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Re: [Qemu-devel] [PATCH 3/4] exec, memory: Call to xen_modified_memory.

From: Avi Kivity
Subject: Re: [Qemu-devel] [PATCH 3/4] exec, memory: Call to xen_modified_memory.
Date: Tue, 17 Jul 2012 16:37:37 +0300
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:13.0) Gecko/20120615 Thunderbird/13.0.1

On 07/17/2012 04:30 PM, Anthony PERARD wrote:
> This patch add some calls to xen_modified_memory to notify Xen about dirtybits
> during migration.
> diff --git a/exec.c b/exec.c
> index c9fa17d..9f7a4f7 100644
> --- a/exec.c
> +++ b/exec.c
> @@ -3438,6 +3438,7 @@ void cpu_physical_memory_rw(target_phys_addr_t addr, 
> uint8_t *buf,
>                      cpu_physical_memory_set_dirty_flags(
>                          addr1, (0xff & ~CODE_DIRTY_FLAG));
>                  }
> +                xen_modified_memory(addr1, TARGET_PAGE_SIZE);
>                  qemu_put_ram_ptr(ptr);
>              }
>          } else {

This is pretty ugly.  An alternative is to set up a periodic bitmap scan
that looks at the qemu dirty bitmap and calls xen_modified_memory() for
dirty page ranges, and clears the bitmap for the next pass.  Is it workable?

(is xen_modified_memory a hypercall, or does it maintain an in-memory

error compiling committee.c: too many arguments to function

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