[PATCH 0/2] Remove 32-bit Xen PV guest support

[PATCH 0/2] Remove 32-bit Xen PV guest support

[Juergen Gross]

The long term plan has been to replace Xen PV guests by PVH. The first
victim of that plan are now 32-bit PV guests, as those are used only
rather seldom these days. Xen on x86 requires 64-bit support and with
Grub2 now supporting PVH officially since version 2.04 there is no
need to keep 32-bit PV guest support alive in the Linux kernel.
Additionally Meltdown mitigation is not available in the kernel running
as 32-bit PV guest, so dropping this mode makes sense from security
point of view, too.

Juergen Gross (2):
  x86/xen: remove 32-bit Xen PV guest support
  x86/paravirt: remove 32-bit support from PARAVIRT_XXL

 arch/x86/entry/entry_32.S                   |  93 --------
 arch/x86/entry/vdso/vdso32/vclock_gettime.c |   1 +
 arch/x86/include/asm/paravirt.h             | 105 +--------
 arch/x86/include/asm/paravirt_types.h       |  20 --
 arch/x86/include/asm/pgtable-3level_types.h |   5 -
 arch/x86/include/asm/proto.h                |   2 +-
 arch/x86/include/asm/segment.h              |   2 +-
 arch/x86/include/asm/traps.h                |   2 +-
 arch/x86/kernel/cpu/common.c                |   8 -
 arch/x86/kernel/paravirt.c                  |  17 --
 arch/x86/kernel/paravirt_patch_32.c         |  36 +--
 arch/x86/xen/Kconfig                        |   3 +-
 arch/x86/xen/Makefile                       |   4 +-
 arch/x86/xen/apic.c                         |  17 --
 arch/x86/xen/enlighten_pv.c                 |  45 +---
 arch/x86/xen/mmu_pv.c                       | 326 +++-------------------------
 arch/x86/xen/p2m.c                          |   4 -
 arch/x86/xen/setup.c                        |  44 +---
 arch/x86/xen/smp_pv.c                       |  19 +-
 arch/x86/xen/xen-asm.S                      |  14 --
 arch/x86/xen/xen-asm_32.S                   | 207 ------------------
 arch/x86/xen/xen-head.S                     |   6 -
 arch/x86/xen/xen-ops.h                      |   5 -
 drivers/xen/Kconfig                         |   4 +-
 24 files changed, 57 insertions(+), 932 deletions(-)
 delete mode 100644 arch/x86/xen/xen-asm_32.S

-- 
2.16.4

[PATCH 1/2] x86/xen: remove 32-bit Xen PV guest support

[Juergen Gross]

Xen is requiring 64-bit machines today. There is no need to carry the
burden of 32-bit PV guest support in the kernel any longer, as new
guests can be either HVM or PVH, or they can use a 64 bit kernel.

Remove the 32-bit Xen PV support from the kernel.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
 arch/x86/entry/entry_32.S      |  93 ------------
 arch/x86/include/asm/proto.h   |   2 +-
 arch/x86/include/asm/segment.h |   2 +-
 arch/x86/include/asm/traps.h   |   2 +-
 arch/x86/xen/Kconfig           |   3 +-
 arch/x86/xen/Makefile          |   4 +-
 arch/x86/xen/apic.c            |  17 ---
 arch/x86/xen/enlighten_pv.c    |  45 +-----
 arch/x86/xen/mmu_pv.c          | 326 ++++-------------------------------------
 arch/x86/xen/p2m.c             |   4 -
 arch/x86/xen/setup.c           |  44 +-----
 arch/x86/xen/smp_pv.c          |  19 +--
 arch/x86/xen/xen-asm.S         |  14 --
 arch/x86/xen/xen-asm_32.S      | 207 --------------------------
 arch/x86/xen/xen-head.S        |   6 -
 arch/x86/xen/xen-ops.h         |   5 -
 drivers/xen/Kconfig            |   4 +-
 17 files changed, 42 insertions(+), 755 deletions(-)
 delete mode 100644 arch/x86/xen/xen-asm_32.S

diff --git a/arch/x86/entry/entry_32.S b/arch/x86/entry/entry_32.S
index 7b23431be5cb..d4464af28212 100644
--- a/arch/x86/entry/entry_32.S
+++ b/arch/x86/entry/entry_32.S
@@ -787,16 +787,6 @@ GLOBAL(__begin_SYSENTER_singlestep_region)
  * will ignore all of the single-step traps generated in this range.
  */
 
-#ifdef CONFIG_XEN_PV
-/*
- * Xen doesn't set %esp to be precisely what the normal SYSENTER
- * entry point expects, so fix it up before using the normal path.
- */
-ENTRY(xen_sysenter_target)
-	addl	$5*4, %esp			/* remove xen-provided frame */
-	jmp	.Lsysenter_past_esp
-#endif
-
 /*
  * 32-bit SYSENTER entry.
  *
@@ -1249,89 +1239,6 @@ ENTRY(spurious_interrupt_bug)
 	jmp	common_exception
 END(spurious_interrupt_bug)
 
-#ifdef CONFIG_XEN_PV
-ENTRY(xen_hypervisor_callback)
-	pushl	$-1				/* orig_ax = -1 => not a system call */
-	SAVE_ALL
-	ENCODE_FRAME_POINTER
-	TRACE_IRQS_OFF
-
-	/*
-	 * Check to see if we got the event in the critical
-	 * region in xen_iret_direct, after we've reenabled
-	 * events and checked for pending events.  This simulates
-	 * iret instruction's behaviour where it delivers a
-	 * pending interrupt when enabling interrupts:
-	 */
-	movl	PT_EIP(%esp), %eax
-	cmpl	$xen_iret_start_crit, %eax
-	jb	1f
-	cmpl	$xen_iret_end_crit, %eax
-	jae	1f
-
-	jmp	xen_iret_crit_fixup
-
-ENTRY(xen_do_upcall)
-1:	mov	%esp, %eax
-	call	xen_evtchn_do_upcall
-#ifndef CONFIG_PREEMPT
-	call	xen_maybe_preempt_hcall
-#endif
-	jmp	ret_from_intr
-ENDPROC(xen_hypervisor_callback)
-
-/*
- * Hypervisor uses this for application faults while it executes.
- * We get here for two reasons:
- *  1. Fault while reloading DS, ES, FS or GS
- *  2. Fault while executing IRET
- * Category 1 we fix up by reattempting the load, and zeroing the segment
- * register if the load fails.
- * Category 2 we fix up by jumping to do_iret_error. We cannot use the
- * normal Linux return path in this case because if we use the IRET hypercall
- * to pop the stack frame we end up in an infinite loop of failsafe callbacks.
- * We distinguish between categories by maintaining a status value in EAX.
- */
-ENTRY(xen_failsafe_callback)
-	pushl	%eax
-	movl	$1, %eax
-1:	mov	4(%esp), %ds
-2:	mov	8(%esp), %es
-3:	mov	12(%esp), %fs
-4:	mov	16(%esp), %gs
-	/* EAX == 0 => Category 1 (Bad segment)
-	   EAX != 0 => Category 2 (Bad IRET) */
-	testl	%eax, %eax
-	popl	%eax
-	lea	16(%esp), %esp
-	jz	5f
-	jmp	iret_exc
-5:	pushl	$-1				/* orig_ax = -1 => not a system call */
-	SAVE_ALL
-	ENCODE_FRAME_POINTER
-	jmp	ret_from_exception
-
-.section .fixup, "ax"
-6:	xorl	%eax, %eax
-	movl	%eax, 4(%esp)
-	jmp	1b
-7:	xorl	%eax, %eax
-	movl	%eax, 8(%esp)
-	jmp	2b
-8:	xorl	%eax, %eax
-	movl	%eax, 12(%esp)
-	jmp	3b
-9:	xorl	%eax, %eax
-	movl	%eax, 16(%esp)
-	jmp	4b
-.previous
-	_ASM_EXTABLE(1b, 6b)
-	_ASM_EXTABLE(2b, 7b)
-	_ASM_EXTABLE(3b, 8b)
-	_ASM_EXTABLE(4b, 9b)
-ENDPROC(xen_failsafe_callback)
-#endif /* CONFIG_XEN_PV */
-
 #ifdef CONFIG_XEN_PVHVM
 BUILD_INTERRUPT3(xen_hvm_callback_vector, HYPERVISOR_CALLBACK_VECTOR,
 		 xen_evtchn_do_upcall)
diff --git a/arch/x86/include/asm/proto.h b/arch/x86/include/asm/proto.h
index 6e81788a30c1..e5a13a138b01 100644
--- a/arch/x86/include/asm/proto.h
+++ b/arch/x86/include/asm/proto.h
@@ -25,7 +25,7 @@ void entry_SYSENTER_compat(void);
 void __end_entry_SYSENTER_compat(void);
 void entry_SYSCALL_compat(void);
 void entry_INT80_compat(void);
-#if defined(CONFIG_X86_64) && defined(CONFIG_XEN_PV)
+#if defined(CONFIG_XEN_PV)
 void xen_entry_INT80_compat(void);
 #endif
 #endif
diff --git a/arch/x86/include/asm/segment.h b/arch/x86/include/asm/segment.h
index ac3892920419..7f485fadfe6e 100644
--- a/arch/x86/include/asm/segment.h
+++ b/arch/x86/include/asm/segment.h
@@ -289,7 +289,7 @@ static inline void vdso_read_cpunode(unsigned *cpu, unsigned *node)
 extern const char early_idt_handler_array[NUM_EXCEPTION_VECTORS][EARLY_IDT_HANDLER_SIZE];
 extern void early_ignore_irq(void);
 
-#if defined(CONFIG_X86_64) && defined(CONFIG_XEN_PV)
+#if defined(CONFIG_XEN_PV)
 extern const char xen_early_idt_handler_array[NUM_EXCEPTION_VECTORS][XEN_EARLY_IDT_HANDLER_SIZE];
 #endif
 
diff --git a/arch/x86/include/asm/traps.h b/arch/x86/include/asm/traps.h
index 7d6f3f3fad78..2b142e58657e 100644
--- a/arch/x86/include/asm/traps.h
+++ b/arch/x86/include/asm/traps.h
@@ -36,7 +36,7 @@ asmlinkage void machine_check(void);
 #endif /* CONFIG_X86_MCE */
 asmlinkage void simd_coprocessor_error(void);
 
-#if defined(CONFIG_X86_64) && defined(CONFIG_XEN_PV)
+#if defined(CONFIG_XEN_PV)
 asmlinkage void xen_divide_error(void);
 asmlinkage void xen_xennmi(void);
 asmlinkage void xen_xendebug(void);
diff --git a/arch/x86/xen/Kconfig b/arch/x86/xen/Kconfig
index e07abefd3d26..dbd7cd38b914 100644
--- a/arch/x86/xen/Kconfig
+++ b/arch/x86/xen/Kconfig
@@ -18,6 +18,7 @@ config XEN_PV
 	bool "Xen PV guest support"
 	default y
 	depends on XEN
+	depends on X86_64
 	select PARAVIRT_XXL
 	select XEN_HAVE_PVMMU
 	select XEN_HAVE_VPMU
@@ -49,7 +50,7 @@ config XEN_PVHVM_SMP
 
 config XEN_512GB
 	bool "Limit Xen pv-domain memory to 512GB"
-	depends on XEN_PV && X86_64
+	depends on XEN_PV
 	default y
 	help
 	  Limit paravirtualized user domains to 512GB of RAM.
diff --git a/arch/x86/xen/Makefile b/arch/x86/xen/Makefile
index 084de77a109e..d42737f31304 100644
--- a/arch/x86/xen/Makefile
+++ b/arch/x86/xen/Makefile
@@ -1,5 +1,5 @@
 # SPDX-License-Identifier: GPL-2.0
-OBJECT_FILES_NON_STANDARD_xen-asm_$(BITS).o := y
+OBJECT_FILES_NON_STANDARD_xen-asm_64.o := y
 
 ifdef CONFIG_FUNCTION_TRACER
 # Do not profile debug and lowlevel utilities
@@ -34,7 +34,7 @@ obj-$(CONFIG_XEN_PV)		+= mmu_pv.o
 obj-$(CONFIG_XEN_PV)		+= irq.o
 obj-$(CONFIG_XEN_PV)		+= multicalls.o
 obj-$(CONFIG_XEN_PV)		+= xen-asm.o
-obj-$(CONFIG_XEN_PV)		+= xen-asm_$(BITS).o
+obj-$(CONFIG_XEN_PV)		+= xen-asm_64.o
 
 obj-$(CONFIG_XEN_PVH)		+= enlighten_pvh.o
 
diff --git a/arch/x86/xen/apic.c b/arch/x86/xen/apic.c
index 5e53bfbe5823..ea6e9c54da9d 100644
--- a/arch/x86/xen/apic.c
+++ b/arch/x86/xen/apic.c
@@ -58,10 +58,6 @@ static u32 xen_apic_read(u32 reg)
 
 	if (reg == APIC_LVR)
 		return 0x14;
-#ifdef CONFIG_X86_32
-	if (reg == APIC_LDR)
-		return SET_APIC_LOGICAL_ID(1UL << smp_processor_id());
-#endif
 	if (reg != APIC_ID)
 		return 0;
 
@@ -127,14 +123,6 @@ static int xen_phys_pkg_id(int initial_apic_id, int index_msb)
 	return initial_apic_id >> index_msb;
 }
 
-#ifdef CONFIG_X86_32
-static int xen_x86_32_early_logical_apicid(int cpu)
-{
-	/* Match with APIC_LDR read. Otherwise setup_local_APIC complains. */
-	return 1 << cpu;
-}
-#endif
-
 static void xen_noop(void)
 {
 }
@@ -197,11 +185,6 @@ static struct apic xen_pv_apic = {
 	.icr_write 			= xen_apic_icr_write,
 	.wait_icr_idle 			= xen_noop,
 	.safe_wait_icr_idle 		= xen_safe_apic_wait_icr_idle,
-
-#ifdef CONFIG_X86_32
-	/* generic_processor_info and setup_local_APIC. */
-	.x86_32_early_logical_apicid	= xen_x86_32_early_logical_apicid,
-#endif
 };
 
 static void __init xen_apic_check(void)
diff --git a/arch/x86/xen/enlighten_pv.c b/arch/x86/xen/enlighten_pv.c
index 4722ba2966ac..cc14bf6354b6 100644
--- a/arch/x86/xen/enlighten_pv.c
+++ b/arch/x86/xen/enlighten_pv.c
@@ -545,13 +545,8 @@ static void xen_load_tls(struct thread_struct *t, unsigned int cpu)
 	 * exception between the new %fs descriptor being loaded and
 	 * %fs being effectively cleared at __switch_to().
 	 */
-	if (paravirt_get_lazy_mode() == PARAVIRT_LAZY_CPU) {
-#ifdef CONFIG_X86_32
-		lazy_load_gs(0);
-#else
+	if (paravirt_get_lazy_mode() == PARAVIRT_LAZY_CPU)
 		loadsegment(fs, 0);
-#endif
-	}
 
 	xen_mc_batch();
 
@@ -562,13 +557,11 @@ static void xen_load_tls(struct thread_struct *t, unsigned int cpu)
 	xen_mc_issue(PARAVIRT_LAZY_CPU);
 }
 
-#ifdef CONFIG_X86_64
 static void xen_load_gs_index(unsigned int idx)
 {
 	if (HYPERVISOR_set_segment_base(SEGBASE_GS_USER_SEL, idx))
 		BUG();
 }
-#endif
 
 static void xen_write_ldt_entry(struct desc_struct *dt, int entrynum,
 				const void *ptr)
@@ -587,7 +580,6 @@ static void xen_write_ldt_entry(struct desc_struct *dt, int entrynum,
 	preempt_enable();
 }
 
-#ifdef CONFIG_X86_64
 struct trap_array_entry {
 	void (*orig)(void);
 	void (*xen)(void);
@@ -657,7 +649,6 @@ static bool __ref get_trap_addr(void **addr, unsigned int ist)
 
 	return true;
 }
-#endif
 
 static int cvt_gate_to_trap(int vector, const gate_desc *val,
 			    struct trap_info *info)
@@ -670,10 +661,8 @@ static int cvt_gate_to_trap(int vector, const gate_desc *val,
 	info->vector = vector;
 
 	addr = gate_offset(val);
-#ifdef CONFIG_X86_64
 	if (!get_trap_addr((void **)&addr, val->bits.ist))
 		return 0;
-#endif	/* CONFIG_X86_64 */
 	info->address = addr;
 
 	info->cs = gate_segment(val);
@@ -877,7 +866,7 @@ static void xen_write_cr4(unsigned long cr4)
 
 	native_write_cr4(cr4);
 }
-#ifdef CONFIG_X86_64
+
 static inline unsigned long xen_read_cr8(void)
 {
 	return 0;
@@ -886,7 +875,6 @@ static inline void xen_write_cr8(unsigned long val)
 {
 	BUG_ON(val);
 }
-#endif
 
 static u64 xen_read_msr_safe(unsigned int msr, int *err)
 {
@@ -911,7 +899,6 @@ static int xen_write_msr_safe(unsigned int msr, unsigned low, unsigned high)
 	ret = 0;
 
 	switch (msr) {
-#ifdef CONFIG_X86_64
 		unsigned which;
 		u64 base;
 
@@ -924,7 +911,6 @@ static int xen_write_msr_safe(unsigned int msr, unsigned low, unsigned high)
 		if (HYPERVISOR_set_segment_base(which, base) != 0)
 			ret = -EIO;
 		break;
-#endif
 
 	case MSR_STAR:
 	case MSR_CSTAR:
@@ -1005,9 +991,7 @@ void __init xen_setup_vcpu_info_placement(void)
 static const struct pv_info xen_info __initconst = {
 	.shared_kernel_pmd = 0,
 
-#ifdef CONFIG_X86_64
 	.extra_user_64bit_cs = FLAT_USER_CS64,
-#endif
 	.name = "Xen",
 };
 
@@ -1022,10 +1006,8 @@ static const struct pv_cpu_ops xen_cpu_ops __initconst = {
 
 	.write_cr4 = xen_write_cr4,
 
-#ifdef CONFIG_X86_64
 	.read_cr8 = xen_read_cr8,
 	.write_cr8 = xen_write_cr8,
-#endif
 
 	.wbinvd = native_wbinvd,
 
@@ -1038,18 +1020,14 @@ static const struct pv_cpu_ops xen_cpu_ops __initconst = {
 	.read_pmc = xen_read_pmc,
 
 	.iret = xen_iret,
-#ifdef CONFIG_X86_64
 	.usergs_sysret64 = xen_sysret64,
-#endif
 
 	.load_tr_desc = paravirt_nop,
 	.set_ldt = xen_set_ldt,
 	.load_gdt = xen_load_gdt,
 	.load_idt = xen_load_idt,
 	.load_tls = xen_load_tls,
-#ifdef CONFIG_X86_64
 	.load_gs_index = xen_load_gs_index,
-#endif
 
 	.alloc_ldt = xen_alloc_ldt,
 	.free_ldt = xen_free_ldt,
@@ -1312,15 +1290,7 @@ asmlinkage __visible void __init xen_start_kernel(void)
 
 	/* keep using Xen gdt for now; no urgent need to change it */
 
-#ifdef CONFIG_X86_32
-	pv_info.kernel_rpl = 1;
-	if (xen_feature(XENFEAT_supervisor_mode_kernel))
-		pv_info.kernel_rpl = 0;
-#else
 	pv_info.kernel_rpl = 0;
-#endif
-	/* set the limit of our address space */
-	xen_reserve_top();
 
 	/*
 	 * We used to do this in xen_arch_setup, but that is too late
@@ -1332,13 +1302,6 @@ asmlinkage __visible void __init xen_start_kernel(void)
 	if (rc != 0)
 		xen_raw_printk("physdev_op failed %d\n", rc);
 
-#ifdef CONFIG_X86_32
-	/* set up basic CPUID stuff */
-	cpu_detect(&new_cpu_data);
-	set_cpu_cap(&new_cpu_data, X86_FEATURE_FPU);
-	new_cpu_data.x86_capability[CPUID_1_EDX] = cpuid_edx(1);
-#endif
-
 	if (xen_start_info->mod_start) {
 	    if (xen_start_info->flags & SIF_MOD_START_PFN)
 		initrd_start = PFN_PHYS(xen_start_info->mod_start);
@@ -1406,12 +1369,8 @@ asmlinkage __visible void __init xen_start_kernel(void)
 	xen_efi_init(&boot_params);
 
 	/* Start the world */
-#ifdef CONFIG_X86_32
-	i386_start_kernel();
-#else
 	cr4_init_shadow(); /* 32b kernel does this in i386_start_kernel() */
 	x86_64_start_reservations((char *)__pa_symbol(&boot_params));
-#endif
 }
 
 static int xen_cpu_up_prepare_pv(unsigned int cpu)
diff --git a/arch/x86/xen/mmu_pv.c b/arch/x86/xen/mmu_pv.c
index beb44e22afdf..d6718782b123 100644
--- a/arch/x86/xen/mmu_pv.c
+++ b/arch/x86/xen/mmu_pv.c
@@ -86,19 +86,8 @@
 #include "mmu.h"
 #include "debugfs.h"
 
-#ifdef CONFIG_X86_32
-/*
- * Identity map, in addition to plain kernel map.  This needs to be
- * large enough to allocate page table pages to allocate the rest.
- * Each page can map 2MB.
- */
-#define LEVEL1_IDENT_ENTRIES	(PTRS_PER_PTE * 4)
-static RESERVE_BRK_ARRAY(pte_t, level1_ident_pgt, LEVEL1_IDENT_ENTRIES);
-#endif
-#ifdef CONFIG_X86_64
 /* l3 pud for userspace vsyscall mapping */
 static pud_t level3_user_vsyscall[PTRS_PER_PUD] __page_aligned_bss;
-#endif /* CONFIG_X86_64 */
 
 /*
  * Protects atomic reservation decrease/increase against concurrent increases.
@@ -439,26 +428,6 @@ static void xen_set_pud(pud_t *ptr, pud_t val)
 	xen_set_pud_hyper(ptr, val);
 }
 
-#ifdef CONFIG_X86_PAE
-static void xen_set_pte_atomic(pte_t *ptep, pte_t pte)
-{
-	trace_xen_mmu_set_pte_atomic(ptep, pte);
-	__xen_set_pte(ptep, pte);
-}
-
-static void xen_pte_clear(struct mm_struct *mm, unsigned long addr, pte_t *ptep)
-{
-	trace_xen_mmu_pte_clear(mm, addr, ptep);
-	__xen_set_pte(ptep, native_make_pte(0));
-}
-
-static void xen_pmd_clear(pmd_t *pmdp)
-{
-	trace_xen_mmu_pmd_clear(pmdp);
-	set_pmd(pmdp, __pmd(0));
-}
-#endif	/* CONFIG_X86_PAE */
-
 __visible pmd_t xen_make_pmd(pmdval_t pmd)
 {
 	pmd = pte_pfn_to_mfn(pmd);
@@ -466,7 +435,6 @@ __visible pmd_t xen_make_pmd(pmdval_t pmd)
 }
 PV_CALLEE_SAVE_REGS_THUNK(xen_make_pmd);
 
-#ifdef CONFIG_X86_64
 __visible pudval_t xen_pud_val(pud_t pud)
 {
 	return pte_mfn_to_pfn(pud.pud);
@@ -571,7 +539,6 @@ __visible p4d_t xen_make_p4d(p4dval_t p4d)
 }
 PV_CALLEE_SAVE_REGS_THUNK(xen_make_p4d);
 #endif  /* CONFIG_PGTABLE_LEVELS >= 5 */
-#endif	/* CONFIG_X86_64 */
 
 static int xen_pmd_walk(struct mm_struct *mm, pmd_t *pmd,
 		int (*func)(struct mm_struct *mm, struct page *, enum pt_level),
@@ -654,14 +621,12 @@ static int __xen_pgd_walk(struct mm_struct *mm, pgd_t *pgd,
 	limit--;
 	BUG_ON(limit >= FIXADDR_TOP);
 
-#ifdef CONFIG_X86_64
 	/*
 	 * 64-bit has a great big hole in the middle of the address
 	 * space, which contains the Xen mappings.
 	 */
 	hole_low = pgd_index(GUARD_HOLE_BASE_ADDR);
 	hole_high = pgd_index(GUARD_HOLE_END_ADDR);
-#endif
 
 	nr = pgd_index(limit) + 1;
 	for (i = 0; i < nr; i++) {
@@ -800,7 +765,6 @@ static void __xen_pgd_pin(struct mm_struct *mm, pgd_t *pgd)
 		xen_mc_batch();
 	}
 
-#ifdef CONFIG_X86_64
 	{
 		pgd_t *user_pgd = xen_get_user_pgd(pgd);
 
@@ -812,14 +776,6 @@ static void __xen_pgd_pin(struct mm_struct *mm, pgd_t *pgd)
 				   PFN_DOWN(__pa(user_pgd)));
 		}
 	}
-#else /* CONFIG_X86_32 */
-#ifdef CONFIG_X86_PAE
-	/* Need to make sure unshared kernel PMD is pinnable */
-	xen_pin_page(mm, pgd_page(pgd[pgd_index(TASK_SIZE)]),
-		     PT_PMD);
-#endif
-	xen_do_pin(MMUEXT_PIN_L3_TABLE, PFN_DOWN(__pa(pgd)));
-#endif /* CONFIG_X86_64 */
 	xen_mc_issue(0);
 }
 
@@ -870,9 +826,7 @@ static int __init xen_mark_pinned(struct mm_struct *mm, struct page *page,
 static void __init xen_after_bootmem(void)
 {
 	static_branch_enable(&xen_struct_pages_ready);
-#ifdef CONFIG_X86_64
 	SetPagePinned(virt_to_page(level3_user_vsyscall));
-#endif
 	xen_pgd_walk(&init_mm, xen_mark_pinned, FIXADDR_TOP);
 }
 
@@ -919,29 +873,18 @@ static int xen_unpin_page(struct mm_struct *mm, struct page *page,
 /* Release a pagetables pages back as normal RW */
 static void __xen_pgd_unpin(struct mm_struct *mm, pgd_t *pgd)
 {
+	pgd_t *user_pgd = xen_get_user_pgd(pgd);
+
 	trace_xen_mmu_pgd_unpin(mm, pgd);
 
 	xen_mc_batch();
 
 	xen_do_pin(MMUEXT_UNPIN_TABLE, PFN_DOWN(__pa(pgd)));
 
-#ifdef CONFIG_X86_64
-	{
-		pgd_t *user_pgd = xen_get_user_pgd(pgd);
-
-		if (user_pgd) {
-			xen_do_pin(MMUEXT_UNPIN_TABLE,
-				   PFN_DOWN(__pa(user_pgd)));
-			xen_unpin_page(mm, virt_to_page(user_pgd), PT_PGD);
-		}
+	if (user_pgd) {
+		xen_do_pin(MMUEXT_UNPIN_TABLE, PFN_DOWN(__pa(user_pgd)));
+		xen_unpin_page(mm, virt_to_page(user_pgd), PT_PGD);
 	}
-#endif
-
-#ifdef CONFIG_X86_PAE
-	/* Need to make sure unshared kernel PMD is unpinned */
-	xen_unpin_page(mm, pgd_page(pgd[pgd_index(TASK_SIZE)]),
-		       PT_PMD);
-#endif
 
 	__xen_pgd_walk(mm, pgd, xen_unpin_page, USER_LIMIT);
 
@@ -1089,7 +1032,6 @@ static void __init pin_pagetable_pfn(unsigned cmd, unsigned long pfn)
 		BUG();
 }
 
-#ifdef CONFIG_X86_64
 static void __init xen_cleanhighmap(unsigned long vaddr,
 				    unsigned long vaddr_end)
 {
@@ -1273,17 +1215,15 @@ static void __init xen_pagetable_cleanhighmap(void)
 	xen_cleanhighmap(addr, roundup(addr + size, PMD_SIZE * 2));
 	xen_start_info->pt_base = (unsigned long)__va(__pa(xen_start_info->pt_base));
 }
-#endif
 
 static void __init xen_pagetable_p2m_setup(void)
 {
 	xen_vmalloc_p2m_tree();
 
-#ifdef CONFIG_X86_64
 	xen_pagetable_p2m_free();
 
 	xen_pagetable_cleanhighmap();
-#endif
+
 	/* And revector! Bye bye old array */
 	xen_start_info->mfn_list = (unsigned long)xen_p2m_addr;
 }
@@ -1430,6 +1370,8 @@ static void __xen_write_cr3(bool kernel, unsigned long cr3)
 }
 static void xen_write_cr3(unsigned long cr3)
 {
+	pgd_t *user_pgd = xen_get_user_pgd(__va(cr3));
+
 	BUG_ON(preemptible());
 
 	xen_mc_batch();  /* disables interrupts */
@@ -1440,20 +1382,14 @@ static void xen_write_cr3(unsigned long cr3)
 
 	__xen_write_cr3(true, cr3);
 
-#ifdef CONFIG_X86_64
-	{
-		pgd_t *user_pgd = xen_get_user_pgd(__va(cr3));
-		if (user_pgd)
-			__xen_write_cr3(false, __pa(user_pgd));
-		else
-			__xen_write_cr3(false, 0);
-	}
-#endif
+	if (user_pgd)
+		__xen_write_cr3(false, __pa(user_pgd));
+	else
+		__xen_write_cr3(false, 0);
 
 	xen_mc_issue(PARAVIRT_LAZY_CPU);  /* interrupts restored */
 }
 
-#ifdef CONFIG_X86_64
 /*
  * At the start of the day - when Xen launches a guest, it has already
  * built pagetables for the guest. We diligently look over them
@@ -1488,49 +1424,39 @@ static void __init xen_write_cr3_init(unsigned long cr3)
 
 	xen_mc_issue(PARAVIRT_LAZY_CPU);  /* interrupts restored */
 }
-#endif
 
 static int xen_pgd_alloc(struct mm_struct *mm)
 {
 	pgd_t *pgd = mm->pgd;
-	int ret = 0;
+	int ret = -ENOMEM;
+	struct page *page = virt_to_page(pgd);
+	pgd_t *user_pgd;
 
 	BUG_ON(PagePinned(virt_to_page(pgd)));
+	BUG_ON(page->private != 0);
 
-#ifdef CONFIG_X86_64
-	{
-		struct page *page = virt_to_page(pgd);
-		pgd_t *user_pgd;
-
-		BUG_ON(page->private != 0);
-
-		ret = -ENOMEM;
-
-		user_pgd = (pgd_t *)__get_free_page(GFP_KERNEL | __GFP_ZERO);
-		page->private = (unsigned long)user_pgd;
+	user_pgd = (pgd_t *)__get_free_page(GFP_KERNEL | __GFP_ZERO);
+	page->private = (unsigned long)user_pgd;
 
-		if (user_pgd != NULL) {
+	if (user_pgd != NULL) {
 #ifdef CONFIG_X86_VSYSCALL_EMULATION
-			user_pgd[pgd_index(VSYSCALL_ADDR)] =
-				__pgd(__pa(level3_user_vsyscall) | _PAGE_TABLE);
+		user_pgd[pgd_index(VSYSCALL_ADDR)] =
+			__pgd(__pa(level3_user_vsyscall) | _PAGE_TABLE);
 #endif
-			ret = 0;
-		}
-
-		BUG_ON(PagePinned(virt_to_page(xen_get_user_pgd(pgd))));
+		ret = 0;
 	}
-#endif
+
+	BUG_ON(PagePinned(virt_to_page(xen_get_user_pgd(pgd))));
+
 	return ret;
 }
 
 static void xen_pgd_free(struct mm_struct *mm, pgd_t *pgd)
 {
-#ifdef CONFIG_X86_64
 	pgd_t *user_pgd = xen_get_user_pgd(pgd);
 
 	if (user_pgd)
 		free_page((unsigned long)user_pgd);
-#endif
 }
 
 /*
@@ -1549,7 +1475,6 @@ static void xen_pgd_free(struct mm_struct *mm, pgd_t *pgd)
  */
 __visible pte_t xen_make_pte_init(pteval_t pte)
 {
-#ifdef CONFIG_X86_64
 	unsigned long pfn;
 
 	/*
@@ -1563,7 +1488,7 @@ __visible pte_t xen_make_pte_init(pteval_t pte)
 	    pfn >= xen_start_info->first_p2m_pfn &&
 	    pfn < xen_start_info->first_p2m_pfn + xen_start_info->nr_p2m_frames)
 		pte &= ~_PAGE_RW;
-#endif
+
 	pte = pte_pfn_to_mfn(pte);
 	return native_make_pte(pte);
 }
@@ -1571,13 +1496,6 @@ PV_CALLEE_SAVE_REGS_THUNK(xen_make_pte_init);
 
 static void __init xen_set_pte_init(pte_t *ptep, pte_t pte)
 {
-#ifdef CONFIG_X86_32
-	/* If there's an existing pte, then don't allow _PAGE_RW to be set */
-	if (pte_mfn(pte) != INVALID_P2M_ENTRY
-	    && pte_val_ma(*ptep) & _PAGE_PRESENT)
-		pte = __pte_ma(((pte_val_ma(*ptep) & _PAGE_RW) | ~_PAGE_RW) &
-			       pte_val_ma(pte));
-#endif
 	__xen_set_pte(ptep, pte);
 }
 
@@ -1712,7 +1630,6 @@ static void xen_release_pmd(unsigned long pfn)
 	xen_release_ptpage(pfn, PT_PMD);
 }
 
-#ifdef CONFIG_X86_64
 static void xen_alloc_pud(struct mm_struct *mm, unsigned long pfn)
 {
 	xen_alloc_ptpage(mm, pfn, PT_PUD);
@@ -1722,20 +1639,6 @@ static void xen_release_pud(unsigned long pfn)
 {
 	xen_release_ptpage(pfn, PT_PUD);
 }
-#endif
-
-void __init xen_reserve_top(void)
-{
-#ifdef CONFIG_X86_32
-	unsigned long top = HYPERVISOR_VIRT_START;
-	struct xen_platform_parameters pp;
-
-	if (HYPERVISOR_xen_version(XENVER_platform_parameters, &pp) == 0)
-		top = pp.virt_start;
-
-	reserve_top_address(-top);
-#endif	/* CONFIG_X86_32 */
-}
 
 /*
  * Like __va(), but returns address in the kernel mapping (which is
@@ -1743,11 +1646,7 @@ void __init xen_reserve_top(void)
  */
 static void * __init __ka(phys_addr_t paddr)
 {
-#ifdef CONFIG_X86_64
 	return (void *)(paddr + __START_KERNEL_map);
-#else
-	return __va(paddr);
-#endif
 }
 
 /* Convert a machine address to physical address */
@@ -1781,56 +1680,7 @@ static void __init set_page_prot(void *addr, pgprot_t prot)
 {
 	return set_page_prot_flags(addr, prot, UVMF_NONE);
 }
-#ifdef CONFIG_X86_32
-static void __init xen_map_identity_early(pmd_t *pmd, unsigned long max_pfn)
-{
-	unsigned pmdidx, pteidx;
-	unsigned ident_pte;
-	unsigned long pfn;
-
-	level1_ident_pgt = extend_brk(sizeof(pte_t) * LEVEL1_IDENT_ENTRIES,
-				      PAGE_SIZE);
-
-	ident_pte = 0;
-	pfn = 0;
-	for (pmdidx = 0; pmdidx < PTRS_PER_PMD && pfn < max_pfn; pmdidx++) {
-		pte_t *pte_page;
-
-		/* Reuse or allocate a page of ptes */
-		if (pmd_present(pmd[pmdidx]))
-			pte_page = m2v(pmd[pmdidx].pmd);
-		else {
-			/* Check for free pte pages */
-			if (ident_pte == LEVEL1_IDENT_ENTRIES)
-				break;
-
-			pte_page = &level1_ident_pgt[ident_pte];
-			ident_pte += PTRS_PER_PTE;
-
-			pmd[pmdidx] = __pmd(__pa(pte_page) | _PAGE_TABLE);
-		}
-
-		/* Install mappings */
-		for (pteidx = 0; pteidx < PTRS_PER_PTE; pteidx++, pfn++) {
-			pte_t pte;
-
-			if (pfn > max_pfn_mapped)
-				max_pfn_mapped = pfn;
-
-			if (!pte_none(pte_page[pteidx]))
-				continue;
-
-			pte = pfn_pte(pfn, PAGE_KERNEL_EXEC);
-			pte_page[pteidx] = pte;
-		}
-	}
 
-	for (pteidx = 0; pteidx < ident_pte; pteidx += PTRS_PER_PTE)
-		set_page_prot(&level1_ident_pgt[pteidx], PAGE_KERNEL_RO);
-
-	set_page_prot(pmd, PAGE_KERNEL_RO);
-}
-#endif
 void __init xen_setup_machphys_mapping(void)
 {
 	struct xen_machphys_mapping mapping;
@@ -1841,13 +1691,8 @@ void __init xen_setup_machphys_mapping(void)
 	} else {
 		machine_to_phys_nr = MACH2PHYS_NR_ENTRIES;
 	}
-#ifdef CONFIG_X86_32
-	WARN_ON((machine_to_phys_mapping + (machine_to_phys_nr - 1))
-		< machine_to_phys_mapping);
-#endif
 }
 
-#ifdef CONFIG_X86_64
 static void __init convert_pfn_mfn(void *v)
 {
 	pte_t *pte = v;
@@ -2178,105 +2023,6 @@ void __init xen_relocate_p2m(void)
 	xen_start_info->nr_p2m_frames = n_frames;
 }
 
-#else	/* !CONFIG_X86_64 */
-static RESERVE_BRK_ARRAY(pmd_t, initial_kernel_pmd, PTRS_PER_PMD);
-static RESERVE_BRK_ARRAY(pmd_t, swapper_kernel_pmd, PTRS_PER_PMD);
-RESERVE_BRK(fixup_kernel_pmd, PAGE_SIZE);
-RESERVE_BRK(fixup_kernel_pte, PAGE_SIZE);
-
-static void __init xen_write_cr3_init(unsigned long cr3)
-{
-	unsigned long pfn = PFN_DOWN(__pa(swapper_pg_dir));
-
-	BUG_ON(read_cr3_pa() != __pa(initial_page_table));
-	BUG_ON(cr3 != __pa(swapper_pg_dir));
-
-	/*
-	 * We are switching to swapper_pg_dir for the first time (from
-	 * initial_page_table) and therefore need to mark that page
-	 * read-only and then pin it.
-	 *
-	 * Xen disallows sharing of kernel PMDs for PAE
-	 * guests. Therefore we must copy the kernel PMD from
-	 * initial_page_table into a new kernel PMD to be used in
-	 * swapper_pg_dir.
-	 */
-	swapper_kernel_pmd =
-		extend_brk(sizeof(pmd_t) * PTRS_PER_PMD, PAGE_SIZE);
-	copy_page(swapper_kernel_pmd, initial_kernel_pmd);
-	swapper_pg_dir[KERNEL_PGD_BOUNDARY] =
-		__pgd(__pa(swapper_kernel_pmd) | _PAGE_PRESENT);
-	set_page_prot(swapper_kernel_pmd, PAGE_KERNEL_RO);
-
-	set_page_prot(swapper_pg_dir, PAGE_KERNEL_RO);
-	xen_write_cr3(cr3);
-	pin_pagetable_pfn(MMUEXT_PIN_L3_TABLE, pfn);
-
-	pin_pagetable_pfn(MMUEXT_UNPIN_TABLE,
-			  PFN_DOWN(__pa(initial_page_table)));
-	set_page_prot(initial_page_table, PAGE_KERNEL);
-	set_page_prot(initial_kernel_pmd, PAGE_KERNEL);
-
-	pv_ops.mmu.write_cr3 = &xen_write_cr3;
-}
-
-/*
- * For 32 bit domains xen_start_info->pt_base is the pgd address which might be
- * not the first page table in the page table pool.
- * Iterate through the initial page tables to find the real page table base.
- */
-static phys_addr_t __init xen_find_pt_base(pmd_t *pmd)
-{
-	phys_addr_t pt_base, paddr;
-	unsigned pmdidx;
-
-	pt_base = min(__pa(xen_start_info->pt_base), __pa(pmd));
-
-	for (pmdidx = 0; pmdidx < PTRS_PER_PMD; pmdidx++)
-		if (pmd_present(pmd[pmdidx]) && !pmd_large(pmd[pmdidx])) {
-			paddr = m2p(pmd[pmdidx].pmd);
-			pt_base = min(pt_base, paddr);
-		}
-
-	return pt_base;
-}
-
-void __init xen_setup_kernel_pagetable(pgd_t *pgd, unsigned long max_pfn)
-{
-	pmd_t *kernel_pmd;
-
-	kernel_pmd = m2v(pgd[KERNEL_PGD_BOUNDARY].pgd);
-
-	xen_pt_base = xen_find_pt_base(kernel_pmd);
-	xen_pt_size = xen_start_info->nr_pt_frames * PAGE_SIZE;
-
-	initial_kernel_pmd =
-		extend_brk(sizeof(pmd_t) * PTRS_PER_PMD, PAGE_SIZE);
-
-	max_pfn_mapped = PFN_DOWN(xen_pt_base + xen_pt_size + 512 * 1024);
-
-	copy_page(initial_kernel_pmd, kernel_pmd);
-
-	xen_map_identity_early(initial_kernel_pmd, max_pfn);
-
-	copy_page(initial_page_table, pgd);
-	initial_page_table[KERNEL_PGD_BOUNDARY] =
-		__pgd(__pa(initial_kernel_pmd) | _PAGE_PRESENT);
-
-	set_page_prot(initial_kernel_pmd, PAGE_KERNEL_RO);
-	set_page_prot(initial_page_table, PAGE_KERNEL_RO);
-	set_page_prot(empty_zero_page, PAGE_KERNEL_RO);
-
-	pin_pagetable_pfn(MMUEXT_UNPIN_TABLE, PFN_DOWN(__pa(pgd)));
-
-	pin_pagetable_pfn(MMUEXT_PIN_L3_TABLE,
-			  PFN_DOWN(__pa(initial_page_table)));
-	xen_write_cr3(__pa(initial_page_table));
-
-	memblock_reserve(xen_pt_base, xen_pt_size);
-}
-#endif	/* CONFIG_X86_64 */
-
 void __init xen_reserve_special_pages(void)
 {
 	phys_addr_t paddr;
@@ -2310,12 +2056,7 @@ static void xen_set_fixmap(unsigned idx, phys_addr_t phys, pgprot_t prot)
 
 	switch (idx) {
 	case FIX_BTMAP_END ... FIX_BTMAP_BEGIN:
-#ifdef CONFIG_X86_32
-	case FIX_WP_TEST:
-# ifdef CONFIG_HIGHMEM
-	case FIX_KMAP_BEGIN ... FIX_KMAP_END:
-# endif
-#elif defined(CONFIG_X86_VSYSCALL_EMULATION)
+#if defined(CONFIG_X86_VSYSCALL_EMULATION)
 	case VSYSCALL_PAGE:
 #endif
 		/* All local page mappings */
@@ -2367,9 +2108,7 @@ static void __init xen_post_allocator_init(void)
 	pv_ops.mmu.set_pte = xen_set_pte;
 	pv_ops.mmu.set_pmd = xen_set_pmd;
 	pv_ops.mmu.set_pud = xen_set_pud;
-#ifdef CONFIG_X86_64
 	pv_ops.mmu.set_p4d = xen_set_p4d;
-#endif
 
 	/* This will work as long as patching hasn't happened yet
 	   (which it hasn't) */
@@ -2377,15 +2116,11 @@ static void __init xen_post_allocator_init(void)
 	pv_ops.mmu.alloc_pmd = xen_alloc_pmd;
 	pv_ops.mmu.release_pte = xen_release_pte;
 	pv_ops.mmu.release_pmd = xen_release_pmd;
-#ifdef CONFIG_X86_64
 	pv_ops.mmu.alloc_pud = xen_alloc_pud;
 	pv_ops.mmu.release_pud = xen_release_pud;
-#endif
 	pv_ops.mmu.make_pte = PV_CALLEE_SAVE(xen_make_pte);
 
-#ifdef CONFIG_X86_64
 	pv_ops.mmu.write_cr3 = &xen_write_cr3;
-#endif
 }
 
 static void xen_leave_lazy_mmu(void)
@@ -2430,17 +2165,11 @@ static const struct pv_mmu_ops xen_mmu_ops __initconst = {
 	.make_pte = PV_CALLEE_SAVE(xen_make_pte_init),
 	.make_pgd = PV_CALLEE_SAVE(xen_make_pgd),
 
-#ifdef CONFIG_X86_PAE
-	.set_pte_atomic = xen_set_pte_atomic,
-	.pte_clear = xen_pte_clear,
-	.pmd_clear = xen_pmd_clear,
-#endif	/* CONFIG_X86_PAE */
 	.set_pud = xen_set_pud_hyper,
 
 	.make_pmd = PV_CALLEE_SAVE(xen_make_pmd),
 	.pmd_val = PV_CALLEE_SAVE(xen_pmd_val),
 
-#ifdef CONFIG_X86_64
 	.pud_val = PV_CALLEE_SAVE(xen_pud_val),
 	.make_pud = PV_CALLEE_SAVE(xen_make_pud),
 	.set_p4d = xen_set_p4d_hyper,
@@ -2452,7 +2181,6 @@ static const struct pv_mmu_ops xen_mmu_ops __initconst = {
 	.p4d_val = PV_CALLEE_SAVE(xen_p4d_val),
 	.make_p4d = PV_CALLEE_SAVE(xen_make_p4d),
 #endif
-#endif	/* CONFIG_X86_64 */
 
 	.activate_mm = xen_activate_mm,
 	.dup_mmap = xen_dup_mmap,
diff --git a/arch/x86/xen/p2m.c b/arch/x86/xen/p2m.c
index 95ce9b5be411..a6cd2936d214 100644
--- a/arch/x86/xen/p2m.c
+++ b/arch/x86/xen/p2m.c
@@ -379,12 +379,8 @@ static void __init xen_rebuild_p2m_list(unsigned long *p2m)
 
 		if (type == P2M_TYPE_PFN || i < chunk) {
 			/* Use initial p2m page contents. */
-#ifdef CONFIG_X86_64
 			mfns = alloc_p2m_page();
 			copy_page(mfns, xen_p2m_addr + pfn);
-#else
-			mfns = xen_p2m_addr + pfn;
-#endif
 			ptep = populate_extra_pte((unsigned long)(p2m + pfn));
 			set_pte(ptep,
 				pfn_pte(PFN_DOWN(__pa(mfns)), PAGE_KERNEL));
diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
index 548d1e0a5ba1..ff401026ad84 100644
--- a/arch/x86/xen/setup.c
+++ b/arch/x86/xen/setup.c
@@ -544,13 +544,10 @@ static unsigned long __init xen_get_pages_limit(void)
 {
 	unsigned long limit;
 
-#ifdef CONFIG_X86_32
-	limit = GB(64) / PAGE_SIZE;
-#else
 	limit = MAXMEM / PAGE_SIZE;
 	if (!xen_initial_domain() && xen_512gb_limit)
 		limit = GB(512) / PAGE_SIZE;
-#endif
+
 	return limit;
 }
 
@@ -721,17 +718,8 @@ static void __init xen_reserve_xen_mfnlist(void)
 	if (!xen_is_e820_reserved(start, size))
 		return;
 
-#ifdef CONFIG_X86_32
-	/*
-	 * Relocating the p2m on 32 bit system to an arbitrary virtual address
-	 * is not supported, so just give up.
-	 */
-	xen_raw_console_write("Xen hypervisor allocated p2m list conflicts with E820 map\n");
-	BUG();
-#else
 	xen_relocate_p2m();
 	memblock_free(start, size);
-#endif
 }
 
 /**
@@ -920,20 +908,6 @@ char * __init xen_memory_setup(void)
 	return "Xen";
 }
 
-/*
- * Set the bit indicating "nosegneg" library variants should be used.
- * We only need to bother in pure 32-bit mode; compat 32-bit processes
- * can have un-truncated segments, so wrapping around is allowed.
- */
-static void __init fiddle_vdso(void)
-{
-#ifdef CONFIG_X86_32
-	u32 *mask = vdso_image_32.data +
-		vdso_image_32.sym_VDSO32_NOTE_MASK;
-	*mask |= 1 << VDSO_NOTE_NONEGSEG_BIT;
-#endif
-}
-
 static int register_callback(unsigned type, const void *func)
 {
 	struct callback_register callback = {
@@ -948,25 +922,17 @@ static int register_callback(unsigned type, const void *func)
 void xen_enable_sysenter(void)
 {
 	int ret;
-	unsigned sysenter_feature;
-
-#ifdef CONFIG_X86_32
-	sysenter_feature = X86_FEATURE_SEP;
-#else
-	sysenter_feature = X86_FEATURE_SYSENTER32;
-#endif
 
-	if (!boot_cpu_has(sysenter_feature))
+	if (!boot_cpu_has(X86_FEATURE_SYSENTER32))
 		return;
 
 	ret = register_callback(CALLBACKTYPE_sysenter, xen_sysenter_target);
-	if(ret != 0)
-		setup_clear_cpu_cap(sysenter_feature);
+	if (ret != 0)
+		setup_clear_cpu_cap(X86_FEATURE_SYSENTER32);
 }
 
 void xen_enable_syscall(void)
 {
-#ifdef CONFIG_X86_64
 	int ret;
 
 	ret = register_callback(CALLBACKTYPE_syscall, xen_syscall_target);
@@ -982,7 +948,6 @@ void xen_enable_syscall(void)
 		if (ret != 0)
 			setup_clear_cpu_cap(X86_FEATURE_SYSCALL32);
 	}
-#endif /* CONFIG_X86_64 */
 }
 
 void __init xen_pvmmu_arch_setup(void)
@@ -1022,7 +987,6 @@ void __init xen_arch_setup(void)
 	disable_cpuidle();
 	disable_cpufreq();
 	WARN_ON(xen_set_default_idle());
-	fiddle_vdso();
 #ifdef CONFIG_NUMA
 	numa_off = 1;
 #endif
diff --git a/arch/x86/xen/smp_pv.c b/arch/x86/xen/smp_pv.c
index 590fcf863006..20977a242003 100644
--- a/arch/x86/xen/smp_pv.c
+++ b/arch/x86/xen/smp_pv.c
@@ -208,15 +208,6 @@ static void __init xen_pv_smp_prepare_boot_cpu(void)
 		 * sure the old memory can be recycled. */
 		make_lowmem_page_readwrite(xen_initial_gdt);
 
-#ifdef CONFIG_X86_32
-	/*
-	 * Xen starts us with XEN_FLAT_RING1_DS, but linux code
-	 * expects __USER_DS
-	 */
-	loadsegment(ds, __USER_DS);
-	loadsegment(es, __USER_DS);
-#endif
-
 	xen_filter_cpu_maps();
 	xen_setup_vcpu_info_placement();
 
@@ -296,10 +287,6 @@ cpu_initialize_context(unsigned int cpu, struct task_struct *idle)
 
 	gdt = get_cpu_gdt_rw(cpu);
 
-#ifdef CONFIG_X86_32
-	ctxt->user_regs.fs = __KERNEL_PERCPU;
-	ctxt->user_regs.gs = __KERNEL_STACK_CANARY;
-#endif
 	memset(&ctxt->fpu_ctxt, 0, sizeof(ctxt->fpu_ctxt));
 
 	/*
@@ -337,12 +324,8 @@ cpu_initialize_context(unsigned int cpu, struct task_struct *idle)
 	ctxt->kernel_ss = __KERNEL_DS;
 	ctxt->kernel_sp = task_top_of_stack(idle);
 
-#ifdef CONFIG_X86_32
-	ctxt->event_callback_cs     = __KERNEL_CS;
-	ctxt->failsafe_callback_cs  = __KERNEL_CS;
-#else
 	ctxt->gs_base_kernel = per_cpu_offset(cpu);
-#endif
+
 	ctxt->event_callback_eip    =
 		(unsigned long)xen_hypervisor_callback;
 	ctxt->failsafe_callback_eip =
diff --git a/arch/x86/xen/xen-asm.S b/arch/x86/xen/xen-asm.S
index 8019edd0125c..54e1e9ca35a4 100644
--- a/arch/x86/xen/xen-asm.S
+++ b/arch/x86/xen/xen-asm.S
@@ -75,11 +75,7 @@ ENTRY(xen_save_fl_direct)
  */
 ENTRY(xen_restore_fl_direct)
 	FRAME_BEGIN
-#ifdef CONFIG_X86_64
 	testw $X86_EFLAGS_IF, %di
-#else
-	testb $X86_EFLAGS_IF>>8, %ah
-#endif
 	setz PER_CPU_VAR(xen_vcpu_info) + XEN_vcpu_info_mask
 	/*
 	 * Preempt here doesn't matter because that will deal with any
@@ -103,15 +99,6 @@ ENTRY(xen_restore_fl_direct)
  */
 ENTRY(check_events)
 	FRAME_BEGIN
-#ifdef CONFIG_X86_32
-	push %eax
-	push %ecx
-	push %edx
-	call xen_force_evtchn_callback
-	pop %edx
-	pop %ecx
-	pop %eax
-#else
 	push %rax
 	push %rcx
 	push %rdx
@@ -131,7 +118,6 @@ ENTRY(check_events)
 	pop %rdx
 	pop %rcx
 	pop %rax
-#endif
 	FRAME_END
 	ret
 ENDPROC(check_events)
diff --git a/arch/x86/xen/xen-asm_32.S b/arch/x86/xen/xen-asm_32.S
deleted file mode 100644
index c15db060a242..000000000000
--- a/arch/x86/xen/xen-asm_32.S
+++ /dev/null
@@ -1,207 +0,0 @@
-/* SPDX-License-Identifier: GPL-2.0 */
-/*
- * Asm versions of Xen pv-ops, suitable for direct use.
- *
- * We only bother with direct forms (ie, vcpu in pda) of the
- * operations here; the indirect forms are better handled in C.
- */
-
-#include <asm/thread_info.h>
-#include <asm/processor-flags.h>
-#include <asm/segment.h>
-#include <asm/asm.h>
-
-#include <xen/interface/xen.h>
-
-#include <linux/linkage.h>
-
-/* Pseudo-flag used for virtual NMI, which we don't implement yet */
-#define XEN_EFLAGS_NMI  0x80000000
-
-/*
- * This is run where a normal iret would be run, with the same stack setup:
- *	8: eflags
- *	4: cs
- *	esp-> 0: eip
- *
- * This attempts to make sure that any pending events are dealt with
- * on return to usermode, but there is a small window in which an
- * event can happen just before entering usermode.  If the nested
- * interrupt ends up setting one of the TIF_WORK_MASK pending work
- * flags, they will not be tested again before returning to
- * usermode. This means that a process can end up with pending work,
- * which will be unprocessed until the process enters and leaves the
- * kernel again, which could be an unbounded amount of time.  This
- * means that a pending signal or reschedule event could be
- * indefinitely delayed.
- *
- * The fix is to notice a nested interrupt in the critical window, and
- * if one occurs, then fold the nested interrupt into the current
- * interrupt stack frame, and re-process it iteratively rather than
- * recursively.  This means that it will exit via the normal path, and
- * all pending work will be dealt with appropriately.
- *
- * Because the nested interrupt handler needs to deal with the current
- * stack state in whatever form its in, we keep things simple by only
- * using a single register which is pushed/popped on the stack.
- */
-
-.macro POP_FS
-1:
-	popw %fs
-.pushsection .fixup, "ax"
-2:	movw $0, (%esp)
-	jmp 1b
-.popsection
-	_ASM_EXTABLE(1b,2b)
-.endm
-
-ENTRY(xen_iret)
-	/* test eflags for special cases */
-	testl $(X86_EFLAGS_VM | XEN_EFLAGS_NMI), 8(%esp)
-	jnz hyper_iret
-
-	push %eax
-	ESP_OFFSET=4	# bytes pushed onto stack
-
-	/* Store vcpu_info pointer for easy access */
-#ifdef CONFIG_SMP
-	pushw %fs
-	movl $(__KERNEL_PERCPU), %eax
-	movl %eax, %fs
-	movl %fs:xen_vcpu, %eax
-	POP_FS
-#else
-	movl %ss:xen_vcpu, %eax
-#endif
-
-	/* check IF state we're restoring */
-	testb $X86_EFLAGS_IF>>8, 8+1+ESP_OFFSET(%esp)
-
-	/*
-	 * Maybe enable events.  Once this happens we could get a
-	 * recursive event, so the critical region starts immediately
-	 * afterwards.  However, if that happens we don't end up
-	 * resuming the code, so we don't have to be worried about
-	 * being preempted to another CPU.
-	 */
-	setz %ss:XEN_vcpu_info_mask(%eax)
-xen_iret_start_crit:
-
-	/* check for unmasked and pending */
-	cmpw $0x0001, %ss:XEN_vcpu_info_pending(%eax)
-
-	/*
-	 * If there's something pending, mask events again so we can
-	 * jump back into xen_hypervisor_callback. Otherwise do not
-	 * touch XEN_vcpu_info_mask.
-	 */
-	jne 1f
-	movb $1, %ss:XEN_vcpu_info_mask(%eax)
-
-1:	popl %eax
-
-	/*
-	 * From this point on the registers are restored and the stack
-	 * updated, so we don't need to worry about it if we're
-	 * preempted
-	 */
-iret_restore_end:
-
-	/*
-	 * Jump to hypervisor_callback after fixing up the stack.
-	 * Events are masked, so jumping out of the critical region is
-	 * OK.
-	 */
-	je xen_hypervisor_callback
-
-1:	iret
-xen_iret_end_crit:
-	_ASM_EXTABLE(1b, iret_exc)
-
-hyper_iret:
-	/* put this out of line since its very rarely used */
-	jmp hypercall_page + __HYPERVISOR_iret * 32
-
-	.globl xen_iret_start_crit, xen_iret_end_crit
-
-/*
- * This is called by xen_hypervisor_callback in entry.S when it sees
- * that the EIP at the time of interrupt was between
- * xen_iret_start_crit and xen_iret_end_crit.  We're passed the EIP in
- * %eax so we can do a more refined determination of what to do.
- *
- * The stack format at this point is:
- *	----------------
- *	 ss		: (ss/esp may be present if we came from usermode)
- *	 esp		:
- *	 eflags		}  outer exception info
- *	 cs		}
- *	 eip		}
- *	---------------- <- edi (copy dest)
- *	 eax		:  outer eax if it hasn't been restored
- *	----------------
- *	 eflags		}  nested exception info
- *	 cs		}   (no ss/esp because we're nested
- *	 eip		}    from the same ring)
- *	 orig_eax	}<- esi (copy src)
- *	 - - - - - - - -
- *	 fs		}
- *	 es		}
- *	 ds		}  SAVE_ALL state
- *	 eax		}
- *	  :		:
- *	 ebx		}<- esp
- *	----------------
- *
- * In order to deliver the nested exception properly, we need to shift
- * everything from the return addr up to the error code so it sits
- * just under the outer exception info.  This means that when we
- * handle the exception, we do it in the context of the outer
- * exception rather than starting a new one.
- *
- * The only caveat is that if the outer eax hasn't been restored yet
- * (ie, it's still on stack), we need to insert its value into the
- * SAVE_ALL state before going on, since it's usermode state which we
- * eventually need to restore.
- */
-ENTRY(xen_iret_crit_fixup)
-	/*
-	 * Paranoia: Make sure we're really coming from kernel space.
-	 * One could imagine a case where userspace jumps into the
-	 * critical range address, but just before the CPU delivers a
-	 * GP, it decides to deliver an interrupt instead.  Unlikely?
-	 * Definitely.  Easy to avoid?  Yes.  The Intel documents
-	 * explicitly say that the reported EIP for a bad jump is the
-	 * jump instruction itself, not the destination, but some
-	 * virtual environments get this wrong.
-	 */
-	movl PT_CS(%esp), %ecx
-	andl $SEGMENT_RPL_MASK, %ecx
-	cmpl $USER_RPL, %ecx
-	je 2f
-
-	lea PT_ORIG_EAX(%esp), %esi
-	lea PT_EFLAGS(%esp), %edi
-
-	/*
-	 * If eip is before iret_restore_end then stack
-	 * hasn't been restored yet.
-	 */
-	cmp $iret_restore_end, %eax
-	jae 1f
-
-	movl 0+4(%edi), %eax		/* copy EAX (just above top of frame) */
-	movl %eax, PT_EAX(%esp)
-
-	lea ESP_OFFSET(%edi), %edi	/* move dest up over saved regs */
-
-	/* set up the copy */
-1:	std
-	mov $PT_EIP / 4, %ecx		/* saved regs up to orig_eax */
-	rep movsl
-	cld
-
-	lea 4(%edi), %esp		/* point esp to new frame */
-2:	jmp xen_do_upcall
-
diff --git a/arch/x86/xen/xen-head.S b/arch/x86/xen/xen-head.S
index c1d8b90aa4e2..03a7af6b7453 100644
--- a/arch/x86/xen/xen-head.S
+++ b/arch/x86/xen/xen-head.S
@@ -37,7 +37,6 @@ ENTRY(startup_xen)
 	mov %_ASM_SI, xen_start_info
 	mov $init_thread_union+THREAD_SIZE, %_ASM_SP
 
-#ifdef CONFIG_X86_64
 	/* Set up %gs.
 	 *
 	 * The base of %gs always points to fixed_percpu_data.  If the
@@ -49,7 +48,6 @@ ENTRY(startup_xen)
 	movq	$INIT_PER_CPU_VAR(fixed_percpu_data),%rax
 	cdq
 	wrmsr
-#endif
 
 	jmp xen_start_kernel
 END(startup_xen)
@@ -75,13 +73,9 @@ END(hypercall_page)
 	ELFNOTE(Xen, XEN_ELFNOTE_GUEST_OS,       .asciz "linux")
 	ELFNOTE(Xen, XEN_ELFNOTE_GUEST_VERSION,  .asciz "2.6")
 	ELFNOTE(Xen, XEN_ELFNOTE_XEN_VERSION,    .asciz "xen-3.0")
-#ifdef CONFIG_X86_32
-	ELFNOTE(Xen, XEN_ELFNOTE_VIRT_BASE,      _ASM_PTR __PAGE_OFFSET)
-#else
 	ELFNOTE(Xen, XEN_ELFNOTE_VIRT_BASE,      _ASM_PTR __START_KERNEL_map)
 	/* Map the p2m table to a 512GB-aligned user address. */
 	ELFNOTE(Xen, XEN_ELFNOTE_INIT_P2M,       .quad (PUD_SIZE * PTRS_PER_PUD))
-#endif
 #ifdef CONFIG_XEN_PV
 	ELFNOTE(Xen, XEN_ELFNOTE_ENTRY,          _ASM_PTR startup_xen)
 #endif
diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h
index 2f111f47ba98..cfe9170e3970 100644
--- a/arch/x86/xen/xen-ops.h
+++ b/arch/x86/xen/xen-ops.h
@@ -12,10 +12,8 @@ extern const char xen_hypervisor_callback[];
 extern const char xen_failsafe_callback[];
 
 void xen_sysenter_target(void);
-#ifdef CONFIG_X86_64
 void xen_syscall_target(void);
 void xen_syscall32_target(void);
-#endif
 
 extern void *xen_initial_gdt;
 
@@ -34,15 +32,12 @@ void xen_setup_mfn_list_list(void);
 void xen_build_mfn_list_list(void);
 void xen_setup_machphys_mapping(void);
 void xen_setup_kernel_pagetable(pgd_t *pgd, unsigned long max_pfn);
-void xen_reserve_top(void);
 void __init xen_reserve_special_pages(void);
 void __init xen_pt_check_e820(void);
 
 void xen_mm_pin_all(void);
 void xen_mm_unpin_all(void);
-#ifdef CONFIG_X86_64
 void __init xen_relocate_p2m(void);
-#endif
 
 bool __init xen_is_e820_reserved(phys_addr_t start, phys_addr_t size);
 unsigned long __ref xen_chk_extra_mem(unsigned long pfn);
diff --git a/drivers/xen/Kconfig b/drivers/xen/Kconfig
index ec6558b79e9d..c359a2c04d80 100644
--- a/drivers/xen/Kconfig
+++ b/drivers/xen/Kconfig
@@ -63,9 +63,7 @@ config XEN_BALLOON_MEMORY_HOTPLUG
 
 config XEN_BALLOON_MEMORY_HOTPLUG_LIMIT
 	int "Hotplugged memory limit (in GiB) for a PV guest"
-	default 512 if X86_64
-	default 4 if X86_32
-	range 0 64 if X86_32
+	default 512
 	depends on XEN_HAVE_PVMMU
 	depends on XEN_BALLOON_MEMORY_HOTPLUG
 	help
-- 
2.16.4

Re: [PATCH 1/2] x86/xen: remove 32-bit Xen PV guest support

[Boris Ostrovsky]

> diff --git a/arch/x86/xen/Makefile b/arch/x86/xen/Makefile
> index 084de77a109e..d42737f31304 100644
> --- a/arch/x86/xen/Makefile
> +++ b/arch/x86/xen/Makefile
> @@ -1,5 +1,5 @@
>  # SPDX-License-Identifier: GPL-2.0
> -OBJECT_FILES_NON_STANDARD_xen-asm_$(BITS).o := y
> +OBJECT_FILES_NON_STANDARD_xen-asm_64.o := y
>  
>  ifdef CONFIG_FUNCTION_TRACER
>  # Do not profile debug and lowlevel utilities
> @@ -34,7 +34,7 @@ obj-$(CONFIG_XEN_PV)		+= mmu_pv.o
>  obj-$(CONFIG_XEN_PV)		+= irq.o
>  obj-$(CONFIG_XEN_PV)		+= multicalls.o
>  obj-$(CONFIG_XEN_PV)		+= xen-asm.o
> -obj-$(CONFIG_XEN_PV)		+= xen-asm_$(BITS).o
> +obj-$(CONFIG_XEN_PV)		+= xen-asm_64.o

We should be able to merge xen-asm_64.S into xen-asm.S, shouldn't we?


> @@ -1312,15 +1290,7 @@ asmlinkage __visible void __init xen_start_kernel(void)
>  
>  	/* keep using Xen gdt for now; no urgent need to change it */
>  
> -#ifdef CONFIG_X86_32
> -	pv_info.kernel_rpl = 1;
> -	if (xen_feature(XENFEAT_supervisor_mode_kernel))
> -		pv_info.kernel_rpl = 0;
> -#else
>  	pv_info.kernel_rpl = 0;

Is kernel_rpl needed anymore?


-boris

Re: [PATCH 1/2] x86/xen: remove 32-bit Xen PV guest support

[Juergen Gross]

On 15.07.19 17:44, Boris Ostrovsky wrote:
> 
>> diff --git a/arch/x86/xen/Makefile b/arch/x86/xen/Makefile
>> index 084de77a109e..d42737f31304 100644
>> --- a/arch/x86/xen/Makefile
>> +++ b/arch/x86/xen/Makefile
>> @@ -1,5 +1,5 @@
>>   # SPDX-License-Identifier: GPL-2.0
>> -OBJECT_FILES_NON_STANDARD_xen-asm_$(BITS).o := y
>> +OBJECT_FILES_NON_STANDARD_xen-asm_64.o := y
>>   
>>   ifdef CONFIG_FUNCTION_TRACER
>>   # Do not profile debug and lowlevel utilities
>> @@ -34,7 +34,7 @@ obj-$(CONFIG_XEN_PV)		+= mmu_pv.o
>>   obj-$(CONFIG_XEN_PV)		+= irq.o
>>   obj-$(CONFIG_XEN_PV)		+= multicalls.o
>>   obj-$(CONFIG_XEN_PV)		+= xen-asm.o
>> -obj-$(CONFIG_XEN_PV)		+= xen-asm_$(BITS).o
>> +obj-$(CONFIG_XEN_PV)		+= xen-asm_64.o
> 
> We should be able to merge xen-asm_64.S into xen-asm.S, shouldn't we?

Yes, probably a good idea to add that.

>> @@ -1312,15 +1290,7 @@ asmlinkage __visible void __init xen_start_kernel(void)
>>   
>>   	/* keep using Xen gdt for now; no urgent need to change it */
>>   
>> -#ifdef CONFIG_X86_32
>> -	pv_info.kernel_rpl = 1;
>> -	if (xen_feature(XENFEAT_supervisor_mode_kernel))
>> -		pv_info.kernel_rpl = 0;
>> -#else
>>   	pv_info.kernel_rpl = 0;
> 
> Is kernel_rpl needed anymore?

Yes, this can be dropped, together with get_kernel_rpl().


Juergen

[PATCH 2/2] x86/paravirt: remove 32-bit support from PARAVIRT_XXL

[Juergen Gross]

The last 32-bit user of stuff under CONFIG_PARAVIRT_XXL is gone.

Remove 32-bit specific parts.

Signed-off-by: Juergen Gross <jgross@suse.com>
---
 arch/x86/entry/vdso/vdso32/vclock_gettime.c |   1 +
 arch/x86/include/asm/paravirt.h             | 105 ++++------------------------
 arch/x86/include/asm/paravirt_types.h       |  20 ------
 arch/x86/include/asm/pgtable-3level_types.h |   5 --
 arch/x86/kernel/cpu/common.c                |   8 ---
 arch/x86/kernel/paravirt.c                  |  17 -----
 arch/x86/kernel/paravirt_patch_32.c         |  36 +---------
 7 files changed, 15 insertions(+), 177 deletions(-)

diff --git a/arch/x86/entry/vdso/vdso32/vclock_gettime.c b/arch/x86/entry/vdso/vdso32/vclock_gettime.c
index 9242b28418d5..36f4ce1405cb 100644
--- a/arch/x86/entry/vdso/vdso32/vclock_gettime.c
+++ b/arch/x86/entry/vdso/vdso32/vclock_gettime.c
@@ -17,6 +17,7 @@
 #undef CONFIG_ILLEGAL_POINTER_VALUE
 #undef CONFIG_SPARSEMEM_VMEMMAP
 #undef CONFIG_NR_CPUS
+#undef CONFIG_PARAVIRT_XXL
 
 #define CONFIG_X86_32 1
 #define CONFIG_PGTABLE_LEVELS 2
diff --git a/arch/x86/include/asm/paravirt.h b/arch/x86/include/asm/paravirt.h
index c25c38a05c1c..60dfa93313a9 100644
--- a/arch/x86/include/asm/paravirt.h
+++ b/arch/x86/include/asm/paravirt.h
@@ -139,7 +139,6 @@ static inline void __write_cr4(unsigned long x)
 	PVOP_VCALL1(cpu.write_cr4, x);
 }
 
-#ifdef CONFIG_X86_64
 static inline unsigned long read_cr8(void)
 {
 	return PVOP_CALL0(unsigned long, cpu.read_cr8);
@@ -149,7 +148,6 @@ static inline void write_cr8(unsigned long x)
 {
 	PVOP_VCALL1(cpu.write_cr8, x);
 }
-#endif
 
 static inline void arch_safe_halt(void)
 {
@@ -283,12 +281,10 @@ static inline void load_TLS(struct thread_struct *t, unsigned cpu)
 	PVOP_VCALL2(cpu.load_tls, t, cpu);
 }
 
-#ifdef CONFIG_X86_64
 static inline void load_gs_index(unsigned int gs)
 {
 	PVOP_VCALL1(cpu.load_gs_index, gs);
 }
-#endif
 
 static inline void write_ldt_entry(struct desc_struct *dt, int entry,
 				   const void *desc)
@@ -375,50 +371,28 @@ static inline pte_t __pte(pteval_t val)
 {
 	pteval_t ret;
 
-	if (sizeof(pteval_t) > sizeof(long))
-		ret = PVOP_CALLEE2(pteval_t, mmu.make_pte, val, (u64)val >> 32);
-	else
-		ret = PVOP_CALLEE1(pteval_t, mmu.make_pte, val);
+	ret = PVOP_CALLEE1(pteval_t, mmu.make_pte, val);
 
 	return (pte_t) { .pte = ret };
 }
 
 static inline pteval_t pte_val(pte_t pte)
 {
-	pteval_t ret;
-
-	if (sizeof(pteval_t) > sizeof(long))
-		ret = PVOP_CALLEE2(pteval_t, mmu.pte_val,
-				   pte.pte, (u64)pte.pte >> 32);
-	else
-		ret = PVOP_CALLEE1(pteval_t, mmu.pte_val, pte.pte);
-
-	return ret;
+	return PVOP_CALLEE1(pteval_t, mmu.pte_val, pte.pte);
 }
 
 static inline pgd_t __pgd(pgdval_t val)
 {
 	pgdval_t ret;
 
-	if (sizeof(pgdval_t) > sizeof(long))
-		ret = PVOP_CALLEE2(pgdval_t, mmu.make_pgd, val, (u64)val >> 32);
-	else
-		ret = PVOP_CALLEE1(pgdval_t, mmu.make_pgd, val);
+	ret = PVOP_CALLEE1(pgdval_t, mmu.make_pgd, val);
 
 	return (pgd_t) { ret };
 }
 
 static inline pgdval_t pgd_val(pgd_t pgd)
 {
-	pgdval_t ret;
-
-	if (sizeof(pgdval_t) > sizeof(long))
-		ret =  PVOP_CALLEE2(pgdval_t, mmu.pgd_val,
-				    pgd.pgd, (u64)pgd.pgd >> 32);
-	else
-		ret =  PVOP_CALLEE1(pgdval_t, mmu.pgd_val, pgd.pgd);
-
-	return ret;
+	return PVOP_CALLEE1(pgdval_t, mmu.pgd_val, pgd.pgd);
 }
 
 #define  __HAVE_ARCH_PTEP_MODIFY_PROT_TRANSACTION
@@ -435,79 +409,48 @@ static inline pte_t ptep_modify_prot_start(struct vm_area_struct *vma, unsigned
 static inline void ptep_modify_prot_commit(struct vm_area_struct *vma, unsigned long addr,
 					   pte_t *ptep, pte_t old_pte, pte_t pte)
 {
-
-	if (sizeof(pteval_t) > sizeof(long))
-		/* 5 arg words */
-		pv_ops.mmu.ptep_modify_prot_commit(vma, addr, ptep, pte);
-	else
-		PVOP_VCALL4(mmu.ptep_modify_prot_commit,
-			    vma, addr, ptep, pte.pte);
+	PVOP_VCALL4(mmu.ptep_modify_prot_commit, vma, addr, ptep, pte.pte);
 }
 
 static inline void set_pte(pte_t *ptep, pte_t pte)
 {
-	if (sizeof(pteval_t) > sizeof(long))
-		PVOP_VCALL3(mmu.set_pte, ptep, pte.pte, (u64)pte.pte >> 32);
-	else
-		PVOP_VCALL2(mmu.set_pte, ptep, pte.pte);
+	PVOP_VCALL2(mmu.set_pte, ptep, pte.pte);
 }
 
 static inline void set_pte_at(struct mm_struct *mm, unsigned long addr,
 			      pte_t *ptep, pte_t pte)
 {
-	if (sizeof(pteval_t) > sizeof(long))
-		/* 5 arg words */
-		pv_ops.mmu.set_pte_at(mm, addr, ptep, pte);
-	else
-		PVOP_VCALL4(mmu.set_pte_at, mm, addr, ptep, pte.pte);
+	PVOP_VCALL4(mmu.set_pte_at, mm, addr, ptep, pte.pte);
 }
 
 static inline void set_pmd(pmd_t *pmdp, pmd_t pmd)
 {
 	pmdval_t val = native_pmd_val(pmd);
 
-	if (sizeof(pmdval_t) > sizeof(long))
-		PVOP_VCALL3(mmu.set_pmd, pmdp, val, (u64)val >> 32);
-	else
-		PVOP_VCALL2(mmu.set_pmd, pmdp, val);
+	PVOP_VCALL2(mmu.set_pmd, pmdp, val);
 }
 
-#if CONFIG_PGTABLE_LEVELS >= 3
 static inline pmd_t __pmd(pmdval_t val)
 {
 	pmdval_t ret;
 
-	if (sizeof(pmdval_t) > sizeof(long))
-		ret = PVOP_CALLEE2(pmdval_t, mmu.make_pmd, val, (u64)val >> 32);
-	else
-		ret = PVOP_CALLEE1(pmdval_t, mmu.make_pmd, val);
+	ret = PVOP_CALLEE1(pmdval_t, mmu.make_pmd, val);
 
 	return (pmd_t) { ret };
 }
 
 static inline pmdval_t pmd_val(pmd_t pmd)
 {
-	pmdval_t ret;
-
-	if (sizeof(pmdval_t) > sizeof(long))
-		ret =  PVOP_CALLEE2(pmdval_t, mmu.pmd_val,
-				    pmd.pmd, (u64)pmd.pmd >> 32);
-	else
-		ret =  PVOP_CALLEE1(pmdval_t, mmu.pmd_val, pmd.pmd);
-
-	return ret;
+	return PVOP_CALLEE1(pmdval_t, mmu.pmd_val, pmd.pmd);
 }
 
 static inline void set_pud(pud_t *pudp, pud_t pud)
 {
 	pudval_t val = native_pud_val(pud);
 
-	if (sizeof(pudval_t) > sizeof(long))
-		PVOP_VCALL3(mmu.set_pud, pudp, val, (u64)val >> 32);
-	else
-		PVOP_VCALL2(mmu.set_pud, pudp, val);
+	PVOP_VCALL2(mmu.set_pud, pudp, val);
 }
-#if CONFIG_PGTABLE_LEVELS >= 4
+
 static inline pud_t __pud(pudval_t val)
 {
 	pudval_t ret;
@@ -572,29 +515,6 @@ static inline void p4d_clear(p4d_t *p4dp)
 	set_p4d(p4dp, __p4d(0));
 }
 
-#endif	/* CONFIG_PGTABLE_LEVELS == 4 */
-
-#endif	/* CONFIG_PGTABLE_LEVELS >= 3 */
-
-#ifdef CONFIG_X86_PAE
-/* Special-case pte-setting operations for PAE, which can't update a
-   64-bit pte atomically */
-static inline void set_pte_atomic(pte_t *ptep, pte_t pte)
-{
-	PVOP_VCALL3(mmu.set_pte_atomic, ptep, pte.pte, pte.pte >> 32);
-}
-
-static inline void pte_clear(struct mm_struct *mm, unsigned long addr,
-			     pte_t *ptep)
-{
-	PVOP_VCALL3(mmu.pte_clear, mm, addr, ptep);
-}
-
-static inline void pmd_clear(pmd_t *pmdp)
-{
-	PVOP_VCALL1(mmu.pmd_clear, pmdp);
-}
-#else  /* !CONFIG_X86_PAE */
 static inline void set_pte_atomic(pte_t *ptep, pte_t pte)
 {
 	set_pte(ptep, pte);
@@ -610,7 +530,6 @@ static inline void pmd_clear(pmd_t *pmdp)
 {
 	set_pmd(pmdp, __pmd(0));
 }
-#endif	/* CONFIG_X86_PAE */
 
 #define  __HAVE_ARCH_START_CONTEXT_SWITCH
 static inline void arch_start_context_switch(struct task_struct *prev)
diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h
index 2474e434a6f7..b73d79091a0b 100644
--- a/arch/x86/include/asm/paravirt_types.h
+++ b/arch/x86/include/asm/paravirt_types.h
@@ -71,9 +71,7 @@ struct pv_info {
 	unsigned int kernel_rpl;
 	int shared_kernel_pmd;
 
-#ifdef CONFIG_X86_64
 	u16 extra_user_64bit_cs;  /* __USER_CS if none */
-#endif
 #endif
 
 	const char *name;
@@ -119,10 +117,8 @@ struct pv_cpu_ops {
 
 	void (*write_cr4)(unsigned long);
 
-#ifdef CONFIG_X86_64
 	unsigned long (*read_cr8)(void);
 	void (*write_cr8)(unsigned long);
-#endif
 
 	/* Segment descriptor handling */
 	void (*load_tr_desc)(void);
@@ -131,9 +127,7 @@ struct pv_cpu_ops {
 	void (*set_ldt)(const void *desc, unsigned entries);
 	unsigned long (*store_tr)(void);
 	void (*load_tls)(struct thread_struct *t, unsigned int cpu);
-#ifdef CONFIG_X86_64
 	void (*load_gs_index)(unsigned int idx);
-#endif
 	void (*write_ldt_entry)(struct desc_struct *ldt, int entrynum,
 				const void *desc);
 	void (*write_gdt_entry)(struct desc_struct *,
@@ -266,21 +260,11 @@ struct pv_mmu_ops {
 	struct paravirt_callee_save pgd_val;
 	struct paravirt_callee_save make_pgd;
 
-#if CONFIG_PGTABLE_LEVELS >= 3
-#ifdef CONFIG_X86_PAE
-	void (*set_pte_atomic)(pte_t *ptep, pte_t pteval);
-	void (*pte_clear)(struct mm_struct *mm, unsigned long addr,
-			  pte_t *ptep);
-	void (*pmd_clear)(pmd_t *pmdp);
-
-#endif	/* CONFIG_X86_PAE */
-
 	void (*set_pud)(pud_t *pudp, pud_t pudval);
 
 	struct paravirt_callee_save pmd_val;
 	struct paravirt_callee_save make_pmd;
 
-#if CONFIG_PGTABLE_LEVELS >= 4
 	struct paravirt_callee_save pud_val;
 	struct paravirt_callee_save make_pud;
 
@@ -293,10 +277,6 @@ struct pv_mmu_ops {
 	void (*set_pgd)(pgd_t *pgdp, pgd_t pgdval);
 #endif	/* CONFIG_PGTABLE_LEVELS >= 5 */
 
-#endif	/* CONFIG_PGTABLE_LEVELS >= 4 */
-
-#endif	/* CONFIG_PGTABLE_LEVELS >= 3 */
-
 	struct pv_lazy_ops lazy_mode;
 
 	/* dom0 ops */
diff --git a/arch/x86/include/asm/pgtable-3level_types.h b/arch/x86/include/asm/pgtable-3level_types.h
index 33845d36897c..3955770d1a4d 100644
--- a/arch/x86/include/asm/pgtable-3level_types.h
+++ b/arch/x86/include/asm/pgtable-3level_types.h
@@ -20,12 +20,7 @@ typedef union {
 } pte_t;
 #endif	/* !__ASSEMBLY__ */
 
-#ifdef CONFIG_PARAVIRT_XXL
-#define SHARED_KERNEL_PMD	((!static_cpu_has(X86_FEATURE_PTI) &&	\
-				 (pv_info.shared_kernel_pmd)))
-#else
 #define SHARED_KERNEL_PMD	(!static_cpu_has(X86_FEATURE_PTI))
-#endif
 
 /*
  * PGDIR_SHIFT determines what a top-level page table entry can map
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 2c57fffebf9b..a34246b01458 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -1257,15 +1257,7 @@ static void generic_identify(struct cpuinfo_x86 *c)
 	 * ESPFIX issue, we can change this.
 	 */
 #ifdef CONFIG_X86_32
-# ifdef CONFIG_PARAVIRT_XXL
-	do {
-		extern void native_iret(void);
-		if (pv_ops.cpu.iret == native_iret)
-			set_cpu_bug(c, X86_BUG_ESPFIX);
-	} while (0);
-# else
 	set_cpu_bug(c, X86_BUG_ESPFIX);
-# endif
 #endif
 }
 
diff --git a/arch/x86/kernel/paravirt.c b/arch/x86/kernel/paravirt.c
index 06f6bb48d018..c9451267b4a3 100644
--- a/arch/x86/kernel/paravirt.c
+++ b/arch/x86/kernel/paravirt.c
@@ -284,10 +284,8 @@ struct pv_info pv_info = {
 	.kernel_rpl = 0,
 	.shared_kernel_pmd = 1,	/* Only used when CONFIG_X86_PAE is set */
 
-#ifdef CONFIG_X86_64
 	.extra_user_64bit_cs = __USER_CS,
 #endif
-#endif
 };
 
 /* 64-bit pagetable entries */
@@ -311,10 +309,8 @@ struct paravirt_patch_template pv_ops = {
 	.cpu.read_cr0		= native_read_cr0,
 	.cpu.write_cr0		= native_write_cr0,
 	.cpu.write_cr4		= native_write_cr4,
-#ifdef CONFIG_X86_64
 	.cpu.read_cr8		= native_read_cr8,
 	.cpu.write_cr8		= native_write_cr8,
-#endif
 	.cpu.wbinvd		= native_wbinvd,
 	.cpu.read_msr		= native_read_msr,
 	.cpu.write_msr		= native_write_msr,
@@ -327,9 +323,7 @@ struct paravirt_patch_template pv_ops = {
 	.cpu.load_idt		= native_load_idt,
 	.cpu.store_tr		= native_store_tr,
 	.cpu.load_tls		= native_load_tls,
-#ifdef CONFIG_X86_64
 	.cpu.load_gs_index	= native_load_gs_index,
-#endif
 	.cpu.write_ldt_entry	= native_write_ldt_entry,
 	.cpu.write_gdt_entry	= native_write_gdt_entry,
 	.cpu.write_idt_entry	= native_write_idt_entry,
@@ -339,9 +333,7 @@ struct paravirt_patch_template pv_ops = {
 
 	.cpu.load_sp0		= native_load_sp0,
 
-#ifdef CONFIG_X86_64
 	.cpu.usergs_sysret64	= native_usergs_sysret64,
-#endif
 	.cpu.iret		= native_iret,
 	.cpu.swapgs		= native_swapgs,
 
@@ -394,18 +386,11 @@ struct paravirt_patch_template pv_ops = {
 	.mmu.ptep_modify_prot_start	= __ptep_modify_prot_start,
 	.mmu.ptep_modify_prot_commit	= __ptep_modify_prot_commit,
 
-#if CONFIG_PGTABLE_LEVELS >= 3
-#ifdef CONFIG_X86_PAE
-	.mmu.set_pte_atomic	= native_set_pte_atomic,
-	.mmu.pte_clear		= native_pte_clear,
-	.mmu.pmd_clear		= native_pmd_clear,
-#endif
 	.mmu.set_pud		= native_set_pud,
 
 	.mmu.pmd_val		= PTE_IDENT,
 	.mmu.make_pmd		= PTE_IDENT,
 
-#if CONFIG_PGTABLE_LEVELS >= 4
 	.mmu.pud_val		= PTE_IDENT,
 	.mmu.make_pud		= PTE_IDENT,
 
@@ -417,8 +402,6 @@ struct paravirt_patch_template pv_ops = {
 
 	.mmu.set_pgd		= native_set_pgd,
 #endif /* CONFIG_PGTABLE_LEVELS >= 5 */
-#endif /* CONFIG_PGTABLE_LEVELS >= 4 */
-#endif /* CONFIG_PGTABLE_LEVELS >= 3 */
 
 	.mmu.pte_val		= PTE_IDENT,
 	.mmu.pgd_val		= PTE_IDENT,
diff --git a/arch/x86/kernel/paravirt_patch_32.c b/arch/x86/kernel/paravirt_patch_32.c
index de138d3912e4..f46a700d781a 100644
--- a/arch/x86/kernel/paravirt_patch_32.c
+++ b/arch/x86/kernel/paravirt_patch_32.c
@@ -1,23 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0
 #include <asm/paravirt.h>
 
-#ifdef CONFIG_PARAVIRT_XXL
-DEF_NATIVE(irq, irq_disable, "cli");
-DEF_NATIVE(irq, irq_enable, "sti");
-DEF_NATIVE(irq, restore_fl, "push %eax; popf");
-DEF_NATIVE(irq, save_fl, "pushf; pop %eax");
-DEF_NATIVE(cpu, iret, "iret");
-DEF_NATIVE(mmu, read_cr2, "mov %cr2, %eax");
-DEF_NATIVE(mmu, write_cr3, "mov %eax, %cr3");
-DEF_NATIVE(mmu, read_cr3, "mov %cr3, %eax");
-
-unsigned paravirt_patch_ident_64(void *insnbuf, unsigned len)
-{
-	/* arg in %edx:%eax, return in %edx:%eax */
-	return 0;
-}
-#endif
-
 #if defined(CONFIG_PARAVIRT_SPINLOCKS)
 DEF_NATIVE(lock, queued_spin_unlock, "movb $0, (%eax)");
 DEF_NATIVE(lock, vcpu_is_preempted, "xor %eax, %eax");
@@ -28,22 +11,8 @@ extern bool pv_is_native_vcpu_is_preempted(void);
 
 unsigned native_patch(u8 type, void *ibuf, unsigned long addr, unsigned len)
 {
-#define PATCH_SITE(ops, x)					\
-	case PARAVIRT_PATCH(ops.x):				\
-		return paravirt_patch_insns(ibuf, len, start_##ops##_##x, end_##ops##_##x)
-
-	switch (type) {
-#ifdef CONFIG_PARAVIRT_XXL
-		PATCH_SITE(irq, irq_disable);
-		PATCH_SITE(irq, irq_enable);
-		PATCH_SITE(irq, restore_fl);
-		PATCH_SITE(irq, save_fl);
-		PATCH_SITE(cpu, iret);
-		PATCH_SITE(mmu, read_cr2);
-		PATCH_SITE(mmu, read_cr3);
-		PATCH_SITE(mmu, write_cr3);
-#endif
 #if defined(CONFIG_PARAVIRT_SPINLOCKS)
+	switch (type) {
 	case PARAVIRT_PATCH(lock.queued_spin_unlock):
 		if (pv_is_native_spin_unlock())
 			return paravirt_patch_insns(ibuf, len,
@@ -57,11 +26,10 @@ unsigned native_patch(u8 type, void *ibuf, unsigned long addr, unsigned len)
 						    start_lock_vcpu_is_preempted,
 						    end_lock_vcpu_is_preempted);
 		break;
-#endif
 
 	default:
 		break;
 	}
-#undef PATCH_SITE
+#endif
 	return paravirt_patch_default(type, ibuf, addr, len);
 }
-- 
2.16.4

Re: [PATCH 0/2] Remove 32-bit Xen PV guest support

[Peter Zijlstra]

On Mon, Jul 15, 2019 at 01:37:37PM +0200, Juergen Gross wrote:
> The long term plan has been to replace Xen PV guests by PVH. The first
> victim of that plan are now 32-bit PV guests, as those are used only
> rather seldom these days. Xen on x86 requires 64-bit support and with
> Grub2 now supporting PVH officially since version 2.04 there is no
> need to keep 32-bit PV guest support alive in the Linux kernel.
> Additionally Meltdown mitigation is not available in the kernel running
> as 32-bit PV guest, so dropping this mode makes sense from security
> point of view, too.
> 
> Juergen Gross (2):
>   x86/xen: remove 32-bit Xen PV guest support
>   x86/paravirt: remove 32-bit support from PARAVIRT_XXL

Hooray!

Re: [PATCH 0/2] Remove 32-bit Xen PV guest support

[Juergen Gross]

On 15.07.19 14:32, Peter Zijlstra wrote:
> On Mon, Jul 15, 2019 at 01:37:37PM +0200, Juergen Gross wrote:
>> The long term plan has been to replace Xen PV guests by PVH. The first
>> victim of that plan are now 32-bit PV guests, as those are used only
>> rather seldom these days. Xen on x86 requires 64-bit support and with
>> Grub2 now supporting PVH officially since version 2.04 there is no
>> need to keep 32-bit PV guest support alive in the Linux kernel.
>> Additionally Meltdown mitigation is not available in the kernel running
>> as 32-bit PV guest, so dropping this mode makes sense from security
>> point of view, too.
>>
>> Juergen Gross (2):
>>    x86/xen: remove 32-bit Xen PV guest support
>>    x86/paravirt: remove 32-bit support from PARAVIRT_XXL
> 
> Hooray!
> 

Always a pleasure to cheer the community up by sending Xen patches. :-D


Juergen

Re: [PATCH 0/2] Remove 32-bit Xen PV guest support

[Andi Kleen]

Juergen Gross <jgross@suse.com> writes:

> The long term plan has been to replace Xen PV guests by PVH. The first
> victim of that plan are now 32-bit PV guests, as those are used only
> rather seldom these days. Xen on x86 requires 64-bit support and with
> Grub2 now supporting PVH officially since version 2.04 there is no
> need to keep 32-bit PV guest support alive in the Linux kernel.
> Additionally Meltdown mitigation is not available in the kernel running
> as 32-bit PV guest, so dropping this mode makes sense from security
> point of view, too.

Normally we have a deprecation period for feature removals like this.
You would make the kernel print a warning for some releases, and when
no user complains you can then remove. If a user complains you can't.

-Andi

Re: [PATCH 0/2] Remove 32-bit Xen PV guest support

[Andy Lutomirski]

On Mon, Jul 15, 2019 at 9:34 AM Andi Kleen <ak@linux.intel.com> wrote:
>
> Juergen Gross <jgross@suse.com> writes:
>
> > The long term plan has been to replace Xen PV guests by PVH. The first
> > victim of that plan are now 32-bit PV guests, as those are used only
> > rather seldom these days. Xen on x86 requires 64-bit support and with
> > Grub2 now supporting PVH officially since version 2.04 there is no
> > need to keep 32-bit PV guest support alive in the Linux kernel.
> > Additionally Meltdown mitigation is not available in the kernel running
> > as 32-bit PV guest, so dropping this mode makes sense from security
> > point of view, too.
>
> Normally we have a deprecation period for feature removals like this.
> You would make the kernel print a warning for some releases, and when
> no user complains you can then remove. If a user complains you can't.
>

As I understand it, the kernel rules do allow changes like this even
if there's a complaint: this is a patch that removes what is
effectively hardware support.  If the maintenance cost exceeds the
value, then removal is fair game.  (Obviously we weight the value to
preserving compatibility quite highly, but in this case, Xen dropped
32-bit hardware support a long time ago.  If the Xen hypervisor says
that 32-bit PV guest support is deprecated, it's deprecated.)

That being said, a warning might not be a bad idea.  What's the
current status of this in upstream Xen?

Re: [Xen-devel] [PATCH 0/2] Remove 32-bit Xen PV guest support

[Andrew Cooper]

On 15/07/2019 18:28, Andy Lutomirski wrote:
> On Mon, Jul 15, 2019 at 9:34 AM Andi Kleen <ak@linux.intel.com> wrote:
>> Juergen Gross <jgross@suse.com> writes:
>>
>>> The long term plan has been to replace Xen PV guests by PVH. The first
>>> victim of that plan are now 32-bit PV guests, as those are used only
>>> rather seldom these days. Xen on x86 requires 64-bit support and with
>>> Grub2 now supporting PVH officially since version 2.04 there is no
>>> need to keep 32-bit PV guest support alive in the Linux kernel.
>>> Additionally Meltdown mitigation is not available in the kernel running
>>> as 32-bit PV guest, so dropping this mode makes sense from security
>>> point of view, too.
>> Normally we have a deprecation period for feature removals like this.
>> You would make the kernel print a warning for some releases, and when
>> no user complains you can then remove. If a user complains you can't.
>>
> As I understand it, the kernel rules do allow changes like this even
> if there's a complaint: this is a patch that removes what is
> effectively hardware support.  If the maintenance cost exceeds the
> value, then removal is fair game.  (Obviously we weight the value to
> preserving compatibility quite highly, but in this case, Xen dropped
> 32-bit hardware support a long time ago.  If the Xen hypervisor says
> that 32-bit PV guest support is deprecated, it's deprecated.)
>
> That being said, a warning might not be a bad idea.  What's the
> current status of this in upstream Xen?

So personally, I'd prefer to see support stay, but at the end of the day
it is Juergen's choice as the maintainer of the code.

Xen itself has been exclusively 64-bit since Xen 4.3 (released in 2013).

Over time, various features like SMEP/SMAP have been making 32bit PV
guests progressively slower, because ring 1 is supervisor rather than
user.  Things have got even worse with IBRS, to the point at which 32bit
PV guests are starting to run like treacle.

There are no current plans to remove support for 32bit PV guests from
Xen, but it is very much in the category of "you shouldn't be using this
mode any more".

~Andrew

P.S. I don't see 64bit PV guest support going anywhere, because there
are still a number of open performance questions due to the inherent
differences between syscall and vmexit, and the difference EPT/NPT
tables make on cross-domain mappings.

Re: [Xen-devel] [PATCH 0/2] Remove 32-bit Xen PV guest support

[Juergen Gross]

On 15.07.19 19:39, Andrew Cooper wrote:
> On 15/07/2019 18:28, Andy Lutomirski wrote:
>> On Mon, Jul 15, 2019 at 9:34 AM Andi Kleen <ak@linux.intel.com> wrote:
>>> Juergen Gross <jgross@suse.com> writes:
>>>
>>>> The long term plan has been to replace Xen PV guests by PVH. The first
>>>> victim of that plan are now 32-bit PV guests, as those are used only
>>>> rather seldom these days. Xen on x86 requires 64-bit support and with
>>>> Grub2 now supporting PVH officially since version 2.04 there is no
>>>> need to keep 32-bit PV guest support alive in the Linux kernel.
>>>> Additionally Meltdown mitigation is not available in the kernel running
>>>> as 32-bit PV guest, so dropping this mode makes sense from security
>>>> point of view, too.
>>> Normally we have a deprecation period for feature removals like this.
>>> You would make the kernel print a warning for some releases, and when
>>> no user complains you can then remove. If a user complains you can't.
>>>
>> As I understand it, the kernel rules do allow changes like this even
>> if there's a complaint: this is a patch that removes what is
>> effectively hardware support.  If the maintenance cost exceeds the
>> value, then removal is fair game.  (Obviously we weight the value to
>> preserving compatibility quite highly, but in this case, Xen dropped
>> 32-bit hardware support a long time ago.  If the Xen hypervisor says
>> that 32-bit PV guest support is deprecated, it's deprecated.)
>>
>> That being said, a warning might not be a bad idea.  What's the
>> current status of this in upstream Xen?
> 
> So personally, I'd prefer to see support stay, but at the end of the day
> it is Juergen's choice as the maintainer of the code.

Especially on the security front we are unsafe with 32-bit PV Linux.
And making it safe will make it so slow that the needed effort is not
spent very well.


Juergen

Re: [PATCH 0/2] Remove 32-bit Xen PV guest support

[Juergen Gross]

On 15.07.19 19:28, Andy Lutomirski wrote:
> On Mon, Jul 15, 2019 at 9:34 AM Andi Kleen <ak@linux.intel.com> wrote:
>>
>> Juergen Gross <jgross@suse.com> writes:
>>
>>> The long term plan has been to replace Xen PV guests by PVH. The first
>>> victim of that plan are now 32-bit PV guests, as those are used only
>>> rather seldom these days. Xen on x86 requires 64-bit support and with
>>> Grub2 now supporting PVH officially since version 2.04 there is no
>>> need to keep 32-bit PV guest support alive in the Linux kernel.
>>> Additionally Meltdown mitigation is not available in the kernel running
>>> as 32-bit PV guest, so dropping this mode makes sense from security
>>> point of view, too.
>>
>> Normally we have a deprecation period for feature removals like this.
>> You would make the kernel print a warning for some releases, and when
>> no user complains you can then remove. If a user complains you can't.
>>
> 
> As I understand it, the kernel rules do allow changes like this even
> if there's a complaint: this is a patch that removes what is
> effectively hardware support.  If the maintenance cost exceeds the
> value, then removal is fair game.  (Obviously we weight the value to
> preserving compatibility quite highly, but in this case, Xen dropped
> 32-bit hardware support a long time ago.  If the Xen hypervisor says
> that 32-bit PV guest support is deprecated, it's deprecated.)
> 
> That being said, a warning might not be a bad idea.  What's the
> current status of this in upstream Xen?

Xen still supports that.

We have asked downstream for their opinion about dropping 32-bit PV
guest support in the kernel about 1 year ago and the common answer was:
no problem, but for users still wanting 32 bit guests we should wait
until PVH support is available in all related products. Grub2 was the
last one missing and as grub2 has released a version with PVH support
I posted this small series now.


Juergen

Re: [Xen-devel] [PATCH 0/2] Remove 32-bit Xen PV guest support

[Jan Beulich]

On 15.07.2019 19:28, Andy Lutomirski wrote:
> On Mon, Jul 15, 2019 at 9:34 AM Andi Kleen <ak@linux.intel.com> wrote:
>>
>> Juergen Gross <jgross@suse.com> writes:
>>
>>> The long term plan has been to replace Xen PV guests by PVH. The first
>>> victim of that plan are now 32-bit PV guests, as those are used only
>>> rather seldom these days. Xen on x86 requires 64-bit support and with
>>> Grub2 now supporting PVH officially since version 2.04 there is no
>>> need to keep 32-bit PV guest support alive in the Linux kernel.
>>> Additionally Meltdown mitigation is not available in the kernel running
>>> as 32-bit PV guest, so dropping this mode makes sense from security
>>> point of view, too.
>>
>> Normally we have a deprecation period for feature removals like this.
>> You would make the kernel print a warning for some releases, and when
>> no user complains you can then remove. If a user complains you can't.
>>
> 
> As I understand it, the kernel rules do allow changes like this even
> if there's a complaint: this is a patch that removes what is
> effectively hardware support.  If the maintenance cost exceeds the
> value, then removal is fair game.  (Obviously we weight the value to
> preserving compatibility quite highly, but in this case, Xen dropped
> 32-bit hardware support a long time ago.  If the Xen hypervisor says
> that 32-bit PV guest support is deprecated, it's deprecated.)

Since it was implied but not explicit from Andrew's reply, just to
make it explicit: So far 32-bit PV guest support has not been
deprecated in Xen itself.

Jan