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

3 files changed, 33 insertions, 184 deletions

diff --git a/arch/x86/platform/efi/efi.c b/arch/x86/platform/efi/efi.c
index b931c4bea284..4e46d2d24352 100644
--- a/arch/x86/platform/efi/efi.c
+++ b/arch/x86/platform/efi/efi.c
@@ -497,6 +497,8 @@ void __init efi_init(void)
 		efi_print_memmap();
 }
 
+#if defined(CONFIG_X86_32) || defined(CONFIG_X86_UV)
+
 void __init efi_set_executable(efi_memory_desc_t *md, bool executable)
 {
 	u64 addr, npages;
@@ -561,6 +563,8 @@ void __init old_map_region(efi_memory_desc_t *md)
 		       (unsigned long long)md->phys_addr);
 }
 
+#endif
+
 /* Merge contiguous regions of the same type and attribute */
 static void __init efi_merge_regions(void)
 {
@@ -659,7 +663,7 @@ static inline void *efi_map_next_entry_reverse(void *entry)
  */
 static void *efi_map_next_entry(void *entry)
 {
-	if (!efi_enabled(EFI_OLD_MEMMAP) && efi_enabled(EFI_64BIT)) {
+	if (!efi_have_uv1_memmap() && efi_enabled(EFI_64BIT)) {
 		/*
 		 * Starting in UEFI v2.5 the EFI_PROPERTIES_TABLE
 		 * config table feature requires us to map all entries
@@ -791,11 +795,11 @@ static void __init kexec_enter_virtual_mode(void)
 
 	/*
 	 * We don't do virtual mode, since we don't do runtime services, on
-	 * non-native EFI. With efi=old_map, we don't do runtime services in
+	 * non-native EFI. With the UV1 memmap, we don't do runtime services in
 	 * kexec kernel because in the initial boot something else might
 	 * have been mapped at these virtual addresses.
 	 */
-	if (efi_is_mixed() || efi_enabled(EFI_OLD_MEMMAP)) {
+	if (efi_is_mixed() || efi_have_uv1_memmap()) {
 		efi_memmap_unmap();
 		clear_bit(EFI_RUNTIME_SERVICES, &efi.flags);
 		return;
@@ -861,9 +865,9 @@ static void __init kexec_enter_virtual_mode(void)
  *
  * The old method which used to update that memory descriptor with the
  * virtual address obtained from ioremap() is still supported when the
- * kernel is booted with efi=old_map on its command line. Same old
- * method enabled the runtime services to be called without having to
- * thunk back into physical mode for every invocation.
+ * kernel is booted on SG1 UV1 hardware. Same old method enabled the
+ * runtime services to be called without having to thunk back into
+ * physical mode for every invocation.
  *
  * The new method does a pagetable switch in a preemption-safe manner
  * so that we're in a different address space when calling a runtime
@@ -976,20 +980,6 @@ void __init efi_enter_virtual_mode(void)
 	efi_dump_pagetable();
 }
 
-static int __init arch_parse_efi_cmdline(char *str)
-{
-	if (!str) {
-		pr_warn("need at least one option\n");
-		return -EINVAL;
-	}
-
-	if (parse_option_str(str, "old_map"))
-		set_bit(EFI_OLD_MEMMAP, &efi.flags);
-
-	return 0;
-}
-early_param("efi", arch_parse_efi_cmdline);
-
 bool efi_is_table_address(unsigned long phys_addr)
 {
 	unsigned int i;
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);
 
diff --git a/arch/x86/platform/efi/quirks.c b/arch/x86/platform/efi/quirks.c
index eb421cb35108..fe46ddf6c761 100644
--- a/arch/x86/platform/efi/quirks.c
+++ b/arch/x86/platform/efi/quirks.c
@@ -384,10 +384,10 @@ static void __init efi_unmap_pages(efi_memory_desc_t *md)
 
 	/*
 	 * To Do: Remove this check after adding functionality to unmap EFI boot
-	 * services code/data regions from direct mapping area because
-	 * "efi=old_map" maps EFI regions in swapper_pg_dir.
+	 * services code/data regions from direct mapping area because the UV1
+	 * memory map maps EFI regions in swapper_pg_dir.
 	 */
-	if (efi_enabled(EFI_OLD_MEMMAP))
+	if (efi_have_uv1_memmap())
 		return;
 
 	/*
@@ -558,7 +558,7 @@ out:
 	return ret;
 }
 
-static const struct dmi_system_id sgi_uv1_dmi[] = {
+static const struct dmi_system_id sgi_uv1_dmi[] __initconst = {
 	{ NULL, "SGI UV1",
 		{	DMI_MATCH(DMI_PRODUCT_NAME,	"Stoutland Platform"),
 			DMI_MATCH(DMI_PRODUCT_VERSION,	"1.0"),
@@ -581,8 +581,15 @@ void __init efi_apply_memmap_quirks(void)
 	}
 
 	/* UV2+ BIOS has a fix for this issue.  UV1 still needs the quirk. */
-	if (dmi_check_system(sgi_uv1_dmi))
-		set_bit(EFI_OLD_MEMMAP, &efi.flags);
+	if (dmi_check_system(sgi_uv1_dmi)) {
+		if (IS_ENABLED(CONFIG_X86_UV)) {
+			set_bit(EFI_UV1_MEMMAP, &efi.flags);
+		} else {
+			pr_warn("EFI runtime disabled, needs CONFIG_X86_UV=y on UV1\n");
+			clear_bit(EFI_RUNTIME_SERVICES, &efi.flags);
+			efi_memmap_unmap();
+		}
+	}
 }
 
 /*
@@ -720,7 +727,7 @@ void efi_recover_from_page_fault(unsigned long phys_addr)
 	/*
 	 * Make sure that an efi runtime service caused the page fault.
 	 * "efi_mm" cannot be used to check if the page fault had occurred
-	 * in the firmware context because efi=old_map doesn't use efi_pgd.
+	 * in the firmware context because the UV1 memmap doesn't use efi_pgd.
 	 */
 	if (efi_rts_work.efi_rts_id == EFI_NONE)
 		return;