Re: [PATCH 12/12] EFI: Runtime services virtual mapping

Dave Young
2013-10-10T08:07:19Z

On 10/08/13 at 06:48pm, Borislav Petkov wrote:
> From: Borislav Petkov <bp@suse.de>
>
> We map the EFI regions needed for runtime services contiguously on
> virtual addresses starting from -4G down for a total max space of 64G.
> This way, we provide for stable runtime services addresses across
> kernels so that a kexec'd kernel can still use them.
>
> This way, they're mapped in a separate pagetable so that we don't
> pollute the kernel namespace (you can see how the whole ioremapping and
> saving and restoring of PGDs is gone now).
>
> Also, add a chicken bit called "efi=old_map" which can be used as a
> fallback to the old runtime services mapping method in case there's some
> b0rkage with a particular EFI implementation (haha, it is hard to hold
> up the sarcasm here...).
>
> Add UEFI RT VA space to Documentation/x86/x86_64/mm.txt, while at it.
>

Tested this new patch, the kexec kernel still get different mappings.
Same reason, in first kernel reserve boot service function the size is
set to 0.

With a little hack patch below (upon my previous test patches for kexec)
kexec and kdump works ok in qemu/ovmf, still not tried on real hardware.

--- bp.orig/arch/x86/platform/efi/efi.c
+++ bp/arch/x86/platform/efi/efi.c
@@ -445,10 +445,18 @@ static void __init print_efi_memmap(void
#endif /* EFI_DEBUG */
}

+static bool inline overlap_with_ktext(u64 start, u64 size)
+{
+ return (start + size >= __pa_symbol(_text)
+ && start <= __pa_symbol(_end));
+}
+
void __init efi_reserve_boot_services(void)
{
void *p;

+ if (kexecboot)
+ return;
for (p = memmap.map; p < memmap.map_end; p += memmap.desc_size) {
efi_memory_desc_t *md = p;
u64 start = md->phys_addr;
@@ -463,13 +471,16 @@ void __init efi_reserve_boot_services(vo
* - Not within any part of the kernel
* - Not the bios reserved area
*/
- if ((start+size >= __pa_symbol(_text)
- && start <= __pa_symbol(_end)) ||
+ if (overlap_with_ktext(start, size) ||
!e820_all_mapped(start, start+size, E820_RAM) ||
memblock_is_region_reserved(start, size)) {
/* Could not reserve, skip it */
- md->num_pages = 0;
- memblock_dbg("Could not reserve boot range "
+ if (overlap_with_ktext(start, size)) {
+ u64 s = __pa_symbol(_text) - start;
+ memblock_reserve(start, s);
+ } else
+ md->num_pages = 0;
+ memblock_dbg("Could not reserve whole boot range "
"[0x%010llx-0x%010llx]\n",
start, start+size-1);
} else
@@ -490,6 +501,8 @@ void __init efi_free_boot_services(void)
{
void *p;

+ if (kexecboot)
+ return;
if (!efi_is_native())
return;