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Re: [Xen-devel] [PATCH] linux/x86-64: allow kernel init memory to be fre
| To: | Jan Beulich <jbeulich@xxxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx> |
|---|---|
| Subject: | Re: [Xen-devel] [PATCH] linux/x86-64: allow kernel init memory to be freed |
| From: | Keir Fraser <keir@xxxxxxxxxxxxx> |
| Date: | Fri, 02 Mar 2007 15:23:40 +0000 |
| Delivery-date: | Fri, 02 Mar 2007 07:22:58 -0800 |
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| Thread-topic: | [Xen-devel] [PATCH] linux/x86-64: allow kernel init memory to be freed |
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On 2/3/07 11:04, "Jan Beulich" <jbeulich@xxxxxxxxxx> wrote:
> + if (addr >= __START_KERNEL_map) {
> + /* make_readonly() reports all kernel addresses. */
> + __make_page_writable(__va(__pa(addr)));
> + __make_page_readonly((void *)addr);
> + }
I'm confused by this:
1. Why does the write-protection need to be changed unconditionally, or
even at all? Is there anything write-protected in the init sections?
2. Is it safe to keep init mappings above START_KERNEL_map at all, even
read-only? I'd have thought we'd be in trouble if the balloon driver manages
to allocate those pages and tries to free them to Xen. Perhaps they should
be blown away entirely?
-- Keir
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