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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH 6/9] x86/np2m: Send flush IPIs only when a vcpu is actively using a shadow p2m
Flush IPIs are sent to all cpus in a shadow p2m's dirty_cpumask when
updated. This mask however is far to broad. A pcpu's bit is set in
the cpumask when a vcpu runs on that pcpu, but is only cleared when a
flush happens. This means that the IPI includes the current pcpu of
vcpus that are not currently running, and also includes any pcpu that
has ever had a vcpu use this p2m since the last flush (which in turn
will cause spurious invalidations if a different vcpu is using a
shadow p2m).
Avoid these IPIs by keeping closer track of where a p2m is being used,
and when a vcpu needs to be flushed:
- On schedule-out, clear v->processor in p2m->dirty_cpumask
- Add a 'generation' counter to the p2m and nestedvcpu structs to
detect changes that would require re-loads on re-entry
- On schedule-in or p2m change:
- Set v->processor in p2m->dirty_cpumask
- flush the vcpu's nested p2m pointer (and update nv->generation) if
the generation changed
Signed-off-by: Sergey Dyasli <sergey.dyasli@xxxxxxxxxx>
Signed-off-by: George Dunlap <george.dunlap@xxxxxxxxxx>
---
Changes since v1:
- Combine patches 5 and 8, and the scheduling bits of patch 11
("x86/np2m: add np2m_generation", "x86/np2m: add np2m_schedule()",
and "x86/np2m: implement sharing of np2m between vCPUs")
- Reword commit message
CC: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CC: Jan Beulich <jbeulich@xxxxxxxx>
CC: Jun Nakajima <jun.nakajima@xxxxxxxxx>
CC: Kevin Tian <kevin.tian@xxxxxxxxx>
---
xen/arch/x86/domain.c | 2 ++
xen/arch/x86/hvm/nestedhvm.c | 1 +
xen/arch/x86/hvm/vmx/vvmx.c | 3 +++
xen/arch/x86/mm/p2m.c | 55 +++++++++++++++++++++++++++++++++++++++++-
xen/include/asm-x86/hvm/vcpu.h | 1 +
xen/include/asm-x86/p2m.h | 6 +++++
6 files changed, 67 insertions(+), 1 deletion(-)
diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
index 466a1a2fac..35ea0d2418 100644
--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -1668,6 +1668,7 @@ void context_switch(struct vcpu *prev, struct vcpu *next)
{
_update_runstate_area(prev);
vpmu_switch_from(prev);
+ np2m_schedule(NP2M_SCHEDLE_OUT);
}
if ( is_hvm_domain(prevd) && !list_empty(&prev->arch.hvm_vcpu.tm_list) )
@@ -1716,6 +1717,7 @@ void context_switch(struct vcpu *prev, struct vcpu *next)
/* Must be done with interrupts enabled */
vpmu_switch_to(next);
+ np2m_schedule(NP2M_SCHEDLE_IN);
}
/* Ensure that the vcpu has an up-to-date time base. */
diff --git a/xen/arch/x86/hvm/nestedhvm.c b/xen/arch/x86/hvm/nestedhvm.c
index 74a464d162..ab50b2ab98 100644
--- a/xen/arch/x86/hvm/nestedhvm.c
+++ b/xen/arch/x86/hvm/nestedhvm.c
@@ -57,6 +57,7 @@ nestedhvm_vcpu_reset(struct vcpu *v)
nv->nv_flushp2m = 0;
nv->nv_p2m = NULL;
nv->stale_np2m = false;
+ nv->np2m_generation = 0;
hvm_asid_flush_vcpu_asid(&nv->nv_n2asid);
diff --git a/xen/arch/x86/hvm/vmx/vvmx.c b/xen/arch/x86/hvm/vmx/vvmx.c
index 48e37158af..a6a558b460 100644
--- a/xen/arch/x86/hvm/vmx/vvmx.c
+++ b/xen/arch/x86/hvm/vmx/vvmx.c
@@ -1367,6 +1367,9 @@ static void virtual_vmexit(struct cpu_user_regs *regs)
!(v->arch.hvm_vcpu.guest_efer & EFER_LMA) )
shadow_to_vvmcs_bulk(v, ARRAY_SIZE(gpdpte_fields), gpdpte_fields);
+ /* This will clear current pCPU bit in p2m->dirty_cpumask */
+ np2m_schedule(NP2M_SCHEDLE_OUT);
+
vmx_vmcs_switch(v->arch.hvm_vmx.vmcs_pa, nvcpu->nv_n1vmcx_pa);
nestedhvm_vcpu_exit_guestmode(v);
diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
index fd48a3b9db..3c6c486c00 100644
--- a/xen/arch/x86/mm/p2m.c
+++ b/xen/arch/x86/mm/p2m.c
@@ -73,6 +73,7 @@ static int p2m_initialise(struct domain *d, struct p2m_domain
*p2m)
p2m->p2m_class = p2m_host;
p2m->np2m_base = P2M_BASE_EADDR;
+ p2m->np2m_generation = 0;
for ( i = 0; i < ARRAY_SIZE(p2m->pod.mrp.list); ++i )
p2m->pod.mrp.list[i] = gfn_x(INVALID_GFN);
@@ -1735,6 +1736,7 @@ p2m_flush_table_locked(struct p2m_domain *p2m)
/* This is no longer a valid nested p2m for any address space */
p2m->np2m_base = P2M_BASE_EADDR;
+ p2m->np2m_generation++;
/* Make sure nobody else is using this p2m table */
nestedhvm_vmcx_flushtlb(p2m);
@@ -1809,6 +1811,7 @@ static void assign_np2m(struct vcpu *v, struct p2m_domain
*p2m)
nv->nv_flushp2m = 0;
nv->nv_p2m = p2m;
+ nv->np2m_generation = p2m->np2m_generation;
cpumask_set_cpu(v->processor, p2m->dirty_cpumask);
}
@@ -1840,7 +1843,9 @@ p2m_get_nestedp2m_locked(struct vcpu *v)
p2m_lock(p2m);
if ( p2m->np2m_base == np2m_base || p2m->np2m_base == P2M_BASE_EADDR )
{
- if ( p2m->np2m_base == P2M_BASE_EADDR )
+ /* Check if np2m was flushed just before the lock */
+ if ( p2m->np2m_base == P2M_BASE_EADDR ||
+ nv->np2m_generation != p2m->np2m_generation )
nvcpu_flush(v);
p2m->np2m_base = np2m_base;
assign_np2m(v, p2m);
@@ -1848,6 +1853,11 @@ p2m_get_nestedp2m_locked(struct vcpu *v)
return p2m;
}
+ else
+ {
+ /* vCPU is switching from some other valid np2m */
+ cpumask_clear_cpu(v->processor, p2m->dirty_cpumask);
+ }
p2m_unlock(p2m);
}
@@ -1881,6 +1891,49 @@ p2m_get_p2m(struct vcpu *v)
return p2m_get_nestedp2m(v);
}
+void np2m_schedule(int dir)
+{
+ struct nestedvcpu *nv = &vcpu_nestedhvm(current);
+ struct p2m_domain *p2m;
+
+ ASSERT(dir == NP2M_SCHEDLE_IN || dir == NP2M_SCHEDLE_OUT);
+
+ if ( !nestedhvm_enabled(current->domain) ||
+ !nestedhvm_vcpu_in_guestmode(current) ||
+ !nestedhvm_paging_mode_hap(current) )
+ return;
+
+ p2m = nv->nv_p2m;
+ if ( p2m )
+ {
+ bool np2m_valid;
+
+ p2m_lock(p2m);
+ np2m_valid = p2m->np2m_base == nhvm_vcpu_p2m_base(current) &&
+ nv->np2m_generation == p2m->np2m_generation;
+ if ( dir == NP2M_SCHEDLE_OUT && np2m_valid )
+ {
+ /*
+ * The np2m is up to date but this vCPU will no longer use it,
+ * which means there are no reasons to send a flush IPI.
+ */
+ cpumask_clear_cpu(current->processor, p2m->dirty_cpumask);
+ }
+ else if ( dir == NP2M_SCHEDLE_IN )
+ {
+ if ( !np2m_valid )
+ {
+ /* This vCPU's np2m was flushed while it was not runnable */
+ hvm_asid_flush_core();
+ vcpu_nestedhvm(current).nv_p2m = NULL;
+ }
+ else
+ cpumask_set_cpu(current->processor, p2m->dirty_cpumask);
+ }
+ p2m_unlock(p2m);
+ }
+}
+
unsigned long paging_gva_to_gfn(struct vcpu *v,
unsigned long va,
uint32_t *pfec)
diff --git a/xen/include/asm-x86/hvm/vcpu.h b/xen/include/asm-x86/hvm/vcpu.h
index 5cfa4b4aa4..afe5ffc6b3 100644
--- a/xen/include/asm-x86/hvm/vcpu.h
+++ b/xen/include/asm-x86/hvm/vcpu.h
@@ -116,6 +116,7 @@ struct nestedvcpu {
bool_t nv_flushp2m; /* True, when p2m table must be flushed */
struct p2m_domain *nv_p2m; /* used p2m table for this vcpu */
bool stale_np2m; /* True when p2m_base in VMCX02 is no longer valid */
+ uint64_t np2m_generation;
struct hvm_vcpu_asid nv_n2asid;
diff --git a/xen/include/asm-x86/p2m.h b/xen/include/asm-x86/p2m.h
index 4a1c10c130..8d4aa8c6bf 100644
--- a/xen/include/asm-x86/p2m.h
+++ b/xen/include/asm-x86/p2m.h
@@ -209,6 +209,7 @@ struct p2m_domain {
* to set it to any other value. */
#define P2M_BASE_EADDR (~0ULL)
uint64_t np2m_base;
+ uint64_t np2m_generation;
/* Nested p2ms: linked list of n2pms allocated to this domain.
* The host p2m hasolds the head of the list and the np2ms are
@@ -371,6 +372,11 @@ struct p2m_domain *p2m_get_nestedp2m_locked(struct vcpu
*v);
*/
struct p2m_domain *p2m_get_p2m(struct vcpu *v);
+#define NP2M_SCHEDLE_IN 0
+#define NP2M_SCHEDLE_OUT 1
+
+void np2m_schedule(int dir);
+
static inline bool_t p2m_is_hostp2m(const struct p2m_domain *p2m)
{
return p2m->p2m_class == p2m_host;
--
2.14.1
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