[PATCH] x86/hyper-v: Validate entire GVA range for non-canonical addresses during PV TLB flush

[Manuel Andreas]

In KVM guests with Hyper-V hypercalls enabled, the hypercalls
HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST and HVCALL_FLUSH_VIRTUAL_ADDRESS_LIST_EX
allow a guest to request invalidation of portions of a virtual TLB.
For this, the hypercall parameter includes a list of GVAs that are supposed
to be invalidated.

Currently, only the base GVA is checked to be canonical. In reality,
this check needs to be performed for the entire range of GVAs.
This still enables guests running on Intel hardware to trigger a
WARN_ONCE in the host (see prior commit below).

This patch simply moves the check for non-canonical addresses to be
performed for every single GVA of the supplied range. This should also
be more in line with the Hyper-V specification, since, although
unlikely, a range starting with an invalid GVA may still contain
GVAs that are valid.

Fixes: fa787ac07b3c ("KVM: x86/hyper-v: Skip non-canonical addresses during PV TLB flush")
Signed-off-by: Manuel Andreas <manuel.andreas@xxxxxx>
---
 arch/x86/kvm/hyperv.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index de92292eb1f5..f4f6accf1a33 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1981,16 +1981,17 @@ int kvm_hv_vcpu_flush_tlb(struct kvm_vcpu *vcpu)
 		if (entries[i] == KVM_HV_TLB_FLUSHALL_ENTRY)
 			goto out_flush_all;
 
-		if (is_noncanonical_invlpg_address(entries[i], vcpu))
-			continue;
-
 		/*
 		 * Lower 12 bits of 'address' encode the number of additional
 		 * pages to flush.
 		 */
 		gva = entries[i] & PAGE_MASK;
-		for (j = 0; j < (entries[i] & ~PAGE_MASK) + 1; j++)
+		for (j = 0; j < (entries[i] & ~PAGE_MASK) + 1; j++) {
+			if (is_noncanonical_invlpg_address(gva + j * PAGE_SIZE, vcpu))
+				continue;
+
 			kvm_x86_call(flush_tlb_gva)(vcpu, gva + j * PAGE_SIZE);
+		}
 
 		++vcpu->stat.tlb_flush;
 	}
-- 
2.50.1