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The PVH entrypoint is 32bit non-PIC code running the uncompressed vmlinux at its load address CONFIG_PHYSICAL_START - default 0x1000000 (16MB). The kernel is loaded at that physical address inside the VM by the VMM software (Xen/QEMU). When running a Xen PVH Dom0, the host reserved addresses are mapped 1-1 into the PVH container. There exist system firmwares (Coreboot/EDK2) with reserved memory at 16MB. This creates a conflict where the PVH kernel cannot be loaded at that address. Modify the PVH entrypoint to be position-indepedent to allow flexibility in load address. Only the 64bit entry path is converted. A 32bit kernel is not PIC, so calling into other parts of the kernel, like xen_prepare_pvh() and mk_pgtable_32(), don't work properly when relocated. This makes the code PIC, but the page tables need to be updated as well to handle running from the kernel high map. The UNWIND_HINT_END_OF_STACK is to silence: vmlinux.o: warning: objtool: pvh_start_xen+0x7f: unreachable instruction after the lret into 64bit code. Signed-off-by: Jason Andryuk <jason.andryuk@amd.com> Reviewed-by: Juergen Gross <jgross@suse.com> Message-ID: <20240823193630.2583107-3-jason.andryuk@amd.com> Signed-off-by: Juergen Gross <jgross@suse.com>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.