Re: [Xen-devel] [v3][PATCH 08/16] hvmloader/e820: construct guest e820 table

["Chen, Tiejun" <tiejun.chen@xxxxxxxxx>]

On 2015/6/11 17:59, Tian, Kevin wrote:
> > From: Chen, Tiejun
> > Sent: Thursday, June 11, 2015 9:15 AM
> >
> > Now we can use that memory map to build our final
> > e820 table but it may need to reorder all e820
> > entries.
> >
> > Signed-off-by: Tiejun Chen <tiejun.chen@xxxxxxxxx>
> > ---
> >   tools/firmware/hvmloader/e820.c | 62
> > +++++++++++++++++++++++++++++++----------
> >   1 file changed, 48 insertions(+), 14 deletions(-)
> >
> > diff --git a/tools/firmware/hvmloader/e820.c b/tools/firmware/hvmloader/e820.c
> > index 2e05e93..c39b0aa 100644
> > --- a/tools/firmware/hvmloader/e820.c
> > +++ b/tools/firmware/hvmloader/e820.c
> > @@ -73,7 +73,8 @@ int build_e820_table(struct e820entry *e820,
> >                        unsigned int lowmem_reserved_base,
> >                        unsigned int bios_image_base)
> >   {
> > -    unsigned int nr = 0;
> > +    unsigned int nr = 0, i, j;
> > +    uint64_t low_mem_pgend = hvm_info->low_mem_pgend << PAGE_SHIFT;
> You may call it low_mem_end to differentiate from original
> low_mem_pgend since one means actual address while the
> other means pfn.
Okay.

> >       if ( !lowmem_reserved_base )
> >               lowmem_reserved_base = 0xA0000;
> > @@ -117,13 +118,6 @@ int build_e820_table(struct e820entry *e820,
> >       e820[nr].type = E820_RESERVED;
> >       nr++;
> >
> > -    /* Low RAM goes here. Reserve space for special pages. */
> > -    BUG_ON((hvm_info->low_mem_pgend << PAGE_SHIFT) < (2u << 20));
> > -    e820[nr].addr = 0x100000;
> > -    e820[nr].size = (hvm_info->low_mem_pgend << PAGE_SHIFT) - e820[nr].addr;
> > -    e820[nr].type = E820_RAM;
> > -    nr++;
> > -
> >       /*
> >        * Explicitly reserve space for special pages.
> >        * This space starts at RESERVED_MEMBASE an extends to cover various
> > @@ -159,16 +153,56 @@ int build_e820_table(struct e820entry *e820,
> >           nr++;
> >       }
> >
> > -
> > -    if ( hvm_info->high_mem_pgend )
> > +    /*
> > +     * Construct the remaining according memory_map.
> "Construct E820 table according to recorded memory map"
Fixed.

> > +     *
> > +     * Note memory_map includes,
> The memory map created by toolstack may include:
Fixed.

> > +     *
> > +     * #1. Low memory region
> > +     *
> > +     * Low RAM starts at least from 1M to make sure all standard regions
> > +     * of the PC memory map, like BIOS, VGA memory-mapped I/O and vgabios,
> > +     * have enough space.
> > +     *
> > +     * #2. RDM region if it exists
> "Reserved regions if they exist"
Fixed.

> > +     *
> > +     * #3. High memory region if it exists
> > +     */
> > +    for ( i = 0; i < memory_map.nr_map; i++ )
> >       {
> > -        e820[nr].addr = ((uint64_t)1 << 32);
> > -        e820[nr].size =
> > -            ((uint64_t)hvm_info->high_mem_pgend << PAGE_SHIFT) - e820[nr].addr;
> > -        e820[nr].type = E820_RAM;
> > +        e820[nr] = memory_map.map[i];
> >           nr++;
> >       }
> >
> > +    /* Low RAM goes here. Reserve space for special pages. */
> > +    BUG_ON(low_mem_pgend < (2u << 20));
> > +    /*
> > +     * We may need to adjust real lowmem end since we may
> > +     * populate RAM to get enough MMIO previously.
> > +     */
> > +    for ( i = 0; i < memory_map.nr_map; i++ )
> since you already translate memory map into e820 earlier, here
> you should use 'nr' instead of memory_map.nr_map.
As we're saying in the code comment above, we're just handling the 
lowmem entry, so I think memory_map.nr_map is enough.
> > +    {
> > +        uint64_t end = e820[i].addr + e820[i].size;
> > +        if ( e820[i].type == E820_RAM &&
> > +             low_mem_pgend > e820[i].addr && low_mem_pgend < end )
> > +            e820[i].size = low_mem_pgend - e820[i].addr;
> > +    }
> Sorry I may miss the code but could you elaborate where the
> low_mem_pgend is changed after memory map is created? If
> it happens within hvmloader, suppose the amount of reduced
> memory from original E820_RAM entry should be added to
> another E820_RAM entry for highmem, right?
You're right so I really should compensate this in highmem entry,

    add_high_mem = end - low_mem_end;

    /*
     * And then we also need to adjust highmem.
     */
    if ( add_high_mem )
    {
        for ( i = 0; i < memory_map.nr_map; i++ )
        {
            if ( e820[i].type == E820_RAM &&
                 e820[i].addr > (1ull << 32))
                e820[i].size += add_high_mem;
        }
    }


Thanks
Tiejun

> > +
> > +    /* Finally we need to reorder all e820 entries. */
> > +    for ( j = 0; j < nr-1; j++ )
> > +    {
> > +        for ( i = j+1; i < nr; i++ )
> > +        {
> > +            if ( e820[j].addr > e820[i].addr )
> > +            {
> > +                struct e820entry tmp;
> > +                tmp = e820[j];
> > +                e820[j] = e820[i];
> > +                e820[i] = tmp;
> > +            }
> > +        }
> > +    }
> > +
> >       return nr;
> >   }
> >
> > --
> > 1.9.1
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