linux-kernel - [PATCH] efi/x86: skip efi_arch_mem

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Date: Mon, 19 Feb 2024 21:11:58 +0000
From: Ashish Kalra <Ashish.Kalra@....com>
To: <tglx@...utronix.de>, <mingo@...hat.com>, <bp@...en8.de>,
	<dave.hansen@...ux.intel.com>, <x86@...nel.org>
CC: <ardb@...nel.org>, <hpa@...or.com>, <linux-efi@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>, <rafael@...nel.org>, <peterz@...radead.org>,
	<adrian.hunter@...el.com>, <sathyanarayanan.kuppuswamy@...ux.intel.com>,
	<elena.reshetova@...el.com>, <jun.nakajima@...el.com>,
	<rick.p.edgecombe@...el.com>, <thomas.lendacky@....com>, <seanjc@...gle.com>,
	<kai.huang@...el.com>, <bhe@...hat.com>, <kexec@...ts.infradead.org>,
	<linux-coco@...ts.linux.dev>, <kirill.shutemov@...ux.intel.com>,
	<anisinha@...hat.com>, <michael.roth@....com>, <bdas@...hat.com>,
	<vkuznets@...hat.com>
Subject: [PATCH] efi/x86: skip efi_arch_mem_reserve() in case of kexec.

From: Ashish Kalra <ashish.kalra@....com>

For kexec use case, need to use and stick to the EFI memmap passed
from the first kernel via boot-params/setup data, hence,
skip efi_arch_mem_reserve() during kexec.

Additionally during SNP guest kexec testing discovered that EFI memmap
is corrupted during chained kexec. kexec_enter_virtual_mode() during
late init will remap the efi_memmap physical pages allocated in
efi_arch_mem_reserve() via memboot & then subsequently cause random
EFI memmap corruption once memblock is freed/teared-down.

Signed-off-by: Ashish Kalra <ashish.kalra@....com>
---
 arch/x86/platform/efi/quirks.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/arch/x86/platform/efi/quirks.c b/arch/x86/platform/efi/quirks.c
index f0cc00032751..d4562d074371 100644
--- a/arch/x86/platform/efi/quirks.c
+++ b/arch/x86/platform/efi/quirks.c
@@ -258,6 +258,16 @@ void __init efi_arch_mem_reserve(phys_addr_t addr, u64 size)
 	int num_entries;
 	void *new;
 
+	/*
+	 * For kexec use case, need to use the EFI memmap passed from the first
+	 * kernel via boot-params/setup data and need to skip this.
+	 * Additionally kexec_enter_virtual_mode() during late init will remap
+	 * the efi_memmap physical pages allocated here via memboot & then
+	 * subsequently cause random EFI memmap corruption once memblock is freed.
+	 */
+	if (efi_setup)
+		return;
+
 	if (efi_mem_desc_lookup(addr, &md) ||
 	    md.type != EFI_BOOT_SERVICES_DATA) {
 		pr_err("Failed to lookup EFI memory descriptor for %pa\n", &addr);
-- 
2.34.1