linux-kernel - Re: kexec regression since 4.9 caused by efi

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Message-ID: <20170316124132.GF6261@codeblueprint.co.uk>
Date:   Thu, 16 Mar 2017 12:41:32 +0000
From:   Matt Fleming <matt@...eblueprint.co.uk>
To:     Dave Young <dyoung@...hat.com>
Cc:     Omar Sandoval <osandov@...ndov.com>,
        Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
        kernel-team@...com, kexec@...ts.infradead.org,
        linux-efi@...r.kernel.org
Subject: Re: kexec regression since 4.9 caused by efi

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;
+
 	size += addr % EFI_PAGE_SIZE;
 	size = round_up(size, EFI_PAGE_SIZE);
 	addr = round_down(addr, EFI_PAGE_SIZE);