From cc81e9486202345d6ca56495cf8b5f3d03fbc563 Mon Sep 17 00:00:00 2001 From: James Hogan Date: Thu, 9 Jun 2016 10:50:45 +0100 Subject: [PATCH] MIPS: KVM: Don't unwind PC when emulating CACHE MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit 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 Cc: Paolo Bonzini Cc: Radim Krčmář Cc: Ralf Baechle Cc: kvm@vger.kernel.org Cc: linux-mips@linux-mips.org Signed-off-by: Paolo Bonzini --- arch/mips/kvm/emulate.c | 16 ++++++++++------ 1 file changed, 10 insertions(+), 6 deletions(-) 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; } -- 2.20.1