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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [xen stable-4.13] xen: do live patching only from main idle loop
commit 0d16bb7e6ad4834c66366d84d419555c384485d9
Author: Juergen Gross <jgross@xxxxxxxx>
AuthorDate: Thu Apr 9 09:04:19 2020 +0200
Commit: Jan Beulich <jbeulich@xxxxxxxx>
CommitDate: Thu Apr 9 09:04:19 2020 +0200
xen: do live patching only from main idle loop
One of the main design goals of core scheduling is to avoid actions
which are not directly related to the domain currently running on a
given cpu or core. Live patching is one of those actions which are
allowed taking place on a cpu only when the idle scheduling unit is
active on that cpu.
Unfortunately live patching tries to force the cpus into the idle loop
just by raising the schedule softirq, which will no longer be
guaranteed to work with core scheduling active. Additionally there are
still some places in the hypervisor calling check_for_livepatch_work()
without being in the idle loop.
It is easy to force a cpu into the main idle loop by scheduling a
tasklet on it. So switch live patching to use tasklets for switching to
idle and raising scheduling events. Additionally the calls of
check_for_livepatch_work() outside the main idle loop can be dropped.
As tasklets are only running on idle vcpus and stop_machine_run()
is activating tasklets on all cpus but the one it has been called on
to rendezvous, it is mandatory for stop_machine_run() to be called on
an idle vcpu, too, as otherwise there is no way for scheduling to
activate the idle vcpu for the tasklet on the sibling of the cpu
stop_machine_run() has been called on.
Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>
Acked-by: Julien Grall <jgrall@xxxxxxxxxx>
Reviewed-by: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>
Tested-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Acked-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
master commit: 005de45c887e0fefde59570686877afeda2c7b4e
master date: 2020-03-02 18:36:50 +0000
---
xen/arch/arm/domain.c | 9 ++++-----
xen/arch/arm/traps.c | 6 ------
xen/arch/x86/domain.c | 9 ++++-----
xen/arch/x86/hvm/svm/svm.c | 2 +-
xen/arch/x86/hvm/vmx/vmcs.c | 2 +-
xen/arch/x86/pv/domain.c | 2 +-
xen/arch/x86/setup.c | 2 +-
xen/common/livepatch.c | 39 ++++++++++++++++++++++++++++++++++-----
8 files changed, 46 insertions(+), 25 deletions(-)
diff --git a/xen/arch/arm/domain.c b/xen/arch/arm/domain.c
index c0a13aa0ab..283eb6bb43 100644
--- a/xen/arch/arm/domain.c
+++ b/xen/arch/arm/domain.c
@@ -72,7 +72,11 @@ void idle_loop(void)
/* Are we here for running vcpu context tasklets, or for idling? */
if ( unlikely(tasklet_work_to_do(cpu)) )
+ {
do_tasklet();
+ /* Livepatch work is always kicked off via a tasklet. */
+ check_for_livepatch_work();
+ }
/*
* Test softirqs twice --- first to see if should even try scrubbing
* and then, after it is done, whether softirqs became pending
@@ -83,11 +87,6 @@ void idle_loop(void)
do_idle();
do_softirq();
- /*
- * We MUST be last (or before dsb, wfi). Otherwise after we get the
- * softirq we would execute dsb,wfi (and sleep) and not patch.
- */
- check_for_livepatch_work();
}
}
diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c
index d028ec9224..1d2b762e22 100644
--- a/xen/arch/arm/traps.c
+++ b/xen/arch/arm/traps.c
@@ -23,7 +23,6 @@
#include <xen/iocap.h>
#include <xen/irq.h>
#include <xen/lib.h>
-#include <xen/livepatch.h>
#include <xen/mem_access.h>
#include <xen/mm.h>
#include <xen/perfc.h>
@@ -2231,11 +2230,6 @@ static void check_for_pcpu_work(void)
{
local_irq_enable();
do_softirq();
- /*
- * Must be the last one - as the IPI will trigger us to come here
- * and we want to patch the hypervisor with almost no stack.
- */
- check_for_livepatch_work();
local_irq_disable();
}
}
diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
index 2ce00fb26f..d42a32c8a9 100644
--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -141,7 +141,11 @@ static void idle_loop(void)
/* Are we here for running vcpu context tasklets, or for idling? */
if ( unlikely(tasklet_work_to_do(cpu)) )
+ {
do_tasklet();
+ /* Livepatch work is always kicked off via a tasklet. */
+ check_for_livepatch_work();
+ }
/*
* Test softirqs twice --- first to see if should even try scrubbing
* and then, after it is done, whether softirqs became pending
@@ -151,11 +155,6 @@ static void idle_loop(void)
!softirq_pending(cpu) )
pm_idle();
do_softirq();
- /*
- * We MUST be last (or before pm_idle). Otherwise after we get the
- * softirq we would execute pm_idle (and sleep) and not patch.
- */
- check_for_livepatch_work();
}
}
diff --git a/xen/arch/x86/hvm/svm/svm.c b/xen/arch/x86/hvm/svm/svm.c
index 6ae43999ff..dc1bd32b9b 100644
--- a/xen/arch/x86/hvm/svm/svm.c
+++ b/xen/arch/x86/hvm/svm/svm.c
@@ -1032,7 +1032,7 @@ static void noreturn svm_do_resume(struct vcpu *v)
hvm_do_resume(v);
- reset_stack_and_jump(svm_asm_do_resume);
+ reset_stack_and_jump_nolp(svm_asm_do_resume);
}
void svm_vmenter_helper(const struct cpu_user_regs *regs)
diff --git a/xen/arch/x86/hvm/vmx/vmcs.c b/xen/arch/x86/hvm/vmx/vmcs.c
index f10f6b78ec..d53eceb23a 100644
--- a/xen/arch/x86/hvm/vmx/vmcs.c
+++ b/xen/arch/x86/hvm/vmx/vmcs.c
@@ -1889,7 +1889,7 @@ void vmx_do_resume(struct vcpu *v)
if ( host_cr4 != read_cr4() )
__vmwrite(HOST_CR4, read_cr4());
- reset_stack_and_jump(vmx_asm_do_vmentry);
+ reset_stack_and_jump_nolp(vmx_asm_do_vmentry);
}
static inline unsigned long vmr(unsigned long field)
diff --git a/xen/arch/x86/pv/domain.c b/xen/arch/x86/pv/domain.c
index ed5111fc47..3308b6b7d4 100644
--- a/xen/arch/x86/pv/domain.c
+++ b/xen/arch/x86/pv/domain.c
@@ -61,7 +61,7 @@ custom_runtime_param("pcid", parse_pcid);
static void noreturn continue_nonidle_domain(struct vcpu *v)
{
check_wakeup_from_wait();
- reset_stack_and_jump(ret_from_intr);
+ reset_stack_and_jump_nolp(ret_from_intr);
}
static int setup_compat_l4(struct vcpu *v)
diff --git a/xen/arch/x86/setup.c b/xen/arch/x86/setup.c
index cc7274eae6..ae61e93024 100644
--- a/xen/arch/x86/setup.c
+++ b/xen/arch/x86/setup.c
@@ -631,7 +631,7 @@ static void __init noreturn reinit_bsp_stack(void)
stack_base[0] = stack;
memguard_guard_stack(stack);
- reset_stack_and_jump(init_done);
+ reset_stack_and_jump_nolp(init_done);
}
/*
diff --git a/xen/common/livepatch.c b/xen/common/livepatch.c
index 7ab1f82290..1f89984c9a 100644
--- a/xen/common/livepatch.c
+++ b/xen/common/livepatch.c
@@ -17,6 +17,7 @@
#include <xen/spinlock.h>
#include <xen/string.h>
#include <xen/symbols.h>
+#include <xen/tasklet.h>
#include <xen/version.h>
#include <xen/virtual_region.h>
#include <xen/vmap.h>
@@ -103,6 +104,7 @@ static struct livepatch_work livepatch_work;
* Having an per-cpu lessens the load.
*/
static DEFINE_PER_CPU(bool_t, work_to_do);
+static DEFINE_PER_CPU(struct tasklet, livepatch_tasklet);
static int get_name(const struct xen_livepatch_name *name, char *n)
{
@@ -1247,17 +1249,16 @@ static int schedule_work(struct payload *data, uint32_t
cmd, uint32_t timeout)
smp_wmb();
livepatch_work.do_work = 1;
- this_cpu(work_to_do) = 1;
+ tasklet_schedule_on_cpu(&this_cpu(livepatch_tasklet), smp_processor_id());
put_cpu_maps();
return 0;
}
-static void reschedule_fn(void *unused)
+static void tasklet_fn(unsigned long unused)
{
this_cpu(work_to_do) = 1;
- raise_softirq(SCHEDULE_SOFTIRQ);
}
static int livepatch_spin(atomic_t *counter, s_time_t timeout,
@@ -1317,7 +1318,7 @@ void check_for_livepatch_work(void)
if ( atomic_inc_and_test(&livepatch_work.semaphore) )
{
struct payload *p;
- unsigned int cpus;
+ unsigned int cpus, i;
p = livepatch_work.data;
if ( !get_cpu_maps() )
@@ -1346,7 +1347,9 @@ void check_for_livepatch_work(void)
{
dprintk(XENLOG_DEBUG, LIVEPATCH "%s: CPU%u - IPIing the other %u
CPUs\n",
p->name, cpu, cpus);
- smp_call_function(reschedule_fn, NULL, 0);
+ for_each_online_cpu ( i )
+ if ( i != cpu )
+ tasklet_schedule_on_cpu(&per_cpu(livepatch_tasklet, i), i);
}
timeout = livepatch_work.timeout + NOW();
@@ -1668,8 +1671,34 @@ static void livepatch_printall(unsigned char key)
spin_unlock(&payload_lock);
}
+static int cpu_callback(
+ struct notifier_block *nfb, unsigned long action, void *hcpu)
+{
+ unsigned int cpu = (unsigned long)hcpu;
+
+ if ( action == CPU_UP_PREPARE )
+ tasklet_init(&per_cpu(livepatch_tasklet, cpu), tasklet_fn, 0);
+
+ return NOTIFY_DONE;
+}
+
+static struct notifier_block cpu_nfb = {
+ .notifier_call = cpu_callback
+};
+
static int __init livepatch_init(void)
{
+ unsigned int cpu;
+
+ for_each_online_cpu ( cpu )
+ {
+ void *hcpu = (void *)(long)cpu;
+
+ cpu_callback(&cpu_nfb, CPU_UP_PREPARE, hcpu);
+ }
+
+ register_cpu_notifier(&cpu_nfb);
+
register_keyhandler('x', livepatch_printall, "print livepatch info", 1);
arch_livepatch_init();
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.13
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