Date: Sat, 14 Dec 2013 09:25:12 +0100 From: =?ISO-8859-1?Q?Roger_Pau_Monn=E9?= <roger.pau@citrix.com> To: Colin Percival <cperciva@freebsd.org>, Mason Loring Bliss <mason@blisses.org>, <freebsd-xen@freebsd.org> Subject: Re: XEN vs XENHVM? Message-ID: <52AC15E8.9050909@citrix.com> In-Reply-To: <52ABC23E.4020408@freebsd.org> References: <20131214022355.GX19296@blisses.org> <52ABC23E.4020408@freebsd.org>
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On 14/12/13 03:28, Colin Percival wrote: > On 12/13/13 18:23, Mason Loring Bliss wrote: >> I was psyched to see that GENERIC kernels in 10 have HVMXEN support by >> default, but then I was left a little confused. >> >> What's the different between a kernel with options XEN and one with options >> HVMXEN? > > The XEN option is for *paravirtualized* Xen -- aka. the original version, > before Intel and AMD added virtualization support into their CPUs. HVM > uses "hardware virtualization", but we also use PV drivers where available. > >> I'd love to be able to run FreeBSD domU systems without having to do >> a custom compile whenever there's an update. I've got a 9.1 system running >> now, using a copy of the XEN config with a couple tweaks, and I see all the >> PV drivers I expect. I'm wondering what's different with XENHVM... Also >> useful would be knowing if there are remaining differences between i386 and >> amd64 as a domU in FreeBSD 10. > > You want to switch to using HVM with PV devices. That should be a simple > tweak to your Xen configuration, and then you'll be able to use a GENERIC > kernel. Just as a note, the support in GENERIC is not only HVM with PV devices, is basically a PV guest inside an HVM container, meaning it also uses PV IPIs and PV timers. The main difference between pure PV and PVHVM is that PV requires a PV MMU implementation in the OS, while PVHVM can use a hardware virtualized MMU (because it's running inside of a HVM container). Roger.
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