[PATCH v3 1/4] efi/x86: skip efi_arch_mem_reserve() in case of kexec.

[Ashish Kalra]

From: Ashish Kalra <ashish.kalra@xxxxxxx>

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@xxxxxxxxxx>
[Dave Young: checking the md attribute instead of checking the efi_setup]
Signed-off-by: Ashish Kalra <ashish.kalra@xxxxxxx>
---
 arch/x86/platform/efi/quirks.c | 23 ++++++++++++++++++++---
 1 file changed, 20 insertions(+), 3 deletions(-)

diff --git a/arch/x86/platform/efi/quirks.c b/arch/x86/platform/efi/quirks.c
index f0cc00032751..2b65b3863912 100644
--- a/arch/x86/platform/efi/quirks.c
+++ b/arch/x86/platform/efi/quirks.c
@@ -255,15 +255,32 @@ void __init efi_arch_mem_reserve(phys_addr_t addr, u64 size)
 	struct efi_memory_map_data data = { 0 };
 	struct efi_mem_range mr;
 	efi_memory_desc_t md;
-	int num_entries;
+	int num_entries, ret;
 	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.
+	 */
+
+	ret = efi_mem_desc_lookup(addr, &md);
+	if (ret) {
 		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