Re: [Xen-devel] [RFC PATCH V3 2/2] qemu: support xen hvm direct kernel boot

["Chun Yan Liu" <cyliu@xxxxxxxx>]

>>> On 6/23/2014 at 06:14 PM, in message
<alpine.DEB.2.02.1406231110050.19982@xxxxxxxxxxxxxxxxxxxxxxx>, Stefano
Stabellini <stefano.stabellini@xxxxxxxxxxxxx> wrote: 
> On Sun, 22 Jun 2014, Chun Yan Liu wrote: 
> > >>> On 6/20/2014 at 08:08 PM, in message 
> > <alpine.DEB.2.02.1406201300410.6594@xxxxxxxxxxxxxxxxxxxxxxx>, Stefano 
> > Stabellini <stefano.stabellini@xxxxxxxxxxxxx> wrote:  
> > > On Fri, 20 Jun 2014, Chunyan Liu wrote:  
> > > > qemu side patch to support xen HVM direct kernel boot:  
> > > > if -kernel exists, calls xen_load_linux(), which will read 
> > > > kernel/initrd  
> > > > and add a linuxboot.bin or multiboot.bin option rom. The  
> > > > linuxboot.bin/multiboot.bin will load kernel/initrd and jump to execute 
> > > >  
> > > > kernel directly. It's working when xen uses seabios.  
> > > >   
> > > > Signed-off-by: Chunyan Liu <cyliu@xxxxxxxx>  
> > > > ---  
> > > >  hw/i386/pc.c           | 22 ++++++++++++++++++++++  
> > > >  hw/i386/pc_piix.c      |  7 +++++++  
> > > >  hw/i386/xen/xen_apic.c |  1 +  
> > > >  include/hw/i386/pc.h   |  5 +++++  
> > > >  4 files changed, 35 insertions(+)  
> > > >   
> > > > diff --git a/hw/i386/pc.c b/hw/i386/pc.c  
> > > > index 3e0ecf1..e005136 100644  
> > > > --- a/hw/i386/pc.c  
> > > > +++ b/hw/i386/pc.c  
> > > > @@ -1183,6 +1183,28 @@ void pc_acpi_init(const char *default_dsdt)  
> > > >      }  
> > > >  }  
> > > >    
> > > > +FWCfgState *xen_load_linux(const char *kernel_filename,  
> > > > +                           const char *kernel_cmdline,  
> > > > +                           const char *initrd_filename,  
> > > > +                           ram_addr_t below_4g_mem_size,  
> > > > +                           PcGuestInfo *guest_info)  
> > > > +{  
> > > > +    int i;  
> > > > +    FWCfgState *fw_cfg;  
> > > > +  
> > > > +    assert(kernel_filename != NULL);  
> > > > +  
> > > > +    fw_cfg = fw_cfg_init(BIOS_CFG_IOPORT, BIOS_CFG_IOPORT + 1, 0, 0);  
> > >   
> > > Is it actually OK to initialize just BIOS_CFG_IOPORT and avoid  
> > > everything else currently done in bochs_bios_init?  
> > > Would it make sense to simply call bochs_bios_init?  
> > >   
> > >   
> > > > +    rom_set_fw(fw_cfg);  
> > > > +  
> > > > +    load_linux(fw_cfg, kernel_filename, initrd_filename, 
> > > > kernel_cmdline,  
>   
> > > below_4g_mem_size);  
> > > > +    for (i = 0; i < nb_option_roms; i++) {  
> > > > +        rom_add_option(option_rom[i].name, option_rom[i].bootindex);  
> > > > +    }  
> > >   
> > > Wouldn't this have the unintended consequence of possibly loading other  
> > > option_roms into the guest memory?  
> >  
> > For xen, no. 
> >  
> > Before this patch, indeed there is another option_rom "kvmvapic" in the  
> list, 
> > but since the option_rom list is never loaded in xen case, that won't harm. 
> >  
> But 
> > as expected, I think in xen case, it should not be in option_rom list at  
> all, since 
> > we won't expect to load it. In v1, I tried to check the option_rom name to 
> > bypass it and load multiboot.bin/linuxboot.bin only. 
> >  
> > In comments, Paolo Bonzini suggests a better way, that is to add following  
> line 
> > in xen_apic_realize(): 
> > + s->vapic_control = 0; 
> > In this way, "kvmvapic" won't be added to the option_rom list. I think that 
> > should be the normal way for xen. 
> >  
> > So, since V2, I updated in this way. 
> > http://lists.gnu.org/archive/html/qemu-devel/2014-06/msg00704.html 
>  
> I see. Paolo's suggestion is a good one. 
>  
> I would add an assert here to ensure that there is only one option 
> rom named "linuxboot.bin", so that we can easily spot if something in 
> the future breaks our assumptions. 

Yes, that's better. Will update. Thanks!

>  
>  
> > >   
> > >   
> > > > +    guest_info->fw_cfg = fw_cfg;  
> > > > +    return fw_cfg;  
> > > > +}  
> > > > +  
> > > >  FWCfgState *pc_memory_init(MemoryRegion *system_memory,  
> > > >                             const char *kernel_filename,  
> > > >                             const char *kernel_cmdline,  
> > > > diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c  
> > > > index a48e263..b737868 100644  
> > > > --- a/hw/i386/pc_piix.c  
> > > > +++ b/hw/i386/pc_piix.c  
> > > > @@ -158,6 +158,13 @@ static void pc_init1(MachineState *machine,  
> > > >                         machine->initrd_filename,  
> > > >                         below_4g_mem_size, above_4g_mem_size,  
> > > >                         rom_memory, &ram_memory, guest_info);  
> > > > +    } else if (machine->kernel_filename != NULL) {  
> > > > +        /* For xen HVM direct kernel boot, load linux here */  
> > > > +        fw_cfg = xen_load_linux(machine->kernel_filename,  
> > > > +                                machine->kernel_cmdline,  
> > > > +                                machine->initrd_filename,  
> > > > +                                below_4g_mem_size,  
> > > > +                                guest_info);  
> > > >      }  
> > > >    
> > > >      gsi_state = g_malloc0(sizeof(*gsi_state));  
> > > > diff --git a/hw/i386/xen/xen_apic.c b/hw/i386/xen/xen_apic.c  
> > > > index 63bb7f7..f5acd6a 100644  
> > > > --- a/hw/i386/xen/xen_apic.c  
> > > > +++ b/hw/i386/xen/xen_apic.c  
> > > > @@ -40,6 +40,7 @@ static void xen_apic_realize(DeviceState *dev, Error  
> > > >  
> > > **errp)  
> > > >  {  
> > > >      APICCommonState *s = APIC_COMMON(dev);  
> > > >    
> > > > +    s->vapic_control = 0;  
> > > >      memory_region_init_io(&s->io_memory, OBJECT(s), &xen_apic_io_ops, 
> > > > s,  
> > > >                            "xen-apic-msi", APIC_SPACE_SIZE);  
> > >   
> > > Why this change? It is not mentioned in the commit message.  
> > >   
> > >   
> > > > diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h  
> > > > index ca7a0bd..171a597 100644  
> > > > --- a/include/hw/i386/pc.h  
> > > > +++ b/include/hw/i386/pc.h  
> > > > @@ -134,6 +134,11 @@ PcGuestInfo *pc_guest_info_init(ram_addr_t   
> > > below_4g_mem_size,  
> > > >  void pc_pci_as_mapping_init(Object *owner, MemoryRegion 
> > > > *system_memory,  
> > > >                              MemoryRegion *pci_address_space);  
> > > >    
> > > > +FWCfgState *xen_load_linux(const char *kernel_filename,  
> > > > +                           const char *kernel_cmdline,  
> > > > +                           const char *initrd_filename,  
> > > > +                           ram_addr_t below_4g_mem_size,  
> > > > +                           PcGuestInfo *guest_info);  
> > > >  FWCfgState *pc_memory_init(MemoryRegion *system_memory,  
> > > >                             const char *kernel_filename,  
> > > >                             const char *kernel_cmdline,  
> > > > --   
> > > > 1.8.4.5  
> > > >   
> > >   
> > > _______________________________________________  
> > > Xen-devel mailing list  
> > > Xen-devel@xxxxxxxxxxxxx  
> > > http://lists.xen.org/xen-devel  
> > >   
> > >   
> >  
>  
>  


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