linux-kernel - [PATCH v4 1/4] efi/x86: skip efi_arch_mem

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Date: Tue, 9 Apr 2024 20:42:23 +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: <rafael@...nel.org>, <peterz@...radead.org>, <adrian.hunter@...el.com>,
	<sathyanarayanan.kuppuswamy@...ux.intel.com>, <jun.nakajima@...el.com>,
	<rick.p.edgecombe@...el.com>, <thomas.lendacky@....com>,
	<michael.roth@....com>, <seanjc@...gle.com>, <kai.huang@...el.com>,
	<bhe@...hat.com>, <kirill.shutemov@...ux.intel.com>, <bdas@...hat.com>,
	<vkuznets@...hat.com>, <dionnaglaze@...gle.com>, <anisinha@...hat.com>,
	<jroedel@...e.de>, <ardb@...nel.org>, <kexec@...ts.infradead.org>,
	<linux-coco@...ts.linux.dev>, <linux-kernel@...r.kernel.org>
Subject: [PATCH v4 1/4] 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 memblock & then subsequently cause random
EFI memmap corruption once memblock is freed/teared-down.

Suggested-by: Dave Young <dyoung@...hat.com>
[Dave Young: checking the md attribute instead of checking the efi_setup]
Signed-off-by: Ashish Kalra <ashish.kalra@....com>
---
 arch/x86/platform/efi/quirks.c | 20 ++++++++++++++++++--
 1 file changed, 18 insertions(+), 2 deletions(-)

diff --git a/arch/x86/platform/efi/quirks.c b/arch/x86/platform/efi/quirks.c
index f0cc00032751..982f5e50a4b3 100644
--- a/arch/x86/platform/efi/quirks.c
+++ b/arch/x86/platform/efi/quirks.c
@@ -258,12 +258,28 @@ void __init efi_arch_mem_reserve(phys_addr_t addr, u64 size)
 	int num_entries;
 	void *new;
 
-	if (efi_mem_desc_lookup(addr, &md) ||
-	    md.type != EFI_BOOT_SERVICES_DATA) {
+	/*
+	 * For kexec use case, we need to use the EFI memmap passed from the first
+	 * kernel via setup data, so we 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_mem_desc_lookup(addr, &md)) {
 		pr_err("Failed to lookup EFI memory descriptor for %pa\n", &addr);
 		return;
 	}
 
+	if (md.type != EFI_BOOT_SERVICES_DATA) {
+		pr_err("Skip reserving non EFI Boot Service Data memory for %pa\n", &addr);
+		return;
+	}
+
+	/* Kexec copied the efi memmap from the first kernel, thus skip the case */
+	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;
-- 
2.34.1