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Re: [PATCH v2 3/3] x86/PVH: Support relocatable dom0 kernels
- To: Jan Beulich <jbeulich@xxxxxxxx>
- From: Jason Andryuk <jason.andryuk@xxxxxxx>
- Date: Mon, 18 Mar 2024 17:19:32 -0400
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- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, George Dunlap <george.dunlap@xxxxxxxxxx>, Julien Grall <julien@xxxxxxx>, Stefano Stabellini <sstabellini@xxxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Mon, 18 Mar 2024 21:19:48 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 2024-03-14 10:19, Jan Beulich wrote:
On 14.03.2024 15:13, Jason Andryuk wrote:
On 2024-03-14 09:21, Jan Beulich wrote:
On 13.03.2024 20:30, Jason Andryuk wrote:
--- a/xen/include/public/elfnote.h
+++ b/xen/include/public/elfnote.h
@@ -194,6 +194,17 @@
*/
#define XEN_ELFNOTE_PHYS32_ENTRY 18
+/*
+ * Physical loading constraints for PVH kernels
+ *
+ * Used to place constraints on the guest physical loading addresses and
+ * alignment for a PVH kernel. This note's value is 3 64bit values in
+ * the following order: minimum, maximum and alignment.
Along the lines of what I said on another sub-thread, I think at least
alignment wants to be optional here. Perhaps, with max going first, min
could also be optional.
Interesting idea.
As indicated in different context by Roger, the values being uniformly
64-bit ones also is questionable.
+ * The presence of this note indicates the kernel is relocatable.
I think it wants making explicit here that the act of relocating is still
left to the kernel.
Ok.
How is this for a new description?
"""
Physical loading constraints for PVH kernels
Used to place constraints on the guest physical loading addresses and
alignment for a PVH kernel.
The presence of this note indicates the kernel supports relocating itself.
The note may include up to three 32bit values.
I'm as unsure about always 32-bit as I am on it being uniformly 64-bit.
One question here is whether this note is intended to be x86-specific.
- a maximum address for the entire image to be loaded below (default
0xfffffff)
One f too few?
Whoops - yes.
- a minimum address for the start of the image (default 0)
- a required start alignment (default 1)
Jan, in the discussion of patch 1, you wrote "Hmm, shouldn't the order
of attempts to figure the alignment be ELF note, ELF header, and then
2Mb?" My latest revision initializes phys_alignment to 1 and updates
that if PHYS32_RELOC specifies an alignment. Do you still want these
other locations checked for alignment values?
Regards,
Jason
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