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

Dave Young
2013-10-10T08:14:34Z

On 10/10/13 at 04:06pm, Dave Young wrote:
> 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.

Even though I still have no idea why kernel text overlap with efi boot
region, anyway map the un-overlapped part is necessary though.

I can post the kexec related patches after your mapping patches settle
down

>
> --- 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;
>
>