Re: [Qemu-devel] [PULL] Urgent memory fix for kvm with unaligned memory slots

[Anthony Liguori]

On 03/01/2012 07:40 AM, Avi Kivity wrote:
> The memory core may generate RAM memory regions that are not page
> aligned, but the kvm code is not prepared to handle them well and will
> abort under certain conditions.  This patch fixes the problem.
>
> Please pull from:
>
>    git://git.kernel.org/pub/scm/virt/kvm/qemu-kvm.git memory/urgent

Pulled.  Thanks.

Regards,

Anthony Liguori

> ----------------------------------------------------------------
> Avi Kivity (1):
>        kvm: fix unaligned slots
>
>   kvm-all.c |   15 ++++++++++++---
>   1 files changed, 12 insertions(+), 3 deletions(-)
>
> diff --git a/kvm-all.c b/kvm-all.c
> index c4babda..4b7a4ae 100644
> --- a/kvm-all.c
> +++ b/kvm-all.c
> @@ -541,17 +541,26 @@ static void kvm_set_phys_mem(MemoryRegionSection
> *section, bool add)
>       target_phys_addr_t start_addr = section->offset_within_address_space;
>       ram_addr_t size = section->size;
>       void *ram = NULL;
> +    unsigned delta;
>
>       /* kvm works in page size chunks, but the function may be called
>          with sub-page size and unaligned start address. */
> -    size = TARGET_PAGE_ALIGN(size);
> -    start_addr = TARGET_PAGE_ALIGN(start_addr);
> +    delta = TARGET_PAGE_ALIGN(size) - size;
> +    if (delta>  size) {
> +        return;
> +    }
> +    start_addr += delta;
> +    size -= delta;
> +    size&= TARGET_PAGE_MASK;
> +    if (!size || (start_addr&  ~TARGET_PAGE_MASK)) {
> +        return;
> +    }
>
>       if (!memory_region_is_ram(mr)) {
>           return;
>       }
>
> -    ram = memory_region_get_ram_ptr(mr) + section->offset_within_region;
> +    ram = memory_region_get_ram_ptr(mr) + section->offset_within_region
> + delta;
>
>       while (1) {
>           mem = kvm_lookup_overlapping_slot(s, start_addr, start_addr +
> size);