From: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
Add GPA limit check to kvm_arch_vcpu_pre_fault_memory() with guest
maxphyaddr and kvm_mmu_max_gfn().
The KVM page fault handler decides which level of TDP to use, 4-level TDP
or 5-level TDP based on guest maxphyaddr (CPUID[0x80000008].EAX[7:0]), the
host maxphyaddr, and whether the host supports 5-level TDP or not. The
4-level TDP can map GPA up to 48 bits, and the 5-level TDP can map GPA up
to 52 bits. If guest maxphyaddr <= 48, KVM uses 4-level TDP even when the
host supports 5-level TDP.
If we pass GPA > beyond the TDP mappable limit to the TDP MMU fault handler
(concretely GPA > 48-bits with 4-level TDP), it will operate on GPA without
upper bits, (GPA & ((1UL < 48) - 1)), not the specified GPA. It is not
expected behavior. It wrongly maps GPA without upper bits with the page
for GPA with upper bits.
KVM_PRE_FAULT_MEMORY calls x86 KVM page fault handler, kvm_tdp_page_fault()
with a user-space-supplied GPA without the limit check so that the user
space can trigger WARN_ON_ONCE(). Check the GPA limit to fix it.
- For non-TDX case (DEFAULT_VM, SW_PROTECTED_VM, or SEV):
When the host supports 5-level TDP, KVM decides to use 4-level TDP if
cpuid_maxphyaddr() <= 48. cpuid_maxhyaddr() check prevents
KVM_PRE_FAULT_MEMORY from passing GFN beyond mappable GFN.
- For TDX case:
We'd like to exclude shared bit (or gfn_direct_mask in [1]) from GPA
passed to the TDP MMU so that the TDP MMU can handle Secure-EPT or
Shared-EPT (direct or mirrored in [1]) without explicitly
setting/clearing the GPA (except setting up the TDP iterator,
tdp_iter_refresh_sptep()). We'd like to make kvm_mmu_max_gfn() per VM
for TDX to be 52 or 47 independent of the guest maxphyaddr with other
patches.
Fixes: 6e01b7601dfe ("KVM: x86: Implement kvm_arch_vcpu_pre_fault_memory()")
Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
---
arch/x86/kvm/mmu/mmu.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/arch/x86/kvm/mmu/mmu.c b/arch/x86/kvm/mmu/mmu.c
index 4e0e9963066f..6ee5af55cee1 100644
--- a/arch/x86/kvm/mmu/mmu.c
+++ b/arch/x86/kvm/mmu/mmu.c
@@ -4756,6 +4756,11 @@ long kvm_arch_vcpu_pre_fault_memory(struct kvm_vcpu *vcpu,
u64 end;
int r;
+ if (range->gpa >= (1UL << cpuid_maxphyaddr(vcpu)))
+ return -E2BIG;
+ if (gpa_to_gfn(range->gpa) > kvm_mmu_max_gfn())
+ return -E2BIG;
+
/*
* reload is efficient when called repeatedly, so we can do it on
* every iteration.
base-commit: c8b8b8190a80b591aa73c27c70a668799f8db547
--
2.45.2
