Re: [Xen-devel] [PATCH v2 4/4] xen-all: Pass max_ram_below_4g to xen_hvm_init.

[Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>]

On Mon, 17 Mar 2014, Don Slutz wrote:
> On 03/16/14 12:10, Stefano Stabellini wrote:
> > On Tue, 11 Mar 2014, Don Slutz wrote:
> > > This is the xen part of "pc & q35: Add new object pc-memory-layout."
> > > 
> > > Signed-off-by: Don Slutz<dslutz@xxxxxxxxxxx>
> > > ---
> > >   hw/i386/pc_piix.c    |  4 ++--
> > >   hw/i386/pc_q35.c     |  4 ++--
> > >   include/hw/xen/xen.h |  4 ++--
> > >   xen-all.c            | 41 ++++++++++++++++++++++-------------------
> > >   xen-stub.c           |  4 ++--
> > >   5 files changed, 30 insertions(+), 27 deletions(-)
> > > 
> > > diff --git a/hw/i386/pc_piix.c b/hw/i386/pc_piix.c
> > > index 964ea33..691fc5d 100644
> > > --- a/hw/i386/pc_piix.c
> > > +++ b/hw/i386/pc_piix.c
> > > @@ -131,8 +131,8 @@ static void pc_init1(QEMUMachineInitArgs *args,
> > >           below_4g_mem_size = args->ram_size;
> > >       }
> > >   -    if (xen_enabled() && xen_hvm_init(&below_4g_mem_size,
> > > &above_4g_mem_size,
> > > -                                      &ram_memory) != 0) {
> > > +    if (xen_enabled() && xen_hvm_init(max_ram_below_4g,
> > > &below_4g_mem_size,
> > > +                                      &above_4g_mem_size, &ram_memory) !=
> > > 0) {
> > >           fprintf(stderr, "xen hardware virtual machine initialisation
> > > failed\n");
> > >           exit(1);
> > >       }
> > > diff --git a/hw/i386/pc_q35.c b/hw/i386/pc_q35.c
> > > index c95e6e2..8e1c417 100644
> > > --- a/hw/i386/pc_q35.c
> > > +++ b/hw/i386/pc_q35.c
> > > @@ -120,8 +120,8 @@ static void pc_q35_init(QEMUMachineInitArgs *args)
> > >           below_4g_mem_size = args->ram_size;
> > >       }
> > >   -    if (xen_enabled() && xen_hvm_init(&below_4g_mem_size,
> > > &above_4g_mem_size,
> > > -                                      &ram_memory) != 0) {
> > > +    if (xen_enabled() && xen_hvm_init(max_ram_below_4g,
> > > &below_4g_mem_size,
> > > +                                      &above_4g_mem_size, &ram_memory) !=
> > > 0) {
> > >           fprintf(stderr, "xen hardware virtual machine initialisation
> > > failed\n");
> > >           exit(1);
> > >       }
> > > diff --git a/include/hw/xen/xen.h b/include/hw/xen/xen.h
> > > index 0769db2..fda559a 100644
> > > --- a/include/hw/xen/xen.h
> > > +++ b/include/hw/xen/xen.h
> > > @@ -41,8 +41,8 @@ int xen_init(QEMUMachine *machine);
> > >   void xenstore_store_pv_console_info(int i, struct CharDriverState *chr);
> > >     #if defined(NEED_CPU_H) && !defined(CONFIG_USER_ONLY)
> > > -int xen_hvm_init(ram_addr_t *below_4g_mem_size, ram_addr_t
> > > *above_4g_mem_size,
> > > -                 MemoryRegion **ram_memory);
> > > +int xen_hvm_init(ram_addr_t max_ram_below_4g, ram_addr_t
> > > *below_4g_mem_size,
> > > +                 ram_addr_t *above_4g_mem_size, MemoryRegion
> > > **ram_memory);
> > >   void xen_ram_alloc(ram_addr_t ram_addr, ram_addr_t size,
> > >                      struct MemoryRegion *mr);
> > >   void xen_modified_memory(ram_addr_t start, ram_addr_t length);
> > > diff --git a/xen-all.c b/xen-all.c
> > > index c64300c..48ba335 100644
> > > --- a/xen-all.c
> > > +++ b/xen-all.c
> > > @@ -155,32 +155,34 @@ qemu_irq *xen_interrupt_controller_init(void)
> > >     /* Memory Ops */
> > >   -static void xen_ram_init(ram_addr_t *below_4g_mem_size,
> > > +static void xen_ram_init(ram_addr_t ram_size, ram_addr_t
> > > max_ram_below_4g,
> > > +                         ram_addr_t *below_4g_mem_size,
> > >                            ram_addr_t *above_4g_mem_size,
> > > -                         ram_addr_t ram_size, MemoryRegion
> > > **ram_memory_p)
> > > +                         MemoryRegion **ram_memory_p)
> > >   {
> > >       MemoryRegion *sysmem = get_system_memory();
> > >       ram_addr_t block_len;
> > >   -    block_len = ram_size;
> > > -    if (ram_size >= HVM_BELOW_4G_RAM_END) {
> > > -        /* Xen does not allocate the memory continuously, and keep a hole
> > > at
> > > -         * HVM_BELOW_4G_MMIO_START of HVM_BELOW_4G_MMIO_LENGTH
> > > -         */
> > > -        block_len += HVM_BELOW_4G_MMIO_LENGTH;
> > > +    if (!max_ram_below_4g) {
> > > +        if (ram_size >= HVM_BELOW_4G_RAM_END) {
> > > +            *above_4g_mem_size = ram_size - HVM_BELOW_4G_RAM_END;
> > > +            *below_4g_mem_size = HVM_BELOW_4G_RAM_END;
> > > +        } else {
> > > +            *above_4g_mem_size = 0;
> > > +            *below_4g_mem_size = ram_size;
> > > +        }
> > > +    }
> > Instead of treating max_ram_below_4g as a special case, couldn't
> > initialize it to HVM_BELOW_4G_RAM_END?
> 
> Since max_ram_below_4g is used and initialize in normal QEMU code
> where HVM_BELOW_4G_RAM_END is not defined, I do not see how to
> do this outside of this routine without adding a new routine for this.
 
You can simply do this at the beginning of xen_ram_init:

max_ram_below_4g = max_ram_below_4g ? max_ram_below_4g : HVM_BELOW_4G_RAM_END;

my comment was about code readability, I didn't mean change any
functionalities.

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