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x86/speculation/l1tf: Limit swap file size to MAX_PA/2

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For the L1TF workaround its necessary to limit the swap file size to below
MAX_PA/2, so that the higher bits of the swap offset inverted never point
to valid memory.

Add a mechanism for the architecture to override the swap file size check
in swapfile.c and add a x86 specific max swapfile check function that
enforces that limit.

The check is only enabled if the CPU is vulnerable to L1TF.

In VMs with 42bit MAX_PA the typical limit is 2TB now, on a native system
with 46bit PA it is 32TB. The limit is only per individual swap file, so
it's always possible to exceed these limits with multiple swap files or
partitions.

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Dave Hansen <dave.hansen@intel.com>
This commit is contained in:
Andi Kleen
2018-06-13 15:48:28 -07:00
committed by Thomas Gleixner
parent 42e4089c78
commit 377eeaa8e1
3 changed files with 47 additions and 16 deletions
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include/linux/swapfile.h
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@@ -10,5 +10,7 @@ extern spinlock_t swap_lock;
extern struct plist_head swap_active_head;
extern struct swap_info_struct *swap_info[];
extern int try_to_unuse(unsigned int, bool, unsigned long);
extern unsigned long generic_max_swapfile_size(void);
extern unsigned long max_swapfile_size(void);
#endif /* _LINUX_SWAPFILE_H */