Re: [PATCH 05/11] arm64: KVM: Stop save/restoring host tpidr_el1 on VHE

Christoffer Dall
2017-06-06T20:00:03Z

On Mon, May 15, 2017 at 06:43:53PM +0100, James Morse wrote:
> Now that a VHE host uses tpidr_el2 for the cpu offset we no longer
> need KVM to save/restore tpidr_el1. Move this from the 'common' code
> into the non-vhe code. While we're at it, on VHE we don't need to
> save the ELR or SPSR as kernel_entry in entry.S will have pushed these
> onto the kernel stack, and will restore them from there. Move these
> to the non-vhe code as we need them to get back to the host.
>
> Finally remove the always-copy-tpidr we hid in the stage2 setup
> code, cpufeature's enable callback will do this for VHE, we only
> need KVM to do it for non-vhe. Add the copy into kvm-init instead.
>

Reviewed-by: Christoffer Dall <cdall-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>

> Signed-off-by: James Morse <james.morse-5wv7dgnIgG8@public.gmane.org>
> ---
> arch/arm64/kvm/hyp-init.S | 4 ++++
> arch/arm64/kvm/hyp/s2-setup.c | 3 ---
> arch/arm64/kvm/hyp/sysreg-sr.c | 16 ++++++++--------
> 3 files changed, 12 insertions(+), 11 deletions(-)
>
> diff --git a/arch/arm64/kvm/hyp-init.S b/arch/arm64/kvm/hyp-init.S
> index 839425c24b1c..b8219801bb28 100644
> --- a/arch/arm64/kvm/hyp-init.S
> +++ b/arch/arm64/kvm/hyp-init.S
> @@ -119,6 +119,10 @@ __do_hyp_init:
> kern_hyp_va x2
> msr vbar_el2, x2
>
> + /* copy tpidr_el1 into tpidr_el2 for use by HYP */
> + mrs x1, tpidr_el1
> + msr tpidr_el2, x1
> +
> /* Hello, World! */
> eret
> ENDPROC(__kvm_hyp_init)
> diff --git a/arch/arm64/kvm/hyp/s2-setup.c b/arch/arm64/kvm/hyp/s2-setup.c
> index eb401dbb285e..b81f4091c909 100644
> --- a/arch/arm64/kvm/hyp/s2-setup.c
> +++ b/arch/arm64/kvm/hyp/s2-setup.c
> @@ -84,8 +84,5 @@ 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/sysreg-sr.c b/arch/arm64/kvm/hyp/sysreg-sr.c
> index 934137647837..c54cc2afb92b 100644
> --- a/arch/arm64/kvm/hyp/sysreg-sr.c
> +++ b/arch/arm64/kvm/hyp/sysreg-sr.c
> @@ -27,8 +27,8 @@ static void __hyp_text __sysreg_do_nothing(struct kvm_cpu_context *ctxt) { }
> /*
> * Non-VHE: Both host and guest must save everything.
> *
> - * VHE: Host must save tpidr*_el[01], actlr_el1, mdscr_el1, sp0, pc,
> - * pstate, and guest must save everything.
> + * VHE: Host must save tpidr*_el0, actlr_el1, mdscr_el1, sp_el0,
> + * and guest must save everything.
> */
>
> static void __hyp_text __sysreg_save_common_state(struct kvm_cpu_context *ctxt)
> @@ -36,11 +36,8 @@ static void __hyp_text __sysreg_save_common_state(struct kvm_cpu_context *ctxt)
> ctxt->sys_regs[ACTLR_EL1] = read_sysreg(actlr_el1);
> ctxt->sys_regs[TPIDR_EL0] = read_sysreg(tpidr_el0);
> ctxt->sys_regs[TPIDRRO_EL0] = read_sysreg(tpidrro_el0);
> - ctxt->sys_regs[TPIDR_EL1] = read_sysreg(tpidr_el1);
> ctxt->sys_regs[MDSCR_EL1] = read_sysreg(mdscr_el1);
> ctxt->gp_regs.regs.sp = read_sysreg(sp_el0);
> - ctxt->gp_regs.regs.pc = read_sysreg_el2(elr);
> - ctxt->gp_regs.regs.pstate = read_sysreg_el2(spsr);
> }
>
> static void __hyp_text __sysreg_save_state(struct kvm_cpu_context *ctxt)
> @@ -62,10 +59,13 @@ static void __hyp_text __sysreg_save_state(struct kvm_cpu_context *ctxt)
> ctxt->sys_regs[AMAIR_EL1] = read_sysreg_el1(amair);
> ctxt->sys_regs[CNTKCTL_EL1] = read_sysreg_el1(cntkctl);
> ctxt->sys_regs[PAR_EL1] = read_sysreg(par_el1);
> + ctxt->sys_regs[TPIDR_EL1] = read_sysreg(tpidr_el1);
>
> ctxt->gp_regs.sp_el1 = read_sysreg(sp_el1);
> ctxt->gp_regs.elr_el1 = read_sysreg_el1(elr);
> ctxt->gp_regs.spsr[KVM_SPSR_EL1]= read_sysreg_el1(spsr);
> + ctxt->gp_regs.regs.pc = read_sysreg_el2(elr);
> + ctxt->gp_regs.regs.pstate = read_sysreg_el2(spsr);
> }
>
> static hyp_alternate_select(__sysreg_call_save_host_state,
> @@ -89,11 +89,8 @@ static void __hyp_text __sysreg_restore_common_state(struct kvm_cpu_context *ctx
> write_sysreg(ctxt->sys_regs[ACTLR_EL1], actlr_el1);
> write_sysreg(ctxt->sys_regs[TPIDR_EL0], tpidr_el0);
> write_sysreg(ctxt->sys_regs[TPIDRRO_EL0], tpidrro_el0);
> - write_sysreg(ctxt->sys_regs[TPIDR_EL1], tpidr_el1);
> write_sysreg(ctxt->sys_regs[MDSCR_EL1], mdscr_el1);
> write_sysreg(ctxt->gp_regs.regs.sp, sp_el0);
> - write_sysreg_el2(ctxt->gp_regs.regs.pc, elr);
> - write_sysreg_el2(ctxt->gp_regs.regs.pstate, spsr);
> }
>
> static void __hyp_text __sysreg_restore_state(struct kvm_cpu_context *ctxt)
> @@ -115,10 +112,13 @@ static void __hyp_text __sysreg_restore_state(struct kvm_cpu_context *ctxt)
> write_sysreg_el1(ctxt->sys_regs[AMAIR_EL1], amair);
> write_sysreg_el1(ctxt->sys_regs[CNTKCTL_EL1], cntkctl);
> write_sysreg(ctxt->sys_regs[PAR_EL1], par_el1);
> + write_sysreg(ctxt->sys_regs[TPIDR_EL1], tpidr_el1);
>
> write_sysreg(ctxt->gp_regs.sp_el1, sp_el1);
> write_sysreg_el1(ctxt->gp_regs.elr_el1, elr);
> write_sysreg_el1(ctxt->gp_regs.spsr[KVM_SPSR_EL1],spsr);
> + write_sysreg_el2(ctxt->gp_regs.regs.pc, elr);
> + write_sysreg_el2(ctxt->gp_regs.regs.pstate, spsr);
> }
>
> static hyp_alternate_select(__sysreg_call_restore_host_state,
> --
> 2.10.1