On 13/02/20 22:30, Chia-I Wu wrote: > 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. > When we tried to do this in the past, we got machine checks everywhere unfortunately due to the same address being mapped with different memory types. Unfortunately I cannot find the entry anymore in bugzilla, but this was not fixed as far as I know. Paolo
