On Tue, Aug 08, 2017 at 05:46:08PM +0100, James Morse wrote:
> Make tpidr_el2 a cpu-offset for per-cpu variables in the same way the
> host uses tpidr_el1. This lets tpidr_el{1,2} have the same value, and
> on VHE they can be the same register.
>
> KVM calls hyp_panic() when anything unexpected happens. This may occur
> while a guest owns the EL1 registers. KVM stashes the vcpu pointer in
> tpidr_el2, which it uses to find the host context in order to restore
> the host EL1 registers before parachuting into the host's panic().
>
> The host context is a struct kvm_cpu_context allocated in the per-cpu
> area, and mapped to hyp. Given the per-cpu offset for this CPU, this is
> easy to find. Change hyp_panic() to take a pointer to the
> struct kvm_cpu_context. Wrap these calls with an asm function that
> retrieves the struct kvm_cpu_context from the host's per-cpu area.
>
> Copy the per-cpu offset from the hosts tpidr_el1 into tpidr_el2 during
> kvm init. (Later patches will make this unnecessary for VHE hosts)
>
> We print out the vcpu pointer as part of the panic message. Add a back
> reference to the 'running vcpu' in the host cpu context to preserve this.
>
> Signed-off-by: James Morse <james.morse@xxxxxxx>
> ---
> Changes since v1:
> * Added a comment explaining how =kvm_host_cpu_state gets from a host-va
> to a hyp va.
> * Added the first paragraph to the commit message.
>
> arch/arm64/include/asm/kvm_host.h | 2 ++
> arch/arm64/kvm/hyp/hyp-entry.S | 12 ++++++++++++
> arch/arm64/kvm/hyp/s2-setup.c | 3 +++
> arch/arm64/kvm/hyp/switch.c | 25 +++++++++++++------------
> 4 files changed, 30 insertions(+), 12 deletions(-)
>
> diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
> index d68630007b14..7733492d9a35 100644
> --- a/arch/arm64/include/asm/kvm_host.h
> +++ b/arch/arm64/include/asm/kvm_host.h
> @@ -191,6 +191,8 @@ struct kvm_cpu_context {
> u64 sys_regs[NR_SYS_REGS];
> u32 copro[NR_COPRO_REGS];
> };
> +
> + struct kvm_vcpu *__hyp_running_vcpu;
> };
>
> typedef struct kvm_cpu_context kvm_cpu_context_t;
> diff --git a/arch/arm64/kvm/hyp/hyp-entry.S b/arch/arm64/kvm/hyp/hyp-entry.S
> index fce7cc507e0a..e4f37b9dd47c 100644
> --- a/arch/arm64/kvm/hyp/hyp-entry.S
> +++ b/arch/arm64/kvm/hyp/hyp-entry.S
> @@ -163,6 +163,18 @@ ENTRY(__hyp_do_panic)
> eret
> ENDPROC(__hyp_do_panic)
>
> +ENTRY(__hyp_panic)
> + /*
> + * '=kvm_host_cpu_state' is a host VA from the constant pool, it may
> + * not be accessible by this address from EL2, hyp_panic() converts
> + * it with kern_hyp_va() before use.
> + */
> + ldr x0, =kvm_host_cpu_state
> + mrs x1, tpidr_el2
> + add x0, x0, x1
> + b hyp_panic
> +ENDPROC(__hyp_panic)
> +
> .macro invalid_vector label, target = __hyp_panic
> .align 2
> \label:
> diff --git a/arch/arm64/kvm/hyp/s2-setup.c b/arch/arm64/kvm/hyp/s2-setup.c
> index b81f4091c909..eb401dbb285e 100644
> --- a/arch/arm64/kvm/hyp/s2-setup.c
> +++ b/arch/arm64/kvm/hyp/s2-setup.c
> @@ -84,5 +84,8 @@ u32 __hyp_text __init_stage2_translation(void)
>
> write_sysreg(val, vtcr_el2);
>
> + /* copy tpidr_el1 into tpidr_el2 for use by HYP */
> + write_sysreg(read_sysreg(tpidr_el1), tpidr_el2);
> +
> return parange;
> }
> diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
> index 945e79c641c4..235d615cee30 100644
> --- a/arch/arm64/kvm/hyp/switch.c
> +++ b/arch/arm64/kvm/hyp/switch.c
> @@ -286,9 +286,9 @@ int __hyp_text __kvm_vcpu_run(struct kvm_vcpu *vcpu)
> u64 exit_code;
>
> vcpu = kern_hyp_va(vcpu);
> - write_sysreg(vcpu, tpidr_el2);
>
> host_ctxt = kern_hyp_va(vcpu->arch.host_cpu_context);
> + host_ctxt->__hyp_running_vcpu = vcpu;
I'm fine with this for now, but eventually when we optimize KVM further
we may want to avoid doing this in every world-switch. One option is to
just set this pointer in vcpu_get and vcpu_load, but would it also be
possible to use the kvm_arm_running_vcpu per-cpu array directly?
> guest_ctxt = &vcpu->arch.ctxt;
>
> __sysreg_save_host_state(host_ctxt);
> @@ -393,7 +393,8 @@ int __hyp_text __kvm_vcpu_run(struct kvm_vcpu *vcpu)
>
> static const char __hyp_panic_string[] = "HYP panic:\nPS:%08llx PC:%016llx ESR:%08llx\nFAR:%016llx HPFAR:%016llx PAR:%016llx\nVCPU:%p\n";
>
> -static void __hyp_text __hyp_call_panic_nvhe(u64 spsr, u64 elr, u64 par)
> +static void __hyp_text __hyp_call_panic_nvhe(u64 spsr, u64 elr, u64 par,
> + struct kvm_vcpu *vcpu)
> {
> unsigned long str_va;
>
> @@ -407,35 +408,35 @@ static void __hyp_text __hyp_call_panic_nvhe(u64 spsr, u64 elr, u64 par)
> __hyp_do_panic(str_va,
> spsr, elr,
> read_sysreg(esr_el2), read_sysreg_el2(far),
> - read_sysreg(hpfar_el2), par,
> - (void *)read_sysreg(tpidr_el2));
> + read_sysreg(hpfar_el2), par, vcpu);
> }
>
> -static void __hyp_text __hyp_call_panic_vhe(u64 spsr, u64 elr, u64 par)
> +static void __hyp_text __hyp_call_panic_vhe(u64 spsr, u64 elr, u64 par,
> + struct kvm_vcpu *vcpu)
> {
> panic(__hyp_panic_string,
> spsr, elr,
> read_sysreg_el2(esr), read_sysreg_el2(far),
> - read_sysreg(hpfar_el2), par,
> - (void *)read_sysreg(tpidr_el2));
> + read_sysreg(hpfar_el2), par, vcpu);
> }
>
> static hyp_alternate_select(__hyp_call_panic,
> __hyp_call_panic_nvhe, __hyp_call_panic_vhe,
> ARM64_HAS_VIRT_HOST_EXTN);
>
> -void __hyp_text __noreturn __hyp_panic(void)
> +void __hyp_text __noreturn hyp_panic(struct kvm_cpu_context *__host_ctxt)
> {
> + struct kvm_vcpu *vcpu = NULL;
> +
> u64 spsr = read_sysreg_el2(spsr);
> u64 elr = read_sysreg_el2(elr);
> u64 par = read_sysreg(par_el1);
>
> if (read_sysreg(vttbr_el2)) {
> - struct kvm_vcpu *vcpu;
> struct kvm_cpu_context *host_ctxt;
>
> - vcpu = (struct kvm_vcpu *)read_sysreg(tpidr_el2);
> - host_ctxt = kern_hyp_va(vcpu->arch.host_cpu_context);
> + host_ctxt = kern_hyp_va(__host_ctxt);
> + vcpu = host_ctxt->__hyp_running_vcpu;
> __timer_save_state(vcpu);
> __deactivate_traps(vcpu);
> __deactivate_vm(vcpu);
> @@ -443,7 +444,7 @@ void __hyp_text __noreturn __hyp_panic(void)
> }
>
> /* Call panic for real */
> - __hyp_call_panic()(spsr, elr, par);
> + __hyp_call_panic()(spsr, elr, par, vcpu);
>
> unreachable();
> }
> --
> 2.13.3
>
Reviewed-by: Christoffer Dall <cdall@xxxxxxxxxx>
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