[PATCH v4 26/40] KVM: arm/arm64: Prepare to handle deferred save/restore of SPSR_EL1

[Marc Zyngier]

On Thu, 15 Feb 2018 21:03:18 +0000,
Christoffer Dall wrote:
> 
> SPSR_EL1 is not used by a VHE host kernel and can be deferred, but we
> need to rework the accesses to this register to access the latest value
> depending on whether or not guest system registers are loaded on the CPU
> or only reside in memory.
> 
> The handling of accessing the various banked SPSRs for 32-bit VMs is a
> bit clunky, but this will be improved in following patches which will
> first prepare and subsequently implement deferred save/restore of the
> 32-bit registers, including the 32-bit SPSRs.
> 
> Signed-off-by: Christoffer Dall <christoffer.dall at linaro.org>
> ---
> 
> Notes:
>     Changes since v2:
>      - New patch (deferred register handling has been reworked)
> 
>  arch/arm/include/asm/kvm_emulate.h   | 12 ++++++++++-
>  arch/arm/kvm/emulate.c               |  2 +-
>  arch/arm64/include/asm/kvm_emulate.h | 41 +++++++++++++++++++++++++++++++-----
>  arch/arm64/kvm/inject_fault.c        |  4 ++--
>  virt/kvm/arm/aarch32.c               |  2 +-
>  5 files changed, 51 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/arm/include/asm/kvm_emulate.h b/arch/arm/include/asm/kvm_emulate.h
> index e27caa4b47a1..6493bd479ddc 100644
> --- a/arch/arm/include/asm/kvm_emulate.h
> +++ b/arch/arm/include/asm/kvm_emulate.h
> @@ -41,7 +41,17 @@ static inline unsigned long *vcpu_reg32(struct kvm_vcpu *vcpu, u8 reg_num)
>  	return vcpu_reg(vcpu, reg_num);
>  }
>  
> -unsigned long *vcpu_spsr(struct kvm_vcpu *vcpu);
> +unsigned long *__vcpu_spsr(struct kvm_vcpu *vcpu);
> +
> +static inline unsigned long vpcu_read_spsr(struct kvm_vcpu *vcpu)
> +{
> +	return *__vcpu_spsr(vcpu);
> +}
> +
> +static inline void vcpu_write_spsr(struct kvm_vcpu *vcpu, unsigned long v)
> +{
> +	*__vcpu_spsr(vcpu) = v;
> +}
>  
>  static inline unsigned long vcpu_get_reg(struct kvm_vcpu *vcpu,
>  					 u8 reg_num)
> diff --git a/arch/arm/kvm/emulate.c b/arch/arm/kvm/emulate.c
> index fa501bf437f3..9046b53d87c1 100644
> --- a/arch/arm/kvm/emulate.c
> +++ b/arch/arm/kvm/emulate.c
> @@ -142,7 +142,7 @@ unsigned long *vcpu_reg(struct kvm_vcpu *vcpu, u8 reg_num)
>  /*
>   * Return the SPSR for the current mode of the virtual CPU.
>   */
> -unsigned long *vcpu_spsr(struct kvm_vcpu *vcpu)
> +unsigned long *__vcpu_spsr(struct kvm_vcpu *vcpu)
>  {
>  	unsigned long mode = *vcpu_cpsr(vcpu) & MODE_MASK;
>  	switch (mode) {
> diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
> index d313aaae5c38..47c2406755fa 100644
> --- a/arch/arm64/include/asm/kvm_emulate.h
> +++ b/arch/arm64/include/asm/kvm_emulate.h
> @@ -26,6 +26,7 @@
>  
>  #include <asm/esr.h>
>  #include <asm/kvm_arm.h>
> +#include <asm/kvm_hyp.h>
>  #include <asm/kvm_mmio.h>
>  #include <asm/ptrace.h>
>  #include <asm/cputype.h>
> @@ -143,13 +144,43 @@ static inline void vcpu_set_reg(struct kvm_vcpu *vcpu, u8 reg_num,
>  		vcpu_gp_regs(vcpu)->regs.regs[reg_num] = val;
>  }
>  
> -/* Get vcpu SPSR for current mode */
> -static inline unsigned long *vcpu_spsr(const struct kvm_vcpu *vcpu)
> +static inline unsigned long vcpu_read_spsr(const struct kvm_vcpu *vcpu)
>  {
> -	if (vcpu_mode_is_32bit(vcpu))
> -		return vcpu_spsr32(vcpu);
> +	unsigned long *p = (unsigned long *)&vcpu_gp_regs(vcpu)->spsr[KVM_SPSR_EL1];
> +
> +	if (vcpu_mode_is_32bit(vcpu)) {
> +		unsigned long *p_32bit = vcpu_spsr32(vcpu);
> +
> +		/* KVM_SPSR_SVC aliases KVM_SPSR_EL1 */
> +		if (p_32bit != (unsigned long *)p)
> +			return *p_32bit;

Clunky, you said? ;-) p is already an unsigned long *, so there's no
need to cast it.

> +	}
> +
> +	if (vcpu->arch.sysregs_loaded_on_cpu)
> +		return read_sysreg_el1(spsr);
> +	else
> +		return *p;
> +}
>  
> -	return (unsigned long *)&vcpu_gp_regs(vcpu)->spsr[KVM_SPSR_EL1];
> +static inline void vcpu_write_spsr(const struct kvm_vcpu *vcpu, unsigned long v)
> +{
> +	unsigned long *p = (unsigned long *)&vcpu_gp_regs(vcpu)->spsr[KVM_SPSR_EL1];
> +
> +	/* KVM_SPSR_SVC aliases KVM_SPSR_EL1 */
> +	if (vcpu_mode_is_32bit(vcpu)) {
> +		unsigned long *p_32bit = vcpu_spsr32(vcpu);
> +
> +		/* KVM_SPSR_SVC aliases KVM_SPSR_EL1 */
> +		if (p_32bit != (unsigned long *)p) {
> +			*p_32bit = v;
> +			return;

Same remark.

> +		}
> +	}
> +
> +	if (vcpu->arch.sysregs_loaded_on_cpu)
> +		write_sysreg_el1(v, spsr);
> +	else
> +		*p = v;
>  }
>  
>  static inline bool vcpu_mode_priv(const struct kvm_vcpu *vcpu)
> diff --git a/arch/arm64/kvm/inject_fault.c b/arch/arm64/kvm/inject_fault.c
> index e08db2f2dd75..8dda1edae727 100644
> --- a/arch/arm64/kvm/inject_fault.c
> +++ b/arch/arm64/kvm/inject_fault.c
> @@ -71,7 +71,7 @@ static void inject_abt64(struct kvm_vcpu *vcpu, bool is_iabt, unsigned long addr
>  	*vcpu_pc(vcpu) = get_except_vector(vcpu, except_type_sync);
>  
>  	*vcpu_cpsr(vcpu) = PSTATE_FAULT_BITS_64;
> -	*vcpu_spsr(vcpu) = cpsr;
> +	vcpu_write_spsr(vcpu, cpsr);
>  
>  	vcpu_write_sys_reg(vcpu, FAR_EL1, addr);
>  
> @@ -106,7 +106,7 @@ static void inject_undef64(struct kvm_vcpu *vcpu)
>  	*vcpu_pc(vcpu) = get_except_vector(vcpu, except_type_sync);
>  
>  	*vcpu_cpsr(vcpu) = PSTATE_FAULT_BITS_64;
> -	*vcpu_spsr(vcpu) = cpsr;
> +	vcpu_write_spsr(vcpu, cpsr);
>  
>  	/*
>  	 * Build an unknown exception, depending on the instruction
> diff --git a/virt/kvm/arm/aarch32.c b/virt/kvm/arm/aarch32.c
> index 8bc479fa37e6..efc84cbe8277 100644
> --- a/virt/kvm/arm/aarch32.c
> +++ b/virt/kvm/arm/aarch32.c
> @@ -178,7 +178,7 @@ static void prepare_fault32(struct kvm_vcpu *vcpu, u32 mode, u32 vect_offset)
>  	*vcpu_cpsr(vcpu) = cpsr;
>  
>  	/* Note: These now point to the banked copies */
> -	*vcpu_spsr(vcpu) = new_spsr_value;
> +	vcpu_write_spsr(vcpu, new_spsr_value);
>  	*vcpu_reg32(vcpu, 14) = *vcpu_pc(vcpu) + return_offset;
>  
>  	/* Branch to exception vector */
> -- 
> 2.14.2
> 

Otherwise:

Reviewed-by: Marc Zyngier <marc.zyngier at arm.com>

	M.

-- 
Jazz is not dead, it just smell funny.