diff mbox

[5/6,v7] kvm: booke: clear host tlb reference flag on guest tlb invalidation

Message ID 1379907769-31452-1-git-send-email-Bharat.Bhushan@freescale.com (mailing list archive)
State New, archived
Headers show

Commit Message

Bharat Bhushan Sept. 23, 2013, 3:42 a.m. UTC
On booke, "struct tlbe_ref" contains host tlb mapping information
(pfn: for guest-pfn to pfn, flags: attribute associated with this mapping)
for a guest tlb entry. So when a guest creates a TLB entry then
"struct tlbe_ref" is set to point to valid "pfn" and set attributes in
"flags" field of the above said structure. When a guest TLB entry is
invalidated then flags field of corresponding "struct tlbe_ref" is
updated to point that this is no more valid, also we selectively clear
some other attribute bits, example: if E500_TLB_BITMAP was set then we clear
E500_TLB_BITMAP, if E500_TLB_TLB0 is set then we clear this.

Ideally we should clear complete "flags" as this entry is invalid and does not
have anything to re-used. The other part of the problem is that when we use
the same entry again then also we do not clear (started doing or-ing etc).

So far it was working because the selectively clearing mentioned above
actually clears "flags" what was set during TLB mapping. But the problem
starts coming when we add more attributes to this then we need to selectively
clear them and which is not needed.

This patch we do both
        - Clear "flags" when invalidating;
        - Clear "flags" when reusing same entry later

Signed-off-by: Bharat Bhushan <bharat.bhushan@freescale.com>
---
v6->7
 - Comment re-phrased

v5->v6
 - Reordered the flag clearing steps as per comment on v5

v4->v5
 - New change

 arch/powerpc/kvm/e500_mmu_host.c |   16 ++++++++--------
 1 files changed, 8 insertions(+), 8 deletions(-)

Comments

Scott Wood Sept. 23, 2013, 10:31 p.m. UTC | #1
On Mon, 2013-09-23 at 09:12 +0530, Bharat Bhushan wrote:
> On booke, "struct tlbe_ref" contains host tlb mapping information
> (pfn: for guest-pfn to pfn, flags: attribute associated with this mapping)
> for a guest tlb entry. So when a guest creates a TLB entry then
> "struct tlbe_ref" is set to point to valid "pfn" and set attributes in
> "flags" field of the above said structure. When a guest TLB entry is
> invalidated then flags field of corresponding "struct tlbe_ref" is
> updated to point that this is no more valid, also we selectively clear
> some other attribute bits, example: if E500_TLB_BITMAP was set then we clear
> E500_TLB_BITMAP, if E500_TLB_TLB0 is set then we clear this.
> 
> Ideally we should clear complete "flags" as this entry is invalid and does not
> have anything to re-used. The other part of the problem is that when we use
> the same entry again then also we do not clear (started doing or-ing etc).
> 
> So far it was working because the selectively clearing mentioned above
> actually clears "flags" what was set during TLB mapping. But the problem
> starts coming when we add more attributes to this then we need to selectively
> clear them and which is not needed.
> 
> This patch we do both
>         - Clear "flags" when invalidating;
>         - Clear "flags" when reusing same entry later
> 
> Signed-off-by: Bharat Bhushan <bharat.bhushan@freescale.com>
> ---
> v6->7
>  - Comment re-phrased

Reviewed-by: Scott Wood <scottwood@freescale.com>

-Scott



--
To unsubscribe from this list: send the line "unsubscribe kvm" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
diff mbox

Patch

diff --git a/arch/powerpc/kvm/e500_mmu_host.c b/arch/powerpc/kvm/e500_mmu_host.c
index 1c6a9d7..7a41a93 100644
--- a/arch/powerpc/kvm/e500_mmu_host.c
+++ b/arch/powerpc/kvm/e500_mmu_host.c
@@ -230,15 +230,15 @@  void inval_gtlbe_on_host(struct kvmppc_vcpu_e500 *vcpu_e500, int tlbsel,
 		ref->flags &= ~(E500_TLB_TLB0 | E500_TLB_VALID);
 	}
 
-	/* Already invalidated in between */
-	if (!(ref->flags & E500_TLB_VALID))
-		return;
-
-	/* Guest tlbe is backed by at most one host tlbe per shadow pid. */
-	kvmppc_e500_tlbil_one(vcpu_e500, gtlbe);
+	/*
+	 * If TLB entry is still valid then it's a TLB0 entry, and thus
+	 * backed by at most one host tlbe per shadow pid
+	 */
+	if (ref->flags & E500_TLB_VALID)
+		kvmppc_e500_tlbil_one(vcpu_e500, gtlbe);
 
 	/* Mark the TLB as not backed by the host anymore */
-	ref->flags &= ~E500_TLB_VALID;
+	ref->flags = 0;
 }
 
 static inline int tlbe_is_writable(struct kvm_book3e_206_tlb_entry *tlbe)
@@ -251,7 +251,7 @@  static inline void kvmppc_e500_ref_setup(struct tlbe_ref *ref,
 					 pfn_t pfn)
 {
 	ref->pfn = pfn;
-	ref->flags |= E500_TLB_VALID;
+	ref->flags = E500_TLB_VALID;
 
 	if (tlbe_is_writable(gtlbe))
 		kvm_set_pfn_dirty(pfn);