On 11/09/2015 07:50 AM, Peter Krempa wrote:

New function qemuDomainGetMlockLimitBytes will now handle the calculation so that it unifies the logic to one place and allows later reuse. --- src/qemu/qemu_command.c | 18 ++---------------- src/qemu/qemu_domain.c | 27 +++++++++++++++++++++++++++ src/qemu/qemu_domain.h | 2 ++ src/qemu/qemu_hotplug.c | 17 ++--------------- 4 files changed, 33 insertions(+), 31 deletions(-)

diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c index 8824541..9acf8e4 100644 --- a/src/qemu/qemu_command.c +++ b/src/qemu/qemu_command.c @@ -11447,22 +11447,8 @@ qemuBuildCommandLine(virConnectPtr conn, goto error; }

- if (mlock) { - unsigned long long memKB; - - /* VFIO requires all of the guest's memory to be - * locked resident, plus some amount for IO - * space. Alex Williamson suggested adding 1GiB for IO - * space just to be safe (some finer tuning might be - * nice, though). - */ - if (virMemoryLimitIsSet(def->mem.hard_limit)) - memKB = def->mem.hard_limit; - else - memKB = virDomainDefGetMemoryActual(def) + 1024 * 1024; - - virCommandSetMaxMemLock(cmd, memKB * 1024); - } + if (mlock) + virCommandSetMaxMemLock(cmd, qemuDomainGetMlockLimitBytes(def));

if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_MSG_TIMESTAMP) && cfg->logTimestamp) diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c index 890d8ed..a06624e 100644 --- a/src/qemu/qemu_domain.c +++ b/src/qemu/qemu_domain.c @@ -3616,3 +3616,30 @@ qemuDomainUpdateCurrentMemorySize(virQEMUDriverPtr driver,

return 0; } + + +/** + * qemuDomainGetMlockLimitBytes: + * + * @def: domain definition + * + * Returns the size of the memory in bytes that needs to be set as + * RLIMIT_MEMLOCK for purpose of VFIO device passthrough. In cases where + * mem.hard_limit is set, the value is preferred,otherwise the value may depend + * on the device or architecture.

How about? Returns the size of memory in bytes to allow a process (domain) to be locked into RAM (e.g setrlimit RLIMIT_MEMLOCK). If a mem.hard_limit is set, then that value is preferred; otherwise, the value returned may depend upon the architecture or devices present, such as a VFIO passthrough device. ACK - John

+ */ +unsigned long long +qemuDomainGetMlockLimitBytes(virDomainDefPtr def) +{ + unsigned long long memKB; + + /* VFIO requires all of the guest's memory to be locked resident, plus some + * amount for IO space. Alex Williamson suggested adding 1GiB for IO space + * just to be safe (some finer tuning might be nice, though). */ + if (virMemoryLimitIsSet(def->mem.hard_limit)) + memKB = def->mem.hard_limit; + else + memKB = virDomainDefGetMemoryActual(def) + 1024 * 1024; + + return memKB << 10; +} diff --git a/src/qemu/qemu_domain.h b/src/qemu/qemu_domain.h index 64cd7e1..e34370b 100644 --- a/src/qemu/qemu_domain.h +++ b/src/qemu/qemu_domain.h @@ -482,4 +482,6 @@ bool qemuDomainMachineIsS390CCW(const virDomainDef *def); int qemuDomainUpdateCurrentMemorySize(virQEMUDriverPtr driver, virDomainObjPtr vm);

+unsigned long long qemuDomainGetMlockLimitBytes(virDomainDefPtr def); + #endif /* __QEMU_DOMAIN_H__ */ diff --git a/src/qemu/qemu_hotplug.c b/src/qemu/qemu_hotplug.c index 8f2fda9..e7fc036 100644 --- a/src/qemu/qemu_hotplug.c +++ b/src/qemu/qemu_hotplug.c @@ -1254,7 +1254,6 @@ qemuDomainAttachHostPCIDevice(virQEMUDriverPtr driver, bool teardowncgroup = false; bool teardownlabel = false; int backend; - unsigned long long memKB; virQEMUDriverConfigPtr cfg = virQEMUDriverGetConfig(driver); unsigned int flags = 0;

@@ -1279,20 +1278,8 @@ qemuDomainAttachHostPCIDevice(virQEMUDriverPtr driver, goto error; }

- /* VFIO requires all of the guest's memory to be locked - * resident (plus an additional 1GiB to cover IO space). During - * hotplug, the guest's memory may already be locked, but it - * doesn't hurt to "change" the limit to the same value. - * NB: the domain's memory tuning parameters are stored as - * Kibibytes, but virProcessSetMaxMemLock expects the value in - * bytes. - */ - if (virMemoryLimitIsSet(vm->def->mem.hard_limit)) - memKB = vm->def->mem.hard_limit; - else - memKB = virDomainDefGetMemoryActual(vm->def) + (1024 * 1024); - - virProcessSetMaxMemLock(vm->pid, memKB * 1024); + /* setup memory locking limits, that are necessary for VFIO */ + virProcessSetMaxMemLock(vm->pid, qemuDomainGetMlockLimitBytes(vm->def)); break;

default:

On Mon, Nov 09, 2015 at 01:09:59PM -0500, John Ferlan wrote:

On 11/09/2015 07:50 AM, Peter Krempa wrote:

...

New function qemuDomainGetMlockLimitBytes will now handle the calculation so that it unifies the logic to one place and allows later reuse. --- src/qemu/qemu_command.c | 18 ++---------------- src/qemu/qemu_domain.c | 27 +++++++++++++++++++++++++++ src/qemu/qemu_domain.h | 2 ++ src/qemu/qemu_hotplug.c | 17 ++--------------- 4 files changed, 33 insertions(+), 31 deletions(-)

diff --git a/src/qemu/qemu_command.c b/src/qemu/qemu_command.c index 8824541..9acf8e4 100644 --- a/src/qemu/qemu_command.c +++ b/src/qemu/qemu_command.c @@ -11447,22 +11447,8 @@ qemuBuildCommandLine(virConnectPtr conn, goto error; }

- if (mlock) { - unsigned long long memKB; - - /* VFIO requires all of the guest's memory to be - * locked resident, plus some amount for IO - * space. Alex Williamson suggested adding 1GiB for IO - * space just to be safe (some finer tuning might be - * nice, though). - */ - if (virMemoryLimitIsSet(def->mem.hard_limit)) - memKB = def->mem.hard_limit; - else - memKB = virDomainDefGetMemoryActual(def) + 1024 * 1024; - - virCommandSetMaxMemLock(cmd, memKB * 1024); - } + if (mlock) + virCommandSetMaxMemLock(cmd, qemuDomainGetMlockLimitBytes(def));

if (virQEMUCapsGet(qemuCaps, QEMU_CAPS_MSG_TIMESTAMP) && cfg->logTimestamp) diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c index 890d8ed..a06624e 100644 --- a/src/qemu/qemu_domain.c +++ b/src/qemu/qemu_domain.c @@ -3616,3 +3616,30 @@ qemuDomainUpdateCurrentMemorySize(virQEMUDriverPtr driver,

return 0; } + + +/** + * qemuDomainGetMlockLimitBytes: + * + * @def: domain definition + * + * Returns the size of the memory in bytes that needs to be set as + * RLIMIT_MEMLOCK for purpose of VFIO device passthrough. In cases where + * mem.hard_limit is set, the value is preferred,otherwise the value may depend + * on the device or architecture.

How about?

Returns the size of memory in bytes to allow a process (domain) to be locked into RAM (e.g setrlimit RLIMIT_MEMLOCK).

While this sentence is inaccurate,

If a mem.hard_limit is set, then that value is preferred; otherwise, the value returned may depend upon the architecture or devices present, such as a VFIO passthrough device.

this one looks better than the original and it has proper spacing after the comma. ACK with the second sentence used. Jan

On 11/09/2015 07:50 AM, Peter Krempa wrote:

If mlock is required either due to use of VFIO hostdevs or due to the fact that it's enabled it needs to be tweaked prior to adding new memory or after removing a module. Add a helper to determine when it's necessary and reuse it both on hotplug and hotunplug.

Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1273491 --- src/qemu/qemu_domain.c | 27 +++++++++++++++++++++++++++ src/qemu/qemu_domain.h | 1 + src/qemu/qemu_hotplug.c | 32 +++++++++++++++++++++++++++++--- 3 files changed, 57 insertions(+), 3 deletions(-)

FWIW: My comments in v1 when someone sets hard_limit, doesn't have VFIO, starts with some memory device objects and expectations. I had a slight memory lapse as to what qemuDomainGetMlockLimitBytes returns. :-) Now that I have recovered from that page fault, when a hard_limit is set, regardless of what memory is added the value used in the call to virProcessSetMaxMemLock won't change... Still we could/should document in formatdomain that memory devices present or added would need be accounted for when considering what hard_limit is set.

diff --git a/src/qemu/qemu_domain.c b/src/qemu/qemu_domain.c index a06624e..6f95f76 100644 --- a/src/qemu/qemu_domain.c +++ b/src/qemu/qemu_domain.c @@ -3643,3 +3643,30 @@ qemuDomainGetMlockLimitBytes(virDomainDefPtr def)

return memKB << 10; } + + +/** + * @def: domain definition + * + * Returns ture if the locked memory limit needs to be set or updated due to + * configuration or passthrough devices. + * */ +bool +qemuDomainRequiresMlock(virDomainDefPtr def) +{ + size_t i; + + if (def->mem.locked) + return true; + + for (i = 0; i < def->nhostdevs; i++) { + virDomainHostdevDefPtr dev = def->hostdevs[i]; + + if (dev->mode == VIR_DOMAIN_HOSTDEV_MODE_SUBSYS && + dev->source.subsys.type == VIR_DOMAIN_HOSTDEV_SUBSYS_TYPE_PCI && + dev->source.subsys.u.pci.backend == VIR_DOMAIN_HOSTDEV_PCI_BACKEND_VFIO) + return true; + } + + return false; +} diff --git a/src/qemu/qemu_domain.h b/src/qemu/qemu_domain.h index e34370b..4be998c 100644 --- a/src/qemu/qemu_domain.h +++ b/src/qemu/qemu_domain.h @@ -483,5 +483,6 @@ int qemuDomainUpdateCurrentMemorySize(virQEMUDriverPtr driver, virDomainObjPtr vm);

unsigned long long qemuDomainGetMlockLimitBytes(virDomainDefPtr def); +bool qemuDomainRequiresMlock(virDomainDefPtr def);

#endif /* __QEMU_DOMAIN_H__ */ diff --git a/src/qemu/qemu_hotplug.c b/src/qemu/qemu_hotplug.c index e7fc036..1e7a653 100644 --- a/src/qemu/qemu_hotplug.c +++ b/src/qemu/qemu_hotplug.c @@ -1768,6 +1768,7 @@ qemuDomainAttachMemory(virQEMUDriverPtr driver, virJSONValuePtr props = NULL; virObjectEventPtr event; bool fix_balloon = false; + bool mlock = false; int id; int ret = -1;

@@ -1802,16 +1803,25 @@ qemuDomainAttachMemory(virQEMUDriverPtr driver, goto cleanup; }

+ mlock = qemuDomainRequiresMlock(vm->def); + + if (mlock && + virProcessSetMaxMemLock(vm->pid, + qemuDomainGetMlockLimitBytes(vm->def)) < 0) { + mlock = false;

Coverity found a need for: virJSONValueFree(props); ACK - with the adjustment John BTW: If you think it matters - if we got the LimitBytes before inserting vm->mem to the domain def, then we could know whether it changed and whether we needed to Set it here and the error path. One would like to believe an initial setting to hard_limit (such as 4G) wouldn't have a failure if someone passed 4G again...

+ goto removedef; + } + qemuDomainObjEnterMonitor(driver, vm); if (qemuMonitorAddObject(priv->mon, backendType, objalias, props) < 0) - goto removedef; + goto exit_monitor;

if (qemuMonitorAddDevice(priv->mon, devstr) < 0) { virErrorPtr err = virSaveLastError(); ignore_value(qemuMonitorDelObject(priv->mon, objalias)); virSetError(err); virFreeError(err); - goto removedef; + goto exit_monitor; }

if (qemuDomainObjExitMonitor(driver, vm) < 0) { @@ -1845,17 +1855,27 @@ qemuDomainAttachMemory(virQEMUDriverPtr driver, virDomainMemoryDefFree(mem); return ret;

- removedef: + exit_monitor: if (qemuDomainObjExitMonitor(driver, vm) < 0) { mem = NULL; goto audit; }

+ removedef: if ((id = virDomainMemoryFindByDef(vm->def, mem)) >= 0) mem = virDomainMemoryRemove(vm->def, id); else mem = NULL;

+ /* reset the mlock limit */ + if (mlock) { + virErrorPtr err = virSaveLastError(); + ignore_value(virProcessSetMaxMemLock(vm->pid, + qemuDomainGetMlockLimitBytes(vm->def))); + virSetError(err); + virFreeError(err); + } + goto audit; }

@@ -2947,6 +2967,12 @@ qemuDomainRemoveMemoryDevice(virQEMUDriverPtr driver, virDomainMemoryRemove(vm->def, idx);

virDomainMemoryDefFree(mem); + + /* decrease the mlock limit after memory unplug if necessary */ + if (qemuDomainRequiresMlock(vm->def)) + ignore_value(virProcessSetMaxMemLock(vm->pid, + qemuDomainGetMlockLimitBytes(vm->def))); + return 0; }