Re: [PATCH 04/10] xen/arm: static memory initialization

[Julien Grall <julien@xxxxxxx>]

Hi Penny,

On 18/05/2021 06:21, Penny Zheng wrote:
> This patch introduces static memory initialization, during system RAM boot up.
>
> New func init_staticmem_pages is the equivalent of init_heap_pages, responsible
> for static memory initialization.
>
> Helper func free_staticmem_pages is the equivalent of free_heap_pages, to free
> nr_pfns pages of static memory.
> For each page, it includes the following steps:
> 1. change page state from in-use(also initialization state) to free state and
> grant PGC_reserved.
> 2. set its owner NULL and make sure this page is not a guest frame any more
> 3. follow the same cache coherency policy in free_heap_pages
> 4. scrub the page in need
>
> Signed-off-by: Penny Zheng <penny.zheng@xxxxxxx>
> ---
>   xen/arch/arm/setup.c    |  2 ++
>   xen/common/page_alloc.c | 70 +++++++++++++++++++++++++++++++++++++++++
>   xen/include/xen/mm.h    |  3 ++
>   3 files changed, 75 insertions(+)
>
> diff --git a/xen/arch/arm/setup.c b/xen/arch/arm/setup.c
> index 444dbbd676..f80162c478 100644
> --- a/xen/arch/arm/setup.c
> +++ b/xen/arch/arm/setup.c
> @@ -818,6 +818,8 @@ static void __init setup_mm(void)
>   
>       setup_frametable_mappings(ram_start, ram_end);
>       max_page = PFN_DOWN(ram_end);
> +
> +    init_staticmem_pages();
>   }
>   #endif
>   
> diff --git a/xen/common/page_alloc.c b/xen/common/page_alloc.c
> index ace6333c18..58b53c6ac2 100644
> --- a/xen/common/page_alloc.c
> +++ b/xen/common/page_alloc.c
> @@ -150,6 +150,9 @@
>   #define p2m_pod_offline_or_broken_hit(pg) 0
>   #define p2m_pod_offline_or_broken_replace(pg) BUG_ON(pg != NULL)
>   #endif
> +#ifdef CONFIG_ARM_64
> +#include <asm/setup.h>
> +#endif
>   
>   /*
>    * Comma-separated list of hexadecimal page numbers containing bad bytes.
> @@ -1512,6 +1515,49 @@ static void free_heap_pages(
>       spin_unlock(&heap_lock);
>   }
>   
> +/* Equivalent of free_heap_pages to free nr_pfns pages of static memory. */
> +static void free_staticmem_pages(struct page_info *pg, unsigned long nr_pfns,
This function is dealing with MFNs, so the second parameter should be 
called nr_mfns.
> +                                 bool need_scrub)
> +{
> +    mfn_t mfn = page_to_mfn(pg);
> +    int i;
> +
> +    for ( i = 0; i < nr_pfns; i++ )
> +    {
> +        switch ( pg[i].count_info & PGC_state )
> +        {
> +        case PGC_state_inuse:
> +            BUG_ON(pg[i].count_info & PGC_broken);
> +            /* Make it free and reserved. */
> +            pg[i].count_info = PGC_state_free | PGC_reserved;
> +            break;
> +
> +        default:
> +            printk(XENLOG_ERR
> +                   "Page state shall be only in PGC_state_inuse. "
> +                   "pg[%u] MFN %"PRI_mfn" count_info=%#lx 
> tlbflush_timestamp=%#x.\n",
> +                   i, mfn_x(mfn) + i,
> +                   pg[i].count_info,
> +                   pg[i].tlbflush_timestamp);
> +            BUG();
> +        }
> +
> +        /*
> +         * Follow the same cache coherence scheme in free_heap_pages.
> +         * If a page has no owner it will need no safety TLB flush.
> +         */
> +        pg[i].u.free.need_tlbflush = (page_get_owner(&pg[i]) != NULL);
> +        if ( pg[i].u.free.need_tlbflush )
> +            page_set_tlbflush_timestamp(&pg[i]);
> +
> +        /* This page is not a guest frame any more. */
> +        page_set_owner(&pg[i], NULL);
> +        set_gpfn_from_mfn(mfn_x(mfn) + i, INVALID_M2P_ENTRY);
The code looks quite similar to free_heap_pages(). Could we possibly 
create an helper which can be called from both?
> +
> +        if ( need_scrub )
> +            scrub_one_page(&pg[i]);
So the scrubbing will be synchronous. Is it what we want?

You also seem to miss the flush the call to flush_page_to_ram().

> +    }
> +}
>   
>   /*
>    * Following rules applied for page offline:
> @@ -1828,6 +1874,30 @@ static void init_heap_pages(
>       }
>   }
>   
> +/* Equivalent of init_heap_pages to do static memory initialization */
> +void __init init_staticmem_pages(void)
> +{
> +    int bank;
> +
> +    /*
> +     * TODO: Considering NUMA-support scenario.
> +     */
> +    for ( bank = 0 ; bank < bootinfo.static_mem.nr_banks; bank++ )
bootinfo is arm specific, so this code should live in arch/arm rather 
than common/.
> +    {
> +        paddr_t bank_start = bootinfo.static_mem.bank[bank].start;
> +        paddr_t bank_size = bootinfo.static_mem.bank[bank].size;
> +        paddr_t bank_end = bank_start + bank_size;
> +
> +        bank_start = round_pgup(bank_start);
> +        bank_end = round_pgdown(bank_end);
> +        if ( bank_end <= bank_start )
> +            return;
> +
> +        free_staticmem_pages(maddr_to_page(bank_start),
> +                            (bank_end - bank_start) >> PAGE_SHIFT, false);
> +    }
> +}
> +
>   static unsigned long avail_heap_pages(
>       unsigned int zone_lo, unsigned int zone_hi, unsigned int node)
>   {
> diff --git a/xen/include/xen/mm.h b/xen/include/xen/mm.h
> index 667f9dac83..8b1a2207b2 100644
> --- a/xen/include/xen/mm.h
> +++ b/xen/include/xen/mm.h
> @@ -85,6 +85,9 @@ bool scrub_free_pages(void);
>   } while ( false )
>   #define FREE_XENHEAP_PAGE(p) FREE_XENHEAP_PAGES(p, 0)
>   
> +/* Static Memory */
> +void init_staticmem_pages(void);
> +
>   /* Map machine page range in Xen virtual address space. */
>   int map_pages_to_xen(
>       unsigned long virt,
Cheers,

--
Julien Grall