Ryan Roberts c36549ff8d Revert "x86/xen: allow nesting of same lazy mode" ... Commit 49147beb0c ("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 bcc6cc8325 ("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>		2025-03-17 00:05:35 -07:00
..
alpha
arc	mm/ioremap: pass pgprot_t to ioremap_prot() instead of unsigned long	2025-03-16 22:06:23 -07:00
arm	arm/pgtable: remove duplicate included header file	2025-03-16 22:06:31 -07:00
arm64	mm: rename GENERIC_PTDUMP and PTDUMP_CORE	2025-03-17 00:05:32 -07:00
csky	mm/ioremap: pass pgprot_t to ioremap_prot() instead of unsigned long	2025-03-16 22:06:23 -07:00
hexagon
loongarch	mm/ioremap: pass pgprot_t to ioremap_prot() instead of unsigned long	2025-03-16 22:06:23 -07:00
m68k	m68k: sun3: add check for __pgd_alloc()	2025-03-05 21:36:12 -08:00
microblaze
mips	mm/ioremap: pass pgprot_t to ioremap_prot() instead of unsigned long	2025-03-16 22:06:23 -07:00
nios2
openrisc
parisc	mm/ioremap: pass pgprot_t to ioremap_prot() instead of unsigned long	2025-03-16 22:06:23 -07:00
powerpc	mm: rename GENERIC_PTDUMP and PTDUMP_CORE	2025-03-17 00:05:32 -07:00
riscv	mm: rename GENERIC_PTDUMP and PTDUMP_CORE	2025-03-17 00:05:32 -07:00
s390	mm: rename GENERIC_PTDUMP and PTDUMP_CORE	2025-03-17 00:05:32 -07:00
sh	mm/ioremap: pass pgprot_t to ioremap_prot() instead of unsigned long	2025-03-16 22:06:23 -07:00
sparc	sparc/mm: avoid calling arch_enter/leave_lazy_mmu() in set_ptes	2025-03-17 00:05:34 -07:00
um
x86	Revert "x86/xen: allow nesting of same lazy mode"	2025-03-17 00:05:35 -07:00
xtensa	mm/ioremap: pass pgprot_t to ioremap_prot() instead of unsigned long	2025-03-16 22:06:23 -07:00
.gitignore
Kconfig