On 11/18/21 18:43, Ben Gardon wrote:
Aha! The dependency on @vcpu can be avoided without having to take a flag from
the caller. The shadow page has everything we need. The check is really "is this
a page for L2 EPT". The kvm_x86_ops.cpu_dirty_log_size gets us the EPT part, and
kvm_mmu_page.guest_mode gets us the L2 part.
Haha that's way cleaner than what I was doing! Seems like an obvious
solution in retrospect. I'll include this in the next version of the
series I send out unless Paolo beats me and just merges it directly.
Happy to give this my reviewed-by.
Yeah, I am including the early cleanup parts because it makes no sense
to hold off on them; and Sean's patch qualifies as well.
I can't blame you for not remembering role.guest_mode. Jim added it for
a decidedly niche reason:
commit 1313cc2bd8f6568dd8801feef446afbe43e6d313
Author: Jim Mattson <jmattson@xxxxxxxxxx>
Date: Wed May 9 17:02:04 2018 -0400
kvm: mmu: Add guest_mode to kvm_mmu_page_role
L1 and L2 need to have disjoint mappings, so that L1's APIC access
page (under VMX) can be omitted from L2's mappings.
Signed-off-by: Jim Mattson <jmattson@xxxxxxxxxx>
Signed-off-by: Krish Sadhukhan <krish.sadhukhan@xxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
though it's actually gotten a lot more important than just that:
commit 992edeaefed682511bd173dabd2f54b1ce5387df
Author: Liran Alon <liran.alon@xxxxxxxxxx>
Date: Wed Nov 20 14:24:52 2019 +0200
KVM: nVMX: Assume TLB entries of L1 and L2 are tagged differently if L0 use EPT
Since commit 1313cc2bd8f6 ("kvm: mmu: Add guest_mode to kvm_mmu_page_role"),
guest_mode was added to mmu-role and therefore if L0 use EPT, it will
always run L1 and L2 with different EPTP. i.e. EPTP01!=EPTP02.
Because TLB entries are tagged with EP4TA, KVM can assume
TLB entries populated while running L2 are tagged differently
than TLB entries populated while running L1.
Paolo
