On Wed, Feb 08, 2017 at 11:19:31PM -0500, Theodore Ts'o wrote:
> How did you determine when crng_initialize() was being called? On a
> VM generally there are fewer interrupts than on real hardware. On
> KVM, for I see the random: fast_init message being printed 3.6 seconds
> into the boot.
>
> On Google Compute Engine, the fast_init message happens 52 seconds into the
> boot.
>
> So what VM where you using? I'm trying to figure out whether this is
> hypothetical or real problem, and on what systems.
Adding a few printk()s to the latest kernel:
@@ -778,6 +778,8 @@ static void crng_initialize(struct crng_state *crng)
int i;
unsigned long rv;
+ printk("crng_initialize called\n");
+
memcpy(&crng->state[0], "expand 32-byte k", 16);
if (crng == &primary_crng)
_extract_entropy(&input_pool, &crng->state[4],
@@ -1149,6 +1151,9 @@ void add_interrupt_randomness(int irq, int irq_flags)
fast_mix(fast_pool);
add_interrupt_bench(cycles);
+ if (fast_pool->count >= 64)
+ printk("add_interrupt_randomness: fast_pool->count >= 64, dumping entropy");
+
if (!crng_ready()) {
if ((fast_pool->count >= 64) &&
crng_fast_load((char *) fast_pool->pool,
And using:
$ qemu-system-x86_64 --version
QEMU emulator version 2.1.2 (Debian 1:2.1+dfsg-12+deb8u6), Copyright (c) 2003-2008 Fabrice Bellard
$ qemu-system-x86_64 -nographic -enable-kvm -m 1024M -kernel bzImage -append "root=/dev/sda1 loglevel=3 console=ttyS0" hd3
I get:
[ 0.010247] mce: CPU supports 10 MCE banks
[ 0.010317] Last level iTLB entries: 4KB 0, 2MB 0, 4MB 0
[ 0.010318] Last level dTLB entries: 4KB 0, 2MB 0, 4MB 0, 1GB 0
[ 0.064002] add_interrupt_randomness: fast_pool->count >= 64, dumping entropy
[ 0.128003] add_interrupt_randomness: fast_pool->count >= 64, dumping entropy
[ 0.160364] Freeing SMP alternatives memory: 36K
[ 0.160428] ftrace: allocating 35771 entries in 140 pages
[ 0.172384] smpboot: Max logical packages: 1
[ 0.173964] ..TIMER: vector=0x30 apic1=0 pin1=2 apic2=-1 pin2=-1
[ 0.184000] add_interrupt_randomness: fast_pool->count >= 64, dumping entropy
[ 0.184000] add_interrupt_randomness: fast_pool->count >= 64, dumping entropy
[ 0.184000] random: fast init done
[ 0.184000] smpboot: CPU0: Intel QEMU Virtual CPU version 2.1.2 (family: 0x6,
model: 0x6, stepping: 0x3)
[ 0.184000] Performance Events: PMU not available due to virtualization, usin
g software events only.
[ 0.184000] crng_initialize called
[ 0.184000] crng_initialize called
[ 0.184000] smp: Bringing up secondary CPUs ...
[ 0.184000] smp: Brought up 1 node, 1 CPU
Sometimes I get three add_interrupt_randomness lines instead of four which
is fine but still cutting things awfully close.
