Date: Thu, 16 Aug 2018 17:53:36 +0100 From: Allan Jude <allanjude@FreeBSD.org> To: freebsd-virtualization@freebsd.org, "Rodney W. Grimes" <freebsd-rwg@pdx.rh.CN85.dnsmgr.net> Cc: Matt Churchyard <matt.churchyard@userve.net>, "freebsd-virtualization@freebsd.org" <freebsd-virtualization@freebsd.org> Subject: Re: Checking bhyve supported features (sysctls) Message-ID: <BC22EE63-357B-47F5-9121-A73B59633FE9@FreeBSD.org> In-Reply-To: <201808161628.w7GGS52P054505@pdx.rh.CN85.dnsmgr.net> References: <201808161628.w7GGS52P054505@pdx.rh.CN85.dnsmgr.net>
next in thread | previous in thread | raw e-mail | index | archive | help
On August 16, 2018 5:28:05 PM GMT+01:00, "Rodney W=2E Grimes" <freebsd-rwg@= pdx=2Erh=2ECN85=2Ednsmgr=2Enet> wrote: >>=20 >> Text manually wrapped to 80, any broken quoting is my fault - rwg >>=20 >> > > Hello, >> > >=20 >> > > I'm looking for better ways to check for bhyve support / >available >> > > features without trying to scan through dmesg output=2E >> >=20 >> > >Yes, it would be very good to remove that, as it usually tries >> > >to grep a non-existent file /var/run/dmesg=2Eboot that is not >> > >created until after vm_bhyve has been called from >/usr/local/etc/rc=2Ed >> > >when you have things set to autostartup >in /etc/rc=2Econf >> >=20 >> >=20 >> > >=20 >> > > I notice that the following 2 sysctl's appear to be set to 1 as >soon=20 >> > > as the vmm module is loaded >> > >=20 >> > > hw=2Evmm=2Evmx=2Einitialized: 1 >> > > hw=2Evmm=2Evmx=2Ecap=2Eunrestricted_guest: 1 >> > >=20 >> > > Will these be available on both Intel & AMD processors as a way >> > > to determine if the module has loaded successfully and can run >guests? >> > >=20 >> > > I also see the below sysctl related to iommu=2E >> > >=20 >> > > hw=2Evmm=2Eiommu=2Einitialized >> > >=20 >> > > Again, will this be set to 1 as soon as the module is loaded if >> > > iommu is supported, or only when it is used? >> > > There also seems to be a vmm=2Eamdvi=2Eenable sysctl=2E >> > > Would both these need checking or is vmm=2Eiommu enough to >> > > determine support on any processor=2E >> >=20 >> > >Probalby the safest way for a shell script to decide if bhyve is >> > >up and running is to stat /dev/vmm, if that exists then the >modules >> > >have loaded and initialized and bhyve should be ready to process >guests=2E >> >=20 >> > Hmm, I don't get /dev/vmm unless I actually have running guests=2E >>=20 >> I'll investigate that, I was pretty sure that you should get this >> as soon as the vmm=2Eko module is finished initialzing, but you might >> be right in that it takes a first vm to cause its creation=2E >> Confirmed, /dev/vmm does not exist until the first vm >> is created=2E >>=20 >> >=20 >> > >sysctl's mentiond above would be a poor way to make this >determination=2E >> >=20 >> > It would be nice if sysctls were better documented=2E >>=20 >> Agreed=2E >>=20 >> > If vmx=2Einitialized is set once vmm has successfully loaded, I can't >see a better way of checking for bhyve support (assuming it's not Intel >specific)=2E This entry definitely exists and is set to 0 if you load the >module on a non-supported system, and set to 1 as soon as vmm loads on >my Intel test system=2E >>=20 >> Given its undocumented status you would be relying on an >> undocumented feature that could change in either name or >> behavior, and that is not desirable=2E >>=20 >> Let me see if I can come up with something else=2E > >I looked at the code for bhyvectl, bhyveload and >byhve=2E They do not actually try to decide if vmm >is supported or not, they simply process the error >from a vm_create() or vm_open() call and exit >with an error code if they can not handle it >(some of the code can handle a vm_create failure >if infact we are trying to create a vm that >already exists)=2E > >If you want to maintain full compatibility a similiar >stratergy may be in order=2E > >Why is it that vm-bhyve specifically needs to know >if the kernel has vmm support or not? >Cant it just be written to handle the errors returned >if the supported functions do not exist? I think the question vm-bhyve wants to answer is: does the CPU have the re= quired features to run a multicore VM=2E These or similar sysctls do seem to be the correct way to communicate that= support=2E --=20 Allan Jude
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?BC22EE63-357B-47F5-9121-A73B59633FE9>