[RFC PATCH 0/3] KVM: x86: honor guest memory type

[Chia-I Wu]

Hi,

Host GPU drivers like to give userspace WC mapping.  When the userspace makes
the mapping available to a guest, it also tells the guest to create a WC
mapping.  However, even when the guest kernel picks the correct memory type,
it gets ignored because of VMX_EPT_IPAT_BIT on Intel.

This series adds a new flag to KVM_SET_USER_MEMORY_REGION, which tells the
host kernel to honor the guest memory type for the memslot.  An alternative
fix is for KVM to unconditionally honor the guest memory type (unless it is
MMIO, to avoid MCEs on Intel).  I believe the alternative fix is how things
are on ARM, and probably also how things are on AMD.

I am new to KVM and HW virtualization technologies.  This series is meant as
an RFC.