On Tue, Jul 28, 2009 at 09:51:26AM -0700, Jordan Justen wrote: > On Tue, Jul 28, 2009 at 7:40 AM, Marcelo Tosatti<mtosatti@xxxxxxxxxx> wrote: > > On Sun, Jul 26, 2009 at 05:23:51PM -0700, Jordan Justen wrote: > >> The bios will now reserve more memory via the E820 functions. > >> > >> Note that the standard KVM BIOS will most likely not make use of > >> this expanded BIOS region. This change will synchronize > >> the BIOS INT15-E820 reservations to match other changes that > >> will allow alternate BIOS images to be larger in size. > >> > >> Previously the BIOS reserved: > >> 0xfffbc000-0xfffbcfff - 4KB - EPT identity mapping pages > >> 0xfffbd000-0xfffbffff - 12KB - TSS pages > >> 0xfffc0000-0xffffffff - 256KB - Max bios.bin (usually top 128KB is used) > >> > >> Now the BIOS will reserve: > >> 0xfeffc000-0xfeffcfff - 4KB - EPT identity mapping pages > >> 0xfeffd000-0xfeffffff - 12KB - TSS Pages > >> 0xff000000-0xffffffff - 16MB - Max bios.bin > >> > >> Signed-off-by: Jordan Justen <jordan.l.justen@xxxxxxxxx> > >> --- > >> kvm/bios/rombios.c | 8 ++++---- > >> 1 files changed, 4 insertions(+), 4 deletions(-) > >> > >> diff --git a/kvm/bios/rombios.c b/kvm/bios/rombios.c > >> index 6186199..2d0c153 100644 > >> --- a/kvm/bios/rombios.c > >> +++ b/kvm/bios/rombios.c > >> @@ -4596,14 +4596,14 @@ ASM_END > >> case 5: > >> /* 4 pages before the bios, 3 pages for vmx tss pages, > >> * the other page for EPT real mode pagetable */ > >> - set_e820_range(ES, regs.u.r16.di, 0xfffbc000L, > >> - 0xfffc0000L, 0, 0, 2); > >> + set_e820_range(ES, regs.u.r16.di, 0xfeffc000L, > >> + 0xff000000L, 0, 0, 2); > >> regs.u.r32.ebx = 6; > > > > So if you use an older kernel, and the kvm_set_identity_map_addr fails, > > you get the e820 entry wrong right? Perhaps you should use the hw/fw_cfg.c > > interface to communicate with the BIOS. > > > > If you use this newer BIOS code with the older kernel code, the > expanded E820 BIOS region of the will cover the older region where the > EPT page tables are at. So, the OS will still know to keep away from > this region. > > There should be no impact if someone uses a newer qemu-kvm with and > older kvm module. Since the normal legacy kvm BIOS is only 128KB, it > will be able to boot fine. (There will be no conflict with reserving > the memory region for the small BIOS.) If a bios.bin is used that is > larger than 256KB, then it will fail in the same way as today, since > there will be a conflict while trying to reserve the 0xfffbc000 - > 0xfffbcfff region. > > The only difference in this case would be that E820 reserves a larger > chunk of memory space, but I can't see how this could cause a problem. > (Previously kvm-bios would reserve 256KB while the BIOS was normally > only 128KB in size.) Indeed. Looks good to me. > > > > >> break; > >> case 6: > >> - /* 256KB BIOS area at the end of 4 GB */ > >> + /* 16MB BIOS area at the end of 4 GB */ > >> set_e820_range(ES, regs.u.r16.di, > >> - 0xfffc0000L, 0x00000000L ,0, 0, 2); > >> + 0xff000000L, 0x00000000L ,0, 0, 2); > >> if (extra_highbits_memory_size || extra_lowbits_memory_size) > >> regs.u.r32.ebx = 7; > >> else > >> -- > >> 1.6.0.4 > >> > >> -- > >> To unsubscribe from this list: send the line "unsubscribe kvm" in > >> the body of a message to majordomo@xxxxxxxxxxxxxxx > >> More majordomo info at http://vger.kernel.org/majordomo-info.html > > -- > > To unsubscribe from this list: send the line "unsubscribe kvm" in > > the body of a message to majordomo@xxxxxxxxxxxxxxx > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
