On Sat, 24 Feb 2018 03:11:30 +0000 "Tan, Jianfeng" <jianfeng....@intel.com> wrote:
> > -----Original Message----- > > From: Tan, Jianfeng > > Sent: Saturday, February 24, 2018 11:08 AM > > To: 'Igor Mammedov' > > Cc: Paolo Bonzini; Jason Wang; Maxime Coquelin; qemu-devel@nongnu.org; > > Michael S . Tsirkin > > Subject: RE: [Qemu-devel] [RFC] exec: eliminate ram naming issue as > > migration > > > > Hi Igor and all, > > > > > -----Original Message----- > > > From: Igor Mammedov [mailto:imamm...@redhat.com] > > > Sent: Thursday, February 8, 2018 7:30 PM > > > To: Tan, Jianfeng > > > Cc: Paolo Bonzini; Jason Wang; Maxime Coquelin; qemu- > > de...@nongnu.org; > > > Michael S . Tsirkin > > > Subject: Re: [Qemu-devel] [RFC] exec: eliminate ram naming issue as > > > migration > > > > > [...] > > > > > It could be solved by adding memdev option to machine, > > > > > which would allow to specify backend object. And then on > > > > > top make -mem-path alias new option to clean thing up. > > > > > > > > Do you mean? > > > > > > > > src vm: -m xG > > > > dst vm: -m xG,memdev=pc.ram -object memory-backend- > > file,id=pc.ram,size=xG,mem-path=xxx,share=on ... > > > Yep, I've meant something like it > > > > > > src vm: -m xG,memdev=SHARED_RAM -object memory-backend- > > file,id=SHARED_RAM,size=xG,mem-path=xxx,share=on > > > dst vm: -m xG,memdev=SHARED_RAM -object memory-backend- > > file,id=SHARED_RAM,size=xG,mem-path=xxx,share=on > > > > After a second thought, I find adding a backend for nonnuma pc RAM is > > roundabout way. > > > > And we actually have an existing way to add a file-backed RAM: commit > > c902760fb25f ("Add option to use file backed guest memory"). Basically, this > > commit adds two options, --mem-path and --mem-prealloc, without specify > > a backend explicitly. > > > > So how about just adding a new option --mem-share to decide if that's a > > private memory or shared memory? That seems much straightforward way Above options are legacy (which we can't remove for compat reasons), their replacement is 'memory-backend-file' backend which has all of the above including 'share' property. So just add 'memdev' property to machine and reuse memory-backend-file with it instead of duplicating functionality in the legacy code. > > to me; after this change we can migrate like: > > > > src vm: -m xG > > dst vm: -m xG --mem-path xxx --mem-share Even though it might work for now, that's still invalid configuration for migration, src side must include the same "--mem-path xxx --mem-share" options as dst. It'd be better to fix management application to start QEMU properly on SRC side. > Attach the patch FYI. Look forward to your thoughts. > > diff --git a/include/sysemu/sysemu.h b/include/sysemu/sysemu.h > index 31612ca..5eaf367 100644 > --- a/include/sysemu/sysemu.h > +++ b/include/sysemu/sysemu.h > @@ -127,6 +127,7 @@ extern bool enable_mlock; > extern uint8_t qemu_extra_params_fw[2]; > extern QEMUClockType rtc_clock; > extern const char *mem_path; > +extern int mem_share; > extern int mem_prealloc; > > #define MAX_NODES 128 > diff --git a/numa.c b/numa.c > index 7b9c33a..322289f 100644 > --- a/numa.c > +++ b/numa.c > @@ -456,7 +456,7 @@ static void allocate_system_memory_nonnuma(MemoryRegion > *mr, Object *owner, > if (mem_path) { > #ifdef __linux__ > Error *err = NULL; > - memory_region_init_ram_from_file(mr, owner, name, ram_size, false, > + memory_region_init_ram_from_file(mr, owner, name, ram_size, > mem_share, > mem_path, &err); > if (err) { > error_report_err(err); > diff --git a/qemu-options.hx b/qemu-options.hx > index 678181c..c968c53 100644 > --- a/qemu-options.hx > +++ b/qemu-options.hx > @@ -389,6 +389,15 @@ STEXI > Allocate guest RAM from a temporarily created file in @var{path}. > ETEXI > > +DEF("mem-share", 0, QEMU_OPTION_memshare, > + "-mem-share make guest memory shareable (use with -mem-path)\n", > + QEMU_ARCH_ALL) > +STEXI > +@item -mem-share > +@findex -mem-share > +Make file-backed guest RAM shareable when using -mem-path. > +ETEXI > + > DEF("mem-prealloc", 0, QEMU_OPTION_mem_prealloc, > "-mem-prealloc preallocate guest memory (use with -mem-path)\n", > QEMU_ARCH_ALL) > diff --git a/vl.c b/vl.c > index 444b750..0ff06c2 100644 > --- a/vl.c > +++ b/vl.c > @@ -140,6 +140,7 @@ int display_opengl; > const char* keyboard_layout = NULL; > ram_addr_t ram_size; > const char *mem_path = NULL; > +int mem_share = 0; > int mem_prealloc = 0; /* force preallocation of physical target memory */ > bool enable_mlock = false; > int nb_nics; > @@ -3395,6 +3396,9 @@ int main(int argc, char **argv, char **envp) > case QEMU_OPTION_mempath: > mem_path = optarg; > break; > + case QEMU_OPTION_memshare: > + mem_share = 1; > + break; > case QEMU_OPTION_mem_prealloc: > mem_prealloc = 1; > break;
