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Re: [Xen-devel] [PATCH v2 16/17] libxc/xc_dom_arm: Copy ACPI tables to guest space



Hi Shannon,

On 12/07/16 04:47, Shannon Zhao wrote:
On 2016/7/6 18:12, Stefano Stabellini wrote:
On Wed, 6 Jul 2016, Julien Grall wrote:
On 05/07/16 18:13, Stefano Stabellini wrote:
On Thu, 23 Jun 2016, Julien Grall wrote:
On 23/06/2016 04:17, Shannon Zhao wrote:
From: Shannon Zhao <shannon.zhao@xxxxxxxxxx>
+static int xc_dom_copy_acpi(struct xc_dom_image *dom)
+{
+    int rc, i;
+    uint32_t pages_num = ROUNDUP(dom->acpitable_size, XC_PAGE_SHIFT) >>
+                         XC_PAGE_SHIFT;
+    const xen_pfn_t base = GUEST_ACPI_BASE >> XC_PAGE_SHIFT;
+    xen_pfn_t *p2m;
+    void *acpi_pages;
+
+    p2m = malloc(pages_num * sizeof(*p2m));
+    for (i = 0; i < pages_num; i++)
+        p2m[i] = base + i;
+
+    rc = xc_domain_populate_physmap_exact(dom->xch, dom->guest_domid,
+                                          pages_num, 0, 0, p2m);

Hmmmm... it looks like this is working because libxl is setting the
maximum
size of the domain with some slack (1MB). However, I guess the slack was
for
something else. Wei, Stefano, Ian, can you confirm?

If I recall correctly, the slack is a magic value coming from the
ancient history of toolstacks.

Does it mean we would need to update the slack to take into account the ACPI
blob?
Yes, we need to take into account the ACPI blob. Probably not in the
slack but directly in mam_memkb.
Sorry, I'm not sure understand this. I found the b_info->max_memkb but
didn't find the slack you said. And how to fix this? Update
b_info->max_memkb or the slack?

You can give a look to LIBXL_MAXMEM_CONSTANT.

I am not very familiar with libxl, so I will let Wei and Stefano giving you advice on how to fix this.

Regards,

--
Julien Grall

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