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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH v2 2/2] xen: add update indicator to vcpu_runstate_info
In order to support reading another vcpu's mapped vcpu_runstate_info
an indicator for an occurring update of the runstate information is
needed.
Add the possibility to activate setting this indicator in the highest
bit of state_entry_time via a vm_assist hypercall. When activated the
update indicator will be set before the runstate information is
modified in guest memory and it will be reset after modification is
done. As state_entry_time is guaranteed to be different after each
update the guest can detect any update (either in progress or while
reading the runstate data) by comparing state_entry_time before and
after reading runstate data: in case the values differ or the update
indicator was set the data might be inconsistent and should be reread.
Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
V2: smp_wmb() instead of wmb() as requested by Andrew Cooper
use sizeof() as requested by Jan Beulich
eliminate new variable update_flag as requested by Jan Beulich
---
xen/arch/arm/domain.c | 21 +++++++++++++++++++++
xen/arch/x86/domain.c | 30 ++++++++++++++++++++++++++++++
xen/include/asm-arm/config.h | 2 +-
xen/include/asm-x86/config.h | 1 +
xen/include/public/vcpu.h | 6 ++++++
xen/include/public/xen.h | 7 +++++++
6 files changed, 66 insertions(+), 1 deletion(-)
diff --git a/xen/arch/arm/domain.c b/xen/arch/arm/domain.c
index 1365b4a..ad50b19 100644
--- a/xen/arch/arm/domain.c
+++ b/xen/arch/arm/domain.c
@@ -239,10 +239,31 @@ static void ctxt_switch_to(struct vcpu *n)
/* Update per-VCPU guest runstate shared memory area (if registered). */
static void update_runstate_area(struct vcpu *v)
{
+ void __user *guest_handle = NULL;
+ unsigned off = 0;
+
if ( guest_handle_is_null(runstate_guest(v)) )
return;
+ if ( VM_ASSIST(v->domain, runstate_update_flag) )
+ {
+ off = offsetof(struct vcpu_runstate_info, state_entry_time) +
+ sizeof(v->runstate.state_entry_time) - 1;
+ guest_handle = v->runstate_guest.p;
+ guest_handle += off;
+ v->runstate.state_entry_time |= XEN_RUNSTATE_UPDATE;
+ __raw_copy_to_guest(guest_handle, (void *)&v->runstate + off, 1);
+ smp_wmb();
+ }
+
__copy_to_guest(runstate_guest(v), &v->runstate, 1);
+
+ if ( guest_handle )
+ {
+ v->runstate.state_entry_time &= ~XEN_RUNSTATE_UPDATE;
+ smp_wmb();
+ __raw_copy_to_guest(guest_handle, (void *)&v->runstate + off, 1);
+ }
}
static void schedule_tail(struct vcpu *prev)
diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
index 989bc74..8890661 100644
--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -1926,12 +1926,35 @@ bool_t update_runstate_area(struct vcpu *v)
{
bool_t rc;
smap_check_policy_t smap_policy;
+ void __user *guest_handle = NULL;
+ unsigned off = 0;
if ( guest_handle_is_null(runstate_guest(v)) )
return 1;
smap_policy = smap_policy_change(v, SMAP_CHECK_ENABLED);
+ if ( VM_ASSIST(v->domain, runstate_update_flag) )
+ {
+ off = offsetof(struct vcpu_runstate_info, state_entry_time) +
+ sizeof(v->runstate.state_entry_time) - 1;
+ if ( has_32bit_shinfo(v->domain) )
+ {
+ guest_handle = v->runstate_guest.compat.p;
+ guest_handle +=
+ offsetof(struct compat_vcpu_runstate_info, state_entry_time) +
+ sizeof(v->runstate.state_entry_time) - 1;
+ }
+ else
+ {
+ guest_handle = v->runstate_guest.native.p;
+ guest_handle += off;
+ }
+ v->runstate.state_entry_time |= XEN_RUNSTATE_UPDATE;
+ __raw_copy_to_guest(guest_handle, (void *)&v->runstate + off, 1);
+ smp_wmb();
+ }
+
if ( has_32bit_shinfo(v->domain) )
{
struct compat_vcpu_runstate_info info;
@@ -1944,6 +1967,13 @@ bool_t update_runstate_area(struct vcpu *v)
rc = __copy_to_guest(runstate_guest(v), &v->runstate, 1) !=
sizeof(v->runstate);
+ if ( guest_handle )
+ {
+ v->runstate.state_entry_time &= ~XEN_RUNSTATE_UPDATE;
+ smp_wmb();
+ __raw_copy_to_guest(guest_handle, (void *)&v->runstate + off, 1);
+ }
+
smap_policy_change(v, smap_policy);
return rc;
diff --git a/xen/include/asm-arm/config.h b/xen/include/asm-arm/config.h
index 563f49b..ce3edc2 100644
--- a/xen/include/asm-arm/config.h
+++ b/xen/include/asm-arm/config.h
@@ -199,7 +199,7 @@ extern unsigned long frametable_virt_end;
#define watchdog_disable() ((void)0)
#define watchdog_enable() ((void)0)
-#define VM_ASSIST_VALID (0)
+#define VM_ASSIST_VALID (1UL << VMASST_TYPE_runstate_update_flag)
#endif /* __ARM_CONFIG_H__ */
/*
diff --git a/xen/include/asm-x86/config.h b/xen/include/asm-x86/config.h
index c10129d..6fd84e7 100644
--- a/xen/include/asm-x86/config.h
+++ b/xen/include/asm-x86/config.h
@@ -332,6 +332,7 @@ extern unsigned long xen_phys_start;
(1UL << VMASST_TYPE_writable_pagetables) | \
(1UL << VMASST_TYPE_pae_extended_cr3) | \
(1UL << VMASST_TYPE_architectural_iopl) | \
+ (1UL << VMASST_TYPE_runstate_update_flag)| \
(1UL << VMASST_TYPE_m2p_strict))
#define VM_ASSIST_VALID NATIVE_VM_ASSIST_VALID
#define COMPAT_VM_ASSIST_VALID (NATIVE_VM_ASSIST_VALID & \
diff --git a/xen/include/public/vcpu.h b/xen/include/public/vcpu.h
index 692b87a..2aa230d 100644
--- a/xen/include/public/vcpu.h
+++ b/xen/include/public/vcpu.h
@@ -84,6 +84,12 @@ struct vcpu_runstate_info {
/* When was current state entered (system time, ns)? */
uint64_t state_entry_time;
/*
+ * Update indicator set in state_entry_time:
+ * When activated via VMASST_TYPE_runstate_update_flag, set during
+ * updates in guest memory mapped copy of vcpu_runstate_info.
+ */
+#define XEN_RUNSTATE_UPDATE (1ULL << 63)
+ /*
* Time spent in each RUNSTATE_* (ns). The sum of these times is
* guaranteed not to drift from system time.
*/
diff --git a/xen/include/public/xen.h b/xen/include/public/xen.h
index 37bbb22..b9e5e0f 100644
--- a/xen/include/public/xen.h
+++ b/xen/include/public/xen.h
@@ -510,6 +510,13 @@ DEFINE_XEN_GUEST_HANDLE(mmuext_op_t);
#define VMASST_TYPE_architectural_iopl 4
/*
+ * All guests: activate update indicator in vcpu_runstate_info
+ * Enable setting the XEN_RUNSTATE_UPDATE flag in guest memory mapped
+ * vcpu_runstate_info during updates of the runstate information.
+ */
+#define VMASST_TYPE_runstate_update_flag 5
+
+/*
* x86/64 guests: strictly hide M2P from user mode.
* This allows the guest to control respective hypervisor behavior:
* - when not set, L4 tables get created with the respective slot blank,
--
2.6.6
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