Re: [libvirt] [PATCH v2 1/3] qemu: Extract logic to determine the mlock limit size for VFIO

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.