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@xxxxxxxxxxx>
>> ---
>> 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.
>
> Thanks,
> -Christoffer
>
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