On 31.07.2020 14:39, Paul Durrant wrote:
> From: Paul Durrant <pdurr...@amazon.com>
>
> Re-factor the code to take advantage of the fact that the APIC access page is
> a 'special' page.
Hmm, that's going quite as far as I was thinking to go: In
particular, you leave in place the set_mmio_p2m_entry() use
in vmx_alloc_vlapic_mapping(). With that replaced, the
re-ordering in epte_get_entry_emt() that you do shouldn't
be necessary; you'd simple drop the checking of the
specific MFN. However, ...
> --- a/xen/arch/x86/hvm/mtrr.c
> +++ b/xen/arch/x86/hvm/mtrr.c
> @@ -814,29 +814,22 @@ int epte_get_entry_emt(struct domain *d, unsigned long
> gfn, mfn_t mfn,
> return -1;
> }
>
> - if ( direct_mmio )
> - {
> - if ( (mfn_x(mfn) ^ mfn_x(d->arch.hvm.vmx.apic_access_mfn)) >> order )
> - return MTRR_TYPE_UNCACHABLE;
> - if ( order )
> - return -1;
... this part of the logic wants retaining, I think, i.e.
reporting back to the guest that the mapping needs splitting.
I'm afraid I have to withdraw my R-b on patch 1 for this
reason, as the check needs to be added there already.
Jan
