[PATCH 11/37] KVM: arm64: Improve debug register save/restore flow
Andrew Jones
drjones at redhat.com
Tue Nov 7 06:48:57 PST 2017
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.
>
> /* 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? As of this patch, that
pattern still exists for the sysregs.
Thanks,
drew
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