linux/arch/x86/include/asm/xen/hypervisor.h

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/******************************************************************************
* hypervisor.h
*
* Linux-specific hypervisor handling.
*
* Copyright (c) 2002-2004, K A Fraser
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License version 2
* as published by the Free Software Foundation; or, when distributed
* separately from the Linux kernel or incorporated into other
* software packages, subject to the following license:
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this source file (the "Software"), to deal in the Software without
* restriction, including without limitation the rights to use, copy, modify,
* merge, publish, distribute, sublicense, and/or sell copies of the Software,
* and to permit persons to whom the Software is furnished to do so, subject to
* the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
* IN THE SOFTWARE.
*/
#ifndef _ASM_X86_XEN_HYPERVISOR_H
#define _ASM_X86_XEN_HYPERVISOR_H
extern struct shared_info *HYPERVISOR_shared_info;
extern struct start_info *xen_start_info;
#include <asm/bug.h>
#include <asm/processor.h>
#define XEN_SIGNATURE "XenVMMXenVMM"
static inline uint32_t xen_cpuid_base(void)
{
return cpuid_base_hypervisor(XEN_SIGNATURE, 2);
}
struct pci_dev;
#ifdef CONFIG_XEN_PV_DOM0
bool xen_initdom_restore_msi(struct pci_dev *dev);
#else
static inline bool xen_initdom_restore_msi(struct pci_dev *dev) { return true; }
#endif
#ifdef CONFIG_HOTPLUG_CPU
void xen_arch_register_cpu(int num);
void xen_arch_unregister_cpu(int num);
#endif
#ifdef CONFIG_PVH
void __init xen_pvh_init(struct boot_params *boot_params);
void __init mem_map_via_hcall(struct boot_params *boot_params_p);
#endif
/* Lazy mode for batching updates / context switch */
enum xen_lazy_mode {
XEN_LAZY_NONE,
XEN_LAZY_MMU,
XEN_LAZY_CPU,
};
DECLARE_PER_CPU(enum xen_lazy_mode, xen_lazy_mode);
static inline void enter_lazy(enum xen_lazy_mode mode)
{
Revert "x86/xen: allow nesting of same lazy mode" Commit 49147beb0ccb ("x86/xen: allow nesting of same lazy mode") was added as a solution for a core-mm code change where arch_[enter|leave]_lazy_mmu_mode() started to be called in a nested manner; see commit bcc6cc832573 ("mm: add default definition of set_ptes()"). However, now that we have fixed the API to avoid nesting, we no longer need this capability in the x86 implementation. Additionally, from code review, I don't believe the fix was ever robust in the case of preemption occurring while in the nested lazy mode. The implementation usually deals with preemption by calling arch_leave_lazy_mmu_mode() from xen_start_context_switch() for the outgoing task if we are in the lazy mmu mode. Then in xen_end_context_switch(), it restarts the lazy mode by calling arch_enter_lazy_mmu_mode() for an incoming task that was in the lazy mode when it was switched out. But arch_leave_lazy_mmu_mode() will only unwind a single level of nesting. If we are in the double nest, then it's not fully unwound and per-cpu variables are left in a bad state. So the correct solution is to remove the possibility of nesting from the higher level (which has now been done) and remove this x86-specific solution. Link: https://lkml.kernel.org/r/20250303141542.3371656-6-ryan.roberts@arm.com Signed-off-by: Ryan Roberts <ryan.roberts@arm.com> Acked-by: David Hildenbrand <david@redhat.com> Acked-by: Juergen Gross <jgross@suse.com> Cc: Andreas Larsson <andreas@gaisler.com> Cc: Borislav Betkov <bp@alien8.de> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: David S. Miller <davem@davemloft.net> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Juegren Gross <jgross@suse.com> Cc: Matthew Wilcow (Oracle) <willy@infradead.org> Cc: Thomas Gleinxer <tglx@linutronix.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2025-03-03 14:15:39 +00:00
BUG_ON(this_cpu_read(xen_lazy_mode) != XEN_LAZY_NONE);
this_cpu_write(xen_lazy_mode, mode);
}
static inline void leave_lazy(enum xen_lazy_mode mode)
{
BUG_ON(this_cpu_read(xen_lazy_mode) != mode);
Revert "x86/xen: allow nesting of same lazy mode" Commit 49147beb0ccb ("x86/xen: allow nesting of same lazy mode") was added as a solution for a core-mm code change where arch_[enter|leave]_lazy_mmu_mode() started to be called in a nested manner; see commit bcc6cc832573 ("mm: add default definition of set_ptes()"). However, now that we have fixed the API to avoid nesting, we no longer need this capability in the x86 implementation. Additionally, from code review, I don't believe the fix was ever robust in the case of preemption occurring while in the nested lazy mode. The implementation usually deals with preemption by calling arch_leave_lazy_mmu_mode() from xen_start_context_switch() for the outgoing task if we are in the lazy mmu mode. Then in xen_end_context_switch(), it restarts the lazy mode by calling arch_enter_lazy_mmu_mode() for an incoming task that was in the lazy mode when it was switched out. But arch_leave_lazy_mmu_mode() will only unwind a single level of nesting. If we are in the double nest, then it's not fully unwound and per-cpu variables are left in a bad state. So the correct solution is to remove the possibility of nesting from the higher level (which has now been done) and remove this x86-specific solution. Link: https://lkml.kernel.org/r/20250303141542.3371656-6-ryan.roberts@arm.com Signed-off-by: Ryan Roberts <ryan.roberts@arm.com> Acked-by: David Hildenbrand <david@redhat.com> Acked-by: Juergen Gross <jgross@suse.com> Cc: Andreas Larsson <andreas@gaisler.com> Cc: Borislav Betkov <bp@alien8.de> Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: David S. Miller <davem@davemloft.net> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Ingo Molnar <mingo@redhat.com> Cc: Juegren Gross <jgross@suse.com> Cc: Matthew Wilcow (Oracle) <willy@infradead.org> Cc: Thomas Gleinxer <tglx@linutronix.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2025-03-03 14:15:39 +00:00
this_cpu_write(xen_lazy_mode, XEN_LAZY_NONE);
}
enum xen_lazy_mode xen_get_lazy_mode(void);
#if defined(CONFIG_XEN_DOM0) && defined(CONFIG_ACPI)
void xen_sanitize_proc_cap_bits(uint32_t *buf);
#else
static inline void xen_sanitize_proc_cap_bits(uint32_t *buf)
{
BUG();
}
#endif
#endif /* _ASM_X86_XEN_HYPERVISOR_H */