Re: [Qemu-devel] [PATCH 6/6] kvm: Fix dirty tracking with large kernel page size

[Alexander Graf]

On 24.02.2012, at 01:23, David Gibson wrote:

> From: Benjamin Herrenschmidt <address@hidden>
> 
> If the kernel page size is larger than TARGET_PAGE_SIZE, which
> happens for example on ppc64 with kernels compiled for 64K pages,
> the dirty tracking doesn't work.
> 
> Cc: Avi Kivity <address@hidden>
> Cc: Marcelo Tossatti <address@hidden>
> 
> Signed-off-by: Benjamin Herrenschmidt <address@hidden>
> Signed-off-by: David Gibson <address@hidden>
> ---
> kvm-all.c |    7 ++++---
> 1 files changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/kvm-all.c b/kvm-all.c
> index 5e188bf..3f8cfd9 100644
> --- a/kvm-all.c
> +++ b/kvm-all.c
> @@ -348,10 +348,11 @@ static int kvm_set_migration_log(int enable)
> static int kvm_get_dirty_pages_log_range(MemoryRegionSection *section,
>                                          unsigned long *bitmap)
> {
> -    unsigned int i, j;
> +  unsigned int i, j;
>     unsigned long page_number, c;
>     target_phys_addr_t addr, addr1;
>     unsigned int len = ((section->size / TARGET_PAGE_SIZE) + HOST_LONG_BITS - 
> 1) / HOST_LONG_BITS;
> +    unsigned long hpratio = getpagesize() / TARGET_PAGE_SIZE;

Actually, looking at this, don't we rather want to cache hpratio? The way this 
is implemented, it would mean we'd do a sysctl for every call, right?


Alex