On 12/18/2015 5:49 AM, Christoffer Dall wrote:
> On Sun, Dec 06, 2015 at 05:07:13PM -0800, Mario Smarduch wrote:
>> This patch tracks armv7 fp/simd hardware state with hcptr register.
>> On vcpu_load saves host fpexc, enables FP access, and sets trapping
>> on fp/simd access. On first fp/simd access trap to handler to save host and
>> restore guest context, clear trapping bits to enable vcpu lazy mode. On
>> vcpu_put if trap bits are cleared save guest and restore host context and
>> always restore host fpexc.
>>
>> Signed-off-by: Mario Smarduch <m.smarduch@xxxxxxxxxxx>
>> ---
>> arch/arm/include/asm/kvm_emulate.h | 50 ++++++++++++++++++++++++++++++++++++
>> arch/arm/include/asm/kvm_host.h | 1 +
>> arch/arm/kvm/Makefile | 2 +-
>> arch/arm/kvm/arm.c | 13 ++++++++++
>> arch/arm/kvm/fpsimd_switch.S | 46 +++++++++++++++++++++++++++++++++
>> arch/arm/kvm/interrupts.S | 32 +++++------------------
>> arch/arm/kvm/interrupts_head.S | 33 ++++++++++--------------
>> arch/arm64/include/asm/kvm_emulate.h | 9 +++++++
>> arch/arm64/include/asm/kvm_host.h | 1 +
>> 9 files changed, 142 insertions(+), 45 deletions(-)
>> create mode 100644 arch/arm/kvm/fpsimd_switch.S
>>
>> diff --git a/arch/arm/include/asm/kvm_emulate.h b/arch/arm/include/asm/kvm_emulate.h
>> index a9c80a2..3de11a2 100644
>> --- a/arch/arm/include/asm/kvm_emulate.h
>> +++ b/arch/arm/include/asm/kvm_emulate.h
>> @@ -243,4 +243,54 @@ 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 */
>
> are you really enabling guest access here or just fiddling with fpexc to
> ensure you trap accesses to hyp ?
That's the end goal, but it is setting the fp enable bit? Your later comment of
combining functions and remove assembler should work.
>
>> +static inline void kvm_enable_vcpu_fpexc(struct kvm_vcpu *vcpu)
>> +{
>> + u32 fpexc;
>> +
>> + asm volatile(
>> + "mrc p10, 7, %0, cr8, cr0, 0\n"
>> + "str %0, [%1]\n"
>> + "mov %0, #(1 << 30)\n"
>> + "mcr p10, 7, %0, cr8, cr0, 0\n"
>> + "isb\n"
>
> why do you need an ISB here? won't there be an implicit one from the
> HVC call later before you need this to take effect?
I would think so, but besides B.2.7.3 I can't find other references on
visibility of context altering instructions.
>
>> + : "+r" (fpexc)
>> + : "r" (&vcpu->arch.host_fpexc)
>> + );
>
> this whole bit can be rewritten something like:
>
> fpexc = fmrx(FPEXC);
> vcpu->arch.host_fpexc = fpexc;
> fpexc |= FPEXC_EN;
> fmxr(FPEXC, fpexc);
Didn't know about fmrx/fmxr functions - much better.
>
>> +}
>> +
>> +/* Called from vcpu_put - restore host fpexc */
>> +static inline void kvm_restore_host_fpexc(struct kvm_vcpu *vcpu)
>> +{
>> + asm volatile(
>> + "mcr p10, 7, %0, cr8, cr0, 0\n"
>> + :
>> + : "r" (vcpu->arch.host_fpexc)
>> + );
>
> similarly here
Ok.
>
>> +}
>> +
>> +/* If trap bits are reset then fp/simd registers are dirty */
>> +static inline bool kvm_vcpu_vfp_isdirty(struct kvm_vcpu *vcpu)
>> +{
>> + return !!(~vcpu->arch.hcptr & (HCPTR_TCP(10) | HCPTR_TCP(11)));
>
> this looks complicated, how about:
>
> return !(vcpu->arch.hcptr & (HCPTR_TCP(10) | HCPTR_TCP(11)));
Yeah, I twisted the meaning of bool.
>
>> +}
>> +
>> +static inline void vcpu_reset_cptr(struct kvm_vcpu *vcpu)
>> +{
>> + vcpu->arch.hcptr |= (HCPTR_TTA | HCPTR_TCP(10) | HCPTR_TCP(11));
>> +}
>> +#else
>> +static inline void kvm_enable_vcpu_fpexc(struct kvm_vcpu *vcpu) {}
>> +static inline void kvm_restore_host_fpexc(struct kvm_vcpu *vcpu) {}
>> +static inline bool kvm_vcpu_vfp_isdirty(struct kvm_vcpu *vcpu)
>> +{
>> + return false;
>> +}
>> +static inline void vcpu_reset_cptr(struct kvm_vcpu *vcpu)
>> +{
>> + vcpu->arch.hcptr = HCPTR_TTA;
>> +}
>> +#endif
>> +
>> #endif /* __ARM_KVM_EMULATE_H__ */
>> diff --git a/arch/arm/include/asm/kvm_host.h b/arch/arm/include/asm/kvm_host.h
>> index 09bb1f2..ecc883a 100644
>> --- a/arch/arm/include/asm/kvm_host.h
>> +++ b/arch/arm/include/asm/kvm_host.h
>> @@ -227,6 +227,7 @@ int kvm_perf_teardown(void);
>> void kvm_mmu_wp_memory_region(struct kvm *kvm, int slot);
>>
>> struct kvm_vcpu *kvm_mpidr_to_vcpu(struct kvm *kvm, unsigned long mpidr);
>> +void kvm_restore_host_vfp_state(struct kvm_vcpu *);
>>
>> static inline void kvm_arch_hardware_disable(void) {}
>> static inline void kvm_arch_hardware_unsetup(void) {}
>> diff --git a/arch/arm/kvm/Makefile b/arch/arm/kvm/Makefile
>> index c5eef02c..411b3e4 100644
>> --- a/arch/arm/kvm/Makefile
>> +++ b/arch/arm/kvm/Makefile
>> @@ -19,7 +19,7 @@ kvm-arm-y = $(KVM)/kvm_main.o $(KVM)/coalesced_mmio.o $(KVM)/eventfd.o $(KVM)/vf
>>
>> obj-y += kvm-arm.o init.o interrupts.o
>> obj-y += arm.o handle_exit.o guest.o mmu.o emulate.o reset.o
>> -obj-y += coproc.o coproc_a15.o coproc_a7.o mmio.o psci.o perf.o
>> +obj-y += coproc.o coproc_a15.o coproc_a7.o mmio.o psci.o perf.o fpsimd_switch.o
>> obj-y += $(KVM)/arm/vgic.o
>> obj-y += $(KVM)/arm/vgic-v2.o
>> obj-y += $(KVM)/arm/vgic-v2-emul.o
>> diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
>> index dc017ad..1de07ab 100644
>> --- a/arch/arm/kvm/arm.c
>> +++ b/arch/arm/kvm/arm.c
>> @@ -291,10 +291,23 @@ void kvm_arch_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
>> vcpu->arch.host_cpu_context = this_cpu_ptr(kvm_host_cpu_state);
>>
>> kvm_arm_set_running_vcpu(vcpu);
>> +
>> + /* Save and enable FPEXC before we load guest context */
>> + kvm_enable_vcpu_fpexc(vcpu);
>
> hmmm, not really sure the 'enable' part of this name is the right choice
> when looking at this. kvm_prepare_vcpu_fpexc ?
>
>> +
>> + /* reset hyp cptr register to trap on tracing and vfp/simd access*/
>> + vcpu_reset_cptr(vcpu);
>
> alternatively you could combine the two functions above into a single
> function called something like "vcpu_trap_vfp_enable()" or
> "vcpu_load_configure_vfp()"
>
> (I sort of feel like we have reserved the _reset_ namespace for stuff we
> actually do at VCPU reset.)
Related to earlier comment I would be in favor of combining and use
'vcpu_trap_vfp_enable()'.
>
>
>> }
>>
>> void kvm_arch_vcpu_put(struct kvm_vcpu *vcpu)
>> {
>> + /* If the fp/simd registers are dirty save guest, restore host. */
>> + if (kvm_vcpu_vfp_isdirty(vcpu))
>> + kvm_restore_host_vfp_state(vcpu);
>> +
>> + /* Restore host FPEXC trashed in vcpu_load */
>> + kvm_restore_host_fpexc(vcpu);
>> +
>> /*
>> * The arch-generic KVM code expects the cpu field of a vcpu to be -1
>> * if the vcpu is no longer assigned to a cpu. This is used for the
>> diff --git a/arch/arm/kvm/fpsimd_switch.S b/arch/arm/kvm/fpsimd_switch.S
>> new file mode 100644
>> index 0000000..d297c54
>> --- /dev/null
>> +++ b/arch/arm/kvm/fpsimd_switch.S
>> @@ -0,0 +1,46 @@
>> +/*
>> + * Copyright (C) 2012 - Virtual Open Systems and Columbia University
>> + * Author: Christoffer Dall <c.dall@xxxxxxxxxxxxxxxxxxxxxx>
>
> Not quite, this is new code, so you should just claim copyright and
> authorship I believe.
Ok didn't know.
>
>> + *
>> + * 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.
>> + *
>> + */
>> +#include <linux/linkage.h>
>> +#include <linux/const.h>
>> +#include <asm/unified.h>
>> +#include <asm/page.h>
>> +#include <asm/ptrace.h>
>> +#include <asm/asm-offsets.h>
>> +#include <asm/kvm_asm.h>
>> +#include <asm/kvm_arm.h>
>> +#include <asm/vfpmacros.h>
>> +#include "interrupts_head.S"
>> +
>> + .text
>> +/**
>> + * void kvm_restore_host_vfp_state(struct vcpu *vcpu) -
>> + * This function is called from host to save the guest, and restore host
>> + * fp/simd hardware context. It's placed outside of hyp start/end region.
>> + */
>> +ENTRY(kvm_restore_host_vfp_state)
>> +#ifdef CONFIG_VFPv3
>> + push {r4-r7}
>> +
>> + add r7, r0, #VCPU_VFP_GUEST
>> + store_vfp_state r7
>> +
>> + add r7, r0, #VCPU_VFP_HOST
>> + ldr r7, [r7]
>> + restore_vfp_state r7
>> +
>> + pop {r4-r7}
>> +#endif
>> + bx lr
>> +ENDPROC(kvm_restore_host_vfp_state)
>> diff --git a/arch/arm/kvm/interrupts.S b/arch/arm/kvm/interrupts.S
>> index 900ef6d..8e25431 100644
>> --- a/arch/arm/kvm/interrupts.S
>> +++ b/arch/arm/kvm/interrupts.S
>> @@ -116,22 +116,15 @@ ENTRY(__kvm_vcpu_run)
>> read_cp15_state store_to_vcpu = 0
>> write_cp15_state read_from_vcpu = 1
>>
>> - @ If the host kernel has not been configured with VFPv3 support,
>> - @ then it is safer if we deny guests from using it as well.
>> -#ifdef CONFIG_VFPv3
>> - @ Set FPEXC_EN so the guest doesn't trap floating point instructions
>> - VFPFMRX r2, FPEXC @ VMRS
>> - push {r2}
>> - orr r2, r2, #FPEXC_EN
>> - VFPFMXR FPEXC, r2 @ VMSR
>> -#endif
>> + @ Enable tracing and possibly fp/simd trapping
>
> Configure trapping of access to tracing and fp/simd registers
ok.
>
>> + ldr r4, [vcpu, #VCPU_HCPTR]
>> + set_hcptr vmentry, #0, r4
>
> if we store something called HCPTR on the VCPU, then that should really
> be HCPTR, so I don't see why we need a macro and this is not just a
> write to the HCPTR directly?
The macro handled some corner cases, but it's getting messy. I'll remove it.
>
>>
>> @ Configure Hyp-role
>> configure_hyp_role vmentry
>>
>> @ Trap coprocessor CRx accesses
>> set_hstr vmentry
>> - set_hcptr vmentry, (HCPTR_TTA | HCPTR_TCP(10) | HCPTR_TCP(11))
>> set_hdcr vmentry
>>
>> @ Write configured ID register into MIDR alias
>> @@ -170,23 +163,12 @@ __kvm_vcpu_return:
>> @ Don't trap coprocessor accesses for host kernel
>> set_hstr vmexit
>> set_hdcr vmexit
>> - set_hcptr vmexit, (HCPTR_TTA | HCPTR_TCP(10) | HCPTR_TCP(11)), after_vfp_restore
>>
>> -#ifdef CONFIG_VFPv3
>> - @ Switch VFP/NEON hardware state to the host's
>> - add r7, vcpu, #VCPU_VFP_GUEST
>> - store_vfp_state r7
>> - add r7, vcpu, #VCPU_VFP_HOST
>> - ldr r7, [r7]
>> - restore_vfp_state r7
>> + /* Preserve HCPTR across exits */
>> + mrc p15, 4, r2, c1, c1, 2
>> + str r2, [vcpu, #VCPU_HCPTR]
>
> can't you do this in the trap handler so you avoid this on every exit
Ah right you could, updated register is retained until next vcpu_load.
>
>>
>> -after_vfp_restore:
>> - @ Restore FPEXC_EN which we clobbered on entry
>> - pop {r2}
>> - VFPFMXR FPEXC, r2
>> -#else
>> -after_vfp_restore:
>> -#endif
>> + set_hcptr vmexit, (HCPTR_TTA | HCPTR_TCP(10) | HCPTR_TCP(11))
>
> again here, I don't think you need a macro, just clear the bits and
> store the register.
>
>>
>> @ Reset Hyp-role
>> configure_hyp_role vmexit
>> diff --git a/arch/arm/kvm/interrupts_head.S b/arch/arm/kvm/interrupts_head.S
>> index 51a5950..7701ccd 100644
>> --- a/arch/arm/kvm/interrupts_head.S
>> +++ b/arch/arm/kvm/interrupts_head.S
>> @@ -593,29 +593,24 @@ ARM_BE8(rev r6, r6 )
>> * (hardware reset value is 0). Keep previous value in r2.
>> * An ISB is emited on vmexit/vmtrap, but executed on vmexit only if
>> * VFP wasn't already enabled (always executed on vmtrap).
>> - * If a label is specified with vmexit, it is branched to if VFP wasn't
>> - * enabled.
>> */
>> -.macro set_hcptr operation, mask, label = none
>> - mrc p15, 4, r2, c1, c1, 2
>> - ldr r3, =\mask
>> +.macro set_hcptr operation, mask, reg
>> + mrc p15, 4, r2, c1, c1, 2
>> .if \operation == vmentry
>> - orr r3, r2, r3 @ Trap coproc-accesses defined in mask
>> + mov r3, \reg @ Trap coproc-accesses defined in mask
>> .else
>> - bic r3, r2, r3 @ Don't trap defined coproc-accesses
>> - .endif
>> - mcr p15, 4, r3, c1, c1, 2
>> - .if \operation != vmentry
>> - .if \operation == vmexit
>> - tst r2, #(HCPTR_TCP(10) | HCPTR_TCP(11))
>> - beq 1f
>> - .endif
>> - isb
>> - .if \label != none
>> - b \label
>> - .endif
>> + ldr r3, =\mask
>> + bic r3, r2, r3 @ Don't trap defined coproc-accesses
>> + .endif
>> + mcr p15, 4, r3, c1, c1, 2
>> + .if \operation != vmentry
>> + .if \operation == vmexit
>> + tst r2, #(HCPTR_TCP(10) | HCPTR_TCP(11))
>> + beq 1f
>> + .endif
>> + isb
>> 1:
>> - .endif
>> + .endif
>
> there are white-space issues here, but I think you can rid of this macro
> entirely now.
>
>> .endm
>>
>> /* Configures the HDCR (Hyp Debug Configuration Register) on entry/return
>> diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
>> index 17e92f0..8dccbd7 100644
>> --- a/arch/arm64/include/asm/kvm_emulate.h
>> +++ b/arch/arm64/include/asm/kvm_emulate.h
>> @@ -290,4 +290,13 @@ static inline unsigned long vcpu_data_host_to_guest(struct kvm_vcpu *vcpu,
>> return data; /* Leave LE untouched */
>> }
>>
>> +static inline void kvm_enable_vcpu_fpexc(struct kvm_vcpu *vcpu) {}
>> +static inline void kvm_restore_host_fpexc(struct kvm_vcpu *vcpu) {}
>> +static inline void vcpu_reset_cptr(struct kvm_vcpu *vcpu) {}
>> +
>> +static inline bool kvm_vcpu_vfp_isdirty(struct kvm_vcpu *vcpu)
>> +{
>> + return false;
>> +}
>> +
>> #endif /* __ARM64_KVM_EMULATE_H__ */
>> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
>> index 4562459..e16fd39 100644
>> --- a/arch/arm64/include/asm/kvm_host.h
>> +++ b/arch/arm64/include/asm/kvm_host.h
>> @@ -248,6 +248,7 @@ static inline void kvm_arch_hardware_unsetup(void) {}
>> static inline void kvm_arch_sync_events(struct kvm *kvm) {}
>> static inline void kvm_arch_vcpu_uninit(struct kvm_vcpu *vcpu) {}
>> static inline void kvm_arch_sched_in(struct kvm_vcpu *vcpu, int cpu) {}
>> +static inline void kvm_restore_host_vfp_state(struct kvm_vcpu *vcpu) {}
>>
>> void kvm_arm_init_debug(void);
>> void kvm_arm_setup_debug(struct kvm_vcpu *vcpu);
>> --
>> 1.9.1
>>
>
> Thanks,
> -Christoffer
>
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