From cc81e9486202345d6ca56495cf8b5f3d03fbc563 Mon Sep 17 00:00:00 2001
From: James Hogan <james.hogan@imgtec.com>
Date: Thu, 9 Jun 2016 10:50:45 +0100
Subject: MIPS: KVM: Don't unwind PC when emulating CACHE
MIME-Version: 1.0
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When a CACHE instruction is emulated by kvm_mips_emulate_cache(), the PC
is first updated to point to the next instruction, and afterwards it
falls through the "dont_update_pc" label, which rewinds the PC back to
its original address.
This works when dynamic translation of emulated instructions is enabled,
since the CACHE instruction is replaced with a SYNCI which works without
trapping, however when dynamic translation is disabled the guest hangs
on CACHE instructions as they always trap and are never stepped over.
Roughly swap the meanings of the "done" and "dont_update_pc" to match
kvm_mips_emulate_CP0(), so that "done" will roll back the PC on failure,
and "dont_update_pc" won't change PC at all (for the sake of exceptions
that have already modified the PC).
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: kvm@vger.kernel.org
Cc: linux-mips@linux-mips.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
arch/mips/kvm/emulate.c | 16 ++++++++++------
1 file changed, 10 insertions(+), 6 deletions(-)
(limited to 'arch/mips/kvm/emulate.c')
diff --git a/arch/mips/kvm/emulate.c b/arch/mips/kvm/emulate.c
index 396df6eb0a12..52bec0fe2fbb 100644
--- a/arch/mips/kvm/emulate.c
+++ b/arch/mips/kvm/emulate.c
@@ -1666,7 +1666,7 @@ enum emulation_result kvm_mips_emulate_cache(uint32_t inst, uint32_t *opc,
cache, op, base, arch->gprs[base], offset);
er = EMULATE_FAIL;
preempt_enable();
- goto dont_update_pc;
+ goto done;
}
@@ -1694,16 +1694,20 @@ skip_fault:
kvm_err("NO-OP CACHE (cache: %#x, op: %#x, base[%d]: %#lx, offset: %#x\n",
cache, op, base, arch->gprs[base], offset);
er = EMULATE_FAIL;
- preempt_enable();
- goto dont_update_pc;
}
preempt_enable();
+done:
+ /* Rollback PC only if emulation was unsuccessful */
+ if (er == EMULATE_FAIL)
+ vcpu->arch.pc = curr_pc;
dont_update_pc:
- /* Rollback PC */
- vcpu->arch.pc = curr_pc;
-done:
+ /*
+ * This is for exceptions whose emulation updates the PC, so do not
+ * overwrite the PC under any circumstances
+ */
+
return er;
}
--
cgit v1.2.3-70-g09d2
From 6df82a7b88dc9b0b519765562b005ef9196d812a Mon Sep 17 00:00:00 2001
From: James Hogan <james.hogan@imgtec.com>
Date: Thu, 9 Jun 2016 10:50:46 +0100
Subject: MIPS: KVM: Fix CACHE triggered exception emulation
MIME-Version: 1.0
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Content-Transfer-Encoding: 8bit
When emulating TLB miss / invalid exceptions during CACHE instruction
emulation, be sure to set up the correct PC and host_cp0_badvaddr state
for the kvm_mips_emlulate_tlb*_ld() function to pick up for guest EPC
and BadVAddr.
PC needs to be rewound otherwise the guest EPC will end up pointing at
the next instruction after the faulting CACHE instruction.
host_cp0_badvaddr must be set because guest CACHE instructions trap with
a Coprocessor Unusable exception, which doesn't update the host BadVAddr
as a TLB exception would.
This doesn't tend to get hit when dynamic translation of emulated
instructions is enabled, since only the first execution of each CACHE
instruction actually goes through this code path, with subsequent
executions hitting the SYNCI instruction that it gets replaced with.
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: kvm@vger.kernel.org
Cc: linux-mips@linux-mips.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
arch/mips/kvm/emulate.c | 3 +++
1 file changed, 3 insertions(+)
(limited to 'arch/mips/kvm/emulate.c')
diff --git a/arch/mips/kvm/emulate.c b/arch/mips/kvm/emulate.c
index 52bec0fe2fbb..645c8a1982a7 100644
--- a/arch/mips/kvm/emulate.c
+++ b/arch/mips/kvm/emulate.c
@@ -1636,6 +1636,7 @@ enum emulation_result kvm_mips_emulate_cache(uint32_t inst, uint32_t *opc,
if (index < 0) {
vcpu->arch.host_cp0_entryhi = (va & VPN2_MASK);
vcpu->arch.host_cp0_badvaddr = va;
+ vcpu->arch.pc = curr_pc;
er = kvm_mips_emulate_tlbmiss_ld(cause, NULL, run,
vcpu);
preempt_enable();
@@ -1647,6 +1648,8 @@ enum emulation_result kvm_mips_emulate_cache(uint32_t inst, uint32_t *opc,
* invalid exception to the guest
*/
if (!TLB_IS_VALID(*tlb, va)) {
+ vcpu->arch.host_cp0_badvaddr = va;
+ vcpu->arch.pc = curr_pc;
er = kvm_mips_emulate_tlbinv_ld(cause, NULL,
run, vcpu);
preempt_enable();
--
cgit v1.2.3-70-g09d2