Re: kexec regression since 4.9 caused by efi

Dave Young
2017-03-17T02:09:51Z

On 03/16/17 at 12:41pm, Matt Fleming wrote:
> On Mon, 13 Mar, at 03:37:48PM, Dave Young wrote:
> >
> > Omar, could you try below patch? Looking at the efi_mem_desc_lookup, it is not
> > correct to be used in efi_arch_mem_reserve, if it passed your test, I
> > can rewrite patch log with more background and send it out:
> >
> > for_each_efi_memory_desc(md) {
> > [snip]
> > if (!(md->attribute & EFI_MEMORY_RUNTIME) &&
> > md->type != EFI_BOOT_SERVICES_DATA &&
> > md->type != EFI_RUNTIME_SERVICES_DATA) {
> > continue;
> > }
> >
> > In above code, it meant to get a md of EFI_MEMORY_RUNTIME of either boot
> > data or runtime data, this is wrong for efi_mem_reserve, because we are
> > reserving boot data which has no EFI_MEMORY_RUNTIME attribute at the
> > running time. Just is happened to work and we did not capture the error.
>
> Wouldn't something like this be simpler?
>
> ---
>
> diff --git a/arch/x86/platform/efi/quirks.c b/arch/x86/platform/efi/quirks.c
> index 30031d5293c4..cdfe8c628959 100644
> --- a/arch/x86/platform/efi/quirks.c
> +++ b/arch/x86/platform/efi/quirks.c
> @@ -201,6 +201,10 @@ void __init efi_arch_mem_reserve(phys_addr_t addr, u64 size)
> return;
> }
>
> + /* No need to reserve regions that will never be freed. */
> + if (md.attribute & EFI_MEMORY_RUNTIME)
> + return;
> +

Matt, I think it should be fine although I think the md type checking in
efi_mem_desc_lookup() is causing confusion and not easy to understand..

How about move the if chunk early like below because it seems no need
to sanity check the addr + size any more if the md is still RUNTIME?

--- linux-x86.orig/arch/x86/platform/efi/quirks.c
+++ linux-x86/arch/x86/platform/efi/quirks.c
@@ -196,6 +196,10 @@ void __init efi_arch_mem_reserve(phys_ad
return;
}

+ /* No need to reserve regions that will never be freed. */
+ if (md.attribute & EFI_MEMORY_RUNTIME)
+ return;
+
if (addr + size > md.phys_addr + (md.num_pages << EFI_PAGE_SHIFT)) {
pr_err("Region spans EFI memory descriptors, %pa\n", &addr);
return;

Thanks
Dave