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x86/entry: Switch XEN/PV hypercall entry to IDTENTRY

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Convert the XEN/PV hypercall to IDTENTRY:

  - Emit the ASM stub with DECLARE_IDTENTRY
  - Remove the ASM idtentry in 64-bit
  - Remove the open coded ASM entry code in 32-bit
  - Remove the old prototypes

The handler stubs need to stay in ASM code as they need corner case handling
and adjustment of the stack pointer.

Provide a new C function which invokes the entry/exit handling and calls
into the XEN handler on the interrupt stack if required.

The exit code is slightly different from the regular idtentry_exit() on
non-preemptible kernels. If the hypercall is preemptible and need_resched()
is set then XEN provides a preempt hypercall scheduling function.

Move this functionality into the entry code so it can use the existing
idtentry functionality.

[ mingo: Build fixes. ]

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Andy Lutomirski <luto@kernel.org>
Acked-by: Juergen Gross <jgross@suse.com>
Tested-by: Juergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/20200521202118.055270078@linutronix.de
This commit is contained in:
Thomas Gleixner 2020-05-21 22:05:26 +02:00
parent 1de16e0c17
commit 2f6474e463
12 changed files with 151 additions and 86 deletions
Download patch file Download diff file Expand all files Collapse all files

78
arch/x86/entry/common.c
View file

@ -27,6 +27,11 @@
#include <linux/syscalls.h>
#include <linux/uaccess.h>
#ifdef CONFIG_XEN_PV
#include <xen/xen-ops.h>
#include <xen/events.h>
#endif
#include <asm/desc.h>
#include <asm/traps.h>
#include <asm/vdso.h>
@ -35,6 +40,7 @@
#include <asm/nospec-branch.h>
#include <asm/io_bitmap.h>
#include <asm/syscall.h>
#include <asm/irq_stack.h>
#define CREATE_TRACE_POINTS
#include <trace/events/syscalls.h>
@ -680,3 +686,75 @@ void noinstr idtentry_exit_user(struct pt_regs *regs)
prepare_exit_to_usermode(regs);
}
#ifdef CONFIG_XEN_PV
#ifndef CONFIG_PREEMPTION
/*
* Some hypercalls issued by the toolstack can take many 10s of
* seconds. Allow tasks running hypercalls via the privcmd driver to
* be voluntarily preempted even if full kernel preemption is
* disabled.
*
* Such preemptible hypercalls are bracketed by
* xen_preemptible_hcall_begin() and xen_preemptible_hcall_end()
* calls.
*/
DEFINE_PER_CPU(bool, xen_in_preemptible_hcall);
EXPORT_SYMBOL_GPL(xen_in_preemptible_hcall);
/*
* In case of scheduling the flag must be cleared and restored after
* returning from schedule as the task might move to a different CPU.
*/
static __always_inline bool get_and_clear_inhcall(void)
{
bool inhcall = __this_cpu_read(xen_in_preemptible_hcall);
__this_cpu_write(xen_in_preemptible_hcall, false);
return inhcall;
}
static __always_inline void restore_inhcall(bool inhcall)
{
__this_cpu_write(xen_in_preemptible_hcall, inhcall);
}
#else
static __always_inline bool get_and_clear_inhcall(void) { return false; }
static __always_inline void restore_inhcall(bool inhcall) { }
#endif
static void __xen_pv_evtchn_do_upcall(void)
{
irq_enter_rcu();
inc_irq_stat(irq_hv_callback_count);
xen_hvm_evtchn_do_upcall();
irq_exit_rcu();
}
__visible noinstr void xen_pv_evtchn_do_upcall(struct pt_regs *regs)
{
struct pt_regs *old_regs;
bool inhcall, rcu_exit;
rcu_exit = idtentry_enter_cond_rcu(regs);
old_regs = set_irq_regs(regs);
instrumentation_begin();
run_on_irqstack_cond(__xen_pv_evtchn_do_upcall, NULL, regs);
instrumentation_begin();
set_irq_regs(old_regs);
inhcall = get_and_clear_inhcall();
if (inhcall && !WARN_ON_ONCE(rcu_exit)) {
instrumentation_begin();
idtentry_exit_cond_resched(regs, true);
instrumentation_end();
restore_inhcall(inhcall);
} else {
idtentry_exit_cond_rcu(regs, rcu_exit);
}
}
#endif /* CONFIG_XEN_PV */