[PATCH v5 17/40] KVM: arm64: Move userspace system registers into separate function

[Julien Grall]

Hi Christoffer,

On 27/02/18 11:34, Christoffer Dall wrote:
> From: Christoffer Dall <christoffer.dall at linaro.org>
> 
> There's a semantic difference between the EL1 registers that control
> operation of a kernel running in EL1 and EL1 registers that only control
> userspace execution in EL0.  Since we can defer saving/restoring the
> latter, move them into their own function.
> 
> The ARMv8 ARM (ARM DDI 0487C.a) Section D10.2.1 recommends that
> ACTLR_EL1 has no effect on the processor when running the VHE host, and
> we can therefore move this register into the EL1 state which is only
> saved/restored on vcpu_put/load for a VHE host.
> 
> We also take this chance to rename the function saving/restoring the
> remaining system register to make it clear this function deals with
> the EL1 system registers.
> 
> Reviewed-by: Andrew Jones <drjones at redhat.com>
> Reviewed-by: Marc Zyngier <marc.zyngier at arm.com>
> Signed-off-by: Christoffer Dall <christoffer.dall at linaro.org>

Reviewed-by: Julien Grall <julien.grall at arm.com>

Cheers,

> ---
> 
> Notes:
>      Changes since v4:
>       - Clarified rationale for deferring ACTLR_EL1 in the commit message.
>      
>      Changes since v3:
>       - Correct the comment about ACTLR_EL1 and adjust commit text.
>      
>      Changes since v2:
>       - Save restore ACTLR_EL1 as part of the EL1 registers state instead of
>         the user register state, as ACTLR_EL1 can't affect the host's execution
>         on VHE systems.
>      
>      Changes since v1:
>       - Added comment about sp_el0 to common save sysreg save/restore functions
> 
>   arch/arm64/kvm/hyp/sysreg-sr.c | 48 ++++++++++++++++++++++++++++++------------
>   1 file changed, 35 insertions(+), 13 deletions(-)
> 
> diff --git a/arch/arm64/kvm/hyp/sysreg-sr.c b/arch/arm64/kvm/hyp/sysreg-sr.c
> index 99fc60516103..d5a5145b4e7c 100644
> --- a/arch/arm64/kvm/hyp/sysreg-sr.c
> +++ b/arch/arm64/kvm/hyp/sysreg-sr.c
> @@ -28,24 +28,33 @@ 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*_el0, actlr_el1, mdscr_el1, sp_el0,
> + * VHE: Host must save tpidr*_el0, mdscr_el1, sp_el0,
>    * and guest must save everything.
>    */
>   
>   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[MDSCR_EL1]	= read_sysreg(mdscr_el1);
> +
> +	/*
> +	 * The host arm64 Linux uses sp_el0 to point to 'current' and it must
> +	 * therefore be saved/restored on every entry/exit to/from the guest.
> +	 */
>   	ctxt->gp_regs.regs.sp		= read_sysreg(sp_el0);
>   }
>   
> -static void __hyp_text __sysreg_save_state(struct kvm_cpu_context *ctxt)
> +static void __hyp_text __sysreg_save_user_state(struct kvm_cpu_context *ctxt)
> +{
> +	ctxt->sys_regs[TPIDR_EL0]	= read_sysreg(tpidr_el0);
> +	ctxt->sys_regs[TPIDRRO_EL0]	= read_sysreg(tpidrro_el0);
> +}
> +
> +static void __hyp_text __sysreg_save_el1_state(struct kvm_cpu_context *ctxt)
>   {
>   	ctxt->sys_regs[MPIDR_EL1]	= read_sysreg(vmpidr_el2);
>   	ctxt->sys_regs[CSSELR_EL1]	= read_sysreg(csselr_el1);
>   	ctxt->sys_regs[SCTLR_EL1]	= read_sysreg_el1(sctlr);
> +	ctxt->sys_regs[ACTLR_EL1]	= read_sysreg(actlr_el1);
>   	ctxt->sys_regs[CPACR_EL1]	= read_sysreg_el1(cpacr);
>   	ctxt->sys_regs[TTBR0_EL1]	= read_sysreg_el1(ttbr0);
>   	ctxt->sys_regs[TTBR1_EL1]	= read_sysreg_el1(ttbr1);
> @@ -73,35 +82,46 @@ static void __hyp_text __sysreg_save_state(struct kvm_cpu_context *ctxt)
>   }
>   
>   static hyp_alternate_select(__sysreg_call_save_host_state,
> -			    __sysreg_save_state, __sysreg_do_nothing,
> +			    __sysreg_save_el1_state, __sysreg_do_nothing,
>   			    ARM64_HAS_VIRT_HOST_EXTN);
>   
>   void __hyp_text __sysreg_save_host_state(struct kvm_cpu_context *ctxt)
>   {
>   	__sysreg_call_save_host_state()(ctxt);
>   	__sysreg_save_common_state(ctxt);
> +	__sysreg_save_user_state(ctxt);
>   }
>   
>   void __hyp_text __sysreg_save_guest_state(struct kvm_cpu_context *ctxt)
>   {
> -	__sysreg_save_state(ctxt);
> +	__sysreg_save_el1_state(ctxt);
>   	__sysreg_save_common_state(ctxt);
> +	__sysreg_save_user_state(ctxt);
>   }
>   
>   static void __hyp_text __sysreg_restore_common_state(struct kvm_cpu_context *ctxt)
>   {
> -	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[MDSCR_EL1],	  mdscr_el1);
> +
> +	/*
> +	 * The host arm64 Linux uses sp_el0 to point to 'current' and it must
> +	 * therefore be saved/restored on every entry/exit to/from the guest.
> +	 */
>   	write_sysreg(ctxt->gp_regs.regs.sp,	  sp_el0);
>   }
>   
> -static void __hyp_text __sysreg_restore_state(struct kvm_cpu_context *ctxt)
> +static void __hyp_text __sysreg_restore_user_state(struct kvm_cpu_context *ctxt)
> +{
> +	write_sysreg(ctxt->sys_regs[TPIDR_EL0],	  	tpidr_el0);
> +	write_sysreg(ctxt->sys_regs[TPIDRRO_EL0], 	tpidrro_el0);
> +}
> +
> +static void __hyp_text __sysreg_restore_el1_state(struct kvm_cpu_context *ctxt)
>   {
>   	write_sysreg(ctxt->sys_regs[MPIDR_EL1],		vmpidr_el2);
>   	write_sysreg(ctxt->sys_regs[CSSELR_EL1],	csselr_el1);
>   	write_sysreg_el1(ctxt->sys_regs[SCTLR_EL1],	sctlr);
> +	write_sysreg(ctxt->sys_regs[ACTLR_EL1],	  	actlr_el1);
>   	write_sysreg_el1(ctxt->sys_regs[CPACR_EL1],	cpacr);
>   	write_sysreg_el1(ctxt->sys_regs[TTBR0_EL1],	ttbr0);
>   	write_sysreg_el1(ctxt->sys_regs[TTBR1_EL1],	ttbr1);
> @@ -129,19 +149,21 @@ static void __hyp_text __sysreg_restore_state(struct kvm_cpu_context *ctxt)
>   }
>   
>   static hyp_alternate_select(__sysreg_call_restore_host_state,
> -			    __sysreg_restore_state, __sysreg_do_nothing,
> +			    __sysreg_restore_el1_state, __sysreg_do_nothing,
>   			    ARM64_HAS_VIRT_HOST_EXTN);
>   
>   void __hyp_text __sysreg_restore_host_state(struct kvm_cpu_context *ctxt)
>   {
>   	__sysreg_call_restore_host_state()(ctxt);
>   	__sysreg_restore_common_state(ctxt);
> +	__sysreg_restore_user_state(ctxt);
>   }
>   
>   void __hyp_text __sysreg_restore_guest_state(struct kvm_cpu_context *ctxt)
>   {
> -	__sysreg_restore_state(ctxt);
> +	__sysreg_restore_el1_state(ctxt);
>   	__sysreg_restore_common_state(ctxt);
> +	__sysreg_restore_user_state(ctxt);
>   }
>   
>   void __hyp_text __sysreg32_save_state(struct kvm_vcpu *vcpu)
> 

-- 
Julien Grall