Re: [Qemu-devel] [Xen-devel] [PATCH] increase maxmem before calling xc_domain_populate_physmap

[Andrew Cooper <andrew.cooper3@citrix.com>]

On 25/11/14 17:45, Stefano Stabellini wrote:
> Increase maxmem before calling xc_domain_populate_physmap_exact to avoid
> the risk of running out of guest memory. This way we can also avoid
> complex memory calculations in libxl at domain construction time.
>
> This patch fixes an abort() when assigning more than 4 NICs to a VM.
>
> Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
>
> diff --git a/xen-hvm.c b/xen-hvm.c
> index 5c69a8d..38e08c3 100644
> --- a/xen-hvm.c
> +++ b/xen-hvm.c
> @@ -218,6 +218,7 @@ void xen_ram_alloc(ram_addr_t ram_addr, ram_addr_t size, MemoryRegion *mr)
>      unsigned long nr_pfn;
>      xen_pfn_t *pfn_list;
>      int i;
> +    xc_dominfo_t info;
>  
>      if (runstate_check(RUN_STATE_INMIGRATE)) {
>          /* RAM already populated in Xen */
> @@ -240,6 +241,13 @@ void xen_ram_alloc(ram_addr_t ram_addr, ram_addr_t size, MemoryRegion *mr)
>          pfn_list[i] = (ram_addr >> TARGET_PAGE_BITS) + i;
>      }
>  
> +    if (xc_domain_getinfo(xen_xc, xen_domid, 1, &info) < 0) {

xc_domain_getinfo()'s interface is mad, and provides no guarantee that
it returns the information for the domain you requested.  It also won't
return -1 on error.  The correct error handing is:

(xc_domain_getinfo(xen_xc, xen_domid, 1, &info) != 1) || (info.domid !=
xen_domid)

~Andrew

> +        hw_error("xc_domain_getinfo failed");
> +    }
> +    if (xc_domain_setmaxmem(xen_xc, xen_domid, info.max_memkb +
> +                            (nr_pfn * XC_PAGE_SIZE / 1024)) < 0) {
> +        hw_error("xc_domain_setmaxmem failed");
> +    }
>      if (xc_domain_populate_physmap_exact(xen_xc, xen_domid, nr_pfn, 0, 0, pfn_list)) {
>          hw_error("xen: failed to populate ram at " RAM_ADDR_FMT, ram_addr);
>      }
>
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