Merge tag 'x86-urgent-2025-03-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull misc x86 fixes and updates from Ingo Molnar:

 - Fix a large number of x86 Kconfig dependency and help text accuracy
   bugs/problems, by Mateusz Jończyk and David Heideberg

 - Fix a VM_PAT interaction with fork() crash. This also touches core
   kernel code

 - Fix an ORC unwinder bug for interrupt entries

 - Fixes and cleanups

 - Fix an AMD microcode loader bug that can promote verification
   failures into success

 - Add early-printk support for MMIO based UARTs on an x86 board that
   had no other serial debugging facility and also experienced early
   boot crashes

* tag 'x86-urgent-2025-03-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  x86/microcode/AMD: Fix __apply_microcode_amd()'s return value
  x86/mm/pat: Fix VM_PAT handling when fork() fails in copy_page_range()
  x86/fpu: Update the outdated comment above fpstate_init_user()
  x86/early_printk: Add support for MMIO-based UARTs
  x86/dumpstack: Fix inaccurate unwinding from exception stacks due to misplaced assignment
  x86/entry: Fix ORC unwinder for PUSH_REGS with save_ret=1
  x86/Kconfig: Fix lists in X86_EXTENDED_PLATFORM help text
  x86/Kconfig: Correct X86_X2APIC help text
  x86/speculation: Remove the extra #ifdef around CALL_NOSPEC
  x86/Kconfig: Document release year of glibc 2.3.3
  x86/Kconfig: Make CONFIG_PCI_CNB20LE_QUIRK depend on X86_32
  x86/Kconfig: Document CONFIG_PCI_MMCONFIG
  x86/Kconfig: Update lists in X86_EXTENDED_PLATFORM
  x86/Kconfig: Move all X86_EXTENDED_PLATFORM options together
  x86/Kconfig: Always enable ARCH_SPARSEMEM_ENABLE
  x86/Kconfig: Enable X86_X2APIC by default and improve help text

Author: torvalds

Documentation/admin-guide/kernel-parameters.txt

@@ -1407,14 +1407,21 @@
 			earlyprintk=serial[,0x...[,baudrate]]
 			earlyprintk=ttySn[,baudrate]
 			earlyprintk=dbgp[debugController#]
-			earlyprintk=pciserial[,force],bus:device.function[,baudrate]
+			earlyprintk=pciserial[,force],bus:device.function[,{nocfg|baudrate}]
 			earlyprintk=xdbc[xhciController#]
 			earlyprintk=bios
+			earlyprintk=mmio,membase[,{nocfg|baudrate}]
 
 			earlyprintk is useful when the kernel crashes before
 			the normal console is initialized. It is not enabled by
 			default because it has some cosmetic problems.
 
+			Only 32-bit memory addresses are supported for "mmio"
+			and "pciserial" devices.
+
+			Use "nocfg" to skip UART configuration, assume
+			BIOS/firmware has configured UART correctly.
+
 			Append ",keep" to not disable it when the real console
 			takes over.
 

arch/x86/Kconfig

@@ -460,20 +460,28 @@ config SMP
 	  If you don't know what to do here, say N.
 
 config X86_X2APIC
-	bool "Support x2apic"
+	bool "x2APIC interrupt controller architecture support"
 	depends on X86_LOCAL_APIC && X86_64 && (IRQ_REMAP || HYPERVISOR_GUEST)
+	default y
 	help
-	  This enables x2apic support on CPUs that have this feature.
+	  x2APIC is an interrupt controller architecture, a component of which
+	  (the local APIC) is present in the CPU. It allows faster access to
+	  the local APIC and supports a larger number of CPUs in the system
+	  than the predecessors.
 
-	  This allows 32-bit apic IDs (so it can support very large systems),
-	  and accesses the local apic via MSRs not via mmio.
+	  x2APIC was introduced in Intel CPUs around 2008 and in AMD EPYC CPUs
+	  in 2019, but it can be disabled by the BIOS. It is also frequently
+	  emulated in virtual machines, even when the host CPU does not support
+	  it. Support in the CPU can be checked by executing
+		grep x2apic /proc/cpuinfo
 
-	  Some Intel systems circa 2022 and later are locked into x2APIC mode
-	  and can not fall back to the legacy APIC modes if SGX or TDX are
-	  enabled in the BIOS. They will boot with very reduced functionality
-	  without enabling this option.
+	  If this configuration option is disabled, the kernel will boot with
+	  very reduced functionality and performance on some platforms that
+	  have x2APIC enabled. On the other hand, on hardware that does not
+	  support x2APIC, a kernel with this option enabled will just fallback
+	  to older APIC implementations.
 
-	  If you don't know what to do here, say N.
+	  If in doubt, say Y.
 
 config X86_POSTED_MSI
 	bool "Enable MSI and MSI-x delivery by posted interrupts"
@@ -544,16 +552,17 @@ config X86_EXTENDED_PLATFORM
 	  CONFIG_64BIT.
 
 	  32-bit platforms (CONFIG_64BIT=n):
-		Goldfish (Android emulator)
-		AMD Elan
+		Goldfish (mostly Android emulator)
+		Intel CE media processor (CE4100) SoC
+		Intel Quark
 		RDC R-321x SoC
-		SGI 320/540 (Visual Workstation)
 
 	  64-bit platforms (CONFIG_64BIT=y):
 		Numascale NumaChip
 		ScaleMP vSMP
 		SGI Ultraviolet
 		Merrifield/Moorefield MID devices
+		Goldfish (mostly Android emulator)
 
 	  If you have one of these systems, or if you want to build a
 	  generic distribution kernel, say Y here - otherwise say N.
@@ -667,6 +676,17 @@ config X86_INTEL_QUARK
 	  Say Y here if you have a Quark based system such as the Arduino
 	  compatible Intel Galileo.
 
+config X86_RDC321X
+	bool "RDC R-321x SoC"
+	depends on X86_32
+	depends on X86_EXTENDED_PLATFORM
+	select M486
+	select X86_REBOOTFIXUPS
+	help
+	  This option is needed for RDC R-321x system-on-chip, also known
+	  as R-8610-(G).
+	  If you don't have one of these chips, you should say N here.
+
 config X86_INTEL_LPSS
 	bool "Intel Low Power Subsystem Support"
 	depends on X86 && ACPI && PCI
@@ -720,17 +740,6 @@ config IOSF_MBI_DEBUG
 
 	  If you don't require the option or are in doubt, say N.
 
-config X86_RDC321X
-	bool "RDC R-321x SoC"
-	depends on X86_32
-	depends on X86_EXTENDED_PLATFORM
-	select M486
-	select X86_REBOOTFIXUPS
-	help
-	  This option is needed for RDC R-321x system-on-chip, also known
-	  as R-8610-(G).
-	  If you don't have one of these chips, you should say N here.
-
 config X86_SUPPORTS_MEMORY_FAILURE
 	def_bool y
 	# MCE code calls memory_failure():
@@ -1565,7 +1574,6 @@ config ARCH_FLATMEM_ENABLE
 
 config ARCH_SPARSEMEM_ENABLE
 	def_bool y
-	depends on X86_64 || NUMA || X86_32
 	select SPARSEMEM_STATIC if X86_32
 	select SPARSEMEM_VMEMMAP_ENABLE if X86_64
 
@@ -2212,7 +2220,7 @@ config HOTPLUG_CPU
 
 config COMPAT_VDSO
 	def_bool n
-	prompt "Disable the 32-bit vDSO (needed for glibc 2.3.3)"
+	prompt "Workaround for glibc 2.3.2 / 2.3.3 (released in year 2003/2004)"
 	depends on COMPAT_32
 	help
 	  Certain buggy versions of glibc will crash if they are
@@ -2901,6 +2909,19 @@ config PCI_MMCONFIG
 	default y
 	depends on PCI && (ACPI || JAILHOUSE_GUEST)
 	depends on X86_64 || (PCI_GOANY || PCI_GOMMCONFIG)
+	help
+	  Add support for accessing the PCI configuration space as a memory
+	  mapped area. It is the recommended method if the system supports
+	  this (it must have PCI Express and ACPI for it to be available).
+
+	  In the unlikely case that enabling this configuration option causes
+	  problems, the mechanism can be switched off with the 'pci=nommconf'
+	  command line parameter.
+
+	  Say N only if you are sure that your platform does not support this
+	  access method or you have problems caused by it.
+
+	  Say Y otherwise.
 
 config PCI_OLPC
 	def_bool y
@@ -2915,13 +2936,21 @@ config MMCONF_FAM10H
 	depends on X86_64 && PCI_MMCONFIG && ACPI
 
 config PCI_CNB20LE_QUIRK
-	bool "Read CNB20LE Host Bridge Windows" if EXPERT
-	depends on PCI
+	bool "Read PCI host bridge windows from the CNB20LE chipset" if EXPERT
+	depends on X86_32 && PCI
 	help
 	  Read the PCI windows out of the CNB20LE host bridge. This allows
 	  PCI hotplug to work on systems with the CNB20LE chipset which do
 	  not have ACPI.
 
+	  The ServerWorks (later Broadcom) CNB20LE was a chipset designed
+	  most probably only for Pentium III.
+
+	  To find out if you have such a chipset, search for a PCI device with
+	  1166:0009 PCI IDs, for example by executing
+		lspci -nn | grep '1166:0009'
+	  The code is inactive if there is none.
+
 	  There's no public spec for this chipset, and this functionality
 	  is known to be incomplete.
 

arch/x86/entry/calling.h

@@ -70,6 +70,8 @@ For 32-bit we have the following conventions - kernel is built with
 	pushq	%rsi		/* pt_regs->si */
 	movq	8(%rsp), %rsi	/* temporarily store the return address in %rsi */
 	movq	%rdi, 8(%rsp)	/* pt_regs->di (overwriting original return address) */
+	/* We just clobbered the return address - use the IRET frame for unwinding: */
+	UNWIND_HINT_IRET_REGS offset=3*8
 	.else
 	pushq   %rdi		/* pt_regs->di */
 	pushq   %rsi		/* pt_regs->si */

arch/x86/include/asm/nospec-branch.h

@@ -435,12 +435,8 @@ static inline void call_depth_return_thunk(void) {}
  * Inline asm uses the %V modifier which is only in newer GCC
  * which is ensured when CONFIG_MITIGATION_RETPOLINE is defined.
  */
-#ifdef CONFIG_MITIGATION_RETPOLINE
 #define CALL_NOSPEC	__CS_PREFIX("%V[thunk_target]")	\
 			"call __x86_indirect_thunk_%V[thunk_target]\n"
-#else
-#define CALL_NOSPEC	"call *%[thunk_target]\n"
-#endif
 
 # define THUNK_TARGET(addr) [thunk_target] "r" (addr)
 

arch/x86/kernel/cpu/microcode/amd.c

@@ -600,7 +600,7 @@ static bool __apply_microcode_amd(struct microcode_amd *mc, u32 *cur_rev,
 	unsigned long p_addr = (unsigned long)&mc->hdr.data_code;
 
 	if (!verify_sha256_digest(mc->hdr.patch_id, *cur_rev, (const u8 *)p_addr, psize))
-		return -1;
+		return false;
 
 	native_wrmsrl(MSR_AMD64_PATCH_LOADER, p_addr);
 

arch/x86/kernel/dumpstack.c

@@ -195,6 +195,7 @@ static void show_trace_log_lvl(struct task_struct *task, struct pt_regs *regs,
 	printk("%sCall Trace:\n", log_lvl);
 
 	unwind_start(&state, task, regs, stack);
+	stack = stack ?: get_stack_pointer(task, regs);
 	regs = unwind_get_entry_regs(&state, &partial);
 
 	/*
@@ -213,9 +214,7 @@ static void show_trace_log_lvl(struct task_struct *task, struct pt_regs *regs,
 	 * - hardirq stack
 	 * - entry stack
 	 */
-	for (stack = stack ?: get_stack_pointer(task, regs);
-	     stack;
-	     stack = stack_info.next_sp) {
+	for (; stack; stack = stack_info.next_sp) {
 		const char *stack_name;
 
 		stack = PTR_ALIGN(stack, sizeof(long));

arch/x86/kernel/early_printk.c

@@ -190,7 +190,6 @@ static __init void early_serial_init(char *s)
 	early_serial_hw_init(divisor);
 }
 
-#ifdef CONFIG_PCI
 static __noendbr void mem32_serial_out(unsigned long addr, int offset, int value)
 {
 	u32 __iomem *vaddr = (u32 __iomem *)addr;
@@ -207,6 +206,45 @@ static __noendbr unsigned int mem32_serial_in(unsigned long addr, int offset)
 }
 ANNOTATE_NOENDBR_SYM(mem32_serial_in);
 
+/*
+ * early_mmio_serial_init() - Initialize MMIO-based early serial console.
+ * @s: MMIO-based serial specification.
+ */
+static __init void early_mmio_serial_init(char *s)
+{
+	unsigned long baudrate;
+	unsigned long membase;
+	char *e;
+
+	if (*s == ',')
+		s++;
+
+	if (!strncmp(s, "0x", 2)) {
+		/* NB: only 32-bit addresses are supported. */
+		membase = simple_strtoul(s, &e, 16);
+		early_serial_base = (unsigned long)early_ioremap(membase, PAGE_SIZE);
+
+		static_call_update(serial_in, mem32_serial_in);
+		static_call_update(serial_out, mem32_serial_out);
+
+		s += strcspn(s, ",");
+		if (*s == ',')
+			s++;
+	}
+
+	if (!strncmp(s, "nocfg", 5)) {
+		baudrate = 0;
+	} else {
+		baudrate = simple_strtoul(s, &e, 0);
+		if (baudrate == 0 || s == e)
+			baudrate = DEFAULT_BAUD;
+	}
+
+	if (baudrate)
+		early_serial_hw_init(115200 / baudrate);
+}
+
+#ifdef CONFIG_PCI
 /*
  * early_pci_serial_init()
  *
@@ -351,6 +389,11 @@ static int __init setup_early_printk(char *buf)
 	keep = (strstr(buf, "keep") != NULL);
 
 	while (*buf != '\0') {
+		if (!strncmp(buf, "mmio", 4)) {
+			early_mmio_serial_init(buf + 4);
+			early_console_register(&early_serial_console, keep);
+			buf += 4;
+		}
 		if (!strncmp(buf, "serial", 6)) {
 			buf += 6;
 			early_serial_init(buf);

arch/x86/kernel/fpu/core.c

@@ -508,7 +508,7 @@ static inline void fpstate_init_fstate(struct fpstate *fpstate)
 /*
  * Used in two places:
  * 1) Early boot to setup init_fpstate for non XSAVE systems
- * 2) fpu_init_fpstate_user() which is invoked from KVM
+ * 2) fpu_alloc_guest_fpstate() which is invoked from KVM
  */
 void fpstate_init_user(struct fpstate *fpstate)
 {

arch/x86/mm/pat/memtype.c

@@ -984,29 +984,42 @@ static int get_pat_info(struct vm_area_struct *vma, resource_size_t *paddr,
 	return -EINVAL;
 }
 
-/*
- * track_pfn_copy is called when vma that is covering the pfnmap gets
- * copied through copy_page_range().
- *
- * If the vma has a linear pfn mapping for the entire range, we get the prot
- * from pte and reserve the entire vma range with single reserve_pfn_range call.
- */
-int track_pfn_copy(struct vm_area_struct *vma)
+int track_pfn_copy(struct vm_area_struct *dst_vma,
+		struct vm_area_struct *src_vma, unsigned long *pfn)
 {
+	const unsigned long vma_size = src_vma->vm_end - src_vma->vm_start;
 	resource_size_t paddr;
-	unsigned long vma_size = vma->vm_end - vma->vm_start;
 	pgprot_t pgprot;
+	int rc;
 
-	if (vma->vm_flags & VM_PAT) {
-		if (get_pat_info(vma, &paddr, &pgprot))
-			return -EINVAL;
-		/* reserve the whole chunk covered by vma. */
-		return reserve_pfn_range(paddr, vma_size, &pgprot, 1);
-	}
+	if (!(src_vma->vm_flags & VM_PAT))
+		return 0;
+
+	/*
+	 * Duplicate the PAT information for the dst VMA based on the src
+	 * VMA.
+	 */
+	if (get_pat_info(src_vma, &paddr, &pgprot))
+		return -EINVAL;
+	rc = reserve_pfn_range(paddr, vma_size, &pgprot, 1);
+	if (rc)
+		return rc;
 
+	/* Reservation for the destination VMA succeeded. */
+	vm_flags_set(dst_vma, VM_PAT);
+	*pfn = PHYS_PFN(paddr);
 	return 0;
 }
 
+void untrack_pfn_copy(struct vm_area_struct *dst_vma, unsigned long pfn)
+{
+	untrack_pfn(dst_vma, pfn, dst_vma->vm_end - dst_vma->vm_start, true);
+	/*
+	 * Reservation was freed, any copied page tables will get cleaned
+	 * up later, but without getting PAT involved again.
+	 */
+}
+
 /*
  * prot is passed in as a parameter for the new mapping. If the vma has
  * a linear pfn mapping for the entire range, or no vma is provided,
@@ -1095,15 +1108,6 @@ void untrack_pfn(struct vm_area_struct *vma, unsigned long pfn,
 	}
 }
 
-/*
- * untrack_pfn_clear is called if the following situation fits:
- *
- * 1) while mremapping a pfnmap for a new region,  with the old vma after
- * its pfnmap page table has been removed.  The new vma has a new pfnmap
- * to the same pfn & cache type with VM_PAT set.
- * 2) while duplicating vm area, the new vma fails to copy the pgtable from
- * old vma.
- */
 void untrack_pfn_clear(struct vm_area_struct *vma)
 {
 	vm_flags_clear(vma, VM_PAT);