On Wed, Apr 24, 2013 at 6:13 AM, Marc Zyngier <marc.zyngier@xxxxxxx> wrote:
> On 24/04/13 00:00, Christoffer Dall wrote:
>> On Mon, Apr 08, 2013 at 05:17:27PM +0100, Marc Zyngier wrote:
>>> As conditional instructions can trap on AArch32, add the thinest
>>> possible emulation layer to keep 32bit guests happy.
>>>
>>> Reviewed-by: Christopher Covington <cov@xxxxxxxxxxxxxx>
>>> Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>
>>> ---
>>> arch/arm64/include/asm/kvm_emulate.h | 13 ++-
>>> arch/arm64/kvm/Makefile | 2 +-
>>> arch/arm64/kvm/emulate.c | 154 +++++++++++++++++++++++++++++++++++
>>> 3 files changed, 166 insertions(+), 3 deletions(-)
>>> create mode 100644 arch/arm64/kvm/emulate.c
>>>
>>> diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
>>> index 37a6567..8d4ab33 100644
>>> --- a/arch/arm64/include/asm/kvm_emulate.h
>>> +++ b/arch/arm64/include/asm/kvm_emulate.h
>>> @@ -31,6 +31,9 @@
>>> unsigned long *vcpu_reg32(const struct kvm_vcpu *vcpu, u8 reg_num);
>>> unsigned long *vcpu_spsr32(const struct kvm_vcpu *vcpu);
>>>
>>> +bool kvm_condition_valid32(const struct kvm_vcpu *vcpu);
>>> +void kvm_skip_instr32(struct kvm_vcpu *vcpu, bool is_wide_instr);
>>> +
>>> void kvm_inject_undefined(struct kvm_vcpu *vcpu);
>>> void kvm_inject_dabt(struct kvm_vcpu *vcpu, unsigned long addr);
>>> void kvm_inject_pabt(struct kvm_vcpu *vcpu, unsigned long addr);
>>> @@ -57,12 +60,18 @@ static inline bool vcpu_mode_is_32bit(const struct kvm_vcpu *vcpu)
>>>
>>> static inline bool kvm_condition_valid(const struct kvm_vcpu *vcpu)
>>> {
>>> - return true; /* No conditionals on arm64 */
>>> + if (vcpu_mode_is_32bit(vcpu))
>>> + return kvm_condition_valid32(vcpu);
>>> +
>>> + return true;
>>> }
>>>
>>> static inline void kvm_skip_instr(struct kvm_vcpu *vcpu, bool is_wide_instr)
>>> {
>>> - *vcpu_pc(vcpu) += 4;
>>> + if (vcpu_mode_is_32bit(vcpu))
>>> + kvm_skip_instr32(vcpu, is_wide_instr);
>>> + else
>>> + *vcpu_pc(vcpu) += 4;
>>> }
>>>
>>> static inline void vcpu_set_thumb(struct kvm_vcpu *vcpu)
>>> diff --git a/arch/arm64/kvm/Makefile b/arch/arm64/kvm/Makefile
>>> index 1668448..88c6639 100644
>>> --- a/arch/arm64/kvm/Makefile
>>> +++ b/arch/arm64/kvm/Makefile
>>> @@ -11,7 +11,7 @@ obj-$(CONFIG_KVM_ARM_HOST) += kvm.o
>>> kvm-$(CONFIG_KVM_ARM_HOST) += $(addprefix ../../../virt/kvm/, kvm_main.o coalesced_mmio.o)
>>> kvm-$(CONFIG_KVM_ARM_HOST) += $(addprefix ../../../arch/arm/kvm/, arm.o mmu.o mmio.o psci.o perf.o)
>>>
>>> -kvm-$(CONFIG_KVM_ARM_HOST) += inject_fault.o regmap.o
>>> +kvm-$(CONFIG_KVM_ARM_HOST) += emulate.o inject_fault.o regmap.o
>>> kvm-$(CONFIG_KVM_ARM_HOST) += hyp.o hyp-init.o handle_exit.o
>>> kvm-$(CONFIG_KVM_ARM_HOST) += guest.o reset.o sys_regs.o sys_regs_generic_v8.o
>>>
>>> diff --git a/arch/arm64/kvm/emulate.c b/arch/arm64/kvm/emulate.c
>>> new file mode 100644
>>> index 0000000..01d4713
>>> --- /dev/null
>>> +++ b/arch/arm64/kvm/emulate.c
>>> @@ -0,0 +1,154 @@
>>> +/*
>>> + * (not much of an) Emulation layer for 32bit guests.
>>> + *
>>> + * Copyright (C) 2012 - Virtual Open Systems and Columbia University
>>> + * Author: Christoffer Dall <c.dall@xxxxxxxxxxxxxxxxxxxxxx>
>>
>> don't you want to add yourself here?
>
> There's really nothing I actually wrote here. Most of it is your code,
> and the rest comes from other parts of arch/arm.
>
> I guess I could always mention myself for the ESR_EL2_* macros... ;-)
>
>>> + *
>>> + * This program is free software: you can redistribute it and/or modify
>>> + * it under the terms of the GNU General Public License version 2 as
>>> + * published by the Free Software Foundation.
>>> + *
>>> + * This program is distributed in the hope that it will be useful,
>>> + * but WITHOUT ANY WARRANTY; without even the implied warranty of
>>> + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
>>> + * GNU General Public License for more details.
>>> + *
>>> + * You should have received a copy of the GNU General Public License
>>> + * along with this program. If not, see <http://www.gnu.org/licenses/>.
>>> + */
>>> +
>>> +#include <linux/kvm_host.h>
>>> +#include <asm/kvm_emulate.h>
>>> +
>>> +/*
>>> + * stolen from arch/arm/kernel/opcodes.c
>>> + *
>>> + * condition code lookup table
>>> + * index into the table is test code: EQ, NE, ... LT, GT, AL, NV
>>> + *
>>> + * bit position in short is condition code: NZCV
>>> + */
>>> +static const unsigned short cc_map[16] = {
>>> + 0xF0F0, /* EQ == Z set */
>>> + 0x0F0F, /* NE */
>>> + 0xCCCC, /* CS == C set */
>>> + 0x3333, /* CC */
>>> + 0xFF00, /* MI == N set */
>>> + 0x00FF, /* PL */
>>> + 0xAAAA, /* VS == V set */
>>> + 0x5555, /* VC */
>>> + 0x0C0C, /* HI == C set && Z clear */
>>> + 0xF3F3, /* LS == C clear || Z set */
>>> + 0xAA55, /* GE == (N==V) */
>>> + 0x55AA, /* LT == (N!=V) */
>>> + 0x0A05, /* GT == (!Z && (N==V)) */
>>> + 0xF5FA, /* LE == (Z || (N!=V)) */
>>> + 0xFFFF, /* AL always */
>>> + 0 /* NV */
>>> +};
>>> +
>>> +static int kvm_vcpu_get_condition(const struct kvm_vcpu *vcpu)
>>> +{
>>> + u32 esr = kvm_vcpu_get_hsr(vcpu);
>>> +
>>> + if (esr & ESR_EL2_CV)
>>> + return (esr & ESR_EL2_COND) >> ESR_EL2_COND_SHIFT;
>>> +
>>> + return -1;
>>> +}
>>> +
>>> +/*
>>> + * Check if a trapped instruction should have been executed or not.
>>> + */
>>> +bool kvm_condition_valid32(const struct kvm_vcpu *vcpu)
>>> +{
>>> + unsigned long cpsr;
>>> + u32 cpsr_cond;
>>> + int cond;
>>> +
>>> + /* Top two bits non-zero? Unconditional. */
>>> + if (kvm_vcpu_get_hsr(vcpu) >> 30)
>>> + return true;
>>> +
>>> + /* Is condition field valid? */
>>> + cond = kvm_vcpu_get_condition(vcpu);
>>> + if (cond == 0xE)
>>> + return true;
>>> +
>>> + cpsr = *vcpu_cpsr(vcpu);
>>> +
>>> + if (cond < 0) {
>>> + /* This can happen in Thumb mode: examine IT state. */
>>> + unsigned long it;
>>> +
>>> + it = ((cpsr >> 8) & 0xFC) | ((cpsr >> 25) & 0x3);
>>> +
>>> + /* it == 0 => unconditional. */
>>> + if (it == 0)
>>> + return true;
>>> +
>>> + /* The cond for this insn works out as the top 4 bits. */
>>> + cond = (it >> 4);
>>> + }
>>> +
>>> + cpsr_cond = cpsr >> 28;
>>> +
>>> + if (!((cc_map[cond] >> cpsr_cond) & 1))
>>> + return false;
>>> +
>>> + return true;
>>> +}
>>> +
>>> +/**
>>> + * adjust_itstate - adjust ITSTATE when emulating instructions in IT-block
>>> + * @vcpu: The VCPU pointer
>>> + *
>>> + * When exceptions occur while instructions are executed in Thumb IF-THEN
>>> + * blocks, the ITSTATE field of the CPSR is not advanved (updated), so we have
>>
>> s/advanved/advanced/
>
> See? You actually hold the copyright on that spelling mistake! ;-)
>>
>>> + * to do this little bit of work manually. The fields map like this:
>>> + *
>>> + * IT[7:0] -> CPSR[26:25],CPSR[15:10]
>>> + */
>>> +static void kvm_adjust_itstate(struct kvm_vcpu *vcpu)
>>> +{
>>> + unsigned long itbits, cond;
>>> + unsigned long cpsr = *vcpu_cpsr(vcpu);
>>> + bool is_arm = !(cpsr & COMPAT_PSR_T_BIT);
>>> +
>>> + BUG_ON(is_arm && (cpsr & COMPAT_PSR_IT_MASK));
>>> +
>>> + if (!(cpsr & COMPAT_PSR_IT_MASK))
>>> + return;
>>> +
>>> + cond = (cpsr & 0xe000) >> 13;
>>> + itbits = (cpsr & 0x1c00) >> (10 - 2);
>>> + itbits |= (cpsr & (0x3 << 25)) >> 25;
>>> +
>>> + /* Perform ITAdvance (see page A-52 in ARM DDI 0406C) */
>>
>> That's actually page A2-52 to be a little more precise...
>
> Yup. Feel free to update the 32bit code as well... ;-)
>
>>> + if ((itbits & 0x7) == 0)
>>> + itbits = cond = 0;
>>> + else
>>> + itbits = (itbits << 1) & 0x1f;
>>> +
>>> + cpsr &= ~COMPAT_PSR_IT_MASK;
>>> + cpsr |= cond << 13;
>>> + cpsr |= (itbits & 0x1c) << (10 - 2);
>>> + cpsr |= (itbits & 0x3) << 25;
>>> + *vcpu_cpsr(vcpu) = cpsr;
>>> +}
>>> +
>>> +/**
>>> + * kvm_skip_instr - skip a trapped instruction and proceed to the next
>>> + * @vcpu: The vcpu pointer
>>> + */
>>> +void kvm_skip_instr32(struct kvm_vcpu *vcpu, bool is_wide_instr)
>>> +{
>>> + bool is_thumb;
>>> +
>>> + is_thumb = !!(*vcpu_cpsr(vcpu) & COMPAT_PSR_T_BIT);
>>
>> again we don't need the '!!' when it's a bool.
>
> I'm still not prepared to consider a bitwise and as a bool, and I'm
> happy for the !! to make the conversion to a bool completely obvious.
>
ok, you could also have 4 of them, or maybe 28 of them, just make sure
it's an even number of them ;)
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