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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH v11 1/3] xen/mem_sharing: VM forking
VM forking is the process of creating a domain with an empty memory space and a
parent domain specified from which to populate the memory when necessary. For
the new domain to be functional the VM state is copied over as part of the fork
operation (HVM params, hap allocation, etc).
Signed-off-by: Tamas K Lengyel <tamas.lengyel@xxxxxxxxx>
---
v11: Fully copy vcpu_info pages
Setup vcpu_runstate for forks
Added TODO note for PV timers
Copy shared_info page
Add copy_settings function, to be shared with fork_reset in the next patch
---
xen/arch/x86/domain.c | 11 +
xen/arch/x86/hvm/hvm.c | 4 +-
xen/arch/x86/mm/hap/hap.c | 3 +-
xen/arch/x86/mm/mem_sharing.c | 368 ++++++++++++++++++++++++++++++
xen/arch/x86/mm/p2m.c | 9 +-
xen/common/domain.c | 3 +
xen/include/asm-x86/hap.h | 1 +
xen/include/asm-x86/hvm/hvm.h | 2 +
xen/include/asm-x86/mem_sharing.h | 17 ++
xen/include/public/memory.h | 5 +
xen/include/xen/sched.h | 5 +
11 files changed, 423 insertions(+), 5 deletions(-)
diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c
index fe63c23676..1ab0ca0942 100644
--- a/xen/arch/x86/domain.c
+++ b/xen/arch/x86/domain.c
@@ -2203,6 +2203,17 @@ int domain_relinquish_resources(struct domain *d)
ret = relinquish_shared_pages(d);
if ( ret )
return ret;
+
+ /*
+ * If the domain is forked, decrement the parent's pause count
+ * and release the domain.
+ */
+ if ( d->parent )
+ {
+ domain_unpause(d->parent);
+ put_domain(d->parent);
+ d->parent = NULL;
+ }
}
#endif
diff --git a/xen/arch/x86/hvm/hvm.c b/xen/arch/x86/hvm/hvm.c
index db5d7b4d30..c551cc31f3 100644
--- a/xen/arch/x86/hvm/hvm.c
+++ b/xen/arch/x86/hvm/hvm.c
@@ -1916,7 +1916,7 @@ int hvm_hap_nested_page_fault(paddr_t gpa, unsigned long
gla,
}
#endif
- /* Spurious fault? PoD and log-dirty also take this path. */
+ /* Spurious fault? PoD, log-dirty and VM forking also take this path. */
if ( p2m_is_ram(p2mt) )
{
rc = 1;
@@ -4430,7 +4430,7 @@ static int hvm_allow_get_param(struct domain *d,
return rc;
}
-static int hvm_get_param(struct domain *d, uint32_t index, uint64_t *value)
+int hvm_get_param(struct domain *d, uint32_t index, uint64_t *value)
{
int rc;
diff --git a/xen/arch/x86/mm/hap/hap.c b/xen/arch/x86/mm/hap/hap.c
index 3d93f3451c..c7c7ff6e99 100644
--- a/xen/arch/x86/mm/hap/hap.c
+++ b/xen/arch/x86/mm/hap/hap.c
@@ -321,8 +321,7 @@ static void hap_free_p2m_page(struct domain *d, struct
page_info *pg)
}
/* Return the size of the pool, rounded up to the nearest MB */
-static unsigned int
-hap_get_allocation(struct domain *d)
+unsigned int hap_get_allocation(struct domain *d)
{
unsigned int pg = d->arch.paging.hap.total_pages
+ d->arch.paging.hap.p2m_pages;
diff --git a/xen/arch/x86/mm/mem_sharing.c b/xen/arch/x86/mm/mem_sharing.c
index 3835bc928f..4a840d09dd 100644
--- a/xen/arch/x86/mm/mem_sharing.c
+++ b/xen/arch/x86/mm/mem_sharing.c
@@ -22,6 +22,7 @@
#include <xen/types.h>
#include <xen/domain_page.h>
+#include <xen/event.h>
#include <xen/spinlock.h>
#include <xen/rwlock.h>
#include <xen/mm.h>
@@ -36,6 +37,8 @@
#include <asm/altp2m.h>
#include <asm/atomic.h>
#include <asm/event.h>
+#include <asm/hap.h>
+#include <asm/hvm/hvm.h>
#include <xsm/xsm.h>
#include "mm-locks.h"
@@ -1444,6 +1447,334 @@ static inline int mem_sharing_control(struct domain *d,
bool enable)
return 0;
}
+/*
+ * Forking a page only gets called when the VM faults due to no entry being
+ * in the EPT for the access. Depending on the type of access we either
+ * populate the physmap with a shared entry for read-only access or
+ * fork the page if its a write access.
+ *
+ * The client p2m is already locked so we only need to lock
+ * the parent's here.
+ */
+int mem_sharing_fork_page(struct domain *d, gfn_t gfn, bool unsharing)
+{
+ int rc = -ENOENT;
+ shr_handle_t handle;
+ struct domain *parent = d->parent;
+ struct p2m_domain *p2m;
+ unsigned long gfn_l = gfn_x(gfn);
+ mfn_t mfn, new_mfn;
+ p2m_type_t p2mt;
+ struct page_info *page;
+
+ if ( !mem_sharing_is_fork(d) )
+ return -ENOENT;
+
+ if ( !unsharing )
+ {
+ /* For read-only accesses we just add a shared entry to the physmap */
+ while ( parent )
+ {
+ if ( !(rc = nominate_page(parent, gfn, 0, &handle)) )
+ break;
+
+ parent = parent->parent;
+ }
+
+ if ( !rc )
+ {
+ /* The client's p2m is already locked */
+ struct p2m_domain *pp2m = p2m_get_hostp2m(parent);
+
+ p2m_lock(pp2m);
+ rc = add_to_physmap(parent, gfn_l, handle, d, gfn_l, false);
+ p2m_unlock(pp2m);
+
+ if ( !rc )
+ return 0;
+ }
+ }
+
+ /*
+ * If it's a write access (ie. unsharing) or if adding a shared entry to
+ * the physmap failed we'll fork the page directly.
+ */
+ p2m = p2m_get_hostp2m(d);
+ parent = d->parent;
+
+ while ( parent )
+ {
+ mfn = get_gfn_query(parent, gfn_l, &p2mt);
+
+ /*
+ * We can't fork grant memory from the parent, only regular ram.
+ */
+ if ( mfn_valid(mfn) && p2m_is_ram(p2mt) )
+ break;
+
+ put_gfn(parent, gfn_l);
+ parent = parent->parent;
+ }
+
+ if ( !parent )
+ return -ENOENT;
+
+ if ( !(page = alloc_domheap_page(d, 0)) )
+ {
+ put_gfn(parent, gfn_l);
+ return -ENOMEM;
+ }
+
+ new_mfn = page_to_mfn(page);
+ copy_domain_page(new_mfn, mfn);
+ set_gpfn_from_mfn(mfn_x(new_mfn), gfn_l);
+
+ put_gfn(parent, gfn_l);
+
+ return p2m->set_entry(p2m, gfn, new_mfn, PAGE_ORDER_4K, p2m_ram_rw,
+ p2m->default_access, -1);
+}
+
+static int bring_up_vcpus(struct domain *cd, struct domain *d)
+{
+ unsigned int i;
+ int ret = -EINVAL;
+
+ if ( d->max_vcpus != cd->max_vcpus ||
+ (ret = cpupool_move_domain(cd, d->cpupool)) )
+ return ret;
+
+ for ( i = 0; i < cd->max_vcpus; i++ )
+ {
+ if ( !d->vcpu[i] || cd->vcpu[i] )
+ continue;
+
+ if ( !vcpu_create(cd, i) )
+ return -EINVAL;
+ }
+
+ domain_update_node_affinity(cd);
+ return 0;
+}
+
+static int copy_vcpu_settings(struct domain *cd, struct domain *d)
+{
+ unsigned int i;
+ struct p2m_domain *p2m = p2m_get_hostp2m(cd);
+ int ret = -EINVAL;
+
+ for ( i = 0; i < cd->max_vcpus; i++ )
+ {
+ const struct vcpu *d_vcpu = d->vcpu[i];
+ struct vcpu *cd_vcpu = cd->vcpu[i];
+ struct vcpu_runstate_info runstate;
+ mfn_t vcpu_info_mfn;
+
+ if ( !d_vcpu || !cd_vcpu )
+ continue;
+
+ /*
+ * Copy & map in the vcpu_info page if the guest uses one
+ */
+ vcpu_info_mfn = d_vcpu->vcpu_info_mfn;
+ if ( !mfn_eq(vcpu_info_mfn, INVALID_MFN) )
+ {
+ mfn_t new_vcpu_info_mfn = cd_vcpu->vcpu_info_mfn;
+
+ /*
+ * Allocate & map the page for it if it hasn't been already
+ */
+ if ( mfn_eq(new_vcpu_info_mfn, INVALID_MFN) )
+ {
+ gfn_t gfn = mfn_to_gfn(d, vcpu_info_mfn);
+ unsigned long gfn_l = gfn_x(gfn);
+ struct page_info *page;
+
+ if ( !(page = alloc_domheap_page(cd, 0)) )
+ return -ENOMEM;
+
+ new_vcpu_info_mfn = page_to_mfn(page);
+ set_gpfn_from_mfn(mfn_x(new_vcpu_info_mfn), gfn_l);
+
+ ret = p2m->set_entry(p2m, gfn, new_vcpu_info_mfn,
PAGE_ORDER_4K,
+ p2m_ram_rw, p2m->default_access, -1);
+ if ( ret )
+ return ret;
+
+ ret = map_vcpu_info(cd_vcpu, gfn_l,
+ d_vcpu->vcpu_info_offset);
+ if ( ret )
+ return ret;
+ }
+
+ copy_domain_page(new_vcpu_info_mfn, vcpu_info_mfn);
+ }
+
+ /*
+ * Setup the vCPU runstate area
+ */
+ if ( guest_handle_is_null(runstate_guest(cd_vcpu)) )
+ {
+ runstate_guest(cd_vcpu) = runstate_guest(d_vcpu);
+ vcpu_runstate_get(cd_vcpu, &runstate);
+ __copy_to_guest(runstate_guest(cd_vcpu), &runstate, 1);
+ }
+
+ /*
+ * TODO: to support VMs with PV interfaces copy additional
+ * settings here, such as PV timers.
+ */
+ }
+
+ return 0;
+}
+
+static int fork_hap_allocation(struct domain *cd, struct domain *d)
+{
+ int rc;
+ bool preempted;
+ unsigned long mb = hap_get_allocation(d);
+
+ if ( mb == hap_get_allocation(cd) )
+ return 0;
+
+ paging_lock(cd);
+ rc = hap_set_allocation(cd, mb << (20 - PAGE_SHIFT), &preempted);
+ paging_unlock(cd);
+
+ return preempted ? -ERESTART : rc;
+}
+
+static void copy_tsc(struct domain *cd, struct domain *d)
+{
+ uint32_t tsc_mode;
+ uint32_t gtsc_khz;
+ uint32_t incarnation;
+ uint64_t elapsed_nsec;
+
+ tsc_get_info(d, &tsc_mode, &elapsed_nsec, >sc_khz, &incarnation);
+ /* Don't bump incarnation on set */
+ tsc_set_info(cd, tsc_mode, elapsed_nsec, gtsc_khz, incarnation - 1);
+}
+
+static int copy_special_pages(struct domain *cd, struct domain *d)
+{
+ mfn_t new_mfn, old_mfn;
+ struct p2m_domain *p2m = p2m_get_hostp2m(cd);
+ static const unsigned int params[] =
+ {
+ HVM_PARAM_STORE_PFN,
+ HVM_PARAM_IOREQ_PFN,
+ HVM_PARAM_BUFIOREQ_PFN,
+ HVM_PARAM_CONSOLE_PFN
+ };
+ unsigned int i;
+ int rc;
+
+ for ( i = 0; i < 4; i++ )
+ {
+ p2m_type_t t;
+ uint64_t value = 0;
+ struct page_info *page;
+
+ if ( hvm_get_param(cd, params[i], &value) || !value )
+ continue;
+
+ old_mfn = get_gfn_query_unlocked(d, value, &t);
+ new_mfn = get_gfn_query_unlocked(cd, value, &t);
+
+ /*
+ * Allocate the page and map it in if it's not present
+ */
+ if ( mfn_eq(new_mfn, INVALID_MFN) )
+ {
+ if ( !(page = alloc_domheap_page(cd, 0)) )
+ return -ENOMEM;
+
+ new_mfn = page_to_mfn(page);
+ set_gpfn_from_mfn(mfn_x(new_mfn), value);
+
+ rc = p2m->set_entry(p2m, _gfn(value), new_mfn, PAGE_ORDER_4K,
+ p2m_ram_rw, p2m->default_access, -1);
+ if ( rc )
+ return rc;
+ }
+
+ copy_domain_page(new_mfn, old_mfn);
+ }
+
+ old_mfn = _mfn(virt_to_mfn(d->shared_info));
+ new_mfn = _mfn(virt_to_mfn(cd->shared_info));
+ copy_domain_page(new_mfn, old_mfn);
+
+ return 0;
+}
+
+static int copy_settings(struct domain *cd, struct domain *d)
+{
+ int rc;
+
+ if ( (rc = copy_vcpu_settings(cd, d)) )
+ return rc;
+
+ if ( (rc = hvm_copy_context_and_params(cd, d)) )
+ return rc;
+
+ if ( (rc = copy_special_pages(cd, d)) )
+ return rc;
+
+ copy_tsc(cd, d);
+
+ return rc;
+}
+
+static int fork(struct domain *cd, struct domain *d)
+{
+ int rc = -EBUSY;
+
+ if ( !cd->controller_pause_count )
+ return rc;
+
+ /*
+ * We only want to get and pause the parent once, not each time this
+ * operation is restarted due to preemption.
+ */
+ if ( !cd->parent_paused )
+ {
+ if ( !get_domain(d) )
+ {
+ ASSERT_UNREACHABLE();
+ return -EBUSY;
+ }
+
+ domain_pause(d);
+ cd->parent_paused = true;
+ cd->max_pages = d->max_pages;
+ }
+
+ /* this is preemptible so it's the first to get done */
+ if ( (rc = fork_hap_allocation(cd, d)) )
+ goto done;
+
+ if ( (rc = bring_up_vcpus(cd, d)) )
+ goto done;
+
+ if ( (rc = copy_settings(cd, d)) )
+ goto done;
+
+ cd->parent = d;
+
+ done:
+ if ( rc && rc != -ERESTART )
+ {
+ domain_unpause(d);
+ put_domain(d);
+ cd->parent_paused = false;
+ }
+
+ return rc;
+}
+
int mem_sharing_memop(XEN_GUEST_HANDLE_PARAM(xen_mem_sharing_op_t) arg)
{
int rc;
@@ -1698,6 +2029,43 @@ int
mem_sharing_memop(XEN_GUEST_HANDLE_PARAM(xen_mem_sharing_op_t) arg)
rc = debug_gref(d, mso.u.debug.u.gref);
break;
+ case XENMEM_sharing_op_fork:
+ {
+ struct domain *pd;
+
+ rc = -EINVAL;
+ if ( mso.u.fork._pad[0] || mso.u.fork._pad[1] ||
+ mso.u.fork._pad[2] )
+ goto out;
+
+ rc = rcu_lock_live_remote_domain_by_id(mso.u.fork.parent_domain,
+ &pd);
+ if ( rc )
+ goto out;
+
+ rc = -EINVAL;
+ if ( pd->max_vcpus != d->max_vcpus )
+ {
+ rcu_unlock_domain(pd);
+ goto out;
+ }
+
+ if ( !mem_sharing_enabled(pd) && (rc = mem_sharing_control(pd, true)) )
+ {
+ rcu_unlock_domain(pd);
+ goto out;
+ }
+
+ rc = fork(d, pd);
+
+ if ( rc == -ERESTART )
+ rc = hypercall_create_continuation(__HYPERVISOR_memory_op,
+ "lh", XENMEM_sharing_op,
+ arg);
+ rcu_unlock_domain(pd);
+ break;
+ }
+
default:
rc = -ENOSYS;
break;
diff --git a/xen/arch/x86/mm/p2m.c b/xen/arch/x86/mm/p2m.c
index 3719deae77..39c07789fa 100644
--- a/xen/arch/x86/mm/p2m.c
+++ b/xen/arch/x86/mm/p2m.c
@@ -509,6 +509,12 @@ mfn_t __get_gfn_type_access(struct p2m_domain *p2m,
unsigned long gfn_l,
mfn = p2m->get_entry(p2m, gfn, t, a, q, page_order, NULL);
+ /* Check if we need to fork the page */
+ if ( (q & P2M_ALLOC) && p2m_is_hole(*t) &&
+ !mem_sharing_fork_page(p2m->domain, gfn, !!(q & P2M_UNSHARE)) )
+ mfn = p2m->get_entry(p2m, gfn, t, a, q, page_order, NULL);
+
+ /* Check if we need to unshare the page */
if ( (q & P2M_UNSHARE) && p2m_is_shared(*t) )
{
ASSERT(p2m_is_hostp2m(p2m));
@@ -588,7 +594,8 @@ struct page_info *p2m_get_page_from_gfn(
return page;
/* Error path: not a suitable GFN at all */
- if ( !p2m_is_ram(*t) && !p2m_is_paging(*t) && !p2m_is_pod(*t) )
+ if ( !p2m_is_ram(*t) && !p2m_is_paging(*t) && !p2m_is_pod(*t) &&
+ !mem_sharing_is_fork(p2m->domain) )
return NULL;
}
diff --git a/xen/common/domain.c b/xen/common/domain.c
index 6ad458fa6b..02998235dd 100644
--- a/xen/common/domain.c
+++ b/xen/common/domain.c
@@ -1269,6 +1269,9 @@ int map_vcpu_info(struct vcpu *v, unsigned long gfn,
unsigned offset)
v->vcpu_info = new_info;
v->vcpu_info_mfn = page_to_mfn(page);
+#ifdef CONFIG_MEM_SHARING
+ v->vcpu_info_offset = offset;
+#endif
/* Set new vcpu_info pointer /before/ setting pending flags. */
smp_wmb();
diff --git a/xen/include/asm-x86/hap.h b/xen/include/asm-x86/hap.h
index b94bfb4ed0..1bf07e49fe 100644
--- a/xen/include/asm-x86/hap.h
+++ b/xen/include/asm-x86/hap.h
@@ -45,6 +45,7 @@ int hap_track_dirty_vram(struct domain *d,
extern const struct paging_mode *hap_paging_get_mode(struct vcpu *);
int hap_set_allocation(struct domain *d, unsigned int pages, bool *preempted);
+unsigned int hap_get_allocation(struct domain *d);
#endif /* XEN_HAP_H */
diff --git a/xen/include/asm-x86/hvm/hvm.h b/xen/include/asm-x86/hvm/hvm.h
index 24da824cbf..35e970b030 100644
--- a/xen/include/asm-x86/hvm/hvm.h
+++ b/xen/include/asm-x86/hvm/hvm.h
@@ -339,6 +339,8 @@ bool hvm_flush_vcpu_tlb(bool (*flush_vcpu)(void *ctxt,
struct vcpu *v),
int hvm_copy_context_and_params(struct domain *src, struct domain *dst);
+int hvm_get_param(struct domain *d, uint32_t index, uint64_t *value);
+
#ifdef CONFIG_HVM
#define hvm_get_guest_tsc(v) hvm_get_guest_tsc_fixed(v, 0)
diff --git a/xen/include/asm-x86/mem_sharing.h
b/xen/include/asm-x86/mem_sharing.h
index 53760a2896..ac968fae3f 100644
--- a/xen/include/asm-x86/mem_sharing.h
+++ b/xen/include/asm-x86/mem_sharing.h
@@ -39,6 +39,9 @@ struct mem_sharing_domain
#define mem_sharing_enabled(d) ((d)->arch.hvm.mem_sharing.enabled)
+#define mem_sharing_is_fork(d) \
+ (mem_sharing_enabled(d) && !!((d)->parent))
+
/* Auditing of memory sharing code? */
#ifndef NDEBUG
#define MEM_SHARING_AUDIT 1
@@ -88,6 +91,9 @@ static inline int mem_sharing_unshare_page(struct domain *d,
return rc;
}
+int mem_sharing_fork_page(struct domain *d, gfn_t gfn,
+ bool unsharing);
+
/*
* If called by a foreign domain, possible errors are
* -EBUSY -> ring full
@@ -117,6 +123,7 @@ int relinquish_shared_pages(struct domain *d);
#else
#define mem_sharing_enabled(d) false
+#define mem_sharing_is_fork(p2m) false
static inline unsigned int mem_sharing_get_nr_saved_mfns(void)
{
@@ -141,6 +148,16 @@ static inline int mem_sharing_notify_enomem(struct domain
*d, unsigned long gfn,
return -EOPNOTSUPP;
}
+static inline int mem_sharing_fork(struct domain *d, struct domain *cd, bool
vcpu)
+{
+ return -EOPNOTSUPP;
+}
+
+static inline int mem_sharing_fork_page(struct domain *d, gfn_t gfn, bool lock)
+{
+ return -EOPNOTSUPP;
+}
+
#endif
#endif /* __MEM_SHARING_H__ */
diff --git a/xen/include/public/memory.h b/xen/include/public/memory.h
index 126d0ff06e..c1dbad060e 100644
--- a/xen/include/public/memory.h
+++ b/xen/include/public/memory.h
@@ -482,6 +482,7 @@ DEFINE_XEN_GUEST_HANDLE(xen_mem_access_op_t);
#define XENMEM_sharing_op_add_physmap 6
#define XENMEM_sharing_op_audit 7
#define XENMEM_sharing_op_range_share 8
+#define XENMEM_sharing_op_fork 9
#define XENMEM_SHARING_OP_S_HANDLE_INVALID (-10)
#define XENMEM_SHARING_OP_C_HANDLE_INVALID (-9)
@@ -532,6 +533,10 @@ struct xen_mem_sharing_op {
uint32_t gref; /* IN: gref to debug */
} u;
} debug;
+ struct mem_sharing_op_fork { /* OP_FORK */
+ domid_t parent_domain; /* IN: parent's domain id */
+ uint16_t _pad[3]; /* Must be set to 0 */
+ } fork;
} u;
};
typedef struct xen_mem_sharing_op xen_mem_sharing_op_t;
diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h
index 3a4f43098c..c6ba5a52a4 100644
--- a/xen/include/xen/sched.h
+++ b/xen/include/xen/sched.h
@@ -248,6 +248,9 @@ struct vcpu
/* Guest-specified relocation of vcpu_info. */
mfn_t vcpu_info_mfn;
+#ifdef CONFIG_MEM_SHARING
+ uint32_t vcpu_info_offset;
+#endif
struct evtchn_fifo_vcpu *evtchn_fifo;
@@ -503,6 +506,8 @@ struct domain
/* Memory sharing support */
#ifdef CONFIG_MEM_SHARING
struct vm_event_domain *vm_event_share;
+ struct domain *parent; /* VM fork parent */
+ bool parent_paused;
#endif
/* Memory paging support */
#ifdef CONFIG_HAS_MEM_PAGING
--
2.20.1
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