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Date: Wed, 08 Dec 2010 12:23:12 -0600
From: Anthony Liguori <aliguori@linux.vnet.ibm.com>
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Subject: [Qemu-devel] Re: [PATCH] Fix segfault with ram_size > 4095M without
	kvm
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To: Luiz Capitulino <lcapitulino@redhat.com>
Cc: ryanh@linux.vnet.ibm.com, amit.shah@redhat.com, Anthony Liguori <aliguori@us.ibm.com>, qemu-devel@nongnu.org, aurelien@aurel32.net

On 12/08/2010 12:01 PM, Luiz Capitulino wrote:
> Currently, x86_64-softmmu qemu segfaults when trying to use>  4095M memsize.
> This patch adds a simple check and error message (much like the 2047 limit on
> 32-bit hosts) on ram_size in the control path after we determine we're
> not using kvm
>
> Upstream qemu-kvm is affected if using the -no-kvm option; this patch address
> the segfault there as well.
>
> Signed-off-by: Ryan Harper<ryanh@us.ibm.com>
> Signed-off-by: Aurelien Jarno<aurelien@aurel32.net>
> ---
> NOTE: this patch was applied in the v0.12.x branch, but it seems it got
>        lost for master
>    

No, it was intentional.  We should fix the segv, this is not a known 
limitation but rather a bug.

Regards,

Anthony Liguori

>   vl.c |    6 ++++++
>   1 files changed, 6 insertions(+), 0 deletions(-)
>
> diff --git a/vl.c b/vl.c
> index 2dbb6db..bb9c21c 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -5792,6 +5792,12 @@ int main(int argc, char **argv, char **envp)
>               fprintf(stderr, "failed to initialize KVM\n");
>               exit(1);
>           }
> +    } else {
> +        /* without kvm enabled, we can only support 4095 MB RAM */
> +        if (ram_size>  (4095UL<<  20)) {
> +            fprintf(stderr, "qemu: without kvm support at most 4095 MB RAM can be simulated\n");
> +            exit(1);
> +        }
>       }
>
>       if (qemu_init_main_loop()) {
>