37c9b25886
commit afd30525a659ac0ae0904f0cb4a2ca75522c3123 upstream.
USERGS_SYSRET64 is used to return from a syscall via SYSRET, but
a Xen PV guest will nevertheless use the IRET hypercall, as there
is no sysret PV hypercall defined.
So instead of testing all the prerequisites for doing a sysret and
then mangling the stack for Xen PV again for doing an iret just use
the iret exit from the beginning.
This can easily be done via an ALTERNATIVE like it is done for the
sysenter compat case already.
It should be noted that this drops the optimization in Xen for not
restoring a few registers when returning to user mode, but it seems
as if the saved instructions in the kernel more than compensate for
this drop (a kernel build in a Xen PV guest was slightly faster with
this patch applied).
While at it remove the stale sysret32 remnants.
[ pawan: Brad Spengler and Salvatore Bonaccorso <carnil@debian.org>
reported a problem with the 5.10 backport commit edc702b4a820
("x86/entry_64: Add VERW just before userspace transition").
When CONFIG_PARAVIRT_XXL=y, CLEAR_CPU_BUFFERS is not executed in
syscall_return_via_sysret path as USERGS_SYSRET64 is runtime
patched to:
.cpu_usergs_sysret64 = { 0x0f, 0x01, 0xf8,
0x48, 0x0f, 0x07 }, // swapgs; sysretq
which is missing CLEAR_CPU_BUFFERS. It turns out dropping
USERGS_SYSRET64 simplifies the code, allowing CLEAR_CPU_BUFFERS
to be explicitly added to syscall_return_via_sysret path. Below
is with CONFIG_PARAVIRT_XXL=y and this patch applied:
syscall_return_via_sysret:
...
<+342>: swapgs
<+345>: xchg %ax,%ax
<+347>: verw -0x1a2(%rip) <------
<+354>: sysretq
]
Signed-off-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Pawan Gupta <pawan.kumar.gupta@linux.intel.com>
Link: https://lkml.kernel.org/r/20210120135555.32594-6-jgross@suse.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
164 lines
4.3 KiB
C
Executable file
164 lines
4.3 KiB
C
Executable file
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef XEN_OPS_H
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#define XEN_OPS_H
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#include <linux/init.h>
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#include <linux/clocksource.h>
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#include <linux/irqreturn.h>
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#include <xen/xen-ops.h>
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/* These are code, but not functions. Defined in entry.S */
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extern const char xen_failsafe_callback[];
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void xen_entry_SYSENTER_compat(void);
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#ifdef CONFIG_X86_64
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void xen_entry_SYSCALL_64(void);
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void xen_entry_SYSCALL_compat(void);
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#endif
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extern void *xen_initial_gdt;
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struct trap_info;
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void xen_copy_trap_info(struct trap_info *traps);
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DECLARE_PER_CPU(struct vcpu_info, xen_vcpu_info);
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DECLARE_PER_CPU(unsigned long, xen_cr3);
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DECLARE_PER_CPU(unsigned long, xen_current_cr3);
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extern struct start_info *xen_start_info;
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extern struct shared_info xen_dummy_shared_info;
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extern struct shared_info *HYPERVISOR_shared_info;
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extern bool xen_fifo_events;
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void xen_setup_mfn_list_list(void);
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void xen_build_mfn_list_list(void);
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void xen_setup_machphys_mapping(void);
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void xen_setup_kernel_pagetable(pgd_t *pgd, unsigned long max_pfn);
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void __init xen_reserve_special_pages(void);
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void __init xen_pt_check_e820(void);
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void xen_mm_pin_all(void);
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void xen_mm_unpin_all(void);
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#ifdef CONFIG_X86_64
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void __init xen_relocate_p2m(void);
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#endif
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bool __init xen_is_e820_reserved(phys_addr_t start, phys_addr_t size);
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unsigned long __ref xen_chk_extra_mem(unsigned long pfn);
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void __init xen_inv_extra_mem(void);
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void __init xen_remap_memory(void);
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phys_addr_t __init xen_find_free_area(phys_addr_t size);
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char * __init xen_memory_setup(void);
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void __init xen_arch_setup(void);
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void xen_enable_sysenter(void);
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void xen_enable_syscall(void);
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void xen_vcpu_restore(void);
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void xen_hvm_init_shared_info(void);
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void xen_unplug_emulated_devices(void);
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void __init xen_build_dynamic_phys_to_machine(void);
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void __init xen_vmalloc_p2m_tree(void);
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void xen_init_irq_ops(void);
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void xen_setup_timer(int cpu);
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void xen_setup_runstate_info(int cpu);
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void xen_teardown_timer(int cpu);
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void xen_setup_cpu_clockevents(void);
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void xen_save_time_memory_area(void);
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void xen_restore_time_memory_area(void);
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void xen_init_time_ops(void);
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void xen_hvm_init_time_ops(void);
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irqreturn_t xen_debug_interrupt(int irq, void *dev_id);
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bool xen_vcpu_stolen(int vcpu);
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extern int xen_have_vcpu_info_placement;
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int xen_vcpu_setup(int cpu);
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void xen_vcpu_info_reset(int cpu);
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void xen_setup_vcpu_info_placement(void);
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#ifdef CONFIG_SMP
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void xen_smp_init(void);
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void __init xen_hvm_smp_init(void);
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extern cpumask_var_t xen_cpu_initialized_map;
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#else
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static inline void xen_smp_init(void) {}
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static inline void xen_hvm_smp_init(void) {}
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#endif
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#ifdef CONFIG_PARAVIRT_SPINLOCKS
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void __init xen_init_spinlocks(void);
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void xen_init_lock_cpu(int cpu);
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void xen_uninit_lock_cpu(int cpu);
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#else
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static inline void xen_init_spinlocks(void)
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{
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}
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static inline void xen_init_lock_cpu(int cpu)
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{
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}
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static inline void xen_uninit_lock_cpu(int cpu)
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{
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}
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#endif
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struct dom0_vga_console_info;
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#ifdef CONFIG_XEN_DOM0
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void __init xen_init_vga(const struct dom0_vga_console_info *, size_t size);
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#else
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static inline void __init xen_init_vga(const struct dom0_vga_console_info *info,
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size_t size)
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{
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}
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#endif
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void __init xen_init_apic(void);
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#ifdef CONFIG_XEN_EFI
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extern void xen_efi_init(struct boot_params *boot_params);
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#else
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static inline void __init xen_efi_init(struct boot_params *boot_params)
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{
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}
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#endif
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__visible void xen_irq_enable_direct(void);
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__visible void xen_irq_disable_direct(void);
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__visible unsigned long xen_save_fl_direct(void);
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__visible void xen_restore_fl_direct(unsigned long);
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__visible unsigned long xen_read_cr2(void);
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__visible unsigned long xen_read_cr2_direct(void);
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/* These are not functions, and cannot be called normally */
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__visible void xen_iret(void);
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extern int xen_panic_handler_init(void);
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int xen_cpuhp_setup(int (*cpu_up_prepare_cb)(unsigned int),
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int (*cpu_dead_cb)(unsigned int));
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void xen_pin_vcpu(int cpu);
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void xen_emergency_restart(void);
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#ifdef CONFIG_XEN_PV
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void xen_pv_pre_suspend(void);
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void xen_pv_post_suspend(int suspend_cancelled);
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#else
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static inline void xen_pv_pre_suspend(void) {}
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static inline void xen_pv_post_suspend(int suspend_cancelled) {}
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#endif
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#ifdef CONFIG_XEN_PVHVM
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void xen_hvm_post_suspend(int suspend_cancelled);
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#else
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static inline void xen_hvm_post_suspend(int suspend_cancelled) {}
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#endif
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#endif /* XEN_OPS_H */
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