[PATCH 11/37] KVM: arm64: Improve debug register save/restore flow
Christoffer Dall
cdall at linaro.org
Fri Dec 1 09:52:03 PST 2017
On Tue, Nov 07, 2017 at 03:48:57PM +0100, Andrew Jones wrote:
> On Thu, Oct 12, 2017 at 12:41:15PM +0200, Christoffer Dall wrote:
> > Instead of having multiple calls from the world switch path to the debug
> > logic, each figuring out if the dirty bit is set and if we should
> > save/restore the debug registes, let's just provide two hooks to the
> > debug save/restore functionality, one for switching to the guest
> > context, and one for switching to the host context, and we get the
> > benefit of only having to evaluate the dirty flag once on each path,
> > plus we give the compiler some more room to inline some of this
> > functionality.
> >
> > Signed-off-by: Christoffer Dall <christoffer.dall at linaro.org>
> > ---
> > arch/arm64/include/asm/kvm_hyp.h | 10 ++-----
> > arch/arm64/kvm/hyp/debug-sr.c | 56 +++++++++++++++++++++++++++-------------
> > arch/arm64/kvm/hyp/switch.c | 6 ++---
> > 3 files changed, 42 insertions(+), 30 deletions(-)
> >
> > diff --git a/arch/arm64/include/asm/kvm_hyp.h b/arch/arm64/include/asm/kvm_hyp.h
> > index 08d3bb6..a0e5a70 100644
> > --- a/arch/arm64/include/asm/kvm_hyp.h
> > +++ b/arch/arm64/include/asm/kvm_hyp.h
> > @@ -139,14 +139,8 @@ void __sysreg_restore_guest_state(struct kvm_cpu_context *ctxt);
> > void __sysreg32_save_state(struct kvm_vcpu *vcpu);
> > void __sysreg32_restore_state(struct kvm_vcpu *vcpu);
> >
> > -void __debug_save_state(struct kvm_vcpu *vcpu,
> > - struct kvm_guest_debug_arch *dbg,
> > - struct kvm_cpu_context *ctxt);
> > -void __debug_restore_state(struct kvm_vcpu *vcpu,
> > - struct kvm_guest_debug_arch *dbg,
> > - struct kvm_cpu_context *ctxt);
> > -void __debug_cond_save_host_state(struct kvm_vcpu *vcpu);
> > -void __debug_cond_restore_host_state(struct kvm_vcpu *vcpu);
> > +void __debug_switch_to_guest(struct kvm_vcpu *vcpu);
> > +void __debug_switch_to_host(struct kvm_vcpu *vcpu);
> >
> > void __fpsimd_save_state(struct user_fpsimd_state *fp_regs);
> > void __fpsimd_restore_state(struct user_fpsimd_state *fp_regs);
> > diff --git a/arch/arm64/kvm/hyp/debug-sr.c b/arch/arm64/kvm/hyp/debug-sr.c
> > index a2291b6..b4cd8e0 100644
> > --- a/arch/arm64/kvm/hyp/debug-sr.c
> > +++ b/arch/arm64/kvm/hyp/debug-sr.c
> > @@ -116,16 +116,13 @@ static void __hyp_text __debug_restore_spe(u64 pmscr_el1)
> > write_sysreg_s(pmscr_el1, PMSCR_EL1);
> > }
> >
> > -void __hyp_text __debug_save_state(struct kvm_vcpu *vcpu,
> > - struct kvm_guest_debug_arch *dbg,
> > - struct kvm_cpu_context *ctxt)
> > +static void __hyp_text __debug_save_state(struct kvm_vcpu *vcpu,
> > + struct kvm_guest_debug_arch *dbg,
> > + struct kvm_cpu_context *ctxt)
> > {
> > u64 aa64dfr0;
> > int brps, wrps;
> >
> > - if (!(vcpu->arch.debug_flags & KVM_ARM64_DEBUG_DIRTY))
> > - return;
> > -
> > aa64dfr0 = read_sysreg(id_aa64dfr0_el1);
> > brps = (aa64dfr0 >> 12) & 0xf;
> > wrps = (aa64dfr0 >> 20) & 0xf;
> > @@ -138,16 +135,13 @@ void __hyp_text __debug_save_state(struct kvm_vcpu *vcpu,
> > ctxt->sys_regs[MDCCINT_EL1] = read_sysreg(mdccint_el1);
> > }
> >
> > -void __hyp_text __debug_restore_state(struct kvm_vcpu *vcpu,
> > - struct kvm_guest_debug_arch *dbg,
> > - struct kvm_cpu_context *ctxt)
> > +static void __hyp_text __debug_restore_state(struct kvm_vcpu *vcpu,
> > + struct kvm_guest_debug_arch *dbg,
> > + struct kvm_cpu_context *ctxt)
> > {
> > u64 aa64dfr0;
> > int brps, wrps;
> >
> > - if (!(vcpu->arch.debug_flags & KVM_ARM64_DEBUG_DIRTY))
> > - return;
> > -
> > aa64dfr0 = read_sysreg(id_aa64dfr0_el1);
> >
> > brps = (aa64dfr0 >> 12) & 0xf;
> > @@ -161,24 +155,50 @@ void __hyp_text __debug_restore_state(struct kvm_vcpu *vcpu,
> > write_sysreg(ctxt->sys_regs[MDCCINT_EL1], mdccint_el1);
> > }
> >
> > -void __hyp_text __debug_cond_save_host_state(struct kvm_vcpu *vcpu)
> > +void __hyp_text __debug_switch_to_guest(struct kvm_vcpu *vcpu)
> > {
> > - __debug_save_state(vcpu, &vcpu->arch.host_debug_state.regs,
> > - kern_hyp_va(vcpu->arch.host_cpu_context));
> > + struct kvm_cpu_context *__host_ctxt;
> > + struct kvm_cpu_context *__guest_ctxt;
> > + struct kvm_guest_debug_arch *__host_dbg;
> > + struct kvm_guest_debug_arch *__guest_dbg;
>
> I caught in your reply to Marc that the __ prefix here is for hyp mode
> accessible code and data, but do we also need to use it for stack data?
> No big deal, but it's not very pretty.
>
sure.
> >
> > /* Non-VHE: Disable and flush SPE data generation
> > * VHE: The vcpu can run. but it can't hide. */
> > if (!has_vhe())
> > __debug_save_spe_nvhe(&vcpu->arch.host_debug_state.pmscr_el1);
> > +
> > + if (!(vcpu->arch.debug_flags & KVM_ARM64_DEBUG_DIRTY))
> > + return;
> > +
> > + __host_ctxt = kern_hyp_va(vcpu->arch.host_cpu_context);
> > + __guest_ctxt = &vcpu->arch.ctxt;
> > + __host_dbg = &vcpu->arch.host_debug_state.regs;
> > + __guest_dbg = kern_hyp_va(vcpu->arch.debug_ptr);
> > +
> > + __debug_save_state(vcpu, __host_dbg, __host_ctxt);
> > + __debug_restore_state(vcpu, __guest_dbg, __guest_ctxt);
> > }
> >
> > -void __hyp_text __debug_cond_restore_host_state(struct kvm_vcpu *vcpu)
> > +void __hyp_text __debug_switch_to_host(struct kvm_vcpu *vcpu)
> > {
> > + struct kvm_cpu_context *__host_ctxt;
> > + struct kvm_cpu_context *__guest_ctxt;
> > + struct kvm_guest_debug_arch *__host_dbg;
> > + struct kvm_guest_debug_arch *__guest_dbg;
> > +
> > if (!has_vhe())
> > __debug_restore_spe(vcpu->arch.host_debug_state.pmscr_el1);
> >
> > - __debug_restore_state(vcpu, &vcpu->arch.host_debug_state.regs,
> > - kern_hyp_va(vcpu->arch.host_cpu_context));
> > + if (!(vcpu->arch.debug_flags & KVM_ARM64_DEBUG_DIRTY))
> > + return;
> > +
> > + __host_ctxt = kern_hyp_va(vcpu->arch.host_cpu_context);
> > + __guest_ctxt = &vcpu->arch.ctxt;
> > + __host_dbg = &vcpu->arch.host_debug_state.regs;
> > + __guest_dbg = kern_hyp_va(vcpu->arch.debug_ptr);
> > +
> > + __debug_save_state(vcpu, __guest_dbg, __guest_ctxt);
> > + __debug_restore_state(vcpu, __host_dbg, __host_ctxt);
> >
> > vcpu->arch.debug_flags &= ~KVM_ARM64_DEBUG_DIRTY;
> > }
> > diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
> > index ef05c59..e270cba 100644
> > --- a/arch/arm64/kvm/hyp/switch.c
> > +++ b/arch/arm64/kvm/hyp/switch.c
> > @@ -271,7 +271,6 @@ int __hyp_text __kvm_vcpu_run(struct kvm_vcpu *vcpu)
> > guest_ctxt = &vcpu->arch.ctxt;
> >
> > __sysreg_save_host_state(host_ctxt);
> > - __debug_cond_save_host_state(vcpu);
> >
> > __activate_traps(vcpu);
> > __activate_vm(vcpu);
> > @@ -285,7 +284,7 @@ int __hyp_text __kvm_vcpu_run(struct kvm_vcpu *vcpu)
> > */
> > __sysreg32_restore_state(vcpu);
> > __sysreg_restore_guest_state(guest_ctxt);
> > - __debug_restore_state(vcpu, kern_hyp_va(vcpu->arch.debug_ptr), guest_ctxt);
> > + __debug_switch_to_guest(vcpu);
> >
> > /* Jump in the fire! */
> > again:
> > @@ -353,12 +352,11 @@ int __hyp_text __kvm_vcpu_run(struct kvm_vcpu *vcpu)
> >
> > __sysreg_restore_host_state(host_ctxt);
> >
> > - __debug_save_state(vcpu, kern_hyp_va(vcpu->arch.debug_ptr), guest_ctxt);
> > /*
> > * This must come after restoring the host sysregs, since a non-VHE
> > * system may enable SPE here and make use of the TTBRs.
> > */
> > - __debug_cond_restore_host_state(vcpu);
> > + __debug_switch_to_host(vcpu);
> >
> > return exit_code;
> > }
> > --
> > 2.9.0
> >
>
> This looks like a nice cleanup, but can you please add a note to the
> commit message about why we don't need to use the
>
> save-host-state
> activate-traps-and-vm
> restore-guest-state
>
> and the reverse, patterns for the debug registers?
I think the current commit message motivates the change fine.
Thanks,
-Christoffer
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