From d60d8b64280c8b36c085eda7821585c1ce911795 Mon Sep 17 00:00:00 2001
From: Christoffer Dall <christoffer.dall@linaro.org>
Date: Fri, 26 Jan 2018 16:06:51 +0100
Subject: KVM: arm/arm64: Fix arch timers with userspace irqchips
When introducing support for irqchip in userspace we needed a way to
mask the timer signal to prevent the guest continuously exiting due to a
screaming timer.
We did this by disabling the corresponding percpu interrupt on the
host interrupt controller, because we cannot rely on the host system
having a GIC, and therefore cannot make any assumptions about having an
active state to hide the timer signal.
Unfortunately, when introducing this feature, it became entirely
possible that a VCPU which belongs to a VM that has a userspace irqchip
can disable the vtimer irq on the host on some physical CPU, and then go
away without ever enabling the vtimer irq on that physical CPU again.
This means that using irqchips in userspace on a system that also
supports running VMs with an in-kernel GIC can prevent forward progress
from in-kernel GIC VMs.
Later on, when we started taking virtual timer interrupts in the arch
timer code, we would also leave this timer state active for userspace
irqchip VMs, because we leave it up to a VGIC-enabled guest to
deactivate the hardware IRQ using the HW bit in the LR.
Both issues are solved by only using the enable/disable trick on systems
that do not have a host GIC which supports the active state, because all
VMs on such systems must use irqchips in userspace. Systems that have a
working GIC with support for an active state use the active state to
mask the timer signal for both userspace and in-kernel irqchips.
Cc: Alexander Graf <agraf@suse.de>
Reviewed-by: Marc Zyngier <marc.zyngier@arm.com>
Cc: <stable@vger.kernel.org> # v4.12+
Fixes: d9e139778376 ("KVM: arm/arm64: Support arch timers with a userspace gic")
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
---
virt/kvm/arm/arch_timer.c | 116 +++++++++++++++++++++++++---------------------
1 file changed, 64 insertions(+), 52 deletions(-)
(limited to 'virt')
diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
index 70268c0bec79..70f4c30918eb 100644
--- a/virt/kvm/arm/arch_timer.c
+++ b/virt/kvm/arm/arch_timer.c
@@ -36,6 +36,8 @@ static struct timecounter *timecounter;
static unsigned int host_vtimer_irq;
static u32 host_vtimer_irq_flags;
+static DEFINE_STATIC_KEY_FALSE(has_gic_active_state);
+
static const struct kvm_irq_level default_ptimer_irq = {
.irq = 30,
.level = 1,
@@ -56,6 +58,12 @@ u64 kvm_phys_timer_read(void)
return timecounter->cc->read(timecounter->cc);
}
+static inline bool userspace_irqchip(struct kvm *kvm)
+{
+ return static_branch_unlikely(&userspace_irqchip_in_use) &&
+ unlikely(!irqchip_in_kernel(kvm));
+}
+
static void soft_timer_start(struct hrtimer *hrt, u64 ns)
{
hrtimer_start(hrt, ktime_add_ns(ktime_get(), ns),
@@ -69,25 +77,6 @@ static void soft_timer_cancel(struct hrtimer *hrt, struct work_struct *work)
cancel_work_sync(work);
}
-static void kvm_vtimer_update_mask_user(struct kvm_vcpu *vcpu)
-{
- struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
-
- /*
- * When using a userspace irqchip with the architected timers, we must
- * prevent continuously exiting from the guest, and therefore mask the
- * physical interrupt by disabling it on the host interrupt controller
- * when the virtual level is high, such that the guest can make
- * forward progress. Once we detect the output level being
- * de-asserted, we unmask the interrupt again so that we exit from the
- * guest when the timer fires.
- */
- if (vtimer->irq.level)
- disable_percpu_irq(host_vtimer_irq);
- else
- enable_percpu_irq(host_vtimer_irq, 0);
-}
-
static irqreturn_t kvm_arch_timer_handler(int irq, void *dev_id)
{
struct kvm_vcpu *vcpu = *(struct kvm_vcpu **)dev_id;
@@ -106,9 +95,9 @@ static irqreturn_t kvm_arch_timer_handler(int irq, void *dev_id)
if (kvm_timer_should_fire(vtimer))
kvm_timer_update_irq(vcpu, true, vtimer);
- if (static_branch_unlikely(&userspace_irqchip_in_use) &&
- unlikely(!irqchip_in_kernel(vcpu->kvm)))
- kvm_vtimer_update_mask_user(vcpu);
+ if (userspace_irqchip(vcpu->kvm) &&
+ !static_branch_unlikely(&has_gic_active_state))
+ disable_percpu_irq(host_vtimer_irq);
return IRQ_HANDLED;
}
@@ -290,8 +279,7 @@ static void kvm_timer_update_irq(struct kvm_vcpu *vcpu, bool new_level,
trace_kvm_timer_update_irq(vcpu->vcpu_id, timer_ctx->irq.irq,
timer_ctx->irq.level);
- if (!static_branch_unlikely(&userspace_irqchip_in_use) ||
- likely(irqchip_in_kernel(vcpu->kvm))) {
+ if (!userspace_irqchip(vcpu->kvm)) {
ret = kvm_vgic_inject_irq(vcpu->kvm, vcpu->vcpu_id,
timer_ctx->irq.irq,
timer_ctx->irq.level,
@@ -350,12 +338,6 @@ static void kvm_timer_update_state(struct kvm_vcpu *vcpu)
phys_timer_emulate(vcpu);
}
-static void __timer_snapshot_state(struct arch_timer_context *timer)
-{
- timer->cnt_ctl = read_sysreg_el0(cntv_ctl);
- timer->cnt_cval = read_sysreg_el0(cntv_cval);
-}
-
static void vtimer_save_state(struct kvm_vcpu *vcpu)
{
struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
@@ -367,8 +349,10 @@ static void vtimer_save_state(struct kvm_vcpu *vcpu)
if (!vtimer->loaded)
goto out;
- if (timer->enabled)
- __timer_snapshot_state(vtimer);
+ if (timer->enabled) {
+ vtimer->cnt_ctl = read_sysreg_el0(cntv_ctl);
+ vtimer->cnt_cval = read_sysreg_el0(cntv_cval);
+ }
/* Disable the virtual timer */
write_sysreg_el0(0, cntv_ctl);
@@ -460,23 +444,43 @@ static void set_cntvoff(u64 cntvoff)
kvm_call_hyp(__kvm_timer_set_cntvoff, low, high);
}
-static void kvm_timer_vcpu_load_vgic(struct kvm_vcpu *vcpu)
+static inline void set_vtimer_irq_phys_active(struct kvm_vcpu *vcpu, bool active)
+{
+ int r;
+ r = irq_set_irqchip_state(host_vtimer_irq, IRQCHIP_STATE_ACTIVE, active);
+ WARN_ON(r);
+}
+
+static void kvm_timer_vcpu_load_gic(struct kvm_vcpu *vcpu)
{
struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
bool phys_active;
- int ret;
- phys_active = kvm_vgic_map_is_active(vcpu, vtimer->irq.irq);
-
- ret = irq_set_irqchip_state(host_vtimer_irq,
- IRQCHIP_STATE_ACTIVE,
- phys_active);
- WARN_ON(ret);
+ if (irqchip_in_kernel(vcpu->kvm))
+ phys_active = kvm_vgic_map_is_active(vcpu, vtimer->irq.irq);
+ else
+ phys_active = vtimer->irq.level;
+ set_vtimer_irq_phys_active(vcpu, phys_active);
}
-static void kvm_timer_vcpu_load_user(struct kvm_vcpu *vcpu)
+static void kvm_timer_vcpu_load_nogic(struct kvm_vcpu *vcpu)
{
- kvm_vtimer_update_mask_user(vcpu);
+ struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
+
+ /*
+ * When using a userspace irqchip with the architected timers and a
+ * host interrupt controller that doesn't support an active state, we
+ * must still prevent continuously exiting from the guest, and
+ * therefore mask the physical interrupt by disabling it on the host
+ * interrupt controller when the virtual level is high, such that the
+ * guest can make forward progress. Once we detect the output level
+ * being de-asserted, we unmask the interrupt again so that we exit
+ * from the guest when the timer fires.
+ */
+ if (vtimer->irq.level)
+ disable_percpu_irq(host_vtimer_irq);
+ else
+ enable_percpu_irq(host_vtimer_irq, host_vtimer_irq_flags);
}
void kvm_timer_vcpu_load(struct kvm_vcpu *vcpu)
@@ -487,10 +491,10 @@ void kvm_timer_vcpu_load(struct kvm_vcpu *vcpu)
if (unlikely(!timer->enabled))
return;
- if (unlikely(!irqchip_in_kernel(vcpu->kvm)))
- kvm_timer_vcpu_load_user(vcpu);
+ if (static_branch_likely(&has_gic_active_state))
+ kvm_timer_vcpu_load_gic(vcpu);
else
- kvm_timer_vcpu_load_vgic(vcpu);
+ kvm_timer_vcpu_load_nogic(vcpu);
set_cntvoff(vtimer->cntvoff);
@@ -555,18 +559,24 @@ static void unmask_vtimer_irq_user(struct kvm_vcpu *vcpu)
{
struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
- if (unlikely(!irqchip_in_kernel(vcpu->kvm))) {
- __timer_snapshot_state(vtimer);
- if (!kvm_timer_should_fire(vtimer)) {
- kvm_timer_update_irq(vcpu, false, vtimer);
- kvm_vtimer_update_mask_user(vcpu);
- }
+ if (!kvm_timer_should_fire(vtimer)) {
+ kvm_timer_update_irq(vcpu, false, vtimer);
+ if (static_branch_likely(&has_gic_active_state))
+ set_vtimer_irq_phys_active(vcpu, false);
+ else
+ enable_percpu_irq(host_vtimer_irq, host_vtimer_irq_flags);
}
}
void kvm_timer_sync_hwstate(struct kvm_vcpu *vcpu)
{
- unmask_vtimer_irq_user(vcpu);
+ struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
+
+ if (unlikely(!timer->enabled))
+ return;
+
+ if (unlikely(!irqchip_in_kernel(vcpu->kvm)))
+ unmask_vtimer_irq_user(vcpu);
}
int kvm_timer_vcpu_reset(struct kvm_vcpu *vcpu)
@@ -753,6 +763,8 @@ int kvm_timer_hyp_init(bool has_gic)
kvm_err("kvm_arch_timer: error setting vcpu affinity\n");
goto out_free_irq;
}
+
+ static_branch_enable(&has_gic_active_state);
}
kvm_info("virtual timer IRQ%d\n", host_vtimer_irq);
--
cgit v1.2.3
From b28676bb8ae4569cced423dc2a88f7cb319d5379 Mon Sep 17 00:00:00 2001
From: Wanpeng Li <wanpeng.li@hotmail.com>
Date: Tue, 13 Feb 2018 15:36:00 +0100
Subject: KVM: mmu: Fix overlap between public and private memslots
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
Reported by syzkaller:
pte_list_remove: ffff9714eb1f8078 0->BUG
------------[ cut here ]------------
kernel BUG at arch/x86/kvm/mmu.c:1157!
invalid opcode: 0000 [#1] SMP
RIP: 0010:pte_list_remove+0x11b/0x120 [kvm]
Call Trace:
drop_spte+0x83/0xb0 [kvm]
mmu_page_zap_pte+0xcc/0xe0 [kvm]
kvm_mmu_prepare_zap_page+0x81/0x4a0 [kvm]
kvm_mmu_invalidate_zap_all_pages+0x159/0x220 [kvm]
kvm_arch_flush_shadow_all+0xe/0x10 [kvm]
kvm_mmu_notifier_release+0x6c/0xa0 [kvm]
? kvm_mmu_notifier_release+0x5/0xa0 [kvm]
__mmu_notifier_release+0x79/0x110
? __mmu_notifier_release+0x5/0x110
exit_mmap+0x15a/0x170
? do_exit+0x281/0xcb0
mmput+0x66/0x160
do_exit+0x2c9/0xcb0
? __context_tracking_exit.part.5+0x4a/0x150
do_group_exit+0x50/0xd0
SyS_exit_group+0x14/0x20
do_syscall_64+0x73/0x1f0
entry_SYSCALL64_slow_path+0x25/0x25
The reason is that when creates new memslot, there is no guarantee for new
memslot not overlap with private memslots. This can be triggered by the
following program:
#include <fcntl.h>
#include <pthread.h>
#include <setjmp.h>
#include <signal.h>
#include <stddef.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/ioctl.h>
#include <sys/stat.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <unistd.h>
#include <linux/kvm.h>
long r[16];
int main()
{
void *p = valloc(0x4000);
r[2] = open("/dev/kvm", 0);
r[3] = ioctl(r[2], KVM_CREATE_VM, 0x0ul);
uint64_t addr = 0xf000;
ioctl(r[3], KVM_SET_IDENTITY_MAP_ADDR, &addr);
r[6] = ioctl(r[3], KVM_CREATE_VCPU, 0x0ul);
ioctl(r[3], KVM_SET_TSS_ADDR, 0x0ul);
ioctl(r[6], KVM_RUN, 0);
ioctl(r[6], KVM_RUN, 0);
struct kvm_userspace_memory_region mr = {
.slot = 0,
.flags = KVM_MEM_LOG_DIRTY_PAGES,
.guest_phys_addr = 0xf000,
.memory_size = 0x4000,
.userspace_addr = (uintptr_t) p
};
ioctl(r[3], KVM_SET_USER_MEMORY_REGION, &mr);
return 0;
}
This patch fixes the bug by not adding a new memslot even if it
overlaps with private memslots.
Reported-by: Dmitry Vyukov <dvyukov@google.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Cc: Dmitry Vyukov <dvyukov@google.com>
Cc: Eric Biggers <ebiggers3@gmail.com>
Cc: stable@vger.kernel.org
Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
---
virt/kvm/kvm_main.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
---
virt/kvm/kvm_main.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)
(limited to 'virt')
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 4501e658e8d6..65dea3ffef68 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -969,8 +969,7 @@ int __kvm_set_memory_region(struct kvm *kvm,
/* Check for overlaps */
r = -EEXIST;
kvm_for_each_memslot(slot, __kvm_memslots(kvm, as_id)) {
- if ((slot->id >= KVM_USER_MEM_SLOTS) ||
- (slot->id == id))
+ if (slot->id == id)
continue;
if (!((base_gfn + npages <= slot->base_gfn) ||
(base_gfn >= slot->base_gfn + slot->npages)))
--
cgit v1.2.3