From 2e0badfaac234ef3ed6b5397ff208d218cd450fb Mon Sep 17 00:00:00 2001 From: James Hogan Date: Mon, 4 Jul 2016 19:35:12 +0100 Subject: [PATCH] MIPS: KVM: Support r6 compact branch emulation MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Add support in KVM for emulation of instructions in the forbidden slot of MIPSr6 compact branches. If we hit an exception on the forbidden slot, then the branch must not have been taken, which makes calculation of the resume PC trivial. Signed-off-by: James Hogan Cc: Paolo Bonzini Cc: Radim KrÄmář Cc: Ralf Baechle Cc: linux-mips@linux-mips.org Cc: kvm@vger.kernel.org Signed-off-by: Paolo Bonzini --- arch/mips/kvm/emulate.c | 52 ++++++++++++++++++++++++++++++++++++----- 1 file changed, 46 insertions(+), 6 deletions(-) diff --git a/arch/mips/kvm/emulate.c b/arch/mips/kvm/emulate.c index 5f0354c80c8e..f0fa9e956056 100644 --- a/arch/mips/kvm/emulate.c +++ b/arch/mips/kvm/emulate.c @@ -161,9 +161,12 @@ unsigned long kvm_compute_return_epc(struct kvm_vcpu *vcpu, nextpc = epc; break; - case blez_op: /* not really i_format */ - case blezl_op: - /* rt field assumed to be zero */ + case blez_op: /* POP06 */ +#ifndef CONFIG_CPU_MIPSR6 + case blezl_op: /* removed in R6 */ +#endif + if (insn.i_format.rt != 0) + goto compact_branch; if ((long)arch->gprs[insn.i_format.rs] <= 0) epc = epc + 4 + (insn.i_format.simmediate << 2); else @@ -171,9 +174,12 @@ unsigned long kvm_compute_return_epc(struct kvm_vcpu *vcpu, nextpc = epc; break; - case bgtz_op: - case bgtzl_op: - /* rt field assumed to be zero */ + case bgtz_op: /* POP07 */ +#ifndef CONFIG_CPU_MIPSR6 + case bgtzl_op: /* removed in R6 */ +#endif + if (insn.i_format.rt != 0) + goto compact_branch; if ((long)arch->gprs[insn.i_format.rs] > 0) epc = epc + 4 + (insn.i_format.simmediate << 2); else @@ -185,6 +191,40 @@ unsigned long kvm_compute_return_epc(struct kvm_vcpu *vcpu, case cop1_op: kvm_err("%s: unsupported cop1_op\n", __func__); break; + +#ifdef CONFIG_CPU_MIPSR6 + /* R6 added the following compact branches with forbidden slots */ + case blezl_op: /* POP26 */ + case bgtzl_op: /* POP27 */ + /* only rt == 0 isn't compact branch */ + if (insn.i_format.rt != 0) + goto compact_branch; + break; + case pop10_op: + case pop30_op: + /* only rs == rt == 0 is reserved, rest are compact branches */ + if (insn.i_format.rs != 0 || insn.i_format.rt != 0) + goto compact_branch; + break; + case pop66_op: + case pop76_op: + /* only rs == 0 isn't compact branch */ + if (insn.i_format.rs != 0) + goto compact_branch; + break; +compact_branch: + /* + * If we've hit an exception on the forbidden slot, then + * the branch must not have been taken. + */ + epc += 8; + nextpc = epc; + break; +#else +compact_branch: + /* Compact branches not supported before R6 */ + break; +#endif } return nextpc; -- 2.20.1