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Re: [PATCH] tools/init-xenstore-domain: fix memory map for PVH stubdom



On 07.07.22 16:45, Anthony PERARD wrote:
On Fri, Jun 24, 2022 at 11:28:06AM +0200, Juergen Gross wrote:
In case of maxmem != memsize the E820 map of the PVH stubdom is wrong,
as it is missing the RAM above memsize.

Additionally the MMIO area should only cover the HVM special pages.

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
  tools/helpers/init-xenstore-domain.c | 16 ++++++++++------
  1 file changed, 10 insertions(+), 6 deletions(-)

diff --git a/tools/helpers/init-xenstore-domain.c 
b/tools/helpers/init-xenstore-domain.c
index b4f3c65a8a..dad8e43c42 100644
--- a/tools/helpers/init-xenstore-domain.c
+++ b/tools/helpers/init-xenstore-domain.c
@@ -157,21 +158,24 @@ static int build(xc_interface *xch)
          config.flags |= XEN_DOMCTL_CDF_hvm | XEN_DOMCTL_CDF_hap;
          config.arch.emulation_flags = XEN_X86_EMU_LAPIC;
          dom->target_pages = mem_size >> XC_PAGE_SHIFT;
-        dom->mmio_size = GB(4) - LAPIC_BASE_ADDRESS;
+        dom->mmio_size = X86_HVM_NR_SPECIAL_PAGES << XC_PAGE_SHIFT;
          dom->lowmem_end = (mem_size > LAPIC_BASE_ADDRESS) ?
                            LAPIC_BASE_ADDRESS : mem_size;
          dom->highmem_end = (mem_size > LAPIC_BASE_ADDRESS) ?
                             GB(4) + mem_size - LAPIC_BASE_ADDRESS : 0;
-        dom->mmio_start = LAPIC_BASE_ADDRESS;
+        dom->mmio_start = (X86_HVM_END_SPECIAL_REGION -
+                           X86_HVM_NR_SPECIAL_PAGES) << XC_PAGE_SHIFT;
          dom->max_vcpus = 1;
          e820[0].addr = 0;
-        e820[0].size = dom->lowmem_end;
+        e820[0].size = (max_size > LAPIC_BASE_ADDRESS) ?
+                       LAPIC_BASE_ADDRESS : max_size;
          e820[0].type = E820_RAM;
-        e820[1].addr = LAPIC_BASE_ADDRESS;
+        e820[1].addr = dom->mmio_start;


So, it isn't expected to have an entry covering the LAPIC addresses,
right? I guess not as seen in df1ca1dfe20.

But based on that same commit info, shouldn't the LAPIC address part of
`dom->mmio_start, dom->mmio_size`? (I don't know how dom->mmio_start is
used, yet, but maybe it's used by Xen or xen libraries to avoid
allocations in the wrong places)

In my understanding this is the purpose of lowmem_end.

OTOH I can modify the patch to be along the lines of df1ca1dfe20.


Juergen

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