Re: [Qemu-devel] [PATCH] kvmvapic: align start address as well as size

[Jan Kiszka <jan.kiszka@siemens.com>]

On 2012-03-06 16:50, Avi Kivity wrote:
> The kvmvapic code remaps a section of ROM as RAM to allow the guest to
> maintain state there.  It is careful to align the section size to a page
> boundary, to avoid creating subpages, but neglects to do the same for
> the start address.  These leads to an assert later on when the memory
> core tries to create a page which is half RAM and half ROM.
> 
> Fix by aligning the start address to a page boundary.
> 
> This can be triggered by running qemu-system-x86_64 -enable-kvm -vga none.
> 
> Signed-off-by: Avi Kivity <avi@redhat.com>
> ---
>  hw/kvmvapic.c |    4 +++-
>  1 files changed, 3 insertions(+), 1 deletions(-)
> 
> diff --git a/hw/kvmvapic.c b/hw/kvmvapic.c
> index 36ccfbc..e8bfeec 100644
> --- a/hw/kvmvapic.c
> +++ b/hw/kvmvapic.c
> @@ -578,8 +578,10 @@ static void vapic_map_rom_writable(VAPICROMState *s)
>      rom_size = ram[rom_paddr + 2] * ROM_BLOCK_SIZE;
>      s->rom_size = rom_size;
>  
> -    /* We need to round up to avoid creating subpages
> +    /* We need to round to avoid creating subpages
>       * from which we cannot run code. */
> +    rom_size += rom_paddr & ~TARGET_PAGE_MASK;
> +    rom_paddr &= TARGET_PAGE_MASK;
>      rom_size = TARGET_PAGE_ALIGN(rom_size);
>  
>      memory_region_init_alias(&s->rom, "kvmvapic-rom", section.mr, rom_paddr,

Reviewed-by: Jan Kiszka <jan.kiszka@siemens.com>

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