On Mon 20-08-18 11:58:35, Vlastimil Babka wrote:
On 32bit PAE kernels on 64bit hardware with enough physical bits, l1tf_pfn_limit() will overflow unsigned long. This in turn affects max_swapfile_size() and can lead to swapon returning -EINVAL. This has been observed in a 32bit guest with 42 bits physical address size, where max_swapfile_size() overflows exactly to 1 << 32, thus zero, and produces the following warning to dmesg:
[ 6.396845] Truncating oversized swap area, only using 0k out of 2047996k
Fix this by using unsigned long long instead.
Reported-by: Dominique Leuenberger dimstar@suse.de Reported-by: Adrian Schroeter adrian@suse.de Fixes: 17dbca119312 ("x86/speculation/l1tf: Add sysfs reporting for l1tf") Fixes: 377eeaa8e11f ("x86/speculation/l1tf: Limit swap file size to MAX_PA/2") Cc: stable@vger.kernel.org Signed-off-by: Vlastimil Babka vbabka@suse.cz
Looks good to me. I would probably use phys_addr_t which would be more descriptive but this is just minor thing.
Acked-by: Michal Hocko mhocko@suse.com
arch/x86/include/asm/processor.h | 4 ++-- arch/x86/mm/init.c | 4 ++-- 2 files changed, 4 insertions(+), 4 deletions(-)
diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index 682286aca881..a0a52274cb4a 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -181,9 +181,9 @@ extern const struct seq_operations cpuinfo_op; extern void cpu_detect(struct cpuinfo_x86 *c); -static inline unsigned long l1tf_pfn_limit(void) +static inline unsigned long long l1tf_pfn_limit(void) {
- return BIT(boot_cpu_data.x86_phys_bits - 1 - PAGE_SHIFT) - 1;
- return BIT_ULL(boot_cpu_data.x86_phys_bits - 1 - PAGE_SHIFT) - 1;
} extern void early_cpu_init(void); diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c index acfab322fbe0..02de3d6065c4 100644 --- a/arch/x86/mm/init.c +++ b/arch/x86/mm/init.c @@ -923,7 +923,7 @@ unsigned long max_swapfile_size(void) if (boot_cpu_has_bug(X86_BUG_L1TF)) { /* Limit the swap file size to MAX_PA/2 for L1TF workaround */
unsigned long l1tf_limit = l1tf_pfn_limit() + 1;
unsigned long long l1tf_limit = l1tf_pfn_limit() + 1;
- We encode swap offsets also with 3 bits below those for pfn
- which makes the usable limit higher.
@@ -931,7 +931,7 @@ unsigned long max_swapfile_size(void) #if CONFIG_PGTABLE_LEVELS > 2 l1tf_limit <<= PAGE_SHIFT - SWP_OFFSET_FIRST_BIT; #endif
pages = min_t(unsigned long, l1tf_limit, pages);
pages = min_t(unsigned long long, l1tf_limit, pages);}
2.18.0