[PATCH 0/2] KVM: MIPS: Misc fixes for 4.10

[PATCH 0/2] KVM: MIPS: Misc fixes for 4.10

[James Hogan]

This series contains a couple of 4.10 fixes.

- Patch 1 fixes when KVM is used by a 64-bit (n64) userland program,
  which can result in a kernel crash when a signal is delivered on the
  way back out from the guest.

- Patch 2 fixes flushing of the entry code from the icache to take place
  on all CPUs rather than only the local one.

Both are tagged for stable.

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

James Hogan (2):
  KVM: MIPS: Don't clobber CP0_Status.UX
  KVM: MIPS: Flush KVM entry code from icache globally

 arch/mips/kvm/entry.c | 5 ++++-
 arch/mips/kvm/mips.c  | 4 ++--
 2 files changed, 6 insertions(+), 3 deletions(-)

-- 
git-series 0.8.10

[PATCH 1/2] KVM: MIPS: Don't clobber CP0_Status.UX

[James Hogan]

On 64-bit kernels, MIPS KVM will clear CP0_Status.UX to prevent the
guest (running in user mode) from accessing the 64-bit memory segments.
However the previous value of CP0_Status.UX is never restored when
exiting from the guest.

If the user process uses 64-bit addressing (the n64 ABI) this can result
in address error exceptions from the kernel if it needs to deliver a
signal before returning to user mode, as the kernel will need to write a
sigframe to high user addresses on the user stack which are disallowed
by CP0_Status.UX=0.

This is fixed by explicitly setting SX and UX again when exiting from
the guest, and explicitly clearing those bits when returning to the
guest. Having the SX and UX bits set when handling guest exits (rather
than only when exiting to userland) will be helpful when we support VZ,
since we shouldn't need to directly read or write guest memory, so it
will be valid for cache management IPIs to access host user addresses.

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
Cc: <stable@vger.kernel.org> # 4.8.x-
---
 arch/mips/kvm/entry.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/arch/mips/kvm/entry.c b/arch/mips/kvm/entry.c
index 6a02b3a3fa65..e92fb190e2d6 100644
--- a/arch/mips/kvm/entry.c
+++ b/arch/mips/kvm/entry.c
@@ -521,6 +521,9 @@ void *kvm_mips_build_exit(void *addr)
 	uasm_i_and(&p, V0, V0, AT);
 	uasm_i_lui(&p, AT, ST0_CU0 >> 16);
 	uasm_i_or(&p, V0, V0, AT);
+#ifdef CONFIG_64BIT
+	uasm_i_ori(&p, V0, V0, ST0_SX | ST0_UX);
+#endif
 	uasm_i_mtc0(&p, V0, C0_STATUS);
 	uasm_i_ehb(&p);
 
@@ -643,7 +646,7 @@ static void *kvm_mips_build_ret_to_guest(void *addr)
 
 	/* Setup status register for running guest in UM */
 	uasm_i_ori(&p, V1, V1, ST0_EXL | KSU_USER | ST0_IE);
-	UASM_i_LA(&p, AT, ~(ST0_CU0 | ST0_MX));
+	UASM_i_LA(&p, AT, ~(ST0_CU0 | ST0_MX | ST0_SX | ST0_UX));
 	uasm_i_and(&p, V1, V1, AT);
 	uasm_i_mtc0(&p, V1, C0_STATUS);
 	uasm_i_ehb(&p);
-- 
git-series 0.8.10

[PATCH 2/2] KVM: MIPS: Flush KVM entry code from icache globally

[James Hogan]

Flush the KVM entry code from the icache on all CPUs, not just the one
that built the entry code.

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
Cc: <stable@vger.kernel.org> # 3.16.x-
---
 arch/mips/kvm/mips.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/mips/kvm/mips.c b/arch/mips/kvm/mips.c
index 06a60b19acfb..29ec9ab3fd55 100644
--- a/arch/mips/kvm/mips.c
+++ b/arch/mips/kvm/mips.c
@@ -360,8 +360,8 @@ struct kvm_vcpu *kvm_arch_vcpu_create(struct kvm *kvm, unsigned int id)
 	dump_handler("kvm_exit", gebase + 0x2000, vcpu->arch.vcpu_run);
 
 	/* Invalidate the icache for these ranges */
-	local_flush_icache_range((unsigned long)gebase,
-				(unsigned long)gebase + ALIGN(size, PAGE_SIZE));
+	flush_icache_range((unsigned long)gebase,
+			   (unsigned long)gebase + ALIGN(size, PAGE_SIZE));
 
 	/*
 	 * Allocate comm page for guest kernel, a TLB will be reserved for
-- 
git-series 0.8.10

Re: [PATCH 0/2] KVM: MIPS: Misc fixes for 4.10

[Radim Krčmář]

2017-01-03 17:42+0000, James Hogan:
> This series contains a couple of 4.10 fixes.
> 
> - Patch 1 fixes when KVM is used by a 64-bit (n64) userland program,
>   which can result in a kernel crash when a signal is delivered on the
>   way back out from the guest.
> 
> - Patch 2 fixes flushing of the entry code from the icache to take place
>   on all CPUs rather than only the local one.
> 
> Both are tagged for stable.

Applied to kvm/master, thanks.