efi/x86: Limit EFI old memory map to SGI UV machines

We carry a quirk in the x86 EFI code to switch back to an older
method of mapping the EFI runtime services memory regions, because
it was deemed risky at the time to implement a new method without
providing a fallback to the old method in case problems arose.

Such problems did arise, but they appear to be limited to SGI UV1
machines, and so these are the only ones for which the fallback gets
enabled automatically (via a DMI quirk). The fallback can be enabled
manually as well, by passing efi=old_map, but there is very little
evidence that suggests that this is something that is being relied
upon in the field.

Given that UV1 support is not enabled by default by the distros
(Ubuntu, Fedora), there is no point in carrying this fallback code
all the time if there are no other users. So let's move it into the
UV support code, and document that efi=old_map now requires this
support code to be enabled.

Note that efi=old_map has been used in the past on other SGI UV
machines to work around kernel regressions in production, so we
keep the option to enable it by hand, but only if the kernel was
built with UV support.

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Link: https://lore.kernel.org/r/20200113172245.27925-8-ardb@kernel.org

1 files changed, 9 insertions, 157 deletions

diff --git a/arch/x86/platform/efi/efi_64.c b/arch/x86/platform/efi/efi_64.c
index 3eb23966e30a..8d1869ff1033 100644
--- a/arch/x86/platform/efi/efi_64.c
+++ b/arch/x86/platform/efi/efi_64.c
@@ -57,134 +57,6 @@ static u64 efi_va = EFI_VA_START;
 
 struct efi_scratch efi_scratch;
 
-static void __init early_code_mapping_set_exec(int executable)
-{
-	efi_memory_desc_t *md;
-
-	if (!(__supported_pte_mask & _PAGE_NX))
-		return;
-
-	/* Make EFI service code area executable */
-	for_each_efi_memory_desc(md) {
-		if (md->type == EFI_RUNTIME_SERVICES_CODE ||
-		    md->type == EFI_BOOT_SERVICES_CODE)
-			efi_set_executable(md, executable);
-	}
-}
-
-static void __init efi_old_memmap_phys_epilog(pgd_t *save_pgd);
-
-static pgd_t * __init efi_old_memmap_phys_prolog(void)
-{
-	unsigned long vaddr, addr_pgd, addr_p4d, addr_pud;
-	pgd_t *save_pgd, *pgd_k, *pgd_efi;
-	p4d_t *p4d, *p4d_k, *p4d_efi;
-	pud_t *pud;
-
-	int pgd;
-	int n_pgds, i, j;
-
-	early_code_mapping_set_exec(1);
-
-	n_pgds = DIV_ROUND_UP((max_pfn << PAGE_SHIFT), PGDIR_SIZE);
-	save_pgd = kmalloc_array(n_pgds, sizeof(*save_pgd), GFP_KERNEL);
-	if (!save_pgd)
-		return NULL;
-
-	/*
-	 * Build 1:1 identity mapping for efi=old_map usage. Note that
-	 * PAGE_OFFSET is PGDIR_SIZE aligned when KASLR is disabled, while
-	 * it is PUD_SIZE ALIGNED with KASLR enabled. So for a given physical
-	 * address X, the pud_index(X) != pud_index(__va(X)), we can only copy
-	 * PUD entry of __va(X) to fill in pud entry of X to build 1:1 mapping.
-	 * This means here we can only reuse the PMD tables of the direct mapping.
-	 */
-	for (pgd = 0; pgd < n_pgds; pgd++) {
-		addr_pgd = (unsigned long)(pgd * PGDIR_SIZE);
-		vaddr = (unsigned long)__va(pgd * PGDIR_SIZE);
-		pgd_efi = pgd_offset_k(addr_pgd);
-		save_pgd[pgd] = *pgd_efi;
-
-		p4d = p4d_alloc(&init_mm, pgd_efi, addr_pgd);
-		if (!p4d) {
-			pr_err("Failed to allocate p4d table!\n");
-			goto out;
-		}
-
-		for (i = 0; i < PTRS_PER_P4D; i++) {
-			addr_p4d = addr_pgd + i * P4D_SIZE;
-			p4d_efi = p4d + p4d_index(addr_p4d);
-
-			pud = pud_alloc(&init_mm, p4d_efi, addr_p4d);
-			if (!pud) {
-				pr_err("Failed to allocate pud table!\n");
-				goto out;
-			}
-
-			for (j = 0; j < PTRS_PER_PUD; j++) {
-				addr_pud = addr_p4d + j * PUD_SIZE;
-
-				if (addr_pud > (max_pfn << PAGE_SHIFT))
-					break;
-
-				vaddr = (unsigned long)__va(addr_pud);
-
-				pgd_k = pgd_offset_k(vaddr);
-				p4d_k = p4d_offset(pgd_k, vaddr);
-				pud[j] = *pud_offset(p4d_k, vaddr);
-			}
-		}
-		pgd_offset_k(pgd * PGDIR_SIZE)->pgd &= ~_PAGE_NX;
-	}
-
-	__flush_tlb_all();
-	return save_pgd;
-out:
-	efi_old_memmap_phys_epilog(save_pgd);
-	return NULL;
-}
-
-static void __init efi_old_memmap_phys_epilog(pgd_t *save_pgd)
-{
-	/*
-	 * After the lock is released, the original page table is restored.
-	 */
-	int pgd_idx, i;
-	int nr_pgds;
-	pgd_t *pgd;
-	p4d_t *p4d;
-	pud_t *pud;
-
-	nr_pgds = DIV_ROUND_UP((max_pfn << PAGE_SHIFT) , PGDIR_SIZE);
-
-	for (pgd_idx = 0; pgd_idx < nr_pgds; pgd_idx++) {
-		pgd = pgd_offset_k(pgd_idx * PGDIR_SIZE);
-		set_pgd(pgd_offset_k(pgd_idx * PGDIR_SIZE), save_pgd[pgd_idx]);
-
-		if (!pgd_present(*pgd))
-			continue;
-
-		for (i = 0; i < PTRS_PER_P4D; i++) {
-			p4d = p4d_offset(pgd,
-					 pgd_idx * PGDIR_SIZE + i * P4D_SIZE);
-
-			if (!p4d_present(*p4d))
-				continue;
-
-			pud = (pud_t *)p4d_page_vaddr(*p4d);
-			pud_free(&init_mm, pud);
-		}
-
-		p4d = (p4d_t *)pgd_page_vaddr(*pgd);
-		p4d_free(&init_mm, p4d);
-	}
-
-	kfree(save_pgd);
-
-	__flush_tlb_all();
-	early_code_mapping_set_exec(0);
-}
-
 EXPORT_SYMBOL_GPL(efi_mm);
 
 /*
@@ -203,7 +75,7 @@ int __init efi_alloc_page_tables(void)
 	pud_t *pud;
 	gfp_t gfp_mask;
 
-	if (efi_enabled(EFI_OLD_MEMMAP))
+	if (efi_have_uv1_memmap())
 		return 0;
 
 	gfp_mask = GFP_KERNEL | __GFP_ZERO;
@@ -244,7 +116,7 @@ void efi_sync_low_kernel_mappings(void)
 	pud_t *pud_k, *pud_efi;
 	pgd_t *efi_pgd = efi_mm.pgd;
 
-	if (efi_enabled(EFI_OLD_MEMMAP))
+	if (efi_have_uv1_memmap())
 		return;
 
 	/*
@@ -338,7 +210,7 @@ int __init efi_setup_page_tables(unsigned long pa_memmap, unsigned num_pages)
 	unsigned npages;
 	pgd_t *pgd = efi_mm.pgd;
 
-	if (efi_enabled(EFI_OLD_MEMMAP))
+	if (efi_have_uv1_memmap())
 		return 0;
 
 	/*
@@ -439,7 +311,7 @@ void __init efi_map_region(efi_memory_desc_t *md)
 	unsigned long size = md->num_pages << PAGE_SHIFT;
 	u64 pa = md->phys_addr;
 
-	if (efi_enabled(EFI_OLD_MEMMAP))
+	if (efi_have_uv1_memmap())
 		return old_map_region(md);
 
 	/*
@@ -496,26 +368,6 @@ void __init efi_map_region_fixed(efi_memory_desc_t *md)
 	__map_region(md, md->virt_addr);
 }
 
-void __iomem *__init efi_ioremap(unsigned long phys_addr, unsigned long size,
-				 u32 type, u64 attribute)
-{
-	unsigned long last_map_pfn;
-
-	if (type == EFI_MEMORY_MAPPED_IO)
-		return ioremap(phys_addr, size);
-
-	last_map_pfn = init_memory_mapping(phys_addr, phys_addr + size);
-	if ((last_map_pfn << PAGE_SHIFT) < phys_addr + size) {
-		unsigned long top = last_map_pfn << PAGE_SHIFT;
-		efi_ioremap(top, size - (top - phys_addr), type, attribute);
-	}
-
-	if (!(attribute & EFI_MEMORY_WB))
-		efi_memory_uc((u64)(unsigned long)__va(phys_addr), size);
-
-	return (void __iomem *)__va(phys_addr);
-}
-
 void __init parse_efi_setup(u64 phys_addr, u32 data_len)
 {
 	efi_setup = phys_addr + sizeof(struct setup_data);
@@ -564,7 +416,7 @@ void __init efi_runtime_update_mappings(void)
 {
 	efi_memory_desc_t *md;
 
-	if (efi_enabled(EFI_OLD_MEMMAP)) {
+	if (efi_have_uv1_memmap()) {
 		if (__supported_pte_mask & _PAGE_NX)
 			runtime_code_page_mkexec();
 		return;
@@ -618,7 +470,7 @@ void __init efi_runtime_update_mappings(void)
 void __init efi_dump_pagetable(void)
 {
 #ifdef CONFIG_EFI_PGT_DUMP
-	if (efi_enabled(EFI_OLD_MEMMAP))
+	if (efi_have_uv1_memmap())
 		ptdump_walk_pgd_level(NULL, swapper_pg_dir);
 	else
 		ptdump_walk_pgd_level(NULL, efi_mm.pgd);
@@ -1045,8 +897,8 @@ efi_status_t __init efi_set_virtual_address_map(unsigned long memory_map_size,
 							 descriptor_version,
 							 virtual_map);
 
-	if (efi_enabled(EFI_OLD_MEMMAP)) {
-		save_pgd = efi_old_memmap_phys_prolog();
+	if (efi_have_uv1_memmap()) {
+		save_pgd = efi_uv1_memmap_phys_prolog();
 		if (!save_pgd)
 			return EFI_ABORTED;
 	} else {
@@ -1065,7 +917,7 @@ efi_status_t __init efi_set_virtual_address_map(unsigned long memory_map_size,
 	kernel_fpu_end();
 
 	if (save_pgd)
-		efi_old_memmap_phys_epilog(save_pgd);
+		efi_uv1_memmap_phys_epilog(save_pgd);
 	else
 		efi_switch_mm(efi_scratch.prev_mm);