x86/mm: Do not zap page table entries mapping unaccepted memory table during kdump

During crashkernel boot only pre-allocated crash memory is presented as
E820_TYPE_RAM.

This can cause page table entries mapping unaccepted memory table to be zapped
during phys_pte_init(), phys_pmd_init(), phys_pud_init() and phys_p4d_init() as
SNP/TDX guest use E820_TYPE_ACPI to store the unaccepted memory table and pass
it between the kernels on kexec/kdump.

E820_TYPE_ACPI covers not only ACPI data, but also EFI tables and might be
required by kernel to function properly.

The problem was discovered during debugging kdump for SNP guest. The unaccepted
memory table stored with E820_TYPE_ACPI and passed between the kernels on kdump
was getting zapped as the PMD entry mapping this is above the E820_TYPE_RAM
range for the reserved crashkernel memory.

Signed-off-by: Ashish Kalra <ashish.kalra@amd.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20240614095904.1345461-14-kirill.shutemov@linux.intel.com

diff --git a/arch/x86/mm/init_64.c b/arch/x86/mm/init_64.c
index 7e177856ee4fe62238c2bb57323a93607233bb0c..28002cc7a37d6d390101eeac84765a88a3da7a9e 100644 (file)
--- a/arch/x86/mm/init_64.c
+++ b/arch/x86/mm/init_64.c
@@ -469,7 +469,9 @@ phys_pte_init(pte_t *pte_page, unsigned long paddr, unsigned long paddr_end,
                            !e820__mapped_any(paddr & PAGE_MASK, paddr_next,
                                             E820_TYPE_RAM) &&
                            !e820__mapped_any(paddr & PAGE_MASK, paddr_next,
-                                            E820_TYPE_RESERVED_KERN))
+                                            E820_TYPE_RESERVED_KERN) &&
+                           !e820__mapped_any(paddr & PAGE_MASK, paddr_next,
+                                            E820_TYPE_ACPI))
                                set_pte_init(pte, __pte(0), init);
                        continue;
                }
@@ -524,7 +526,9 @@ phys_pmd_init(pmd_t *pmd_page, unsigned long paddr, unsigned long paddr_end,
                            !e820__mapped_any(paddr & PMD_MASK, paddr_next,
                                             E820_TYPE_RAM) &&
                            !e820__mapped_any(paddr & PMD_MASK, paddr_next,
-                                            E820_TYPE_RESERVED_KERN))
+                                            E820_TYPE_RESERVED_KERN) &&
+                           !e820__mapped_any(paddr & PMD_MASK, paddr_next,
+                                            E820_TYPE_ACPI))
                                set_pmd_init(pmd, __pmd(0), init);
                        continue;
                }
@@ -611,7 +615,9 @@ phys_pud_init(pud_t *pud_page, unsigned long paddr, unsigned long paddr_end,
                            !e820__mapped_any(paddr & PUD_MASK, paddr_next,
                                             E820_TYPE_RAM) &&
                            !e820__mapped_any(paddr & PUD_MASK, paddr_next,
-                                            E820_TYPE_RESERVED_KERN))
+                                            E820_TYPE_RESERVED_KERN) &&
+                           !e820__mapped_any(paddr & PUD_MASK, paddr_next,
+                                            E820_TYPE_ACPI))
                                set_pud_init(pud, __pud(0), init);
                        continue;
                }
@@ -698,7 +704,9 @@ phys_p4d_init(p4d_t *p4d_page, unsigned long paddr, unsigned long paddr_end,
                            !e820__mapped_any(paddr & P4D_MASK, paddr_next,
                                             E820_TYPE_RAM) &&
                            !e820__mapped_any(paddr & P4D_MASK, paddr_next,
-                                            E820_TYPE_RESERVED_KERN))
+                                            E820_TYPE_RESERVED_KERN) &&
+                           !e820__mapped_any(paddr & P4D_MASK, paddr_next,
+                                            E820_TYPE_ACPI))
                                set_p4d_init(p4d, __p4d(0), init);
                        continue;
                }