On Wed, 27 May 2020 16:26:46 +0200 Igor Mammedov <imamm...@redhat.com> wrote:
> On Wed, 27 May 2020 15:06:28 +0200 > Paolo Bonzini <pbonz...@redhat.com> wrote: > > > On 27/05/20 14:25, Igor Mammedov wrote: > > >> (2) we loose a gigabyte page. > > > I'm not sure waht exactly we loose in this case. > > > Lets assume we allocating guest 5G of continuous RAM using 1G > > > huge pages, > > > in this case I'd think that on host side MMIO overlay won't > > > affect RAM blob > > > on guest side pagetables will be fragmented due to MMIO holes, > > > but guest still > > > could use huge pages smaller ones in fragmented area and 1G > > > where there is no fragmentation. > > > > Access to the 3G-4G area would not be able to use 1G EPT pages. > Could it use 2Mb pages instead of 1Gb? > Do we really care about 1 gigabyte huge page in microvm intended usecase? > (fast starting VMs for microservices like FaaS, which unlikely would use much > memory to begin with) my interest in having single memory region, is in possibility of drop in conversion to [nv|pc-dimm] later on without breaking ABI. (I'm not sure that we actually need it though) > > But why use 2G split instead of 3G? There's only very little MMIO and > > no PCI hole (including no huge MMCONFIG BAR) on microvm. > > > > Paolo > > > >
