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x86/xen: remove 32-bit Xen PV guest support

Browse Source 
Xen is requiring 64-bit machines today and since Xen 4.14 it can be
built without 32-bit PV guest support. 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>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
This commit is contained in:
Juergen Gross
2020-06-29 10:35:39 +02:00
parent d7b461caa6
commit a13f2ef168
18 changed files with 50 additions and 840 deletions
Download Patch File Download Diff File Expand all files Collapse all files

109
arch/x86/entry/entry_32.S
View File

@@ -449,8 +449,6 @@
.macro SWITCH_TO_KERNEL_STACK
ALTERNATIVE "", "jmp .Lend_\@", X86_FEATURE_XENPV
BUG_IF_WRONG_CR3
SWITCH_TO_KERNEL_CR3 scratch_reg=%eax
@@ -599,8 +597,6 @@
*/
.macro SWITCH_TO_ENTRY_STACK
ALTERNATIVE "", "jmp .Lend_\@", X86_FEATURE_XENPV
/* Bytes to copy */
movl $PTREGS_SIZE, %ecx
@@ -872,17 +868,6 @@ SYM_ENTRY(__begin_SYSENTER_singlestep_region, SYM_L_GLOBAL, SYM_A_NONE)
* 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.
*/
SYM_CODE_START(xen_sysenter_target)
addl $5*4, %esp /* remove xen-provided frame */
jmp .Lsysenter_past_esp
SYM_CODE_END(xen_sysenter_target)
#endif
/*
* 32-bit SYSENTER entry.
*
@@ -965,9 +950,8 @@ SYM_FUNC_START(entry_SYSENTER_32)
movl %esp, %eax
call do_SYSENTER_32
/* XEN PV guests always use IRET path */
ALTERNATIVE "testl %eax, %eax; jz .Lsyscall_32_done", \
"jmp .Lsyscall_32_done", X86_FEATURE_XENPV
testl %eax, %eax
jz .Lsyscall_32_done
STACKLEAK_ERASE
@@ -1165,95 +1149,6 @@ SYM_FUNC_END(entry_INT80_32)
#endif
.endm
#ifdef CONFIG_PARAVIRT
SYM_CODE_START(native_iret)
iret
_ASM_EXTABLE(native_iret, asm_iret_error)
SYM_CODE_END(native_iret)
#endif
#ifdef CONFIG_XEN_PV
/*
* See comment in entry_64.S for further explanation
*
* Note: This is not an actual IDT entry point. It's a XEN specific entry
* point and therefore named to match the 64-bit trampoline counterpart.
*/
SYM_FUNC_START(xen_asm_exc_xen_hypervisor_callback)
/*
* 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:
*/
cmpl $xen_iret_start_crit, (%esp)
jb 1f
cmpl $xen_iret_end_crit, (%esp)
jae 1f
call xen_iret_crit_fixup
1:
pushl $-1 /* orig_ax = -1 => not a system call */
SAVE_ALL
ENCODE_FRAME_POINTER
mov %esp, %eax
call xen_pv_evtchn_do_upcall
jmp handle_exception_return
SYM_FUNC_END(xen_asm_exc_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.
*/
SYM_FUNC_START(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 asm_iret_error
5: pushl $-1 /* orig_ax = -1 => not a system call */
SAVE_ALL
ENCODE_FRAME_POINTER
jmp handle_exception_return
.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)
SYM_FUNC_END(xen_failsafe_callback)
#endif /* CONFIG_XEN_PV */
SYM_CODE_START_LOCAL_NOALIGN(handle_exception)
/* the function address is in %gs's slot on the stack */
SAVE_ALL switch_stacks=1 skip_gs=1 unwind_espfix=1

30
arch/x86/entry/vdso/vdso32/note.S
View File

@@ -16,33 +16,3 @@ ELFNOTE_START(Linux, 0, "a")
ELFNOTE_END
BUILD_SALT
#ifdef CONFIG_XEN
/*
* Add a special note telling glibc's dynamic linker a fake hardware
* flavor that it will use to choose the search path for libraries in the
* same way it uses real hardware capabilities like "mmx".
* We supply "nosegneg" as the fake capability, to indicate that we
* do not like negative offsets in instructions using segment overrides,
* since we implement those inefficiently. This makes it possible to
* install libraries optimized to avoid those access patterns in someplace
* like /lib/i686/tls/nosegneg. Note that an /etc/ld.so.conf.d/file
* corresponding to the bits here is needed to make ldconfig work right.
* It should contain:
* hwcap 1 nosegneg
* to match the mapping of bit to name that we give here.
*
* At runtime, the fake hardware feature will be considered to be present
* if its bit is set in the mask word. So, we start with the mask 0, and
* at boot time we set VDSO_NOTE_NONEGSEG_BIT if running under Xen.
*/
#include "../../xen/vdso.h" /* Defines VDSO_NOTE_NONEGSEG_BIT. */
ELFNOTE_START(GNU, 2, "a")
.long 1 /* ncaps */
VDSO32_NOTE_MASK: /* Symbol used by arch/x86/xen/setup.c */
.long 0 /* mask */
.byte VDSO_NOTE_NONEGSEG_BIT; .asciz "nosegneg" /* bit, name */
ELFNOTE_END
#endif

2
arch/x86/include/asm/proto.h
View File

@@ -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)
#ifdef CONFIG_XEN_PV
void xen_entry_INT80_compat(void);
#endif
#endif

2
arch/x86/include/asm/segment.h
View File

@@ -301,7 +301,7 @@ 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)
#ifdef CONFIG_XEN_PV
extern const char xen_early_idt_handler_array[NUM_EXCEPTION_VECTORS][XEN_EARLY_IDT_HANDLER_SIZE];
#endif

31
arch/x86/kernel/head_32.S
View File

@@ -134,38 +134,7 @@ SYM_CODE_START(startup_32)
movl %eax,pa(initial_page_table+0xffc)
#endif
#ifdef CONFIG_PARAVIRT
/* This is can only trip for a broken bootloader... */
cmpw $0x207, pa(boot_params + BP_version)
jb .Ldefault_entry
/* Paravirt-compatible boot parameters. Look to see what architecture
we're booting under. */
movl pa(boot_params + BP_hardware_subarch), %eax
cmpl $num_subarch_entries, %eax
jae .Lbad_subarch
movl pa(subarch_entries)(,%eax,4), %eax
subl $__PAGE_OFFSET, %eax
jmp *%eax
.Lbad_subarch:
SYM_INNER_LABEL_ALIGN(xen_entry, SYM_L_WEAK)
/* Unknown implementation; there's really
nothing we can do at this point. */
ud2a
__INITDATA
subarch_entries:
.long .Ldefault_entry /* normal x86/PC */
.long xen_entry /* Xen hypervisor */
.long .Ldefault_entry /* Moorestown MID */
num_subarch_entries = (. - subarch_entries) / 4
.previous
#else
jmp .Ldefault_entry
#endif /* CONFIG_PARAVIRT */
SYM_CODE_END(startup_32)
#ifdef CONFIG_HOTPLUG_CPU

3
arch/x86/xen/Kconfig
View File

@@ -19,6 +19,7 @@ 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
@@ -50,7 +51,7 @@ 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.

17
arch/x86/xen/apic.c
View File

@@ -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)

64
arch/x86/xen/enlighten_pv.c
View File

@@ -119,14 +119,6 @@ static void __init xen_banner(void)
printk(KERN_INFO "Xen version: %d.%d%s%s\n",
version >> 16, version & 0xffff, extra.extraversion,
xen_feature(XENFEAT_mmu_pt_update_preserve_ad) ? " (preserve-AD)" : "");
#ifdef CONFIG_X86_32
pr_warn("WARNING! WARNING! WARNING! WARNING! WARNING! WARNING! WARNING!\n"
"Support for running as 32-bit PV-guest under Xen will soon be removed\n"
"from the Linux kernel!\n"
"Please use either a 64-bit kernel or switch to HVM or PVH mode!\n"
"WARNING! WARNING! WARNING! WARNING! WARNING! WARNING! WARNING!\n");
#endif
}
static void __init xen_pv_init_platform(void)
@@ -538,30 +530,12 @@ static void load_TLS_descriptor(struct thread_struct *t,
static void xen_load_tls(struct thread_struct *t, unsigned int cpu)
{
/*
* XXX sleazy hack: If we're being called in a lazy-cpu zone
* and lazy gs handling is enabled, it means we're in a
* context switch, and %gs has just been saved. This means we
* can zero it out to prevent faults on exit from the
* hypervisor if the next process has no %gs. Either way, it
* has been saved, and the new value will get loaded properly.
* This will go away as soon as Xen has been modified to not
* save/restore %gs for normal hypercalls.
*
* On x86_64, this hack is not used for %gs, because gs points
* to KERNEL_GS_BASE (and uses it for PDA references), so we
* must not zero %gs on x86_64
*
* For x86_64, we need to zero %fs, otherwise we may get an
* In lazy mode we need to zero %fs, otherwise we may get an
* 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();
@@ -572,13 +546,11 @@ 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)
@@ -597,7 +569,6 @@ static void xen_write_ldt_entry(struct desc_struct *dt, int entrynum,
preempt_enable();
}
#ifdef CONFIG_X86_64
void noist_exc_debug(struct pt_regs *regs);
DEFINE_IDTENTRY_RAW(xenpv_exc_nmi)
@@ -697,7 +668,6 @@ 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)
@@ -710,10 +680,8 @@ 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);
@@ -958,15 +926,12 @@ static u64 xen_read_msr_safe(unsigned int msr, int *err)
static int xen_write_msr_safe(unsigned int msr, unsigned low, unsigned high)
{
int ret;
#ifdef CONFIG_X86_64
unsigned int which;
u64 base;
#endif
ret = 0;
switch (msr) {
#ifdef CONFIG_X86_64
case MSR_FS_BASE: which = SEGBASE_FS; goto set;
case MSR_KERNEL_GS_BASE: which = SEGBASE_GS_USER; goto set;
case MSR_GS_BASE: which = SEGBASE_GS_KERNEL; goto set;
@@ -976,7 +941,6 @@ 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:
@@ -1058,9 +1022,7 @@ 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",
};
@@ -1086,18 +1048,14 @@ 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,
@@ -1364,15 +1322,7 @@ 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
@@ -1384,12 +1334,6 @@ 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)
@@ -1458,12 +1402,8 @@ 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)

356
arch/x86/xen/mmu_pv.c
View File

File diff suppressed because it is too large Load Diff

6
arch/x86/xen/p2m.c
View File

@@ -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));
@@ -467,7 +463,7 @@ EXPORT_SYMBOL_GPL(get_phys_to_machine);
* Allocate new pmd(s). It is checked whether the old pmd is still in place.
* If not, nothing is changed. This is okay as the only reason for allocating
* a new pmd is to replace p2m_missing_pte or p2m_identity_pte by a individual
* pmd. In case of PAE/x86-32 there are multiple pmds to allocate!
* pmd.
*/
static pte_t *alloc_p2m_pmd(unsigned long addr, pte_t *pte_pg)
{

36
arch/x86/xen/setup.c
View File

@@ -32,7 +32,6 @@
#include <xen/features.h>
#include <xen/hvc-console.h>
#include "xen-ops.h"
#include "vdso.h"
#include "mmu.h"
#define GB(x) ((uint64_t)(x) * 1024 * 1024 * 1024)
@@ -545,13 +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;
}
@@ -722,17 +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
}
/**
@@ -921,20 +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 = {
@@ -951,11 +924,7 @@ 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))
return;
@@ -967,7 +936,6 @@ void xen_enable_sysenter(void)
void xen_enable_syscall(void)
{
#ifdef CONFIG_X86_64
int ret;
ret = register_callback(CALLBACKTYPE_syscall, xen_syscall_target);
@@ -983,7 +951,6 @@ void xen_enable_syscall(void)
if (ret != 0)
setup_clear_cpu_cap(X86_FEATURE_SYSCALL32);
}
#endif /* CONFIG_X86_64 */
}
static void __init xen_pvmmu_arch_setup(void)
@@ -1024,7 +991,6 @@ 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

18
arch/x86/xen/smp_pv.c
View File

@@ -212,15 +212,6 @@ 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();
@@ -301,10 +292,6 @@ 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));
/*
@@ -342,12 +329,7 @@ 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_asm_exc_xen_hypervisor_callback;
ctxt->failsafe_callback_eip =

6
arch/x86/xen/vdso.h
View File

@@ -1,6 +0,0 @@
/* SPDX-License-Identifier: GPL-2.0 */
/* Bit used for the pseudo-hwcap for non-negative segments. We use
bit 1 to avoid bugs in some versions of glibc when bit 0 is
used; the choice is otherwise arbitrary. */
#define VDSO_NOTE_NONEGSEG_BIT 1

14
arch/x86/xen/xen-asm.S
View File

@@ -76,11 +76,7 @@ SYM_FUNC_END(xen_save_fl_direct)
*/
SYM_FUNC_START(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
@@ -104,15 +100,6 @@ SYM_FUNC_END(xen_restore_fl_direct)
*/
SYM_FUNC_START(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
@@ -132,7 +119,6 @@ SYM_FUNC_START(check_events)
pop %rdx
pop %rcx
pop %rax
#endif
FRAME_END
ret
SYM_FUNC_END(check_events)

185
arch/x86/xen/xen-asm_32.S
View File

@@ -1,185 +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
SYM_CODE_START(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 exc_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_asm_exc_xen_hypervisor_callback
1: iret
xen_iret_end_crit:
_ASM_EXTABLE(1b, asm_iret_error)
hyper_iret:
/* put this out of line since its very rarely used */
jmp hypercall_page + __HYPERVISOR_iret * 32
SYM_CODE_END(xen_iret)
.globl xen_iret_start_crit, xen_iret_end_crit
/*
* This is called by xen_asm_exc_xen_hypervisor_callback in entry_32.S when it sees
* that the EIP at the time of interrupt was between
* xen_iret_start_crit and xen_iret_end_crit.
*
* 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 }
* ----------------
* eax : outer eax if it hasn't been restored
* ----------------
* eflags }
* cs } nested exception info
* eip }
* return address : (into xen_asm_exc_xen_hypervisor_callback)
*
* In order to deliver the nested exception properly, we need to discard the
* nested exception frame such 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 (i.e.
* it's still on stack), we need to restore its value here.
*/
.pushsection .noinstr.text, "ax"
SYM_CODE_START(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
* PF, it decides to deliver an interrupt instead. Unlikely?
* Definitely. Easy to avoid? Yes.
*/
testb $2, 2*4(%esp) /* nested CS */
jnz 2f
/*
* If eip is before iret_restore_end then stack
* hasn't been restored yet.
*/
cmpl $iret_restore_end, 1*4(%esp)
jae 1f
movl 4*4(%esp), %eax /* load outer EAX */
ret $4*4 /* discard nested EIP, CS, and EFLAGS as
* well as the just restored EAX */
1:
ret $3*4 /* discard nested EIP, CS, and EFLAGS */
2:
ret
SYM_CODE_END(xen_iret_crit_fixup)
.popsection

6
arch/x86/xen/xen-head.S
View File

@@ -35,13 +35,8 @@ SYM_CODE_START(startup_xen)
rep __ASM_SIZE(stos)
mov %_ASM_SI, xen_start_info
#ifdef CONFIG_X86_64
mov initial_stack(%rip), %rsp
#else
mov initial_stack, %esp
#endif
#ifdef CONFIG_X86_64
/* Set up %gs.
*
* The base of %gs always points to fixed_percpu_data. If the
@@ -53,7 +48,6 @@ SYM_CODE_START(startup_xen)
movq $INIT_PER_CPU_VAR(fixed_percpu_data),%rax
cdq
wrmsr
#endif
call xen_start_kernel
SYM_CODE_END(startup_xen)

1
arch/x86/xen/xen-ops.h
View File

@@ -33,7 +33,6 @@ 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);

4
drivers/xen/Kconfig
View File

@@ -52,9 +52,7 @@ 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