On Wed, May 23, 2018 at 08:35:13PM +0100, Alex Bennée wrote:
>
> Dave Martin <dave.mar...@arm.com> writes:
>
> > To make the lazy FPSIMD context switch trap code easier to hack on,
> > this patch converts it to C.
> >
> > This is not amazingly efficient, but the trap should typically only
> > be taken once per host context switch.
> >
> > Signed-off-by: Dave Martin <dave.mar...@arm.com>
> > Reviewed-by: Marc Zyngier <marc.zyng...@arm.com>
> > ---
> > arch/arm64/kvm/hyp/entry.S | 57
> > +++++++++++++++++----------------------------
> > arch/arm64/kvm/hyp/switch.c | 24 +++++++++++++++++++
> > 2 files changed, 46 insertions(+), 35 deletions(-)
> >
> > diff --git a/arch/arm64/kvm/hyp/entry.S b/arch/arm64/kvm/hyp/entry.S
> > index e41a161..40f349b 100644
> > --- a/arch/arm64/kvm/hyp/entry.S
> > +++ b/arch/arm64/kvm/hyp/entry.S
> > @@ -172,40 +172,27 @@ ENTRY(__fpsimd_guest_restore)
> > // x1: vcpu
> > // x2-x29,lr: vcpu regs
> > // vcpu x0-x1 on the stack
> > - stp x2, x3, [sp, #-16]!
> > - stp x4, lr, [sp, #-16]!
> > -
> > -alternative_if_not ARM64_HAS_VIRT_HOST_EXTN
> > - mrs x2, cptr_el2
> > - bic x2, x2, #CPTR_EL2_TFP
> > - msr cptr_el2, x2
> > -alternative_else
> > - mrs x2, cpacr_el1
> > - orr x2, x2, #CPACR_EL1_FPEN
> > - msr cpacr_el1, x2
> > -alternative_endif
> > - isb
> > -
> > - mov x3, x1
> > -
> > - ldr x0, [x3, #VCPU_HOST_CONTEXT]
> > - kern_hyp_va x0
> > - add x0, x0, #CPU_GP_REG_OFFSET(CPU_FP_REGS)
> > - bl __fpsimd_save_state
> > -
> > - add x2, x3, #VCPU_CONTEXT
> > - add x0, x2, #CPU_GP_REG_OFFSET(CPU_FP_REGS)
> > - bl __fpsimd_restore_state
> > -
> > - // Skip restoring fpexc32 for AArch64 guests
> > - mrs x1, hcr_el2
> > - tbnz x1, #HCR_RW_SHIFT, 1f
> > - ldr x4, [x3, #VCPU_FPEXC32_EL2]
> > - msr fpexc32_el2, x4
> > -1:
> > - ldp x4, lr, [sp], #16
> > - ldp x2, x3, [sp], #16
> > - ldp x0, x1, [sp], #16
> > -
> > + stp x2, x3, [sp, #-144]!
> > + stp x4, x5, [sp, #16]
> > + stp x6, x7, [sp, #32]
> > + stp x8, x9, [sp, #48]
> > + stp x10, x11, [sp, #64]
> > + stp x12, x13, [sp, #80]
> > + stp x14, x15, [sp, #96]
> > + stp x16, x17, [sp, #112]
> > + stp x18, lr, [sp, #128]
> > +
> > + bl __hyp_switch_fpsimd
> > +
> > + ldp x4, x5, [sp, #16]
> > + ldp x6, x7, [sp, #32]
> > + ldp x8, x9, [sp, #48]
> > + ldp x10, x11, [sp, #64]
> > + ldp x12, x13, [sp, #80]
> > + ldp x14, x15, [sp, #96]
> > + ldp x16, x17, [sp, #112]
> > + ldp x18, lr, [sp, #128]
> > + ldp x0, x1, [sp, #144]
> > + ldp x2, x3, [sp], #160
> > eret
> > ENDPROC(__fpsimd_guest_restore)
> > diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
> > index d964523..c0796c4 100644
> > --- a/arch/arm64/kvm/hyp/switch.c
> > +++ b/arch/arm64/kvm/hyp/switch.c
> > @@ -318,6 +318,30 @@ static bool __hyp_text __skip_instr(struct kvm_vcpu
> > *vcpu)
> > }
> > }
> >
> > +void __hyp_text __hyp_switch_fpsimd(u64 esr __always_unused,
> > + struct kvm_vcpu *vcpu)
> > +{
> > + kvm_cpu_context_t *host_ctxt;
> > +
> > + if (has_vhe())
> > + write_sysreg(read_sysreg(cpacr_el1) | CPACR_EL1_FPEN,
> > + cpacr_el1);
> > + else
> > + write_sysreg(read_sysreg(cptr_el2) & ~(u64)CPTR_EL2_TFP,
> > + cptr_el2);
>
> Is there no way to do alternative() in C or does it always come down to
> different inline asms?
>
has_vhe() should resolve to a static key, and I prefer this over the
previous alternative construct we had for selecting function calls in C,
as that resultet in having to follow too many levels of indirection.
Thanks,
-Christoffer
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