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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 10/15] xen/arm: mm: Allocate xen page tables in domheap rather than xenheap
Date: Wed, 12 May 2021 15:44:41 -0700 (PDT)	[thread overview]
Message-ID: <alpine.DEB.2.21.2105121529180.5018@sstabellini-ThinkPad-T480s> (raw)
In-Reply-To: <20210425201318.15447-11-julien@xen.org>

On Sun, 25 Apr 2021, Julien Grall wrote:
> From: Julien Grall <jgrall@amazon.com>
> 
> xen_{un,}map_table() already uses the helper to map/unmap pages
> on-demand (note this is currently a NOP on arm64). So switching to
> domheap don't have any disavantage.
> 
> But this as the benefit:
>     - to keep the page tables unmapped if an arch decided to do so
>     - reduce xenheap use on arm32 which can be pretty small
> 
> Signed-off-by: Julien Grall <jgrall@amazon.com>

Thanks for the patch. It looks OK but let me ask a couple of questions
to clarify my doubts.

This change should have no impact to arm64, right?

For arm32, I wonder why we were using map_domain_page before in
xen_map_table: it wasn't necessary, was it? In fact, one could even say
that it was wrong?


> ---
>     Changes in v2:
>         - New patch
> ---
>  xen/arch/arm/mm.c | 36 +++++++++++++++++++++---------------
>  1 file changed, 21 insertions(+), 15 deletions(-)
> 
> diff --git a/xen/arch/arm/mm.c b/xen/arch/arm/mm.c
> index 19ecf73542ce..ae5a07ea956b 100644
> --- a/xen/arch/arm/mm.c
> +++ b/xen/arch/arm/mm.c
> @@ -969,21 +969,6 @@ void *ioremap(paddr_t pa, size_t len)
>      return ioremap_attr(pa, len, PAGE_HYPERVISOR_NOCACHE);
>  }
>  
> -static int create_xen_table(lpae_t *entry)
> -{
> -    void *p;
> -    lpae_t pte;
> -
> -    p = alloc_xenheap_page();
> -    if ( p == NULL )
> -        return -ENOMEM;
> -    clear_page(p);
> -    pte = mfn_to_xen_entry(virt_to_mfn(p), MT_NORMAL);
> -    pte.pt.table = 1;
> -    write_pte(entry, pte);
> -    return 0;
> -}
> -
>  static lpae_t *xen_map_table(mfn_t mfn)
>  {
>      /*
> @@ -1024,6 +1009,27 @@ static void xen_unmap_table(const lpae_t *table)
>      unmap_domain_page(table);
>  }
>  
> +static int create_xen_table(lpae_t *entry)
> +{
> +    struct page_info *pg;
> +    void *p;
> +    lpae_t pte;
> +
> +    pg = alloc_domheap_page(NULL, 0);
> +    if ( pg == NULL )
> +        return -ENOMEM;
> +
> +    p = xen_map_table(page_to_mfn(pg));
> +    clear_page(p);
> +    xen_unmap_table(p);
> +
> +    pte = mfn_to_xen_entry(page_to_mfn(pg), MT_NORMAL);
> +    pte.pt.table = 1;
> +    write_pte(entry, pte);
> +
> +    return 0;
> +}
> +
>  #define XEN_TABLE_MAP_FAILED 0
>  #define XEN_TABLE_SUPER_PAGE 1
>  #define XEN_TABLE_NORMAL_PAGE 2
> -- 
> 2.17.1
> 


  reply	other threads:[~2021-05-12 22:45 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
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 [this message]
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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