[PATCH BACKPORT 4.7 0/4] MIPS: KVM: Fix MMU/TLB management issues

[PATCH BACKPORT 4.7 0/4] MIPS: KVM: Fix MMU/TLB management issues

[James Hogan]

These patches backport fixes for several issues in the management of
MIPS KVM TLB faults to v4.7.

Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Cc: <stable@vger.kernel.org>

James Hogan (4):
  MIPS: KVM: Fix mapped fault broken commpage handling
  MIPS: KVM: Add missing gfn range check
  MIPS: KVM: Fix gfn range check in kseg0 tlb faults
  MIPS: KVM: Propagate kseg0/mapped tlb fault errors

 arch/mips/kvm/emulate.c | 40 +++++++++++++++++--------
 arch/mips/kvm/tlb.c     | 66 +++++++++++++++++++++++++++---------------
 2 files changed, 71 insertions(+), 35 deletions(-)

-- 
git-series 0.8.8

[PATCH BACKPORT 4.7 1/4] MIPS: KVM: Fix mapped fault broken commpage handling

[James Hogan]

commit c604cffa93478f8888bec62b23d6073dad03d43a upstream.

kvm_mips_handle_mapped_seg_tlb_fault() appears to map the guest page at
virtual address 0 to PFN 0 if the guest has created its own mapping
there. The intention is unclear, but it may have been an attempt to
protect the zero page from being mapped to anything but the comm page in
code paths you wouldn't expect from genuine commpage accesses (guest
kernel mode cache instructions on that address, hitting trapping
instructions when executing from that address with a coincidental TLB
eviction during the KVM handling, and guest user mode accesses to that
address).

Fix this to check for mappings exactly at KVM_GUEST_COMMPAGE_ADDR (it
may not be at address 0 since commit 42aa12e74e91 ("MIPS: KVM: Move
commpage so 0x0 is unmapped")), and set the corresponding EntryLo to be
interpreted as 0 (invalid).

Fixes: 858dd5d45733 ("KVM/MIPS32: MMU/TLB operations for the Guest.")
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
[james.hogan@imgtec.com: Backport to v4.7]
Signed-off-by: James Hogan <james.hogan@imgtec.com>
---
 arch/mips/kvm/tlb.c | 45 ++++++++++++++++++++++++++-------------------
 1 file changed, 26 insertions(+), 19 deletions(-)

diff --git a/arch/mips/kvm/tlb.c b/arch/mips/kvm/tlb.c
index ed021ae7867a..79d90a34775e 100644
--- a/arch/mips/kvm/tlb.c
+++ b/arch/mips/kvm/tlb.c
@@ -373,25 +373,32 @@ int kvm_mips_handle_mapped_seg_tlb_fault(struct kvm_vcpu *vcpu,
 	unsigned long entryhi = 0, entrylo0 = 0, entrylo1 = 0;
 	struct kvm *kvm = vcpu->kvm;
 	kvm_pfn_t pfn0, pfn1;
+	long tlb_lo[2];
 	int ret;
 
-	if ((tlb->tlb_hi & VPN2_MASK) == 0) {
-		pfn0 = 0;
-		pfn1 = 0;
-	} else {
-		if (kvm_mips_map_page(kvm, mips3_tlbpfn_to_paddr(tlb->tlb_lo0)
-					   >> PAGE_SHIFT) < 0)
-			return -1;
-
-		if (kvm_mips_map_page(kvm, mips3_tlbpfn_to_paddr(tlb->tlb_lo1)
-					   >> PAGE_SHIFT) < 0)
-			return -1;
-
-		pfn0 = kvm->arch.guest_pmap[mips3_tlbpfn_to_paddr(tlb->tlb_lo0)
-					    >> PAGE_SHIFT];
-		pfn1 = kvm->arch.guest_pmap[mips3_tlbpfn_to_paddr(tlb->tlb_lo1)
-					    >> PAGE_SHIFT];
-	}
+	tlb_lo[0] = tlb->tlb_lo0;
+	tlb_lo[1] = tlb->tlb_lo1;
+
+	/*
+	 * The commpage address must not be mapped to anything else if the guest
+	 * TLB contains entries nearby, or commpage accesses will break.
+	 */
+	if (!((tlb->tlb_hi ^ KVM_GUEST_COMMPAGE_ADDR) &
+			VPN2_MASK & (PAGE_MASK << 1)))
+		tlb_lo[(KVM_GUEST_COMMPAGE_ADDR >> PAGE_SHIFT) & 1] = 0;
+
+	if (kvm_mips_map_page(kvm, mips3_tlbpfn_to_paddr(tlb_lo[0])
+				   >> PAGE_SHIFT) < 0)
+		return -1;
+
+	if (kvm_mips_map_page(kvm, mips3_tlbpfn_to_paddr(tlb_lo[1])
+				   >> PAGE_SHIFT) < 0)
+		return -1;
+
+	pfn0 = kvm->arch.guest_pmap[mips3_tlbpfn_to_paddr(tlb_lo[0])
+				    >> PAGE_SHIFT];
+	pfn1 = kvm->arch.guest_pmap[mips3_tlbpfn_to_paddr(tlb_lo[1])
+				    >> PAGE_SHIFT];
 
 	if (hpa0)
 		*hpa0 = pfn0 << PAGE_SHIFT;
@@ -401,9 +408,9 @@ int kvm_mips_handle_mapped_seg_tlb_fault(struct kvm_vcpu *vcpu,
 
 	/* Get attributes from the Guest TLB */
 	entrylo0 = mips3_paddr_to_tlbpfn(pfn0 << PAGE_SHIFT) | (0x3 << 3) |
-		   (tlb->tlb_lo0 & MIPS3_PG_D) | (tlb->tlb_lo0 & MIPS3_PG_V);
+		   (tlb_lo[0] & MIPS3_PG_D) | (tlb_lo[0] & MIPS3_PG_V);
 	entrylo1 = mips3_paddr_to_tlbpfn(pfn1 << PAGE_SHIFT) | (0x3 << 3) |
-		   (tlb->tlb_lo1 & MIPS3_PG_D) | (tlb->tlb_lo1 & MIPS3_PG_V);
+		   (tlb_lo[1] & MIPS3_PG_D) | (tlb_lo[1] & MIPS3_PG_V);
 
 	kvm_debug("@ %#lx tlb_lo0: 0x%08lx tlb_lo1: 0x%08lx\n", vcpu->arch.pc,
 		  tlb->tlb_lo0, tlb->tlb_lo1);
-- 
git-series 0.8.8

[PATCH BACKPORT 4.7 2/4] MIPS: KVM: Add missing gfn range check

[James Hogan]

commit 8985d50382359e5bf118fdbefc859d0dbf6cebc7 upstream.

kvm_mips_handle_mapped_seg_tlb_fault() calculates the guest frame number
based on the guest TLB EntryLo values, however it is not range checked
to ensure it lies within the guest_pmap. If the physical memory the
guest refers to is out of range then dump the guest TLB and emit an
internal error.

Fixes: 858dd5d45733 ("KVM/MIPS32: MMU/TLB operations for the Guest.")
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
[james.hogan@imgtec.com: Backport to v4.7]
Signed-off-by: James Hogan <james.hogan@imgtec.com>
---
 arch/mips/kvm/tlb.c | 23 +++++++++++++++--------
 1 file changed, 15 insertions(+), 8 deletions(-)

diff --git a/arch/mips/kvm/tlb.c b/arch/mips/kvm/tlb.c
index 79d90a34775e..6c17ee73b8a3 100644
--- a/arch/mips/kvm/tlb.c
+++ b/arch/mips/kvm/tlb.c
@@ -373,6 +373,7 @@ int kvm_mips_handle_mapped_seg_tlb_fault(struct kvm_vcpu *vcpu,
 	unsigned long entryhi = 0, entrylo0 = 0, entrylo1 = 0;
 	struct kvm *kvm = vcpu->kvm;
 	kvm_pfn_t pfn0, pfn1;
+	gfn_t gfn0, gfn1;
 	long tlb_lo[2];
 	int ret;
 
@@ -387,18 +388,24 @@ int kvm_mips_handle_mapped_seg_tlb_fault(struct kvm_vcpu *vcpu,
 			VPN2_MASK & (PAGE_MASK << 1)))
 		tlb_lo[(KVM_GUEST_COMMPAGE_ADDR >> PAGE_SHIFT) & 1] = 0;
 
-	if (kvm_mips_map_page(kvm, mips3_tlbpfn_to_paddr(tlb_lo[0])
-				   >> PAGE_SHIFT) < 0)
+	gfn0 = mips3_tlbpfn_to_paddr(tlb_lo[0]) >> PAGE_SHIFT;
+	gfn1 = mips3_tlbpfn_to_paddr(tlb_lo[1]) >> PAGE_SHIFT;
+	if (gfn0 >= kvm->arch.guest_pmap_npages ||
+	    gfn1 >= kvm->arch.guest_pmap_npages) {
+		kvm_err("%s: Invalid gfn: [%#llx, %#llx], EHi: %#lx\n",
+			__func__, gfn0, gfn1, tlb->tlb_hi);
+		kvm_mips_dump_guest_tlbs(vcpu);
+		return -1;
+	}
+
+	if (kvm_mips_map_page(kvm, gfn0) < 0)
 		return -1;
 
-	if (kvm_mips_map_page(kvm, mips3_tlbpfn_to_paddr(tlb_lo[1])
-				   >> PAGE_SHIFT) < 0)
+	if (kvm_mips_map_page(kvm, gfn1) < 0)
 		return -1;
 
-	pfn0 = kvm->arch.guest_pmap[mips3_tlbpfn_to_paddr(tlb_lo[0])
-				    >> PAGE_SHIFT];
-	pfn1 = kvm->arch.guest_pmap[mips3_tlbpfn_to_paddr(tlb_lo[1])
-				    >> PAGE_SHIFT];
+	pfn0 = kvm->arch.guest_pmap[gfn0];
+	pfn1 = kvm->arch.guest_pmap[gfn1];
 
 	if (hpa0)
 		*hpa0 = pfn0 << PAGE_SHIFT;
-- 
git-series 0.8.8

[PATCH BACKPORT 4.7 3/4] MIPS: KVM: Fix gfn range check in kseg0 tlb faults

[James Hogan]

commit 0741f52d1b980dbeb290afe67d88fc2928edd8ab upstream.

Two consecutive gfns are loaded into host TLB, so ensure the range check
isn't off by one if guest_pmap_npages is odd.

Fixes: 858dd5d45733 ("KVM/MIPS32: MMU/TLB operations for the Guest.")
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
[james.hogan@imgtec.com: Backport to v4.7]
Signed-off-by: James Hogan <james.hogan@imgtec.com>
---
 arch/mips/kvm/tlb.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/mips/kvm/tlb.c b/arch/mips/kvm/tlb.c
index 6c17ee73b8a3..b872cb0b0f5d 100644
--- a/arch/mips/kvm/tlb.c
+++ b/arch/mips/kvm/tlb.c
@@ -284,7 +284,7 @@ int kvm_mips_handle_kseg0_tlb_fault(unsigned long badvaddr,
 	}
 
 	gfn = (KVM_GUEST_CPHYSADDR(badvaddr) >> PAGE_SHIFT);
-	if (gfn >= kvm->arch.guest_pmap_npages) {
+	if ((gfn | 1) >= kvm->arch.guest_pmap_npages) {
 		kvm_err("%s: Invalid gfn: %#llx, BadVaddr: %#lx\n", __func__,
 			gfn, badvaddr);
 		kvm_mips_dump_host_tlbs();
-- 
git-series 0.8.8

[PATCH BACKPORT 4.7 4/4] MIPS: KVM: Propagate kseg0/mapped tlb fault errors

[James Hogan]

commit 9b731bcfdec4c159ad2e4312e25d69221709b96a upstream.

Propagate errors from kvm_mips_handle_kseg0_tlb_fault() and
kvm_mips_handle_mapped_seg_tlb_fault(), usually triggering an internal
error since they normally indicate the guest accessed bad physical
memory or the commpage in an unexpected way.

Fixes: 858dd5d45733 ("KVM/MIPS32: MMU/TLB operations for the Guest.")
Fixes: e685c689f3a8 ("KVM/MIPS32: Privileged instruction/target branch emulation.")
Signed-off-by: James Hogan <james.hogan@imgtec.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-mips@linux-mips.org
Cc: kvm@vger.kernel.org
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
[james.hogan@imgtec.com: Backport to v4.7]
Signed-off-by: James Hogan <james.hogan@imgtec.com>
---
 arch/mips/kvm/emulate.c | 40 ++++++++++++++++++++++++++++------------
 arch/mips/kvm/tlb.c     | 14 ++++++++++----
 2 files changed, 38 insertions(+), 16 deletions(-)

diff --git a/arch/mips/kvm/emulate.c b/arch/mips/kvm/emulate.c
index 645c8a1982a7..2b42a74ed771 100644
--- a/arch/mips/kvm/emulate.c
+++ b/arch/mips/kvm/emulate.c
@@ -1615,8 +1615,14 @@ enum emulation_result kvm_mips_emulate_cache(uint32_t inst, uint32_t *opc,
 
 	preempt_disable();
 	if (KVM_GUEST_KSEGX(va) == KVM_GUEST_KSEG0) {
-		if (kvm_mips_host_tlb_lookup(vcpu, va) < 0)
-			kvm_mips_handle_kseg0_tlb_fault(va, vcpu);
+		if (kvm_mips_host_tlb_lookup(vcpu, va) < 0 &&
+		    kvm_mips_handle_kseg0_tlb_fault(va, vcpu)) {
+			kvm_err("%s: handling mapped kseg0 tlb fault for %lx, vcpu: %p, ASID: %#lx\n",
+				__func__, va, vcpu, read_c0_entryhi());
+			er = EMULATE_FAIL;
+			preempt_enable();
+			goto done;
+		}
 	} else if ((KVM_GUEST_KSEGX(va) < KVM_GUEST_KSEG0) ||
 		   KVM_GUEST_KSEGX(va) == KVM_GUEST_KSEG23) {
 		int index;
@@ -1654,14 +1660,19 @@ enum emulation_result kvm_mips_emulate_cache(uint32_t inst, uint32_t *opc,
 								run, vcpu);
 				preempt_enable();
 				goto dont_update_pc;
-			} else {
-				/*
-				 * We fault an entry from the guest tlb to the
-				 * shadow host TLB
-				 */
-				kvm_mips_handle_mapped_seg_tlb_fault(vcpu, tlb,
-								     NULL,
-								     NULL);
+			}
+			/*
+			 * We fault an entry from the guest tlb to the
+			 * shadow host TLB
+			 */
+			if (kvm_mips_handle_mapped_seg_tlb_fault(vcpu, tlb,
+								 NULL, NULL)) {
+				kvm_err("%s: handling mapped seg tlb fault for %lx, index: %u, vcpu: %p, ASID: %#lx\n",
+					__func__, va, index, vcpu,
+					read_c0_entryhi());
+				er = EMULATE_FAIL;
+				preempt_enable();
+				goto done;
 			}
 		}
 	} else {
@@ -2625,8 +2636,13 @@ enum emulation_result kvm_mips_handle_tlbmiss(unsigned long cause,
 			 * OK we have a Guest TLB entry, now inject it into the
 			 * shadow host TLB
 			 */
-			kvm_mips_handle_mapped_seg_tlb_fault(vcpu, tlb, NULL,
-							     NULL);
+			if (kvm_mips_handle_mapped_seg_tlb_fault(vcpu, tlb,
+								 NULL, NULL)) {
+				kvm_err("%s: handling mapped seg tlb fault for %lx, index: %u, vcpu: %p, ASID: %#lx\n",
+					__func__, va, index, vcpu,
+					read_c0_entryhi());
+				er = EMULATE_FAIL;
+			}
 		}
 	}
 
diff --git a/arch/mips/kvm/tlb.c b/arch/mips/kvm/tlb.c
index b872cb0b0f5d..ad2270ff83d1 100644
--- a/arch/mips/kvm/tlb.c
+++ b/arch/mips/kvm/tlb.c
@@ -790,10 +790,16 @@ uint32_t kvm_get_inst(uint32_t *opc, struct kvm_vcpu *vcpu)
 				local_irq_restore(flags);
 				return KVM_INVALID_INST;
 			}
-			kvm_mips_handle_mapped_seg_tlb_fault(vcpu,
-							     &vcpu->arch.
-							     guest_tlb[index],
-							     NULL, NULL);
+			if (kvm_mips_handle_mapped_seg_tlb_fault(vcpu,
+						&vcpu->arch.guest_tlb[index],
+						NULL, NULL)) {
+				kvm_err("%s: handling mapped seg tlb fault failed for %p, index: %u, vcpu: %p, ASID: %#lx\n",
+					__func__, opc, index, vcpu,
+					read_c0_entryhi());
+				kvm_mips_dump_guest_tlbs(vcpu);
+				local_irq_restore(flags);
+				return KVM_INVALID_INST;
+			}
 			inst = *(opc);
 		}
 		local_irq_restore(flags);
-- 
git-series 0.8.8

Re: [PATCH BACKPORT 4.7 0/4] MIPS: KVM: Fix MMU/TLB management issues

[Greg KH]

On Thu, Aug 18, 2016 at 10:01:25AM +0100, James Hogan wrote:
> These patches backport fixes for several issues in the management of
> MIPS KVM TLB faults to v4.7.

Thanks for these, now applied.

greg k-h

Re: [PATCH BACKPORT 4.7 0/4] MIPS: KVM: Fix MMU/TLB management issues

[James Hogan]

[-- Attachment #1: Type: text/plain, Size: 636 bytes --]

On Thu, Aug 18, 2016 at 11:42:17AM +0200, Greg KH wrote:
> On Thu, Aug 18, 2016 at 10:01:25AM +0100, James Hogan wrote:
> > These patches backport fixes for several issues in the management of
> > MIPS KVM TLB faults to v4.7.
> 
> Thanks for these, now applied.

Thanks Greg,

btw, is it okay to tag for stable in this way, knowing full well that
they'll all conflict and require backports?

Depending on your FAILED emails before sending backports just seemed
easier from my point of view, but if that increases any manual effort on
the part of the stable maintainers I can do it differently in future.

Cheers
James

[-- Attachment #2: Digital signature --]
[-- Type: application/pgp-signature, Size: 819 bytes --]

Re: [PATCH BACKPORT 4.7 0/4] MIPS: KVM: Fix MMU/TLB management issues

[Greg KH]

On Thu, Aug 18, 2016 at 11:00:36AM +0100, James Hogan wrote:
> On Thu, Aug 18, 2016 at 11:42:17AM +0200, Greg KH wrote:
> > On Thu, Aug 18, 2016 at 10:01:25AM +0100, James Hogan wrote:
> > > These patches backport fixes for several issues in the management of
> > > MIPS KVM TLB faults to v4.7.
> > 
> > Thanks for these, now applied.
> 
> Thanks Greg,
> 
> btw, is it okay to tag for stable in this way, knowing full well that
> they'll all conflict and require backports?
> 
> Depending on your FAILED emails before sending backports just seemed
> easier from my point of view, but if that increases any manual effort on
> the part of the stable maintainers I can do it differently in future.

That's fine with me, but if you know they are going to need to be
backported, you can send those before you get the FAILED message so that
I know to use those instead.

thanks,

greg k-h