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Re: [Xen-devel] [V9 3/3] Differentiate IO/mem resources tracked by ioreq server

On 1/6/2016 4:59 PM, Jan Beulich wrote:
On 31.12.15 at 10:33, <yu.c.zhang@xxxxxxxxxxxxxxx> wrote:
On 12/21/2015 10:45 PM, Jan Beulich wrote:
On 15.12.15 at 03:05, <shuai.ruan@xxxxxxxxxxxxxxx> wrote:
--- a/xen/include/asm-x86/hvm/domain.h
+++ b/xen/include/asm-x86/hvm/domain.h
@@ -48,8 +48,8 @@ struct hvm_ioreq_vcpu {
       bool_t           pending;

-#define MAX_NR_IO_RANGES  256
+#define MAX_NR_IO_RANGES  8192

I'm sure I've objected before to this universal bumping of the limit:
Even if I were to withdraw my objection to the higher limit on the
new kind of tracked resource, I would continue to object to all
other resources getting their limits bumped too.

Hah. So how about we keep MAX_NR_IO_RANGES as 256, and use a new value,
say MAX_NR_WR_MEM_RANGES, set to 8192 in this patch? :)

That would at least limit the damage to the newly introduced type.
But I suppose you realize it would still be a resource consumption
concern. In order for this to not become a security issue, you
might e.g. stay with the conservative old limit and allow a command
line or even better guest config file override to it (effectively making
the admin state his consent with the higher resource use).

Thanks, Jan. I'll try to use the guest config file to set this limit. :)



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