Patch 6
Subsystems (4)
PATCH 6/6 Patch 6
For the L1TF workaround we want 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 way 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 <[email protected]>
--- arch/x86/mm/init.c | 17 +++++++++++++++++ include/linux/swapfile.h | 2 ++ mm/swapfile.c | 44 ++++++++++++++++++++++++++++---------------- 3 files changed, 47 insertions(+), 16 deletions(-)
arch/x86/mm/init.c +17 -0
@@ -4,6 +4,8 @@#include <linux/swap.h> #include <linux/memblock.h> #include <linux/bootmem.h> /* for max_low_pfn */ +#include <linux/swapfile.h> +#include <linux/swapops.h> #include <asm/set_memory.h> #include <asm/e820/api.h>
@@ -878,3 +880,18 @@ void update_cache_mode_entry(unsigned entry, enum page_cache_mode cache) __cachemode2pte_tbl[cache] =__cm_idx2pte (entry); __pte2cachemode_tbl[entry] = cache; } + +unsigned long max_swapfile_size (void ) +{ +unsigned long pages; + + pages =generic_max_swapfile_size (); + +if (boot_cpu_has (X86_BUG_L1TF )) { +/* Limit the swap file size to MAX_PA/2 for the L1TF workaround */ + pages = min_t(unsigned long, +1ULL << (boot_cpu_data.x86_phys_bits -1 -PAGE_SHIFT ), + pages); + } +return pages; +}
include/linux/swapfile.h +2 -0
@@ -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 */
mm/swapfile.c +28 -16
56 lines not on this page · raw message
Signature · 1 line
2.15.0