Re: [PATCH 3/3] Update VMX_EPT_IDENTITY_PAGETABLE_ADDR to synchronize with kernel code.

Marcelo Tosatti
2009-07-16T18:18:30Z

On Thu, Jul 16, 2009 at 11:02:22AM -0700, Jordan Justen wrote:
> Although VMX_EPT_IDENTITY_PAGETABLE_ADDR does not appear to be used within
> qemu-kvm, this change mirrors a similar change in the kernel kvm code.
>
> The purpose is to move the KVM 'EPT Identity Pages' from:
> 0xfffbc000-0xfffbcfff
> to:
> 0xfeffc000-0xfeffcfff
>
> The step is required to free up the 0xff000000-0xffffffff (16MB) range
> for use with bios.bin.
>
> The KVM kernel change depends upon a change to kvm/bios/rombios.c so the bios
> INT15-E820 function will properly reserve the new location.
>
> Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>
> ---
> kvm/include/x86/asm/vmx.h | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
>
> 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

Won't this conflict with an older BIOS? (the e820 reserved entry on
older qemu-kvm+bios will not cover the EPT identity table on kernels
with this patch).

Perhaps add a new ioctl (similar to the tss one) to so userspace can set
the address?

>
>
> #define ASM_VMX_VMCLEAR_RAX ".byte 0x66, 0x0f, 0xc7, 0x30"
> --
> 1.6.0.4
>
> --
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