Extend make_spte to mask in and out bits depending on MBEC enablement.
Note: For the RFC/v1 series, I've added several 'For Review' items that
may require a bit deeper inspection, as well as some long winded
comments/annotations. These will be cleaned up for the next iteration
of the series after initial review.
Signed-off-by: Jon Kohler <jon@xxxxxxxxxxx>
Co-developed-by: Sergey Dyasli <sergey.dyasli@xxxxxxxxxxx>
Signed-off-by: Sergey Dyasli <sergey.dyasli@xxxxxxxxxxx>
---
arch/x86/kvm/mmu/paging_tmpl.h | 3 +++
arch/x86/kvm/mmu/spte.c | 30 ++++++++++++++++++++++++++----
2 files changed, 29 insertions(+), 4 deletions(-)
diff --git a/arch/x86/kvm/mmu/paging_tmpl.h b/arch/x86/kvm/mmu/paging_tmpl.h
index a3a5cacda614..7675239f2dd1 100644
--- a/arch/x86/kvm/mmu/paging_tmpl.h
+++ b/arch/x86/kvm/mmu/paging_tmpl.h
@@ -840,6 +840,9 @@ static int FNAME(page_fault)(struct kvm_vcpu *vcpu, struct kvm_page_fault *fault
* then we should prevent the kernel from executing it
* if SMEP is enabled.
*/
+ // FOR REVIEW:
+ // ACC_USER_EXEC_MASK seems not necessary to add here since
+ // SMEP is for kernel-only.
if (is_cr4_smep(vcpu->arch.mmu))
walker.pte_access &= ~ACC_EXEC_MASK;
}
diff --git a/arch/x86/kvm/mmu/spte.c b/arch/x86/kvm/mmu/spte.c
index 6f4994b3e6d0..89bdae3f9ada 100644
--- a/arch/x86/kvm/mmu/spte.c
+++ b/arch/x86/kvm/mmu/spte.c
@@ -178,6 +178,9 @@ bool make_spte(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
else if (kvm_mmu_page_ad_need_write_protect(sp))
spte |= SPTE_TDP_AD_WRPROT_ONLY;
+ // For LKML Review:
+ // In MBEC case, you can have exec only and also bit 10
+ // set for user exec only. Do we need to cater for that here?
spte |= shadow_present_mask;
if (!prefetch)
spte |= spte_shadow_accessed_mask(spte);
@@ -197,12 +200,31 @@ bool make_spte(struct kvm_vcpu *vcpu, struct kvm_mmu_page *sp,
if (level > PG_LEVEL_4K && (pte_access & ACC_EXEC_MASK) &&
is_nx_huge_page_enabled(vcpu->kvm)) {
pte_access &= ~ACC_EXEC_MASK;
+ if (vcpu->arch.pt_guest_exec_control)
+ pte_access &= ~ACC_USER_EXEC_MASK;
}
- if (pte_access & ACC_EXEC_MASK)
- spte |= shadow_x_mask;
- else
- spte |= shadow_nx_mask;
+ // For LKML Review:
+ // We could probably optimize the logic here, but typing it out
+ // long hand for now to make it clear how we're changing the control
+ // flow to support MBEC.
+ if (!vcpu->arch.pt_guest_exec_control) { // non-mbec logic
+ if (pte_access & ACC_EXEC_MASK)
+ spte |= shadow_x_mask;
+ else
+ spte |= shadow_nx_mask;
+ } else { // mbec logic
+ if (pte_access & ACC_EXEC_MASK) { /* mbec: kernel exec */
+ if (pte_access & ACC_USER_EXEC_MASK)
+ spte |= shadow_x_mask | shadow_ux_mask; // KMX = 1, UMX = 1
+ else
+ spte |= shadow_x_mask; // KMX = 1, UMX = 0
+ } else if (pte_access & ACC_USER_EXEC_MASK) { /* mbec: user exec, no kernel exec */
+ spte |= shadow_ux_mask; // KMX = 0, UMX = 1
+ } else { /* mbec: nx */
+ spte |= shadow_nx_mask; // KMX = 0, UMX = 0
+ }
+ }
if (pte_access & ACC_USER_MASK)
spte |= shadow_user_mask;
--
2.43.0
