Re: [PATCH] Update qemu-kvm to allow a larger BIOS image.

[Jordan Justen <jljusten@gmail.com>]

On Wed, Jul 15, 2009 at 8:08 PM, Sheng Yang<sheng@linux.intel.com> wrote:
> On Thursday 16 July 2009 10:58:53 Jordan Justen wrote:
>> On Wed, Jul 15, 2009 at 6:34 PM, Sheng Yang <sheng@linux.intel.com> wrote:
>> > On Thursday 16 July 2009 08:12:15 Jordan Justen wrote:
>> > >
>> > > Motivation for making these changes:
>> > >
>> > > A larger firmware image size allows alternative BIOS images to be
>> > > used with KVM.  Some possible uses are to enable UEFI firmware
>> > > or coreboot firmware.  Additionally, an alternative firmware might
>> > > include a linux kernel+initrd payload, which would require several
>> > > megabytes.
>> >
>> > I think if you update bios to UEFI, the E820 should be represented by
>> > UEFI rather than current bios?
>>
>> Yeah, that is true.  But, that firmware would be separate from the qemu-kvm
>> tree at this time, right?
>
> Yes, so currently from QEmu-kvm side, I think it may not necessary to update,
> for the patches haven't followed up yet...

Of the two patches (1. kvm kernel module, 2. qemu-kvm), I think it
is best if the qemu-kvm change happens first.  Since the qemu-kvm
patch will cause the qemu-kvm bios to add more memory regions
as reserved, the new change to qemu-kvm will be compatible with
both the old and new versions of the kvm kernel module.

>> But, in this patch it is critical that the 'VMX TSS Pages' are moved within
>> qemu-kvm so the conflict with the larger bios.bin is removed.
>
> Well, for we are using a small size bios now, and larger bios would be totally
> another story, I don't think push the modification now to the upstream make
> sense. These modification can go with further patches with UEFI at any time in
> the future.

I am working on this UEFI firmware project which currently supports QEMU:
https://edk2.tianocore.org/OVMF.html

I would like it to also support KVM, and I found that it can already boot the
UEFI shell on KVM if these two patches are applied.

If these patches make some progress, I will update OVMF to reserve the
appropriate memory regions.

> --
> regards
> Yang, Sheng
>
>>
>> > --
>> > regards
>> > Yang, Sheng
>> >
>> > > Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>
>> > > ---
>> > >  kvm/bios/rombios.c        |    8 ++++----
>> > >  kvm/include/x86/asm/vmx.h |    2 +-
>> > >  qemu-kvm-x86.c            |    2 +-
>> > >  3 files changed, 6 insertions(+), 6 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;
>> > >                          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
>> > > diff --git a/kvm/include/x86/asm/vmx.h b/kvm/include/x86/asm/vmx.h
>> > > index df8d4f9..99e2bb9 100644
>> > > --- a/kvm/include/x86/asm/vmx.h
>> > > +++ b/kvm/include/x86/asm/vmx.h
>> > > @@ -403,7 +403,7 @@ enum vmcs_field {
>> > >  #define VMX_EPT_EXECUTABLE_MASK                      0x4ull
>> > >  #define VMX_EPT_IGMT_BIT                     (1ull << 6)
>> > >
>> > > -#define VMX_EPT_IDENTITY_PAGETABLE_ADDR              0xfffbc000ul
>> > > +#define VMX_EPT_IDENTITY_PAGETABLE_ADDR              0xfeffc000ul
>> > >
>> > >
>> > >  #define ASM_VMX_VMCLEAR_RAX       ".byte 0x66, 0x0f, 0xc7, 0x30"
>> > > diff --git a/qemu-kvm-x86.c b/qemu-kvm-x86.c
>> > > index daf60b6..b5306aa 100644
>> > > --- a/qemu-kvm-x86.c
>> > > +++ b/qemu-kvm-x86.c
>> > > @@ -63,7 +63,7 @@ static int kvm_init_tss(kvm_context_t kvm)
>> > >                * this address is 3 pages before the bios, and the bios
>> > > should present * as unavaible memory
>> > >                */
>> > > -             r = kvm_set_tss_addr(kvm, 0xfffbd000);
>> > > +             r = kvm_set_tss_addr(kvm, 0xfeffd000);
>> > >               if (r < 0) {
>> > >                       fprintf(stderr, "kvm_init_tss: unable to set tss
>> > > addr\n"); return r;
>> >
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