* [Xen-devel] [PATCH v11 0/3] VM forking
@ 2020-02-28 18:40 Tamas K Lengyel
2020-02-28 18:40 ` [Xen-devel] [PATCH v11 1/3] xen/mem_sharing: " Tamas K Lengyel
` (3 more replies)
0 siblings, 4 replies; 13+ messages in thread
From: Tamas K Lengyel @ 2020-02-28 18:40 UTC (permalink / raw)
To: xen-devel
Cc: Stefano Stabellini, Tamas K Lengyel, Wei Liu,
Konrad Rzeszutek Wilk, Andrew Cooper, Ian Jackson, George Dunlap,
Tamas K Lengyel, Jan Beulich, Anthony PERARD, Julien Grall,
Roger Pau Monné
The following series implements VM forking for Intel HVM guests to allow for
the fast creation of identical VMs without the assosciated high startup costs
of booting or restoring the VM from a savefile.
JIRA issue: https://xenproject.atlassian.net/browse/XEN-89
The fork operation is implemented as part of the "xl fork-vm" command:
xl fork-vm -C <config> -Q <qemu-save-file> -m <max-vcpus> <parent_domid>
By default a fully functional fork is created. The user is in charge however to
create the appropriate config file for the fork and to generate the QEMU save
file before the fork-vm call is made. The config file needs to give the
fork a new name at minimum but other settings may also require changes. Certain
settings in the config file of both the parent and the fork have to be set to
default. Details are documented.
The interface also allows to split the forking into two steps:
xl fork-vm --launch-dm no \
-m <max-vcpus> \
-p <parent_domid>
xl fork-vm --launch-dm late \
-C <config_file_for_fork> \
-Q <qemu_save_file> \
<fork_domid>
The split creation model is useful when the VM needs to be created as fast as
possible. The forked VM can be unpaused without the device model being launched
to be monitored and accessed via VMI. Note however that without its device
model running (depending on what is executing in the VM) it is bound to
misbehave or even crash when its trying to access devices that would be
emulated by QEMU. We anticipate that for certain use-cases this would be an
acceptable situation, in case for example when fuzzing is performed of code
segments that don't access such devices.
Launching the device model requires the QEMU Xen savefile to be generated
manually from the parent VM. This can be accomplished simply by connecting to
its QMP socket and issuing the "xen-save-devices-state" command. For example
using the standard tool socat these commands can be used to generate the file:
socat - UNIX-CONNECT:/var/run/xen/qmp-libxl-<parent_domid>
{ "execute": "qmp_capabilities" }
{ "execute": "xen-save-devices-state", \
"arguments": { "filename": "/path/to/save/qemu_state", \
"live": false} }
At runtime the forked VM starts running with an empty p2m which gets lazily
populated when the VM generates EPT faults, similar to how altp2m views are
populated. If the memory access is a read-only access, the p2m entry is
populated with a memory shared entry with its parent. For write memory accesses
or in case memory sharing wasn't possible (for example in case a reference is
held by a third party), a new page is allocated and the page contents are
copied over from the parent VM. Forks can be further forked if needed, thus
allowing for further memory savings.
A VM fork reset hypercall is also added that allows the fork to be reset to the
state it was just after a fork, also accessible via xl:
xl fork-vm --fork-reset -p <fork_domid>
This is an optimization for cases where the forks are very short-lived and run
without a device model, so resetting saves some time compared to creating a
brand new fork provided the fork has not aquired a lot of memory. If the fork
has a lot of memory deduplicated it is likely going to be faster to create a
new fork from scratch and asynchronously destroying the old one.
The series has been tested with Windows VMs and functions as expected. Linux
VMs when forked from a running VM will have a frozen VNC screen. Linux VMs at
this time can only be forked with a working device model when the parent VM was
restored from a snapshot using "xl restore -p". This is a known limitation.
Also note that PVHVM/PVH Linux guests have not been tested. Forking most likely
works but PV devices and drivers would require additional wiring to set things
up properly since the guests are unaware of the forking taking place, unlike
the save/restore routine where the guest is made aware of the procedure.
Forking time has been measured to be 0.0007s, device model launch to be around
1s depending largely on the number of devices being emulated. Fork resets have
been measured to be 0.0001s under the optimal circumstances.
New in v11:
Fully copy & reset vcpu_info pages
Setup vcpu_runstate for forks
Added TODO note for PV timers
Copy & reset shared_info page
Copy & reset HVM special pages
New in v10:
Rebased on staging and minor fixes for things pointed out by Roger
Allocate pages for vcpu_info if used by parent
Document limitation of guest settings that have to be set to default
Require max-vcpus to be specified by toolstack-side
Code movement in toolstack & compile tested on ARM
Implement hypercall continuation for reset operation
Patch 1-2 implements the VM fork & reset operation hypervisor side bits
Patch 3 adds the toolstack-side code implementing VM forking and reset
Tamas K Lengyel (3):
xen/mem_sharing: VM forking
x86/mem_sharing: reset a fork
xen/tools: VM forking toolstack side
docs/man/xl.1.pod.in | 44 +++
tools/libxc/include/xenctrl.h | 13 +
tools/libxc/xc_memshr.c | 22 ++
tools/libxl/libxl.h | 11 +
tools/libxl/libxl_create.c | 361 ++++++++++++----------
tools/libxl/libxl_dm.c | 2 +-
tools/libxl/libxl_dom.c | 43 ++-
tools/libxl/libxl_internal.h | 7 +
tools/libxl/libxl_types.idl | 1 +
tools/libxl/libxl_x86.c | 41 +++
tools/xl/Makefile | 2 +-
tools/xl/xl.h | 5 +
tools/xl/xl_cmdtable.c | 15 +
tools/xl/xl_forkvm.c | 147 +++++++++
tools/xl/xl_vmcontrol.c | 14 +
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 | 483 ++++++++++++++++++++++++++++++
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 | 9 +
xen/include/xen/sched.h | 5 +
26 files changed, 1104 insertions(+), 171 deletions(-)
create mode 100644 tools/xl/xl_forkvm.c
--
2.20.1
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel
^ permalink raw reply [flat|nested] 13+ messages in thread
* [Xen-devel] [PATCH v11 1/3] xen/mem_sharing: VM forking
2020-02-28 18:40 [Xen-devel] [PATCH v11 0/3] VM forking Tamas K Lengyel
@ 2020-02-28 18:40 ` Tamas K Lengyel
2020-03-17 15:59 ` Jan Beulich
2020-02-28 18:40 ` [Xen-devel] [PATCH v11 2/3] x86/mem_sharing: reset a fork Tamas K Lengyel
` (2 subsequent siblings)
3 siblings, 1 reply; 13+ messages in thread
From: Tamas K Lengyel @ 2020-02-28 18:40 UTC (permalink / raw)
To: xen-devel
Cc: Stefano Stabellini, Tamas K Lengyel, Wei Liu,
Konrad Rzeszutek Wilk, Andrew Cooper, Ian Jackson, George Dunlap,
Tamas K Lengyel, Jan Beulich, Julien Grall, Roger Pau Monné
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@intel.com>
---
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
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel
^ permalink raw reply related [flat|nested] 13+ messages in thread
* [Xen-devel] [PATCH v11 2/3] x86/mem_sharing: reset a fork
2020-02-28 18:40 [Xen-devel] [PATCH v11 0/3] VM forking Tamas K Lengyel
2020-02-28 18:40 ` [Xen-devel] [PATCH v11 1/3] xen/mem_sharing: " Tamas K Lengyel
@ 2020-02-28 18:40 ` Tamas K Lengyel
2020-03-18 11:36 ` Jan Beulich
2020-02-28 18:40 ` [Xen-devel] [PATCH v11 3/3] xen/tools: VM forking toolstack side Tamas K Lengyel
2020-03-16 13:07 ` [Xen-devel] [PATCH v11 0/3] VM forking Tamas K Lengyel
3 siblings, 1 reply; 13+ messages in thread
From: Tamas K Lengyel @ 2020-02-28 18:40 UTC (permalink / raw)
To: xen-devel
Cc: Tamas K Lengyel, Tamas K Lengyel, Wei Liu, Konrad Rzeszutek Wilk,
Andrew Cooper, Ian Jackson, George Dunlap, Stefano Stabellini,
Jan Beulich, Julien Grall, Roger Pau Monné
Implement hypercall that allows a fork to shed all memory that got allocated
for it during its execution and re-load its vCPU context from the parent VM.
This allows the forked VM to reset into the same state the parent VM is in a
faster way then creating a new fork would be. Measurements show about a 2x
speedup during normal fuzzing operations. Performance may vary depending how
much memory got allocated for the forked VM. If it has been completely
deduplicated from the parent VM then creating a new fork would likely be more
performant.
Signed-off-by: Tamas K Lengyel <tamas.lengyel@intel.com>
---
v11: use copy_settings function to reset special pages
---
xen/arch/x86/mm/mem_sharing.c | 115 ++++++++++++++++++++++++++++++++++
xen/include/public/memory.h | 4 ++
2 files changed, 119 insertions(+)
diff --git a/xen/arch/x86/mm/mem_sharing.c b/xen/arch/x86/mm/mem_sharing.c
index 4a840d09dd..a458096b01 100644
--- a/xen/arch/x86/mm/mem_sharing.c
+++ b/xen/arch/x86/mm/mem_sharing.c
@@ -1775,6 +1775,91 @@ static int fork(struct domain *cd, struct domain *d)
return rc;
}
+/*
+ * The fork reset operation is intended to be used on short-lived forks only.
+ */
+static int fork_reset(struct domain *d, struct domain *cd,
+ struct mem_sharing_op_fork_reset *fr)
+{
+ int rc = 0;
+ struct p2m_domain* p2m = p2m_get_hostp2m(cd);
+ struct page_info *page, *tmp;
+ unsigned long list_position = 0, preempt_count = 0, restart = fr->opaque;
+
+ domain_pause(cd);
+
+ page_list_for_each_safe(page, tmp, &cd->page_list)
+ {
+ p2m_type_t p2mt;
+ p2m_access_t p2ma;
+ gfn_t gfn;
+ mfn_t mfn;
+ bool shared = false;
+
+ list_position++;
+
+ /* Resume were we left of before preemption */
+ if ( restart && list_position < restart )
+ continue;
+
+ mfn = page_to_mfn(page);
+ if ( mfn_valid(mfn) )
+ {
+
+ gfn = mfn_to_gfn(cd, mfn);
+ mfn = __get_gfn_type_access(p2m, gfn_x(gfn), &p2mt, &p2ma,
+ 0, NULL, false);
+
+ if ( p2m_is_ram(p2mt) && !p2m_is_shared(p2mt) )
+ {
+ /* take an extra reference, must work for a shared page */
+ if( !get_page(page, cd) )
+ {
+ ASSERT_UNREACHABLE();
+ return -EINVAL;
+ }
+
+ shared = true;
+ preempt_count += 0x10;
+
+ /*
+ * Must succeed, it's a shared page that exists and
+ * thus its size is guaranteed to be 4k so we are not splitting
+ * large pages.
+ */
+ rc = p2m->set_entry(p2m, gfn, INVALID_MFN, PAGE_ORDER_4K,
+ p2m_invalid, p2m_access_rwx, -1);
+ ASSERT(!rc);
+
+ put_page_alloc_ref(page);
+ put_page(page);
+ }
+ }
+
+ if ( !shared )
+ preempt_count++;
+
+ /* Preempt every 2MiB (shared) or 32MiB (unshared) - arbitrary. */
+ if ( preempt_count >= 0x2000 )
+ {
+ if ( hypercall_preempt_check() )
+ {
+ rc = -ERESTART;
+ break;
+ }
+ preempt_count = 0;
+ }
+ }
+
+ if ( rc )
+ fr->opaque = list_position;
+ else
+ rc = copy_settings(cd, d);
+
+ domain_unpause(cd);
+ return rc;
+}
+
int mem_sharing_memop(XEN_GUEST_HANDLE_PARAM(xen_mem_sharing_op_t) arg)
{
int rc;
@@ -2066,6 +2151,36 @@ int mem_sharing_memop(XEN_GUEST_HANDLE_PARAM(xen_mem_sharing_op_t) arg)
break;
}
+ case XENMEM_sharing_op_fork_reset:
+ {
+ struct domain *pd;
+
+ rc = -ENOSYS;
+ if ( !mem_sharing_is_fork(d) )
+ goto out;
+
+ rc = rcu_lock_live_remote_domain_by_id(d->parent->domain_id, &pd);
+ if ( rc )
+ goto out;
+
+ rc = fork_reset(pd, d, &mso.u.fork_reset);
+
+ rcu_unlock_domain(pd);
+
+ if ( rc > 0 )
+ {
+ if ( __copy_to_guest(arg, &mso, 1) )
+ rc = -EFAULT;
+ else
+ rc = hypercall_create_continuation(__HYPERVISOR_memory_op,
+ "lh", XENMEM_sharing_op,
+ arg);
+ }
+ else
+ mso.u.fork_reset.opaque = 0;
+ break;
+ }
+
default:
rc = -ENOSYS;
break;
diff --git a/xen/include/public/memory.h b/xen/include/public/memory.h
index c1dbad060e..7ca07c01dd 100644
--- a/xen/include/public/memory.h
+++ b/xen/include/public/memory.h
@@ -483,6 +483,7 @@ DEFINE_XEN_GUEST_HANDLE(xen_mem_access_op_t);
#define XENMEM_sharing_op_audit 7
#define XENMEM_sharing_op_range_share 8
#define XENMEM_sharing_op_fork 9
+#define XENMEM_sharing_op_fork_reset 10
#define XENMEM_SHARING_OP_S_HANDLE_INVALID (-10)
#define XENMEM_SHARING_OP_C_HANDLE_INVALID (-9)
@@ -537,6 +538,9 @@ struct xen_mem_sharing_op {
domid_t parent_domain; /* IN: parent's domain id */
uint16_t _pad[3]; /* Must be set to 0 */
} fork;
+ struct mem_sharing_op_fork_reset { /* OP_FORK_RESET */
+ uint64_aligned_t opaque; /* Must be set to 0 */
+ } fork_reset;
} u;
};
typedef struct xen_mem_sharing_op xen_mem_sharing_op_t;
--
2.20.1
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel
^ permalink raw reply related [flat|nested] 13+ messages in thread
* [Xen-devel] [PATCH v11 3/3] xen/tools: VM forking toolstack side
2020-02-28 18:40 [Xen-devel] [PATCH v11 0/3] VM forking Tamas K Lengyel
2020-02-28 18:40 ` [Xen-devel] [PATCH v11 1/3] xen/mem_sharing: " Tamas K Lengyel
2020-02-28 18:40 ` [Xen-devel] [PATCH v11 2/3] x86/mem_sharing: reset a fork Tamas K Lengyel
@ 2020-02-28 18:40 ` Tamas K Lengyel
2020-03-16 13:07 ` [Xen-devel] [PATCH v11 0/3] VM forking Tamas K Lengyel
3 siblings, 0 replies; 13+ messages in thread
From: Tamas K Lengyel @ 2020-02-28 18:40 UTC (permalink / raw)
To: xen-devel; +Cc: Anthony PERARD, Ian Jackson, Tamas K Lengyel, Wei Liu
Add necessary bits to implement "xl fork-vm" commands. The command allows the
user to specify how to launch the device model allowing for a late-launch model
in which the user can execute the fork without the device model and decide to
only later launch it.
Signed-off-by: Tamas K Lengyel <tamas.lengyel@intel.com>
---
docs/man/xl.1.pod.in | 44 +++++
tools/libxc/include/xenctrl.h | 13 ++
tools/libxc/xc_memshr.c | 22 +++
tools/libxl/libxl.h | 11 ++
tools/libxl/libxl_create.c | 361 +++++++++++++++++++---------------
tools/libxl/libxl_dm.c | 2 +-
tools/libxl/libxl_dom.c | 43 +++-
tools/libxl/libxl_internal.h | 7 +
tools/libxl/libxl_types.idl | 1 +
tools/libxl/libxl_x86.c | 41 ++++
tools/xl/Makefile | 2 +-
tools/xl/xl.h | 5 +
tools/xl/xl_cmdtable.c | 15 ++
tools/xl/xl_forkvm.c | 147 ++++++++++++++
tools/xl/xl_vmcontrol.c | 14 ++
15 files changed, 562 insertions(+), 166 deletions(-)
create mode 100644 tools/xl/xl_forkvm.c
diff --git a/docs/man/xl.1.pod.in b/docs/man/xl.1.pod.in
index 09339282e6..59c03c6427 100644
--- a/docs/man/xl.1.pod.in
+++ b/docs/man/xl.1.pod.in
@@ -708,6 +708,50 @@ above).
=back
+=item B<fork-vm> [I<OPTIONS>] I<domain-id>
+
+Create a fork of a running VM. The domain will be paused after the operation
+and remains paused while forks of it exist. Experimental and x86 only.
+Forks can only be made of domains with HAP enabled and on Intel hardware. The
+parent domain must be created with the xl toolstack and its configuration must
+not manually define max_grant_frames, max_maptrack_frames or max_event_channels.
+
+B<OPTIONS>
+
+=over 4
+
+=item B<-p>
+
+Leave the fork paused after creating it.
+
+=item B<--launch-dm>
+
+Specify whether the device model (QEMU) should be launched for the fork. Late
+launch allows to start the device model for an already running fork.
+
+=item B<-C>
+
+The config file to use when launching the device model. Currently required when
+launching the device model. Most config settings MUST match the parent domain
+exactly, only change VM name, disk path and network configurations.
+
+=item B<-Q>
+
+The path to the qemu save file to use when launching the device model. Currently
+required when launching the device model.
+
+=item B<--fork-reset>
+
+Perform a reset operation of an already running fork. Note that resetting may
+be less performant then creating a new fork depending on how much memory the
+fork has deduplicated during its runtime.
+
+=item B<--max-vcpus>
+
+Specify the max-vcpus matching the parent domain when not launching the dm.
+
+=back
+
=item B<sharing> [I<domain-id>]
Display the number of shared pages for a specified domain. If no domain is
diff --git a/tools/libxc/include/xenctrl.h b/tools/libxc/include/xenctrl.h
index fc6e57a1a0..00cb4cf1f7 100644
--- a/tools/libxc/include/xenctrl.h
+++ b/tools/libxc/include/xenctrl.h
@@ -2225,6 +2225,19 @@ int xc_memshr_range_share(xc_interface *xch,
uint64_t first_gfn,
uint64_t last_gfn);
+int xc_memshr_fork(xc_interface *xch,
+ uint32_t source_domain,
+ uint32_t client_domain);
+
+/*
+ * Note: this function is only intended to be used on short-lived forks that
+ * haven't yet aquired a lot of memory. In case the fork has a lot of memory
+ * it is likely more performant to create a new fork with xc_memshr_fork.
+ *
+ * With VMs that have a lot of memory this call may block for a long time.
+ */
+int xc_memshr_fork_reset(xc_interface *xch, uint32_t forked_domain);
+
/* Debug calls: return the number of pages referencing the shared frame backing
* the input argument. Should be one or greater.
*
diff --git a/tools/libxc/xc_memshr.c b/tools/libxc/xc_memshr.c
index 97e2e6a8d9..d0e4ee225b 100644
--- a/tools/libxc/xc_memshr.c
+++ b/tools/libxc/xc_memshr.c
@@ -239,6 +239,28 @@ int xc_memshr_debug_gref(xc_interface *xch,
return xc_memshr_memop(xch, domid, &mso);
}
+int xc_memshr_fork(xc_interface *xch, uint32_t pdomid, uint32_t domid)
+{
+ xen_mem_sharing_op_t mso;
+
+ memset(&mso, 0, sizeof(mso));
+
+ mso.op = XENMEM_sharing_op_fork;
+ mso.u.fork.parent_domain = pdomid;
+
+ return xc_memshr_memop(xch, domid, &mso);
+}
+
+int xc_memshr_fork_reset(xc_interface *xch, uint32_t domid)
+{
+ xen_mem_sharing_op_t mso;
+
+ memset(&mso, 0, sizeof(mso));
+ mso.op = XENMEM_sharing_op_fork_reset;
+
+ return xc_memshr_memop(xch, domid, &mso);
+}
+
int xc_memshr_audit(xc_interface *xch)
{
xen_mem_sharing_op_t mso;
diff --git a/tools/libxl/libxl.h b/tools/libxl/libxl.h
index 35e13428b2..6b968bdcb4 100644
--- a/tools/libxl/libxl.h
+++ b/tools/libxl/libxl.h
@@ -2657,6 +2657,17 @@ int libxl_psr_get_hw_info(libxl_ctx *ctx, libxl_psr_feat_type type,
unsigned int lvl, unsigned int *nr,
libxl_psr_hw_info **info);
void libxl_psr_hw_info_list_free(libxl_psr_hw_info *list, unsigned int nr);
+
+int libxl_domain_fork_vm(libxl_ctx *ctx, uint32_t pdomid, uint32_t max_vcpus, uint32_t *domid)
+ LIBXL_EXTERNAL_CALLERS_ONLY;
+
+int libxl_domain_fork_launch_dm(libxl_ctx *ctx, libxl_domain_config *d_config,
+ uint32_t domid,
+ const libxl_asyncprogress_how *aop_console_how)
+ LIBXL_EXTERNAL_CALLERS_ONLY;
+
+int libxl_domain_fork_reset(libxl_ctx *ctx, uint32_t domid)
+ LIBXL_EXTERNAL_CALLERS_ONLY;
#endif
/* misc */
diff --git a/tools/libxl/libxl_create.c b/tools/libxl/libxl_create.c
index ccc9e70990..eba8ce419b 100644
--- a/tools/libxl/libxl_create.c
+++ b/tools/libxl/libxl_create.c
@@ -536,12 +536,12 @@ out:
return ret;
}
-int libxl__domain_make(libxl__gc *gc, libxl_domain_config *d_config,
- libxl__domain_build_state *state,
- uint32_t *domid, bool soft_reset)
+static int libxl__domain_make_xs_entries(libxl__gc *gc, libxl_domain_config *d_config,
+ libxl__domain_build_state *state,
+ uint32_t domid)
{
libxl_ctx *ctx = libxl__gc_owner(gc);
- int ret, rc, nb_vm;
+ int rc, nb_vm;
const char *dom_type;
char *uuid_string;
char *dom_path, *vm_path, *libxl_path;
@@ -553,9 +553,6 @@ int libxl__domain_make(libxl__gc *gc, libxl_domain_config *d_config,
/* convenience aliases */
libxl_domain_create_info *info = &d_config->c_info;
- libxl_domain_build_info *b_info = &d_config->b_info;
-
- assert(soft_reset || *domid == INVALID_DOMID);
uuid_string = libxl__uuid2string(gc, info->uuid);
if (!uuid_string) {
@@ -563,137 +560,7 @@ int libxl__domain_make(libxl__gc *gc, libxl_domain_config *d_config,
goto out;
}
- if (!soft_reset) {
- struct xen_domctl_createdomain create = {
- .ssidref = info->ssidref,
- .max_vcpus = b_info->max_vcpus,
- .max_evtchn_port = b_info->event_channels,
- .max_grant_frames = b_info->max_grant_frames,
- .max_maptrack_frames = b_info->max_maptrack_frames,
- };
-
- if (info->type != LIBXL_DOMAIN_TYPE_PV) {
- create.flags |= XEN_DOMCTL_CDF_hvm;
- create.flags |=
- libxl_defbool_val(info->hap) ? XEN_DOMCTL_CDF_hap : 0;
- create.flags |=
- libxl_defbool_val(info->oos) ? 0 : XEN_DOMCTL_CDF_oos_off;
- }
-
- assert(info->passthrough != LIBXL_PASSTHROUGH_DEFAULT);
- LOG(DETAIL, "passthrough: %s",
- libxl_passthrough_to_string(info->passthrough));
-
- if (info->passthrough != LIBXL_PASSTHROUGH_DISABLED)
- create.flags |= XEN_DOMCTL_CDF_iommu;
-
- if (info->passthrough == LIBXL_PASSTHROUGH_SYNC_PT)
- create.iommu_opts |= XEN_DOMCTL_IOMMU_no_sharept;
-
- /* Ultimately, handle is an array of 16 uint8_t, same as uuid */
- libxl_uuid_copy(ctx, (libxl_uuid *)&create.handle, &info->uuid);
-
- ret = libxl__arch_domain_prepare_config(gc, d_config, &create);
- if (ret < 0) {
- LOGED(ERROR, *domid, "fail to get domain config");
- rc = ERROR_FAIL;
- goto out;
- }
-
- for (;;) {
- uint32_t local_domid;
- bool recent;
-
- if (info->domid == RANDOM_DOMID) {
- uint16_t v;
-
- ret = libxl__random_bytes(gc, (void *)&v, sizeof(v));
- if (ret < 0)
- break;
-
- v &= DOMID_MASK;
- if (!libxl_domid_valid_guest(v))
- continue;
-
- local_domid = v;
- } else {
- local_domid = info->domid; /* May not be valid */
- }
-
- ret = xc_domain_create(ctx->xch, &local_domid, &create);
- if (ret < 0) {
- /*
- * If we generated a random domid and creation failed
- * because that domid already exists then simply try
- * again.
- */
- if (errno == EEXIST && info->domid == RANDOM_DOMID)
- continue;
-
- LOGED(ERROR, local_domid, "domain creation fail");
- rc = ERROR_FAIL;
- goto out;
- }
-
- /* A new domain now exists */
- *domid = local_domid;
-
- rc = libxl__is_domid_recent(gc, local_domid, &recent);
- if (rc)
- goto out;
-
- /* The domid is not recent, so we're done */
- if (!recent)
- break;
-
- /*
- * If the domid was specified then there's no point in
- * trying again.
- */
- if (libxl_domid_valid_guest(info->domid)) {
- LOGED(ERROR, local_domid, "domain id recently used");
- rc = ERROR_FAIL;
- goto out;
- }
-
- /*
- * The domain is recent and so cannot be used. Clear domid
- * here since, if xc_domain_destroy() fails below there is
- * little point calling it again in the error path.
- */
- *domid = INVALID_DOMID;
-
- ret = xc_domain_destroy(ctx->xch, local_domid);
- if (ret < 0) {
- LOGED(ERROR, local_domid, "domain destroy fail");
- rc = ERROR_FAIL;
- goto out;
- }
-
- /* The domain was successfully destroyed, so we can try again */
- }
-
- rc = libxl__arch_domain_save_config(gc, d_config, state, &create);
- if (rc < 0)
- goto out;
- }
-
- /*
- * If soft_reset is set the the domid will have been valid on entry.
- * If it was not set then xc_domain_create() should have assigned a
- * valid value. Either way, if we reach this point, domid should be
- * valid.
- */
- assert(libxl_domid_valid_guest(*domid));
-
- ret = xc_cpupool_movedomain(ctx->xch, info->poolid, *domid);
- if (ret < 0) {
- LOGED(ERROR, *domid, "domain move fail");
- rc = ERROR_FAIL;
- goto out;
- }
-
- dom_path = libxl__xs_get_dompath(gc, *domid);
+ dom_path = libxl__xs_get_dompath(gc, domid);
if (!dom_path) {
rc = ERROR_FAIL;
goto out;
@@ -701,12 +568,12 @@ int libxl__domain_make(libxl__gc *gc, libxl_domain_config *d_config,
vm_path = GCSPRINTF("/vm/%s", uuid_string);
if (!vm_path) {
- LOGD(ERROR, *domid, "cannot allocate create paths");
+ LOGD(ERROR, domid, "cannot allocate create paths");
rc = ERROR_FAIL;
goto out;
}
- libxl_path = libxl__xs_libxl_path(gc, *domid);
+ libxl_path = libxl__xs_libxl_path(gc, domid);
if (!libxl_path) {
rc = ERROR_FAIL;
goto out;
@@ -717,10 +584,10 @@ int libxl__domain_make(libxl__gc *gc, libxl_domain_config *d_config,
roperm[0].id = 0;
roperm[0].perms = XS_PERM_NONE;
- roperm[1].id = *domid;
+ roperm[1].id = domid;
roperm[1].perms = XS_PERM_READ;
- rwperm[0].id = *domid;
+ rwperm[0].id = domid;
rwperm[0].perms = XS_PERM_NONE;
retry_transaction:
@@ -738,7 +605,7 @@ retry_transaction:
noperm, ARRAY_SIZE(noperm));
xs_write(ctx->xsh, t, GCSPRINTF("%s/vm", dom_path), vm_path, strlen(vm_path));
- rc = libxl__domain_rename(gc, *domid, 0, info->name, t);
+ rc = libxl__domain_rename(gc, domid, 0, info->name, t);
if (rc)
goto out;
@@ -815,7 +682,7 @@ retry_transaction:
vm_list = libxl_list_vm(ctx, &nb_vm);
if (!vm_list) {
- LOGD(ERROR, *domid, "cannot get number of running guests");
+ LOGD(ERROR, domid, "cannot get number of running guests");
rc = ERROR_FAIL;
goto out;
}
@@ -839,7 +706,7 @@ retry_transaction:
t = 0;
goto retry_transaction;
}
- LOGED(ERROR, *domid, "domain creation ""xenstore transaction commit failed");
+ LOGED(ERROR, domid, "domain creation ""xenstore transaction commit failed");
rc = ERROR_FAIL;
goto out;
}
@@ -851,6 +718,155 @@ retry_transaction:
return rc;
}
+int libxl__domain_make(libxl__gc *gc, libxl_domain_config *d_config,
+ libxl__domain_build_state *state,
+ uint32_t *domid, bool soft_reset)
+{
+ libxl_ctx *ctx = libxl__gc_owner(gc);
+ int ret, rc;
+
+ /* convenience aliases */
+ libxl_domain_create_info *info = &d_config->c_info;
+ libxl_domain_build_info *b_info = &d_config->b_info;
+
+ assert(soft_reset || *domid == INVALID_DOMID);
+
+ if (!soft_reset) {
+ struct xen_domctl_createdomain create = {
+ .ssidref = info->ssidref,
+ .max_vcpus = b_info->max_vcpus,
+ .max_evtchn_port = b_info->event_channels,
+ .max_grant_frames = b_info->max_grant_frames,
+ .max_maptrack_frames = b_info->max_maptrack_frames,
+ };
+
+ if (info->type != LIBXL_DOMAIN_TYPE_PV) {
+ create.flags |= XEN_DOMCTL_CDF_hvm;
+ create.flags |=
+ libxl_defbool_val(info->hap) ? XEN_DOMCTL_CDF_hap : 0;
+ create.flags |=
+ libxl_defbool_val(info->oos) ? 0 : XEN_DOMCTL_CDF_oos_off;
+ }
+
+ assert(info->passthrough != LIBXL_PASSTHROUGH_DEFAULT);
+ LOG(DETAIL, "passthrough: %s",
+ libxl_passthrough_to_string(info->passthrough));
+
+ if (info->passthrough != LIBXL_PASSTHROUGH_DISABLED)
+ create.flags |= XEN_DOMCTL_CDF_iommu;
+
+ if (info->passthrough == LIBXL_PASSTHROUGH_SYNC_PT)
+ create.iommu_opts |= XEN_DOMCTL_IOMMU_no_sharept;
+
+ /* Ultimately, handle is an array of 16 uint8_t, same as uuid */
+ libxl_uuid_copy(ctx, (libxl_uuid *)&create.handle, &info->uuid);
+
+ ret = libxl__arch_domain_prepare_config(gc, d_config, &create);
+ if (ret < 0) {
+ LOGED(ERROR, *domid, "fail to get domain config");
+ rc = ERROR_FAIL;
+ goto out;
+ }
+
+ for (;;) {
+ uint32_t local_domid;
+ bool recent;
+
+ if (info->domid == RANDOM_DOMID) {
+ uint16_t v;
+
+ ret = libxl__random_bytes(gc, (void *)&v, sizeof(v));
+ if (ret < 0)
+ break;
+
+ v &= DOMID_MASK;
+ if (!libxl_domid_valid_guest(v))
+ continue;
+
+ local_domid = v;
+ } else {
+ local_domid = info->domid; /* May not be valid */
+ }
+
+ ret = xc_domain_create(ctx->xch, &local_domid, &create);
+ if (ret < 0) {
+ /*
+ * If we generated a random domid and creation failed
+ * because that domid already exists then simply try
+ * again.
+ */
+ if (errno == EEXIST && info->domid == RANDOM_DOMID)
+ continue;
+
+ LOGED(ERROR, local_domid, "domain creation fail");
+ rc = ERROR_FAIL;
+ goto out;
+ }
+
+ /* A new domain now exists */
+ *domid = local_domid;
+
+ rc = libxl__is_domid_recent(gc, local_domid, &recent);
+ if (rc)
+ goto out;
+
+ /* The domid is not recent, so we're done */
+ if (!recent)
+ break;
+
+ /*
+ * If the domid was specified then there's no point in
+ * trying again.
+ */
+ if (libxl_domid_valid_guest(info->domid)) {
+ LOGED(ERROR, local_domid, "domain id recently used");
+ rc = ERROR_FAIL;
+ goto out;
+ }
+
+ /*
+ * The domain is recent and so cannot be used. Clear domid
+ * here since, if xc_domain_destroy() fails below there is
+ * little point calling it again in the error path.
+ */
+ *domid = INVALID_DOMID;
+
+ ret = xc_domain_destroy(ctx->xch, local_domid);
+ if (ret < 0) {
+ LOGED(ERROR, local_domid, "domain destroy fail");
+ rc = ERROR_FAIL;
+ goto out;
+ }
+
+ /* The domain was successfully destroyed, so we can try again */
+ }
+
+ rc = libxl__arch_domain_save_config(gc, d_config, state, &create);
+ if (rc < 0)
+ goto out;
+ }
+
+ /*
+ * If soft_reset is set the the domid will have been valid on entry.
+ * If it was not set then xc_domain_create() should have assigned a
+ * valid value. Either way, if we reach this point, domid should be
+ * valid.
+ */
+ assert(libxl_domid_valid_guest(*domid));
+
+ ret = xc_cpupool_movedomain(ctx->xch, info->poolid, *domid);
+ if (ret < 0) {
+ LOGED(ERROR, *domid, "domain move fail");
+ rc = ERROR_FAIL;
+ goto out;
+ }
+
+ rc = libxl__domain_make_xs_entries(gc, d_config, state, *domid);
+
+out:
+ return rc;
+}
+
static int store_libxl_entry(libxl__gc *gc, uint32_t domid,
libxl_domain_build_info *b_info)
{
@@ -1172,16 +1188,32 @@ static void initiate_domain_create(libxl__egc *egc,
ret = libxl__domain_config_setdefault(gc,d_config,domid);
if (ret) goto error_out;
- ret = libxl__domain_make(gc, d_config, &dcs->build_state, &domid,
- dcs->soft_reset);
- if (ret) {
- LOGD(ERROR, domid, "cannot make domain: %d", ret);
+ if ( !d_config->dm_restore_file )
+ {
+ ret = libxl__domain_make(gc, d_config, &dcs->build_state, &domid,
+ dcs->soft_reset);
dcs->guest_domid = domid;
+
+ if (ret) {
+ LOGD(ERROR, domid, "cannot make domain: %d", ret);
+ ret = ERROR_FAIL;
+ goto error_out;
+ }
+ } else if ( dcs->guest_domid != INVALID_DOMID ) {
+ domid = dcs->guest_domid;
+
+ ret = libxl__domain_make_xs_entries(gc, d_config, &dcs->build_state, domid);
+ if (ret) {
+ LOGD(ERROR, domid, "cannot make domain: %d", ret);
+ ret = ERROR_FAIL;
+ goto error_out;
+ }
+ } else {
+ LOGD(ERROR, domid, "cannot make domain");
ret = ERROR_FAIL;
goto error_out;
}
- dcs->guest_domid = domid;
dcs->sdss.dm.guest_domid = 0; /* means we haven't spawned */
/* post-4.13 todo: move these next bits of defaulting to
@@ -1217,7 +1249,7 @@ static void initiate_domain_create(libxl__egc *egc,
if (ret)
goto error_out;
- if (restore_fd >= 0 || dcs->soft_reset) {
+ if (restore_fd >= 0 || dcs->soft_reset || d_config->dm_restore_file) {
LOGD(DEBUG, domid, "restoring, not running bootloader");
domcreate_bootloader_done(egc, &dcs->bl, 0);
} else {
@@ -1293,7 +1325,16 @@ static void domcreate_bootloader_done(libxl__egc *egc,
dcs->sdss.dm.callback = domcreate_devmodel_started;
dcs->sdss.callback = domcreate_devmodel_started;
- if (restore_fd < 0 && !dcs->soft_reset) {
+ if (restore_fd < 0 && !dcs->soft_reset && !d_config->dm_restore_file) {
+ rc = libxl__domain_build(gc, d_config, domid, state);
+ domcreate_rebuild_done(egc, dcs, rc);
+ return;
+ }
+
+ if ( d_config->dm_restore_file ) {
+ dcs->srs.dcs = dcs;
+ dcs->srs.ao = ao;
+ state->forked_vm = true;
rc = libxl__domain_build(gc, d_config, domid, state);
domcreate_rebuild_done(egc, dcs, rc);
return;
@@ -1491,6 +1532,7 @@ static void domcreate_rebuild_done(libxl__egc *egc,
/* convenience aliases */
const uint32_t domid = dcs->guest_domid;
libxl_domain_config *const d_config = dcs->guest_config;
+ libxl__domain_build_state *const state = &dcs->build_state;
if (ret) {
LOGD(ERROR, domid, "cannot (re-)build domain: %d", ret);
@@ -1498,6 +1540,9 @@ static void domcreate_rebuild_done(libxl__egc *egc,
goto error_out;
}
+ if ( d_config->dm_restore_file )
+ state->saved_state = GCSPRINTF("%s", d_config->dm_restore_file);
+
store_libxl_entry(gc, domid, &d_config->b_info);
libxl__multidev_begin(ao, &dcs->multidev);
@@ -1886,7 +1931,7 @@ static void domain_create_cb(libxl__egc *egc,
libxl__domain_create_state *dcs,
int rc, uint32_t domid);
-static int do_domain_create(libxl_ctx *ctx, libxl_domain_config *d_config,
+int libxl__do_domain_create(libxl_ctx *ctx, libxl_domain_config *d_config,
uint32_t *domid, int restore_fd, int send_back_fd,
const libxl_domain_restore_params *params,
const libxl_asyncop_how *ao_how,
@@ -1899,6 +1944,8 @@ static int do_domain_create(libxl_ctx *ctx, libxl_domain_config *d_config,
GCNEW(cdcs);
cdcs->dcs.ao = ao;
cdcs->dcs.guest_config = d_config;
+ cdcs->dcs.guest_domid = *domid;
+
libxl_domain_config_init(&cdcs->dcs.guest_config_saved);
libxl_domain_config_copy(ctx, &cdcs->dcs.guest_config_saved, d_config);
cdcs->dcs.restore_fd = cdcs->dcs.libxc_fd = restore_fd;
@@ -2143,8 +2190,8 @@ int libxl_domain_create_new(libxl_ctx *ctx, libxl_domain_config *d_config,
const libxl_asyncprogress_how *aop_console_how)
{
unset_disk_colo_restore(d_config);
- return do_domain_create(ctx, d_config, domid, -1, -1, NULL,
- ao_how, aop_console_how);
+ return libxl__do_domain_create(ctx, d_config, domid, -1, -1, NULL,
+ ao_how, aop_console_how);
}
int libxl_domain_create_restore(libxl_ctx *ctx, libxl_domain_config *d_config,
@@ -2160,8 +2207,8 @@ int libxl_domain_create_restore(libxl_ctx *ctx, libxl_domain_config *d_config,
unset_disk_colo_restore(d_config);
}
- return do_domain_create(ctx, d_config, domid, restore_fd, send_back_fd,
- params, ao_how, aop_console_how);
+ return libxl__do_domain_create(ctx, d_config, domid, restore_fd, send_back_fd,
+ params, ao_how, aop_console_how);
}
int libxl_domain_soft_reset(libxl_ctx *ctx,
diff --git a/tools/libxl/libxl_dm.c b/tools/libxl/libxl_dm.c
index f4007bbe50..b615f1fc88 100644
--- a/tools/libxl/libxl_dm.c
+++ b/tools/libxl/libxl_dm.c
@@ -2803,7 +2803,7 @@ static void device_model_spawn_outcome(libxl__egc *egc,
libxl__domain_build_state *state = dmss->build_state;
- if (state->saved_state) {
+ if (state->saved_state && !state->forked_vm) {
ret2 = unlink(state->saved_state);
if (ret2) {
LOGED(ERROR, dmss->guest_domid, "%s: failed to remove device-model state %s",
diff --git a/tools/libxl/libxl_dom.c b/tools/libxl/libxl_dom.c
index 71cb578923..3bc7117b99 100644
--- a/tools/libxl/libxl_dom.c
+++ b/tools/libxl/libxl_dom.c
@@ -249,9 +249,12 @@ int libxl__build_pre(libxl__gc *gc, uint32_t domid,
libxl_domain_build_info *const info = &d_config->b_info;
libxl_ctx *ctx = libxl__gc_owner(gc);
char *xs_domid, *con_domid;
- int rc;
+ int rc = 0;
uint64_t size;
+ if ( state->forked_vm )
+ goto skip_fork;
+
if (xc_domain_max_vcpus(ctx->xch, domid, info->max_vcpus) != 0) {
LOG(ERROR, "Couldn't set max vcpu count");
return ERROR_FAIL;
@@ -362,7 +365,6 @@ int libxl__build_pre(libxl__gc *gc, uint32_t domid,
}
}
-
rc = libxl__arch_extra_memory(gc, info, &size);
if (rc < 0) {
LOGE(ERROR, "Couldn't get arch extra constant memory size");
@@ -374,6 +376,11 @@ int libxl__build_pre(libxl__gc *gc, uint32_t domid,
return ERROR_FAIL;
}
+ rc = libxl__arch_domain_create(gc, d_config, domid);
+ if ( rc )
+ goto out;
+
+skip_fork:
xs_domid = xs_read(ctx->xsh, XBT_NULL, "/tool/xenstored/domid", NULL);
state->store_domid = xs_domid ? atoi(xs_domid) : 0;
free(xs_domid);
@@ -385,8 +392,7 @@ int libxl__build_pre(libxl__gc *gc, uint32_t domid,
state->store_port = xc_evtchn_alloc_unbound(ctx->xch, domid, state->store_domid);
state->console_port = xc_evtchn_alloc_unbound(ctx->xch, domid, state->console_domid);
- rc = libxl__arch_domain_create(gc, d_config, domid);
-
+out:
return rc;
}
@@ -444,6 +450,9 @@ int libxl__build_post(libxl__gc *gc, uint32_t domid,
char **ents;
int i, rc;
+ if ( state->forked_vm )
+ goto skip_fork;
+
if (info->num_vnuma_nodes && !info->num_vcpu_soft_affinity) {
rc = set_vnuma_affinity(gc, domid, info);
if (rc)
@@ -466,6 +475,7 @@ int libxl__build_post(libxl__gc *gc, uint32_t domid,
}
}
+skip_fork:
ents = libxl__calloc(gc, 12 + (info->max_vcpus * 2) + 2, sizeof(char *));
ents[0] = "memory/static-max";
ents[1] = GCSPRINTF("%"PRId64, info->max_memkb);
@@ -728,14 +738,16 @@ static int hvm_build_set_params(xc_interface *handle, uint32_t domid,
libxl_domain_build_info *info,
int store_evtchn, unsigned long *store_mfn,
int console_evtchn, unsigned long *console_mfn,
- domid_t store_domid, domid_t console_domid)
+ domid_t store_domid, domid_t console_domid,
+ bool forked_vm)
{
struct hvm_info_table *va_hvm;
uint8_t *va_map, sum;
uint64_t str_mfn, cons_mfn;
int i;
- if (info->type == LIBXL_DOMAIN_TYPE_HVM) {
+ if ( info->type == LIBXL_DOMAIN_TYPE_HVM && !forked_vm )
+ {
va_map = xc_map_foreign_range(handle, domid,
XC_PAGE_SIZE, PROT_READ | PROT_WRITE,
HVM_INFO_PFN);
@@ -1051,6 +1063,23 @@ int libxl__build_hvm(libxl__gc *gc, uint32_t domid,
struct xc_dom_image *dom = NULL;
bool device_model = info->type == LIBXL_DOMAIN_TYPE_HVM ? true : false;
+ if ( state->forked_vm )
+ {
+ rc = hvm_build_set_params(ctx->xch, domid, info, state->store_port,
+ &state->store_mfn, state->console_port,
+ &state->console_mfn, state->store_domid,
+ state->console_domid, state->forked_vm);
+
+ if ( rc )
+ return rc;
+
+ return xc_dom_gnttab_seed(ctx->xch, domid, true,
+ state->console_mfn,
+ state->store_mfn,
+ state->console_domid,
+ state->store_domid);
+ }
+
xc_dom_loginit(ctx->xch);
/*
@@ -1175,7 +1204,7 @@ int libxl__build_hvm(libxl__gc *gc, uint32_t domid,
rc = hvm_build_set_params(ctx->xch, domid, info, state->store_port,
&state->store_mfn, state->console_port,
&state->console_mfn, state->store_domid,
- state->console_domid);
+ state->console_domid, false);
if (rc != 0) {
LOG(ERROR, "hvm build set params failed");
goto out;
diff --git a/tools/libxl/libxl_internal.h b/tools/libxl/libxl_internal.h
index 4891722a6b..caa981f2fe 100644
--- a/tools/libxl/libxl_internal.h
+++ b/tools/libxl/libxl_internal.h
@@ -1374,6 +1374,7 @@ typedef struct {
char *saved_state;
int dm_monitor_fd;
+ bool forked_vm;
libxl__file_reference pv_kernel;
libxl__file_reference pv_ramdisk;
@@ -4815,6 +4816,12 @@ _hidden int libxl__domain_pvcontrol(libxl__egc *egc,
/* Check whether a domid is recent */
int libxl__is_domid_recent(libxl__gc *gc, uint32_t domid, bool *recent);
+_hidden int libxl__do_domain_create(libxl_ctx *ctx, libxl_domain_config *d_config,
+ uint32_t *domid, int restore_fd, int send_back_fd,
+ const libxl_domain_restore_params *params,
+ const libxl_asyncop_how *ao_how,
+ const libxl_asyncprogress_how *aop_console_how);
+
#endif
/*
diff --git a/tools/libxl/libxl_types.idl b/tools/libxl/libxl_types.idl
index d0d431614f..55c282b1cd 100644
--- a/tools/libxl/libxl_types.idl
+++ b/tools/libxl/libxl_types.idl
@@ -957,6 +957,7 @@ libxl_domain_config = Struct("domain_config", [
("on_watchdog", libxl_action_on_shutdown),
("on_crash", libxl_action_on_shutdown),
("on_soft_reset", libxl_action_on_shutdown),
+ ("dm_restore_file", string, {'const': True}),
], dir=DIR_IN)
libxl_diskinfo = Struct("diskinfo", [
diff --git a/tools/libxl/libxl_x86.c b/tools/libxl/libxl_x86.c
index f8bc828e62..f4312411fc 100644
--- a/tools/libxl/libxl_x86.c
+++ b/tools/libxl/libxl_x86.c
@@ -2,6 +2,7 @@
#include "libxl_arch.h"
#include <xc_dom.h>
+#include <xen-xsm/flask/flask.h>
int libxl__arch_domain_prepare_config(libxl__gc *gc,
libxl_domain_config *d_config,
@@ -842,6 +843,46 @@ int libxl__arch_passthrough_mode_setdefault(libxl__gc *gc,
return rc;
}
+/*
+ * The parent domain is expected to be created with default settings for
+ * - max_evtch_port
+ * - max_grant_frames
+ * - max_maptrack_frames
+ */
+int libxl_domain_fork_vm(libxl_ctx *ctx, uint32_t pdomid, uint32_t max_vcpus, uint32_t *domid)
+{
+ int rc;
+ struct xen_domctl_createdomain create = {0};
+ create.flags |= XEN_DOMCTL_CDF_hvm;
+ create.flags |= XEN_DOMCTL_CDF_hap;
+ create.flags |= XEN_DOMCTL_CDF_oos_off;
+ create.arch.emulation_flags = (XEN_X86_EMU_ALL & ~XEN_X86_EMU_VPCI);
+ create.ssidref = SECINITSID_DOMU;
+ create.max_vcpus = max_vcpus;
+ create.max_evtchn_port = 1023;
+ create.max_grant_frames = LIBXL_MAX_GRANT_FRAMES_DEFAULT;
+ create.max_maptrack_frames = LIBXL_MAX_MAPTRACK_FRAMES_DEFAULT;
+
+ if ( (rc = xc_domain_create(ctx->xch, domid, &create)) )
+ return rc;
+
+ if ( (rc = xc_memshr_fork(ctx->xch, pdomid, *domid)) )
+ xc_domain_destroy(ctx->xch, *domid);
+
+ return rc;
+}
+
+int libxl_domain_fork_launch_dm(libxl_ctx *ctx, libxl_domain_config *d_config,
+ uint32_t domid,
+ const libxl_asyncprogress_how *aop_console_how)
+{
+ return libxl__do_domain_create(ctx, d_config, &domid, -1, -1, 0, 0, aop_console_how);
+}
+
+int libxl_domain_fork_reset(libxl_ctx *ctx, uint32_t domid)
+{
+ return xc_memshr_fork_reset(ctx->xch, domid);
+}
/*
* Local variables:
diff --git a/tools/xl/Makefile b/tools/xl/Makefile
index af4912e67a..073222233b 100644
--- a/tools/xl/Makefile
+++ b/tools/xl/Makefile
@@ -15,7 +15,7 @@ LDFLAGS += $(PTHREAD_LDFLAGS)
CFLAGS_XL += $(CFLAGS_libxenlight)
CFLAGS_XL += -Wshadow
-XL_OBJS-$(CONFIG_X86) = xl_psr.o
+XL_OBJS-$(CONFIG_X86) = xl_psr.o xl_forkvm.o
XL_OBJS = xl.o xl_cmdtable.o xl_sxp.o xl_utils.o $(XL_OBJS-y)
XL_OBJS += xl_parse.o xl_cpupool.o xl_flask.o
XL_OBJS += xl_vtpm.o xl_block.o xl_nic.o xl_usb.o
diff --git a/tools/xl/xl.h b/tools/xl/xl.h
index 06569c6c4a..1105c34b15 100644
--- a/tools/xl/xl.h
+++ b/tools/xl/xl.h
@@ -31,6 +31,7 @@ struct cmd_spec {
};
struct domain_create {
+ uint32_t ddomid; /* fork launch dm for this domid */
int debug;
int daemonize;
int monitor; /* handle guest reboots etc */
@@ -45,6 +46,7 @@ struct domain_create {
const char *config_file;
char *extra_config; /* extra config string */
const char *restore_file;
+ const char *dm_restore_file;
char *colo_proxy_script;
bool userspace_colo_proxy;
int migrate_fd; /* -1 means none */
@@ -128,6 +130,8 @@ int main_pciassignable_remove(int argc, char **argv);
int main_pciassignable_list(int argc, char **argv);
#ifndef LIBXL_HAVE_NO_SUSPEND_RESUME
int main_restore(int argc, char **argv);
+int main_fork_launch_dm(int argc, char **argv);
+int main_fork_reset(int argc, char **argv);
int main_migrate_receive(int argc, char **argv);
int main_save(int argc, char **argv);
int main_migrate(int argc, char **argv);
@@ -212,6 +216,7 @@ int main_psr_cat_cbm_set(int argc, char **argv);
int main_psr_cat_show(int argc, char **argv);
int main_psr_mba_set(int argc, char **argv);
int main_psr_mba_show(int argc, char **argv);
+int main_fork_vm(int argc, char **argv);
#endif
int main_qemu_monitor_command(int argc, char **argv);
diff --git a/tools/xl/xl_cmdtable.c b/tools/xl/xl_cmdtable.c
index 08335394e5..ef634abf32 100644
--- a/tools/xl/xl_cmdtable.c
+++ b/tools/xl/xl_cmdtable.c
@@ -187,6 +187,21 @@ struct cmd_spec cmd_table[] = {
"Restore a domain from a saved state",
"- for internal use only",
},
+#if defined(__i386__) || defined(__x86_64__)
+ { "fork-vm",
+ &main_fork_vm, 0, 1,
+ "Fork a domain from the running parent domid. Experimental. Most config settings must match parent.",
+ "[options] <Domid>",
+ "-h Print this help.\n"
+ "-C <config> Use config file for VM fork.\n"
+ "-Q <qemu-save-file> Use qemu save file for VM fork.\n"
+ "--launch-dm <yes|no|late> Launch device model (QEMU) for VM fork.\n"
+ "--fork-reset Reset VM fork.\n"
+ "--max-vcpus Specify max-vcpus matching the parent domain when not launching dm\n"
+ "-p Do not unpause fork VM after operation.\n"
+ "-d Enable debug messages.\n"
+ },
+#endif
#endif
{ "dump-core",
&main_dump_core, 0, 1,
diff --git a/tools/xl/xl_forkvm.c b/tools/xl/xl_forkvm.c
new file mode 100644
index 0000000000..a7ee5b4771
--- /dev/null
+++ b/tools/xl/xl_forkvm.c
@@ -0,0 +1,147 @@
+/*
+ * Copyright 2020 Intel Corporation
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published
+ * by the Free Software Foundation; version 2.1 only. with the special
+ * exception on linking described in file LICENSE.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Lesser General Public License for more details.
+ */
+
+#include <fcntl.h>
+#include <inttypes.h>
+#include <stdlib.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/utsname.h>
+#include <time.h>
+#include <unistd.h>
+
+#include <libxl.h>
+#include <libxl_utils.h>
+#include <libxlutil.h>
+
+#include "xl.h"
+#include "xl_utils.h"
+#include "xl_parse.h"
+
+int main_fork_vm(int argc, char **argv)
+{
+ int rc, debug = 0;
+ uint32_t domid_in = INVALID_DOMID, domid_out = INVALID_DOMID;
+ int launch_dm = 1;
+ bool reset = 0;
+ bool pause = 0;
+ const char *config_file = NULL;
+ const char *dm_restore_file = NULL;
+ uint32_t max_vcpus = 0;
+
+ int opt;
+ static struct option opts[] = {
+ {"launch-dm", 1, 0, 'l'},
+ {"fork-reset", 0, 0, 'r'},
+ {"max-vcpus", 1, 0, 'm'},
+ COMMON_LONG_OPTS
+ };
+
+ SWITCH_FOREACH_OPT(opt, "phdC:Q:l:rm:N:D:B:V:", opts, "fork-vm", 1) {
+ case 'd':
+ debug = 1;
+ break;
+ case 'p':
+ pause = 1;
+ break;
+ case 'm':
+ max_vcpus = atoi(optarg);
+ break;
+ case 'C':
+ config_file = optarg;
+ break;
+ case 'Q':
+ dm_restore_file = optarg;
+ break;
+ case 'l':
+ if ( !strcmp(optarg, "no") )
+ launch_dm = 0;
+ if ( !strcmp(optarg, "yes") )
+ launch_dm = 1;
+ if ( !strcmp(optarg, "late") )
+ launch_dm = 2;
+ break;
+ case 'r':
+ reset = 1;
+ break;
+ case 'N': /* fall-through */
+ case 'D': /* fall-through */
+ case 'B': /* fall-through */
+ case 'V':
+ fprintf(stderr, "Unimplemented option(s)\n");
+ return EXIT_FAILURE;
+ }
+
+ if (argc-optind == 1) {
+ domid_in = atoi(argv[optind]);
+ } else {
+ help("fork-vm");
+ return EXIT_FAILURE;
+ }
+
+ if (launch_dm && (!config_file || !dm_restore_file)) {
+ fprintf(stderr, "Currently you must provide both -C and -Q options\n");
+ return EXIT_FAILURE;
+ }
+
+ if (reset) {
+ domid_out = domid_in;
+ if (libxl_domain_fork_reset(ctx, domid_in) == EXIT_FAILURE)
+ return EXIT_FAILURE;
+ }
+
+ if (launch_dm == 2 || reset) {
+ domid_out = domid_in;
+ rc = EXIT_SUCCESS;
+ } else {
+ if ( !max_vcpus )
+ {
+ fprintf(stderr, "Currently you must parent's max_vcpu for this option\n");
+ return EXIT_FAILURE;
+ }
+
+ rc = libxl_domain_fork_vm(ctx, domid_in, max_vcpus, &domid_out);
+ }
+
+ if (rc == EXIT_SUCCESS) {
+ if ( launch_dm ) {
+ struct domain_create dom_info;
+ memset(&dom_info, 0, sizeof(dom_info));
+ dom_info.ddomid = domid_out;
+ dom_info.dm_restore_file = dm_restore_file;
+ dom_info.debug = debug;
+ dom_info.paused = pause;
+ dom_info.config_file = config_file;
+ dom_info.migrate_fd = -1;
+ dom_info.send_back_fd = -1;
+ rc = create_domain(&dom_info) < 0 ? EXIT_FAILURE : EXIT_SUCCESS;
+ } else if ( !pause )
+ rc = libxl_domain_unpause(ctx, domid_out, NULL);
+ }
+
+ if (rc == EXIT_SUCCESS)
+ fprintf(stderr, "fork-vm command successfully returned domid: %u\n", domid_out);
+ else if ( domid_out != INVALID_DOMID )
+ libxl_domain_destroy(ctx, domid_out, 0);
+
+ return rc;
+}
+
+/*
+ * Local variables:
+ * mode: C
+ * c-basic-offset: 4
+ * indent-tabs-mode: nil
+ * End:
+ */
diff --git a/tools/xl/xl_vmcontrol.c b/tools/xl/xl_vmcontrol.c
index 2e2d427492..782fbbc24b 100644
--- a/tools/xl/xl_vmcontrol.c
+++ b/tools/xl/xl_vmcontrol.c
@@ -676,6 +676,12 @@ int create_domain(struct domain_create *dom_info)
int restoring = (restore_file || (migrate_fd >= 0));
+#if defined(__i386__) || defined(__x86_64__)
+ /* VM forking */
+ uint32_t ddomid = dom_info->ddomid; // launch dm for this domain iff set
+ const char *dm_restore_file = dom_info->dm_restore_file;
+#endif
+
libxl_domain_config_init(&d_config);
if (restoring) {
@@ -926,6 +932,14 @@ start:
* restore/migrate-receive it again.
*/
restoring = 0;
+#if defined(__i386__) || defined(__x86_64__)
+ } else if ( ddomid ) {
+ d_config.dm_restore_file = dm_restore_file;
+ ret = libxl_domain_fork_launch_dm(ctx, &d_config, ddomid,
+ autoconnect_console_how);
+ domid = ddomid;
+ ddomid = INVALID_DOMID;
+#endif
} else if (domid_soft_reset != INVALID_DOMID) {
/* Do soft reset. */
ret = libxl_domain_soft_reset(ctx, &d_config, domid_soft_reset,
--
2.20.1
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel
^ permalink raw reply related [flat|nested] 13+ messages in thread
* Re: [Xen-devel] [PATCH v11 0/3] VM forking
2020-02-28 18:40 [Xen-devel] [PATCH v11 0/3] VM forking Tamas K Lengyel
` (2 preceding siblings ...)
2020-02-28 18:40 ` [Xen-devel] [PATCH v11 3/3] xen/tools: VM forking toolstack side Tamas K Lengyel
@ 2020-03-16 13:07 ` Tamas K Lengyel
3 siblings, 0 replies; 13+ messages in thread
From: Tamas K Lengyel @ 2020-03-16 13:07 UTC (permalink / raw)
To: Tamas K Lengyel
Cc: Stefano Stabellini, Julien Grall, Wei Liu, Konrad Rzeszutek Wilk,
Andrew Cooper, Ian Jackson, George Dunlap, Jan Beulich,
Anthony PERARD, Xen-devel, Roger Pau Monné
On Fri, Feb 28, 2020 at 11:41 AM Tamas K Lengyel
<tamas.lengyel@intel.com> wrote:
>
> The following series implements VM forking for Intel HVM guests to allow for
> the fast creation of identical VMs without the assosciated high startup costs
> of booting or restoring the VM from a savefile.
>
> JIRA issue: https://xenproject.atlassian.net/browse/XEN-89
>
> The fork operation is implemented as part of the "xl fork-vm" command:
> xl fork-vm -C <config> -Q <qemu-save-file> -m <max-vcpus> <parent_domid>
>
> By default a fully functional fork is created. The user is in charge however to
> create the appropriate config file for the fork and to generate the QEMU save
> file before the fork-vm call is made. The config file needs to give the
> fork a new name at minimum but other settings may also require changes. Certain
> settings in the config file of both the parent and the fork have to be set to
> default. Details are documented.
>
> The interface also allows to split the forking into two steps:
> xl fork-vm --launch-dm no \
> -m <max-vcpus> \
> -p <parent_domid>
> xl fork-vm --launch-dm late \
> -C <config_file_for_fork> \
> -Q <qemu_save_file> \
> <fork_domid>
>
> The split creation model is useful when the VM needs to be created as fast as
> possible. The forked VM can be unpaused without the device model being launched
> to be monitored and accessed via VMI. Note however that without its device
> model running (depending on what is executing in the VM) it is bound to
> misbehave or even crash when its trying to access devices that would be
> emulated by QEMU. We anticipate that for certain use-cases this would be an
> acceptable situation, in case for example when fuzzing is performed of code
> segments that don't access such devices.
>
> Launching the device model requires the QEMU Xen savefile to be generated
> manually from the parent VM. This can be accomplished simply by connecting to
> its QMP socket and issuing the "xen-save-devices-state" command. For example
> using the standard tool socat these commands can be used to generate the file:
> socat - UNIX-CONNECT:/var/run/xen/qmp-libxl-<parent_domid>
> { "execute": "qmp_capabilities" }
> { "execute": "xen-save-devices-state", \
> "arguments": { "filename": "/path/to/save/qemu_state", \
> "live": false} }
>
> At runtime the forked VM starts running with an empty p2m which gets lazily
> populated when the VM generates EPT faults, similar to how altp2m views are
> populated. If the memory access is a read-only access, the p2m entry is
> populated with a memory shared entry with its parent. For write memory accesses
> or in case memory sharing wasn't possible (for example in case a reference is
> held by a third party), a new page is allocated and the page contents are
> copied over from the parent VM. Forks can be further forked if needed, thus
> allowing for further memory savings.
>
> A VM fork reset hypercall is also added that allows the fork to be reset to the
> state it was just after a fork, also accessible via xl:
> xl fork-vm --fork-reset -p <fork_domid>
>
> This is an optimization for cases where the forks are very short-lived and run
> without a device model, so resetting saves some time compared to creating a
> brand new fork provided the fork has not aquired a lot of memory. If the fork
> has a lot of memory deduplicated it is likely going to be faster to create a
> new fork from scratch and asynchronously destroying the old one.
>
> The series has been tested with Windows VMs and functions as expected. Linux
> VMs when forked from a running VM will have a frozen VNC screen. Linux VMs at
> this time can only be forked with a working device model when the parent VM was
> restored from a snapshot using "xl restore -p". This is a known limitation.
> Also note that PVHVM/PVH Linux guests have not been tested. Forking most likely
> works but PV devices and drivers would require additional wiring to set things
> up properly since the guests are unaware of the forking taking place, unlike
> the save/restore routine where the guest is made aware of the procedure.
>
> Forking time has been measured to be 0.0007s, device model launch to be around
> 1s depending largely on the number of devices being emulated. Fork resets have
> been measured to be 0.0001s under the optimal circumstances.
>
> New in v11:
> Fully copy & reset vcpu_info pages
> Setup vcpu_runstate for forks
> Added TODO note for PV timers
> Copy & reset shared_info page
> Copy & reset HVM special pages
>
> New in v10:
> Rebased on staging and minor fixes for things pointed out by Roger
> Allocate pages for vcpu_info if used by parent
> Document limitation of guest settings that have to be set to default
> Require max-vcpus to be specified by toolstack-side
> Code movement in toolstack & compile tested on ARM
> Implement hypercall continuation for reset operation
>
> Patch 1-2 implements the VM fork & reset operation hypervisor side bits
>
> Patch 3 adds the toolstack-side code implementing VM forking and reset
>
> Tamas K Lengyel (3):
> xen/mem_sharing: VM forking
> x86/mem_sharing: reset a fork
> xen/tools: VM forking toolstack side
>
> docs/man/xl.1.pod.in | 44 +++
> tools/libxc/include/xenctrl.h | 13 +
> tools/libxc/xc_memshr.c | 22 ++
> tools/libxl/libxl.h | 11 +
> tools/libxl/libxl_create.c | 361 ++++++++++++----------
> tools/libxl/libxl_dm.c | 2 +-
> tools/libxl/libxl_dom.c | 43 ++-
> tools/libxl/libxl_internal.h | 7 +
> tools/libxl/libxl_types.idl | 1 +
> tools/libxl/libxl_x86.c | 41 +++
> tools/xl/Makefile | 2 +-
> tools/xl/xl.h | 5 +
> tools/xl/xl_cmdtable.c | 15 +
> tools/xl/xl_forkvm.c | 147 +++++++++
> tools/xl/xl_vmcontrol.c | 14 +
> 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 | 483 ++++++++++++++++++++++++++++++
> 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 | 9 +
> xen/include/xen/sched.h | 5 +
> 26 files changed, 1104 insertions(+), 171 deletions(-)
> create mode 100644 tools/xl/xl_forkvm.c
Patch series ping. There hasn't been any comments on this in the last
three weeks.
Thanks,
Tamas
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel
^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [Xen-devel] [PATCH v11 1/3] xen/mem_sharing: VM forking
2020-02-28 18:40 ` [Xen-devel] [PATCH v11 1/3] xen/mem_sharing: " Tamas K Lengyel
@ 2020-03-17 15:59 ` Jan Beulich
2020-03-17 16:23 ` Tamas K Lengyel
0 siblings, 1 reply; 13+ messages in thread
From: Jan Beulich @ 2020-03-17 15:59 UTC (permalink / raw)
To: Tamas K Lengyel
Cc: Stefano Stabellini, Julien Grall, Wei Liu, Konrad Rzeszutek Wilk,
Andrew Cooper, Ian Jackson, George Dunlap, Tamas K Lengyel,
xen-devel, Roger Pau Monné
On 28.02.2020 19:40, Tamas K Lengyel wrote:
> --- 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)) )
No need for !! here.
> @@ -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;
This looks pretty broad a condition, i.e. all possible types would
make it through here for a fork. Wouldn't it make sense to limit
to to p2m_is_hole() page types, like you check for in
__get_gfn_type_access()?
> --- 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
Seeing something like this makes me wonder whether forking shouldn't
have its own Kconfig control.
> --- 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))
Again not need for !! (for a different reason).
Also, does the build break if you made this an inline function
(as we generally prefer)?
> @@ -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;
> +}
Can these be reached? If not, please add ASSERT_UNREACHABLE().
> @@ -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 */
Especially in the public interface - no new name space
violations please. I.e. please drop the leading underscore.
I also struggle to see why this is an array of three
elements. In fact I don't see why the padding field would be
needed at all - one other union member only gets padded to
its alignment (which is what I'd expect), while others
(presumably older ones) don't have any padding at all. Here
there's no implicit structure's alignment padding that wants
making explicit.
> --- 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;
There's no need for a fixed width type here afaics - unsigned
int and probably even unsigned short would seem to both be
fine.
Jan
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel
^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [Xen-devel] [PATCH v11 1/3] xen/mem_sharing: VM forking
2020-03-17 15:59 ` Jan Beulich
@ 2020-03-17 16:23 ` Tamas K Lengyel
2020-03-17 16:35 ` Jan Beulich
0 siblings, 1 reply; 13+ messages in thread
From: Tamas K Lengyel @ 2020-03-17 16:23 UTC (permalink / raw)
To: Jan Beulich
Cc: Stefano Stabellini, Julien Grall, Wei Liu, Konrad Rzeszutek Wilk,
Andrew Cooper, Ian Jackson, George Dunlap, Xen-devel,
Tamas K Lengyel, Roger Pau Monné
On Tue, Mar 17, 2020 at 10:02 AM Jan Beulich <jbeulich@suse.com> wrote:
>
> On 28.02.2020 19:40, Tamas K Lengyel wrote:
> > --- 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)) )
>
> No need for !! here.
I don't think it really matters but sure.
>
> > @@ -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;
>
> This looks pretty broad a condition, i.e. all possible types would
> make it through here for a fork. Wouldn't it make sense to limit
> to to p2m_is_hole() page types, like you check for in
> __get_gfn_type_access()?
No need to put that check here. By allowing to go further when we have
a forked VM, this code-path will call get_gfn_type_access, which does
that check. It's better to have that check at one place instead of all
over unnecessarily.
>
> > --- 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
>
> Seeing something like this makes me wonder whether forking shouldn't
> have its own Kconfig control.
For now I think it's fine to have it under mem_sharing.
>
> > --- 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))
>
> Again not need for !! (for a different reason).
Which is?
>
> Also, does the build break if you made this an inline function
> (as we generally prefer)?
Any particular reason for that (inline vs define)?
>
> > @@ -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;
> > +}
This actually is no longer needed at all.
> > +
> > +static inline int mem_sharing_fork_page(struct domain *d, gfn_t gfn, bool lock)
> > +{
> > + return -EOPNOTSUPP;
> > +}
>
> Can these be reached? If not, please add ASSERT_UNREACHABLE().
This can be reached.
>
> > @@ -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 */
>
> Especially in the public interface - no new name space
> violations please. I.e. please drop the leading underscore.
> I also struggle to see why this is an array of three
> elements. In fact I don't see why the padding field would be
> needed at all - one other union member only gets padded to
> its alignment (which is what I'd expect), while others
> (presumably older ones) don't have any padding at all. Here
> there's no implicit structure's alignment padding that wants
> making explicit.
I don't know what you are asking. Drop the padding? I prefer each
union member to be padded to 64-bit, reduces cognitive load trying to
figure out what the size and alginment of each member struct would be.
>
> > --- 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;
>
> There's no need for a fixed width type here afaics - unsigned
> int and probably even unsigned short would seem to both be
> fine.
OK.
Thanks,
Tamas
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel
^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [Xen-devel] [PATCH v11 1/3] xen/mem_sharing: VM forking
2020-03-17 16:23 ` Tamas K Lengyel
@ 2020-03-17 16:35 ` Jan Beulich
2020-03-17 16:58 ` Tamas K Lengyel
0 siblings, 1 reply; 13+ messages in thread
From: Jan Beulich @ 2020-03-17 16:35 UTC (permalink / raw)
To: Tamas K Lengyel
Cc: Stefano Stabellini, Julien Grall, Wei Liu, Konrad Rzeszutek Wilk,
Andrew Cooper, Ian Jackson, George Dunlap, Xen-devel,
Tamas K Lengyel, Roger Pau Monné
On 17.03.2020 17:23, Tamas K Lengyel wrote:
> On Tue, Mar 17, 2020 at 10:02 AM Jan Beulich <jbeulich@suse.com> wrote:
>> On 28.02.2020 19:40, Tamas K Lengyel wrote:
>>> @@ -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;
>>
>> This looks pretty broad a condition, i.e. all possible types would
>> make it through here for a fork. Wouldn't it make sense to limit
>> to to p2m_is_hole() page types, like you check for in
>> __get_gfn_type_access()?
>
> No need to put that check here. By allowing to go further when we have
> a forked VM, this code-path will call get_gfn_type_access, which does
> that check. It's better to have that check at one place instead of all
> over unnecessarily.
Well, if worse performance (due to more cases where the lock will
be taken) is not of concern - so be it.
>>> --- 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))
>>
>> Again not need for !! (for a different reason).
>
> Which is?
Further up the reason was that you pass the value as argument
for a boolean function parameter. Here the reason is that is an
operand of &&.
>> Also, does the build break if you made this an inline function
>> (as we generally prefer)?
>
> Any particular reason for that (inline vs define)?
Inline functions add type safety for the arguments, which
#define-s don't do.
>>> @@ -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 */
>>
>> Especially in the public interface - no new name space
>> violations please. I.e. please drop the leading underscore.
>> I also struggle to see why this is an array of three
>> elements. In fact I don't see why the padding field would be
>> needed at all - one other union member only gets padded to
>> its alignment (which is what I'd expect), while others
>> (presumably older ones) don't have any padding at all. Here
>> there's no implicit structure's alignment padding that wants
>> making explicit.
>
> I don't know what you are asking. Drop the padding? I prefer each
> union member to be padded to 64-bit, reduces cognitive load trying to
> figure out what the size and alginment of each member struct would be.
Personally I'd suggest to drop the padding, as it actually
grows the size of the structure. But if you feel strongly
about keeping it, then I'll be okay with just the field's
name changed.
Jan
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel
^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [Xen-devel] [PATCH v11 1/3] xen/mem_sharing: VM forking
2020-03-17 16:35 ` Jan Beulich
@ 2020-03-17 16:58 ` Tamas K Lengyel
0 siblings, 0 replies; 13+ messages in thread
From: Tamas K Lengyel @ 2020-03-17 16:58 UTC (permalink / raw)
To: Jan Beulich
Cc: Stefano Stabellini, Julien Grall, Wei Liu, Konrad Rzeszutek Wilk,
Andrew Cooper, Ian Jackson, George Dunlap, Xen-devel,
Tamas K Lengyel, Roger Pau Monné
On Tue, Mar 17, 2020 at 10:35 AM Jan Beulich <jbeulich@suse.com> wrote:
>
> On 17.03.2020 17:23, Tamas K Lengyel wrote:
> > On Tue, Mar 17, 2020 at 10:02 AM Jan Beulich <jbeulich@suse.com> wrote:
> >> On 28.02.2020 19:40, Tamas K Lengyel wrote:
> >>> @@ -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;
> >>
> >> This looks pretty broad a condition, i.e. all possible types would
> >> make it through here for a fork. Wouldn't it make sense to limit
> >> to to p2m_is_hole() page types, like you check for in
> >> __get_gfn_type_access()?
> >
> > No need to put that check here. By allowing to go further when we have
> > a forked VM, this code-path will call get_gfn_type_access, which does
> > that check. It's better to have that check at one place instead of all
> > over unnecessarily.
>
> Well, if worse performance (due to more cases where the lock will
> be taken) is not of concern - so be it.
>
> >>> --- 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))
> >>
> >> Again not need for !! (for a different reason).
> >
> > Which is?
>
> Further up the reason was that you pass the value as argument
> for a boolean function parameter. Here the reason is that is an
> operand of &&.
>
> >> Also, does the build break if you made this an inline function
> >> (as we generally prefer)?
> >
> > Any particular reason for that (inline vs define)?
>
> Inline functions add type safety for the arguments, which
> #define-s don't do.
Ack.
>
> >>> @@ -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 */
> >>
> >> Especially in the public interface - no new name space
> >> violations please. I.e. please drop the leading underscore.
> >> I also struggle to see why this is an array of three
> >> elements. In fact I don't see why the padding field would be
> >> needed at all - one other union member only gets padded to
> >> its alignment (which is what I'd expect), while others
> >> (presumably older ones) don't have any padding at all. Here
> >> there's no implicit structure's alignment padding that wants
> >> making explicit.
> >
> > I don't know what you are asking. Drop the padding? I prefer each
> > union member to be padded to 64-bit, reduces cognitive load trying to
> > figure out what the size and alginment of each member struct would be.
>
> Personally I'd suggest to drop the padding, as it actually
> grows the size of the structure. But if you feel strongly
> about keeping it, then I'll be okay with just the field's
> name changed.
It grows the structure size to 64-bit, yes, but it doesn't grow the
size of union as other members are much larger. I'll remove the
underscore from the pad name but I still prefer it aligned.
Tamas
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel
^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [Xen-devel] [PATCH v11 2/3] x86/mem_sharing: reset a fork
2020-02-28 18:40 ` [Xen-devel] [PATCH v11 2/3] x86/mem_sharing: reset a fork Tamas K Lengyel
@ 2020-03-18 11:36 ` Jan Beulich
2020-03-18 14:00 ` Tamas K Lengyel
0 siblings, 1 reply; 13+ messages in thread
From: Jan Beulich @ 2020-03-18 11:36 UTC (permalink / raw)
To: Tamas K Lengyel
Cc: Tamas K Lengyel, Julien Grall, Wei Liu, Konrad Rzeszutek Wilk,
Andrew Cooper, Ian Jackson, George Dunlap, Stefano Stabellini,
xen-devel, Roger Pau Monné
On 28.02.2020 19:40, Tamas K Lengyel wrote:
> --- a/xen/arch/x86/mm/mem_sharing.c
> +++ b/xen/arch/x86/mm/mem_sharing.c
> @@ -1775,6 +1775,91 @@ static int fork(struct domain *cd, struct domain *d)
> return rc;
> }
>
> +/*
> + * The fork reset operation is intended to be used on short-lived forks only.
> + */
> +static int fork_reset(struct domain *d, struct domain *cd,
Could I talk you into using pd instead of d, to even more
clearly distinguish which of the two domain's is meant? Also
in principle this might be possible to be a pointer to const,
albeit I realize this may need changes you likely don't want
to do in a prereq patch (and maybe there's actually a reason
why it can't be).
> + struct mem_sharing_op_fork_reset *fr)
> +{
> + int rc = 0;
> + struct p2m_domain* p2m = p2m_get_hostp2m(cd);
Star and blank want to switch places here.
> + struct page_info *page, *tmp;
> + unsigned long list_position = 0, preempt_count = 0, restart = fr->opaque;
> +
> + domain_pause(cd);
> +
> + page_list_for_each_safe(page, tmp, &cd->page_list)
You may not iterate a domain's page list without holding its
page-alloc lock. Even if the domain is paused, other entities
(like the controlling domain) may cause the list to be altered.
With this the question then of course becomes whether holding
that lock for this long is acceptable. I guess you need to
somehow mark the pages you've processed, either by a flag or
by moving between separate lists. Domain cleanup does something
along these lines.
> + {
> + p2m_type_t p2mt;
> + p2m_access_t p2ma;
> + gfn_t gfn;
> + mfn_t mfn;
> + bool shared = false;
> +
> + list_position++;
> +
> + /* Resume were we left of before preemption */
> + if ( restart && list_position < restart )
> + continue;
This assumes the list to not have been changed across a continuation,
which isn't going to fly.
> + mfn = page_to_mfn(page);
> + if ( mfn_valid(mfn) )
All pages on a domain's list should have a valid MFN - what are you
trying to protect against here?
> + {
> +
> + gfn = mfn_to_gfn(cd, mfn);
Stray blank line above here?
> + mfn = __get_gfn_type_access(p2m, gfn_x(gfn), &p2mt, &p2ma,
> + 0, NULL, false);
> +
> + if ( p2m_is_ram(p2mt) && !p2m_is_shared(p2mt) )
> + {
> + /* take an extra reference, must work for a shared page */
The comment (and also the next one further down) looks contradictory
to the if() immediately ahead, at least to me. Could you clarify the
situation, please?
> + if( !get_page(page, cd) )
> + {
> + ASSERT_UNREACHABLE();
> + return -EINVAL;
> + }
> +
> + shared = true;
> + preempt_count += 0x10;
> +
> + /*
> + * Must succeed, it's a shared page that exists and
> + * thus its size is guaranteed to be 4k so we are not splitting
> + * large pages.
> + */
> + rc = p2m->set_entry(p2m, gfn, INVALID_MFN, PAGE_ORDER_4K,
> + p2m_invalid, p2m_access_rwx, -1);
> + ASSERT(!rc);
> +
> + put_page_alloc_ref(page);
> + put_page(page);
> + }
> + }
> +
> + if ( !shared )
> + preempt_count++;
> +
> + /* Preempt every 2MiB (shared) or 32MiB (unshared) - arbitrary. */
> + if ( preempt_count >= 0x2000 )
> + {
> + if ( hypercall_preempt_check() )
> + {
> + rc = -ERESTART;
You use a negative return value here, but ...
> + break;
> + }
> + preempt_count = 0;
> + }
> + }
> +
> + if ( rc )
> + fr->opaque = list_position;
> + else
> + rc = copy_settings(cd, d);
> +
> + domain_unpause(cd);
> + return rc;
> +}
> +
> int mem_sharing_memop(XEN_GUEST_HANDLE_PARAM(xen_mem_sharing_op_t) arg)
> {
> int rc;
> @@ -2066,6 +2151,36 @@ int mem_sharing_memop(XEN_GUEST_HANDLE_PARAM(xen_mem_sharing_op_t) arg)
> break;
> }
>
> + case XENMEM_sharing_op_fork_reset:
> + {
> + struct domain *pd;
> +
> + rc = -ENOSYS;
> + if ( !mem_sharing_is_fork(d) )
> + goto out;
> +
> + rc = rcu_lock_live_remote_domain_by_id(d->parent->domain_id, &pd);
> + if ( rc )
> + goto out;
> +
> + rc = fork_reset(pd, d, &mso.u.fork_reset);
> +
> + rcu_unlock_domain(pd);
> +
> + if ( rc > 0 )
... you check for a positive value here. I didn't get around to
look at earlier versions, so I can only guess the -ERESTART above
was changed to later on.
Jan
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel
^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [Xen-devel] [PATCH v11 2/3] x86/mem_sharing: reset a fork
2020-03-18 11:36 ` Jan Beulich
@ 2020-03-18 14:00 ` Tamas K Lengyel
2020-03-18 14:12 ` Jan Beulich
0 siblings, 1 reply; 13+ messages in thread
From: Tamas K Lengyel @ 2020-03-18 14:00 UTC (permalink / raw)
To: Jan Beulich
Cc: Julien Grall, Stefano Stabellini, Tamas K Lengyel, Wei Liu,
Konrad Rzeszutek Wilk, Andrew Cooper, Ian Jackson, George Dunlap,
Xen-devel, Roger Pau Monné
On Wed, Mar 18, 2020 at 5:36 AM Jan Beulich <jbeulich@suse.com> wrote:
>
> On 28.02.2020 19:40, Tamas K Lengyel wrote:
> > --- a/xen/arch/x86/mm/mem_sharing.c
> > +++ b/xen/arch/x86/mm/mem_sharing.c
> > @@ -1775,6 +1775,91 @@ static int fork(struct domain *cd, struct domain *d)
> > return rc;
> > }
> >
> > +/*
> > + * The fork reset operation is intended to be used on short-lived forks only.
> > + */
> > +static int fork_reset(struct domain *d, struct domain *cd,
>
> Could I talk you into using pd instead of d, to even more
> clearly distinguish which of the two domain's is meant? Also
> in principle this might be possible to be a pointer to const,
> albeit I realize this may need changes you likely don't want
> to do in a prereq patch (and maybe there's actually a reason
> why it can't be).
The names c and cd are used across the mem_sharing codebase, for
consistency I'm keeping that.
>
> > + struct mem_sharing_op_fork_reset *fr)
> > +{
> > + int rc = 0;
> > + struct p2m_domain* p2m = p2m_get_hostp2m(cd);
>
> Star and blank want to switch places here.
>
> > + struct page_info *page, *tmp;
> > + unsigned long list_position = 0, preempt_count = 0, restart = fr->opaque;
> > +
> > + domain_pause(cd);
> > +
> > + page_list_for_each_safe(page, tmp, &cd->page_list)
>
> You may not iterate a domain's page list without holding its
> page-alloc lock. Even if the domain is paused, other entities
> (like the controlling domain) may cause the list to be altered.
> With this the question then of course becomes whether holding
> that lock for this long is acceptable. I guess you need to
> somehow mark the pages you've processed, either by a flag or
> by moving between separate lists. Domain cleanup does something
> along these lines.
>
> > + {
> > + p2m_type_t p2mt;
> > + p2m_access_t p2ma;
> > + gfn_t gfn;
> > + mfn_t mfn;
> > + bool shared = false;
> > +
> > + list_position++;
> > +
> > + /* Resume were we left of before preemption */
> > + if ( restart && list_position < restart )
> > + continue;
>
> This assumes the list to not have been changed across a continuation,
> which isn't going to fly.
OK, I'm going to drop continuation here completely. I was reluctant to
add it to begin with since this hypercall should only be called when
the number of pages is low so there wouldn't be continuation anyway.
This is work I'm unable to assign more time for, if someone in the
future really needs continuation they are welcome to figure it out.
>
> > + mfn = page_to_mfn(page);
> > + if ( mfn_valid(mfn) )
>
> All pages on a domain's list should have a valid MFN - what are you
> trying to protect against here?
I saw no documentation stating what you stated above. If that's the
case it can be dropped.
>
> > + {
> > +
> > + gfn = mfn_to_gfn(cd, mfn);
>
> Stray blank line above here?
>
> > + mfn = __get_gfn_type_access(p2m, gfn_x(gfn), &p2mt, &p2ma,
> > + 0, NULL, false);
> > +
> > + if ( p2m_is_ram(p2mt) && !p2m_is_shared(p2mt) )
> > + {
> > + /* take an extra reference, must work for a shared page */
>
> The comment (and also the next one further down) looks contradictory
> to the if() immediately ahead, at least to me. Could you clarify the
> situation, please?
I don't understand your question. The comment explains exactly what
happens. Taking an extra reference must work. If it didn't, trigger an
ASSERT_UNREACHABLE. Which part is confusing?
>
> > + if( !get_page(page, cd) )
> > + {
> > + ASSERT_UNREACHABLE();
> > + return -EINVAL;
> > + }
> > +
> > + shared = true;
> > + preempt_count += 0x10;
> > +
> > + /*
> > + * Must succeed, it's a shared page that exists and
> > + * thus its size is guaranteed to be 4k so we are not splitting
> > + * large pages.
> > + */
> > + rc = p2m->set_entry(p2m, gfn, INVALID_MFN, PAGE_ORDER_4K,
> > + p2m_invalid, p2m_access_rwx, -1);
> > + ASSERT(!rc);
> > +
> > + put_page_alloc_ref(page);
> > + put_page(page);
> > + }
> > + }
> > +
> > + if ( !shared )
> > + preempt_count++;
> > +
> > + /* Preempt every 2MiB (shared) or 32MiB (unshared) - arbitrary. */
> > + if ( preempt_count >= 0x2000 )
> > + {
> > + if ( hypercall_preempt_check() )
> > + {
> > + rc = -ERESTART;
>
> You use a negative return value here, but ...
>
> > + break;
> > + }
> > + preempt_count = 0;
> > + }
> > + }
> > +
> > + if ( rc )
> > + fr->opaque = list_position;
> > + else
> > + rc = copy_settings(cd, d);
> > +
> > + domain_unpause(cd);
> > + return rc;
> > +}
> > +
> > int mem_sharing_memop(XEN_GUEST_HANDLE_PARAM(xen_mem_sharing_op_t) arg)
> > {
> > int rc;
> > @@ -2066,6 +2151,36 @@ int mem_sharing_memop(XEN_GUEST_HANDLE_PARAM(xen_mem_sharing_op_t) arg)
> > break;
> > }
> >
> > + case XENMEM_sharing_op_fork_reset:
> > + {
> > + struct domain *pd;
> > +
> > + rc = -ENOSYS;
> > + if ( !mem_sharing_is_fork(d) )
> > + goto out;
> > +
> > + rc = rcu_lock_live_remote_domain_by_id(d->parent->domain_id, &pd);
> > + if ( rc )
> > + goto out;
> > +
> > + rc = fork_reset(pd, d, &mso.u.fork_reset);
> > +
> > + rcu_unlock_domain(pd);
> > +
> > + if ( rc > 0 )
>
> ... you check for a positive value here. I didn't get around to
> look at earlier versions, so I can only guess the -ERESTART above
> was changed to later on.
I'm dropping continuation for the next revision so this no longer matters.
Thanks,
Tamas
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel
^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [Xen-devel] [PATCH v11 2/3] x86/mem_sharing: reset a fork
2020-03-18 14:00 ` Tamas K Lengyel
@ 2020-03-18 14:12 ` Jan Beulich
2020-03-18 15:13 ` Tamas K Lengyel
0 siblings, 1 reply; 13+ messages in thread
From: Jan Beulich @ 2020-03-18 14:12 UTC (permalink / raw)
To: Tamas K Lengyel
Cc: Julien Grall, Stefano Stabellini, Tamas K Lengyel, Wei Liu,
Konrad Rzeszutek Wilk, Andrew Cooper, Ian Jackson, George Dunlap,
Xen-devel, Roger Pau Monné
On 18.03.2020 15:00, Tamas K Lengyel wrote:
> On Wed, Mar 18, 2020 at 5:36 AM Jan Beulich <jbeulich@suse.com> wrote:
>> On 28.02.2020 19:40, Tamas K Lengyel wrote:
>>> + mfn = page_to_mfn(page);
>>> + if ( mfn_valid(mfn) )
>>
>> All pages on a domain's list should have a valid MFN - what are you
>> trying to protect against here?
>
> I saw no documentation stating what you stated above. If that's the
> case it can be dropped.
Only pages coming from the allocator (or, in some special cases,
otherwise valid) get put on a domain's page list. By coming from
the allocator their MFNs are impicitly valid.
>>> + mfn = __get_gfn_type_access(p2m, gfn_x(gfn), &p2mt, &p2ma,
>>> + 0, NULL, false);
>>> +
>>> + if ( p2m_is_ram(p2mt) && !p2m_is_shared(p2mt) )
>>> + {
>>> + /* take an extra reference, must work for a shared page */
>>
>> The comment (and also the next one further down) looks contradictory
>> to the if() immediately ahead, at least to me. Could you clarify the
>> situation, please?
>
> I don't understand your question. The comment explains exactly what
> happens. Taking an extra reference must work. If it didn't, trigger an
> ASSERT_UNREACHABLE. Which part is confusing?
The comment says "a shared page" whereas the condition includes
"!p2m_is_shared(p2mt)", which I understand to mean a page which is
not shared.
As to you dropping continuations again - please have at least a
bold comment clarifying that their addition is a requirement for
the code to ever reach "supported" status. (Any other obvious but
intentional omissions could also be named there.)
Jan
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel
^ permalink raw reply [flat|nested] 13+ messages in thread
* Re: [Xen-devel] [PATCH v11 2/3] x86/mem_sharing: reset a fork
2020-03-18 14:12 ` Jan Beulich
@ 2020-03-18 15:13 ` Tamas K Lengyel
0 siblings, 0 replies; 13+ messages in thread
From: Tamas K Lengyel @ 2020-03-18 15:13 UTC (permalink / raw)
To: Jan Beulich
Cc: Julien Grall, Stefano Stabellini, Tamas K Lengyel, Wei Liu,
Konrad Rzeszutek Wilk, Andrew Cooper, Ian Jackson, George Dunlap,
Xen-devel, Roger Pau Monné
On Wed, Mar 18, 2020 at 8:13 AM Jan Beulich <jbeulich@suse.com> wrote:
>
> On 18.03.2020 15:00, Tamas K Lengyel wrote:
> > On Wed, Mar 18, 2020 at 5:36 AM Jan Beulich <jbeulich@suse.com> wrote:
> >> On 28.02.2020 19:40, Tamas K Lengyel wrote:
> >>> + mfn = page_to_mfn(page);
> >>> + if ( mfn_valid(mfn) )
> >>
> >> All pages on a domain's list should have a valid MFN - what are you
> >> trying to protect against here?
> >
> > I saw no documentation stating what you stated above. If that's the
> > case it can be dropped.
>
> Only pages coming from the allocator (or, in some special cases,
> otherwise valid) get put on a domain's page list. By coming from
> the allocator their MFNs are impicitly valid.
>
> >>> + mfn = __get_gfn_type_access(p2m, gfn_x(gfn), &p2mt, &p2ma,
> >>> + 0, NULL, false);
> >>> +
> >>> + if ( p2m_is_ram(p2mt) && !p2m_is_shared(p2mt) )
> >>> + {
> >>> + /* take an extra reference, must work for a shared page */
> >>
> >> The comment (and also the next one further down) looks contradictory
> >> to the if() immediately ahead, at least to me. Could you clarify the
> >> situation, please?
> >
> > I don't understand your question. The comment explains exactly what
> > happens. Taking an extra reference must work. If it didn't, trigger an
> > ASSERT_UNREACHABLE. Which part is confusing?
>
> The comment says "a shared page" whereas the condition includes
> "!p2m_is_shared(p2mt)", which I understand to mean a page which is
> not shared.
>
> As to you dropping continuations again - please have at least a
> bold comment clarifying that their addition is a requirement for
> the code to ever reach "supported" status. (Any other obvious but
> intentional omissions could also be named there.)
>
Sure, I had that comment in place before. There are no plans to have
this code be "supported", we are fine with it being experimental.
Tamas
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel
^ permalink raw reply [flat|nested] 13+ messages in thread
end of thread, other threads:[~2020-03-18 15:15 UTC | newest]
Thread overview: 13+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-02-28 18:40 [Xen-devel] [PATCH v11 0/3] VM forking Tamas K Lengyel
2020-02-28 18:40 ` [Xen-devel] [PATCH v11 1/3] xen/mem_sharing: " Tamas K Lengyel
2020-03-17 15:59 ` Jan Beulich
2020-03-17 16:23 ` Tamas K Lengyel
2020-03-17 16:35 ` Jan Beulich
2020-03-17 16:58 ` Tamas K Lengyel
2020-02-28 18:40 ` [Xen-devel] [PATCH v11 2/3] x86/mem_sharing: reset a fork Tamas K Lengyel
2020-03-18 11:36 ` Jan Beulich
2020-03-18 14:00 ` Tamas K Lengyel
2020-03-18 14:12 ` Jan Beulich
2020-03-18 15:13 ` Tamas K Lengyel
2020-02-28 18:40 ` [Xen-devel] [PATCH v11 3/3] xen/tools: VM forking toolstack side Tamas K Lengyel
2020-03-16 13:07 ` [Xen-devel] [PATCH v11 0/3] VM forking Tamas K Lengyel
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).