Re: [Qemu-devel] [PATCH] fix xen hvm direct kernel boot

[Chun Yan Liu]

>>> On 5/31/2016 at 12:10 AM, in message
<address@hidden>, Stefano
Stabellini <address@hidden> wrote: 
> On Fri, 29 Apr 2016, Chunyan Liu wrote: 
> > Since commit a1666142: acpi-build: make ROMs RAM blocks resizeable, 
> > xen HVM direct kernel boot failed. Xen HVM direct kernel boot will 
> > insert a linuxboot.bin or multiboot.bin to /genroms, before this 
> > commit, in acpi_setup, for rom linuxboot.bin/multiboot.bin, it 
> > only needs 0x20000 size; after the commit, it will reserve x16 
> > size for resize, that is 0x200000 size. It causes xen_ram_alloc 
> > failed due to running out of memory. 
> >  
> > To resolve it, either: 
> > 1. keep using original rom size instead of max size, don't reserve x16  
> size. 
> > 2. guest maxmem needs to be increased. (commit c1d322e6 "xen-hvm: increase 
> >    maxmem before calling xc_domain_populate_physmap" solved the problem for 
> >    a time, by accident. But then it is reverted in commit ffffbb369 due to 
> >    other problem.) 
> >  
> > For 2, more discussion is needed about howto. So this patch tries 1, to 
> > use unresizable rom size in xen case in rom_set_mr. 
> >  
> > Signed-off-by: Chunyan Liu <address@hidden> 
>  
> Thank you for the patch! 
>  
>  
> >  hw/core/loader.c | 6 +++++- 
> >  1 file changed, 5 insertions(+), 1 deletion(-) 
> >  
> > diff --git a/hw/core/loader.c b/hw/core/loader.c 
> > index c049957..5150101 100644 
> > --- a/hw/core/loader.c 
> > +++ b/hw/core/loader.c 
> > @@ -55,6 +55,7 @@ 
> >  #include "exec/address-spaces.h" 
> >  #include "hw/boards.h" 
> >  #include "qemu/cutils.h" 
> > +#include "hw/xen/xen.h" 
> >   
> >  #include <zlib.h> 
> >   
> > @@ -818,7 +819,10 @@ static void *rom_set_mr(Rom *rom, Object *owner, const 
> >  
> char *name) 
> >      void *data; 
> >   
> >      rom->mr = g_malloc(sizeof(*rom->mr)); 
> > -    memory_region_init_resizeable_ram(rom->mr, owner, name, 
> > +    if (xen_enabled()) 
> > +        memory_region_init_ram(rom->mr, owner, name, rom->datasize,  
> &error_fatal); 
> > +    else 
> > +        memory_region_init_resizeable_ram(rom->mr, owner, name, 
> >                                        rom->datasize, rom->romsize, 
> >                                        fw_cfg_resized, 
> >                                        &error_fatal); 
>  
> Wouldn't it be better to change ram_block_add so that it calls 
> xen_ram_alloc with used_length rather than max_length? 

Seems that's right. But after that changes, when doing direct kernel boot,
it reports:
qemu-system-x86_64: /home/cyliu/git/qemu/include/exec/ram_addr.h:48:
ramblock_ptr: Assertion `offset_in_ramblock(block, offset)' failed.

Looking at it.

Chunyan
>  
> I think that on Xen we want to only allocate used_length bytes, but 
> reserve max_length of address space. 
>  
>  
>