZE - 1))

Should we add a one-line in-code comment saying that the definitions
below are for 4KB pages? It is not immediately obvious any longer.


> +#define LPAE_SHIFT          LPAE_SHIFT_GS(PAGE_SHIFT)
> +#define LPAE_ENTRIES        LPAE_ENTRIES_GS(PAGE_SHIFT)
> +#define LPAE_ENTRY_MASK     LPAE_ENTRY_MASK_GS(PAGE_SHIFT)
>
> +#define LEVEL_SHIFT(lvl)    LEVEL_SHIFT_GS(PAGE_SHIFT, lvl)
> +#define LEVEL_ORDER(lvl)    LEVEL_ORDER_GS(PAGE_SHIFT, lvl)
> +#define LEVEL_SIZE(lvl)     LEVEL_SIZE_GS(PAGE_SHIFT, lvl)
> +#define LEVEL_MASK(lvl)     (~(LEVEL_SIZE(lvl) - 1))

I would avoid adding these 4 macros. It would be OK if they were just
used within this file but lpae.h is a header: they could end up be used
anywhere in the xen/ code and they have a very generic name. My
suggestion would be to skip them and just do:

#define THIRD_SHIFT         LEVEL_SHIFT_GS(PAGE_SHIFT, 3)

etc.


> +/* Convenience aliases */
> +#define THIRD_SHIFT         LEVEL_SHIFT(3)
> +#define THIRD_ORDER         LEVEL_ORDER(3)
> +#define THIRD_SIZE          LEVEL_SIZE(3)
> +#define THIRD_MASK          LEVEL_MASK(3)
> +
> +#define SECOND_SHIFT        LEVEL_SHIFT(2)
> +#define SECOND_ORDER        LEVEL_ORDER(2)
> +#define SECOND_SIZE         LEVEL_SIZE(2)
> +#define SECOND_MASK         LEVEL_MASK(2)
> +
> +#define FIRST_SHIFT         LEVEL_SHIFT(1)
> +#define FIRST_ORDER         LEVEL_ORDER(1)
> +#define FIRST_SIZE          LEVEL_SIZE(1)
> +#define FIRST_MASK          LEVEL_MASK(1)
> +
> +#define ZEROETH_SHIFT       LEVEL_SHIFT(0)
> +#define ZEROETH_ORDER       LEVEL_ORDER(0)
> +#define ZEROETH_SIZE        LEVEL_SIZE(0)
> +#define ZEROETH_MASK        LEVEL_MASK(0)
>  
>  /* Calculate the offsets into the pagetables for a given VA */
>  #define zeroeth_linear_offset(va) ((va) >> ZEROETH_SHIFT)
> -- 
> 2.17.1
> 


  reply	other threads:[~2021-05-11 22:27 UTC|newest]

Thread overview: 58+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-25 20:13 [PATCH RFCv2 00/15] xen/arm: mm: Remove open-coding mappings Julien Grall
2021-04-25 20:13 ` [PATCH RFCv2 01/15] xen/arm: lpae: Rename LPAE_ENTRIES_MASK_GS to LPAE_ENTRY_MASK_GS Julien Grall
2021-05-11 22:12   ` Stefano Stabellini
2021-04-25 20:13 ` [PATCH RFCv2 02/15] xen/arm: lpae: Use the generic helpers to defined the Xen PT helpers Julien Grall
2021-05-11 22:26   ` Stefano Stabellini [this message]
2021-05-12 14:26     ` Julien Grall
2021-05-12 21:30       ` Stefano Stabellini
2021-05-12 22:16         ` Julien Grall
2021-05-13 22:44           ` Stefano Stabellini
2021-07-03 17:32             ` Julien Grall
2021-07-13 20:53               ` Stefano Stabellini
2021-07-14 17:40                 ` Julien Grall
2021-04-25 20:13 ` [PATCH RFCv2 03/15] xen/arm: p2m: Replace level_{orders, masks} arrays with LEVEL_{ORDER, MASK} Julien Grall
2021-05-11 22:33   ` Stefano Stabellini
2021-05-12 14:39     ` Julien Grall
2021-04-25 20:13 ` [PATCH RFCv2 04/15] xen/arm: mm: Allow other mapping size in xen_pt_update_entry() Julien Grall
2021-05-11 22:42   ` Stefano Stabellini
2021-04-25 20:13 ` [PATCH RFCv2 05/15] xen/arm: mm: Avoid flushing the TLBs when mapping are inserted Julien Grall
2021-05-11 22:51   ` Stefano Stabellini
2021-04-25 20:13 ` [PATCH RFCv2 06/15] xen/arm: mm: Don't open-code Xen PT update in remove_early_mappings() Julien Grall
2021-05-11 22:58   ` Stefano Stabellini
2021-04-25 20:13 ` [PATCH RFCv2 07/15] xen/arm: mm: Re-implement early_fdt_map() using map_pages_to_xen() Julien Grall
2021-05-12 21:41   ` Stefano Stabellini
2021-05-12 22:18     ` Julien Grall
2021-04-25 20:13 ` [PATCH RFCv2 08/15] xen/arm32: mm: Check if the virtual address is shared before updating it Julien Grall
2021-05-12 22:00   ` Stefano Stabellini
2021-05-12 22:23     ` Julien Grall
2021-05-13 22:32       ` Stefano Stabellini
2021-05-13 22:59         ` Julien Grall
2021-05-14  1:04           ` Stefano Stabellini
2021-04-25 20:13 ` [PATCH RFCv2 09/15] xen/arm32: mm: Re-implement setup_xenheap_mappings() using map_pages_to_xen() Julien Grall
2021-05-12 22:07   ` Stefano Stabellini
2021-05-13 17:55     ` Julien Grall
2021-04-25 20:13 ` [PATCH RFCv2 10/15] xen/arm: mm: Allocate xen page tables in domheap rather than xenheap Julien Grall
2021-05-12 22:44   ` Stefano Stabellini
2021-05-13 18:09     ` Julien Grall
2021-05-13 22:27       ` Stefano Stabellini
2021-05-15  8:48         ` Julien Grall
2021-05-18  0:37           ` Stefano Stabellini
2021-04-25 20:13 ` [PATCH RFCv2 11/15] xen/arm: mm: Allow page-table allocation from the boot allocator Julien Grall
2021-05-13 22:58   ` Stefano Stabellini
2021-04-25 20:13 ` [PATCH RFCv2 12/15] xen/arm: add Persistent Map (PMAP) infrastructure Julien Grall
2021-04-26  9:41   ` Xia, Hongyan
2021-07-03 17:57     ` Julien Grall
2021-04-28 21:47   ` Wei Liu
2021-05-14 23:25   ` Stefano Stabellini
2021-05-15  8:54     ` Julien Grall
2021-04-25 20:13 ` [PATCH RFCv2 13/15] xen/arm: mm: Use the PMAP helpers in xen_{,un}map_table() Julien Grall
2021-05-14 23:35   ` Stefano Stabellini
2021-05-15  9:03     ` Julien Grall
2021-04-25 20:13 ` [PATCH RFCv2 14/15] xen/arm: mm: Rework setup_xenheap_mappings() Julien Grall
2021-05-14 23:51   ` Stefano Stabellini
2021-05-15  9:21     ` Julien Grall
2021-05-18  0:50       ` Stefano Stabellini
2021-04-25 20:13 ` [PATCH RFCv2 15/15] xen/arm: mm: Re-implement setup_frame_table_mappings() with map_pages_to_xen() Julien Grall
2021-05-15  0:02   ` Stefano Stabellini
2021-05-15  9:25     ` Julien Grall
2021-05-18  0:51       ` Stefano Stabellini

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