From: m.smarduch@samsung•com (Mario Smarduch)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH v6 1/6] arm/arm64: KVM: Introduce armv7 fp/simd vcpu fields and helpers
Date: Tue, 12 Jan 2016 16:57:15 -0800 [thread overview]
Message-ID: <5695A0EB.5020609@samsung.com> (raw)
In-Reply-To: <20160112141207.GF15554@cbox>
On 1/12/2016 6:12 AM, Christoffer Dall wrote:
> On Mon, Jan 11, 2016 at 03:39:21PM -0800, Mario Smarduch wrote:
>>
>>
>> On 1/10/2016 8:32 AM, Christoffer Dall wrote:
>>> Hi Mario,
>>>
>>> I spotted one more potential issue...
>>>
>>> On Sat, Dec 26, 2015 at 01:54:55PM -0800, Mario Smarduch wrote:
>>>> Add helper functions to enable access to fp/smid on guest entry and save host
>>>> fpexc on vcpu put, check if fp/simd registers are dirty and add new vcpu
>>>> fields.
>>>>
>>>> Signed-off-by: Mario Smarduch <m.smarduch@samsung•com>
>>>> ---
>>>> arch/arm/include/asm/kvm_emulate.h | 42 ++++++++++++++++++++++++++++++++++++
>>>> arch/arm/include/asm/kvm_host.h | 6 ++++++
>>>> arch/arm64/include/asm/kvm_emulate.h | 8 +++++++
>>>> 3 files changed, 56 insertions(+)
>>>>
>>>> diff --git a/arch/arm/include/asm/kvm_emulate.h b/arch/arm/include/asm/kvm_emulate.h
>>>> index 3095df0..d4d9da1 100644
>>>> --- a/arch/arm/include/asm/kvm_emulate.h
>>>> +++ b/arch/arm/include/asm/kvm_emulate.h
>>>> @@ -24,6 +24,8 @@
>>>> #include <asm/kvm_mmio.h>
>>>> #include <asm/kvm_arm.h>
>>>> #include <asm/cputype.h>
>>>> +#include <asm/vfp.h>
>>>> +#include "../vfp/vfpinstr.h"
>>>>
>>>> unsigned long *vcpu_reg(struct kvm_vcpu *vcpu, u8 reg_num);
>>>> unsigned long *vcpu_spsr(struct kvm_vcpu *vcpu);
>>>> @@ -255,4 +257,44 @@ static inline unsigned long vcpu_data_host_to_guest(struct kvm_vcpu *vcpu,
>>>> }
>>>> }
>>>>
>>>> +#ifdef CONFIG_VFPv3
>>>> +/* Called from vcpu_load - save fpexc and enable guest access to fp/simd unit */
>>>> +static inline void vcpu_trap_vfp_enable(struct kvm_vcpu *vcpu)
>>>> +{
>>>> + u32 fpexc;
>>>> +
>>>> + /* Save host fpexc, and enable guest access to fp unit */
>>>> + fpexc = fmrx(FPEXC);
>>>> + vcpu->arch.host_fpexc = fpexc;
>>>> + fpexc |= FPEXC_EN;
>>>> + fmxr(FPEXC, fpexc);
>>>> +
>>>> + /* Configure HCPTR to trap on tracing and fp/simd access */
>>>> + vcpu->arch.hcptr = HCPTR_TTA | HCPTR_TCP(10) | HCPTR_TCP(11);
>>>> +}
>>>> +
>>>> +/* Called from vcpu_put - restore host fpexc */
>>>> +static inline void vcpu_restore_host_fpexc(struct kvm_vcpu *vcpu)
>>>> +{
>>>> + fmxr(FPEXC, vcpu->arch.host_fpexc);
>>>> +}
>>>> +
>>>> +/* If trap bits are reset then fp/simd registers are dirty */
>>>> +static inline bool vcpu_vfp_isdirty(struct kvm_vcpu *vcpu)
>>>> +{
>>>> + return !(vcpu->arch.hcptr & (HCPTR_TCP(10) | HCPTR_TCP(11)));
>>>> +}
>>>> +#else
>>>> +static inline void vcpu_trap_vfp_enable(struct kvm_vcpu *vcpu)
>>>> +{
>>>> + vcpu->arch.hcptr = HCPTR_TTA;
>>>
>>> Is it correct not to trap VFP registers when the host kernel does not
>>> have CONFIG_VFPv3? I think this is a change in functionality compared
>>> to the current kernels is it not?
>>
>> With CPU_V7 VFPv3 gets selected, without it fp should be emulated,
>> with exceptions taken in guest kernel. I don't see a reason why
>> fp hcptr access should be enabled in that case.
>>
>
> If you have to guests with CONFIG_VFPV3 but your host doesn't have
> CONFIG_VFPV3, you will never context-switch the VFP registers between
> the two VMs, and mayhem will ensue.
>
> Unless I'm missing something very obvious?
Hi Christoffer,
- on host I disabled VFP/VFPv3 and got a lot of Illegal instructions
and many other problems. Perhaps disabling for armv7 this option may need
re-evaluation.
- Enabling VFPv3 on host and running guest with no vfpv3 appears
to work with few glitches.
- and vpfv3 host/guest works just fine.
Appears disabling vfpv3 on armv7 requires another investigation (atleast
on my end).
BTW this is on fast models.
- Mario
>
> -Christoffer
>
next prev parent reply other threads:[~2016-01-13 0:57 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-12-26 21:54 [PATCH v6 0/6] arm/arm64: KVM: Enhance armv7/8 fp/simd lazy switch Mario Smarduch
2015-12-26 21:54 ` [PATCH v6 1/6] arm/arm64: KVM: Introduce armv7 fp/simd vcpu fields and helpers Mario Smarduch
2016-01-05 15:00 ` Christoffer Dall
2016-01-05 19:28 ` Mario Smarduch
2016-01-10 16:32 ` Christoffer Dall
2016-01-11 23:17 ` Mario Smarduch
2016-01-10 16:32 ` Christoffer Dall
2016-01-11 23:39 ` Mario Smarduch
2016-01-12 14:12 ` Christoffer Dall
2016-01-13 0:57 ` Mario Smarduch [this message]
2016-01-14 3:03 ` Mario Smarduch
2016-01-14 13:27 ` Christoffer Dall
2016-01-14 13:55 ` Marc Zyngier
2016-01-15 2:02 ` Mario Smarduch
2016-01-15 9:03 ` Marc Zyngier
2016-01-16 1:21 ` Mario Smarduch
2016-01-21 2:29 ` Mario Smarduch
2015-12-26 21:54 ` [PATCH v6 2/6] arm: KVM: Introduce host fp/simd context switch function Mario Smarduch
2016-01-10 16:31 ` Christoffer Dall
2015-12-26 21:54 ` [PATCH v6 3/6] arm/arm64: KVM: Enable armv7 fp/simd enhanced context switch Mario Smarduch
2016-01-10 16:32 ` Christoffer Dall
2015-12-26 21:54 ` [PATCH v6 4/6] arm: KVM: Delete unused macros Mario Smarduch
2016-01-10 16:32 ` Christoffer Dall
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