Re: [PATCH v2 14/21] arm64: KVM: VHE: Implement VHE activate/deactivate_traps

[Christoffer Dall]

On Mon, Jan 25, 2016 at 03:53:48PM +0000, Marc Zyngier wrote:
> Running the kernel in HYP mode requires the HCR_E2H bit to be set
> at all times, and the HCR_TGE bit to be set when running as a host
> (and cleared when running as a guest). At the same time, the vector
>  must be set to the current role of the kernel (either host or
> hypervisor), and a couple of system registers differ between VHE
> and non-VHE.
> 
> We implement these by using another set of alternate functions
> that get dynamically patched.
> 
> Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>
> ---
>  arch/arm64/include/asm/kvm_arm.h     |  1 +
>  arch/arm64/include/asm/kvm_emulate.h |  3 +++
>  arch/arm64/kvm/hyp/switch.c          | 52 +++++++++++++++++++++++++++++++++---
>  3 files changed, 53 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/kvm_arm.h b/arch/arm64/include/asm/kvm_arm.h
> index 738a95f..73d3826 100644
> --- a/arch/arm64/include/asm/kvm_arm.h
> +++ b/arch/arm64/include/asm/kvm_arm.h
> @@ -23,6 +23,7 @@
>  #include <asm/types.h>
>  
>  /* Hyp Configuration Register (HCR) bits */
> +#define HCR_E2H		(UL(1) << 34)
>  #define HCR_ID		(UL(1) << 33)
>  #define HCR_CD		(UL(1) << 32)
>  #define HCR_RW_SHIFT	31
> diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h
> index 3066328..5ae0c69 100644
> --- a/arch/arm64/include/asm/kvm_emulate.h
> +++ b/arch/arm64/include/asm/kvm_emulate.h
> @@ -29,6 +29,7 @@
>  #include <asm/kvm_mmio.h>
>  #include <asm/ptrace.h>
>  #include <asm/cputype.h>
> +#include <asm/virt.h>
>  
>  unsigned long *vcpu_reg32(const struct kvm_vcpu *vcpu, u8 reg_num);
>  unsigned long *vcpu_spsr32(const struct kvm_vcpu *vcpu);
> @@ -43,6 +44,8 @@ void kvm_inject_pabt(struct kvm_vcpu *vcpu, unsigned long addr);
>  static inline void vcpu_reset_hcr(struct kvm_vcpu *vcpu)
>  {
>  	vcpu->arch.hcr_el2 = HCR_GUEST_FLAGS;
> +	if (is_kernel_in_hyp_mode())
> +		vcpu->arch.hcr_el2 |= HCR_E2H;
>  	if (test_bit(KVM_ARM_VCPU_EL1_32BIT, vcpu->arch.features))
>  		vcpu->arch.hcr_el2 &= ~HCR_RW;
>  }
> diff --git a/arch/arm64/kvm/hyp/switch.c b/arch/arm64/kvm/hyp/switch.c
> index 6f264dc..77f7c94 100644
> --- a/arch/arm64/kvm/hyp/switch.c
> +++ b/arch/arm64/kvm/hyp/switch.c
> @@ -15,6 +15,8 @@
>   * along with this program.  If not, see <http://www.gnu.org/licenses/>.
>   */
>  
> +#include <asm/kvm_asm.h>
> +
>  #include "hyp.h"
>  
>  static bool __hyp_text __fpsimd_enabled_nvhe(void)
> @@ -36,6 +38,27 @@ bool __hyp_text __fpsimd_enabled(void)
>  	return __fpsimd_is_enabled()();
>  }
>  
> +static void __hyp_text __activate_traps_vhe(void)
> +{
> +	u64 val;
> +
> +	val = read_sysreg(cpacr_el1);
> +	val |= 1 << 28;
> +	val &= ~(3 << 20);

could you define these bitfields as well?

> +	write_sysreg(val, cpacr_el1);
> +
> +	write_sysreg(__kvm_hyp_vector, vbar_el1);
> +}
> +
> +static void __hyp_text __activate_traps_nvhe(void)
> +{
> +	write_sysreg(CPTR_EL2_TTA | CPTR_EL2_TFP, cptr_el2);
> +}
> +
> +static hyp_alternate_select(__activate_traps_arch,
> +			    __activate_traps_nvhe, __activate_traps_vhe,
> +			    ARM64_HAS_VIRT_HOST_EXTN);
> +
>  static void __hyp_text __activate_traps(struct kvm_vcpu *vcpu)
>  {
>  	u64 val;
> @@ -55,16 +78,39 @@ static void __hyp_text __activate_traps(struct kvm_vcpu *vcpu)
>  	write_sysreg(val, hcr_el2);
>  	/* Trap on AArch32 cp15 c15 accesses (EL1 or EL0) */
>  	write_sysreg(1 << 15, hstr_el2);
> -	write_sysreg(CPTR_EL2_TTA | CPTR_EL2_TFP, cptr_el2);
>  	write_sysreg(vcpu->arch.mdcr_el2, mdcr_el2);
> +	__activate_traps_arch()();
>  }
>  
> -static void __hyp_text __deactivate_traps(struct kvm_vcpu *vcpu)
> +static void __hyp_text __deactivate_traps_vhe(void)
> +{
> +	extern char vectors[];	/* kernel exception vectors */
> +	u64 val;
> +
> +	write_sysreg(HCR_RW | HCR_TGE | HCR_E2H, hcr_el2);

perhaps we should define the EL2_HOST_HCR bit settings somewhere
globally and reuse that here?

> +
> +	val = read_sysreg(cpacr_el1);
> +	val |= 3 << 20;
> +	write_sysreg(val, cpacr_el1);
> +
> +	write_sysreg(vectors, vbar_el1);
> +}
> +
> +static void __hyp_text __deactivate_traps_nvhe(void)
>  {
>  	write_sysreg(HCR_RW, hcr_el2);
> +	write_sysreg(0, cptr_el2);

I'm noticing here that there's actually a bunch of RES1 bits in the
cptr_el2, so perhaps we should fix this as we're at it?

> +}
> +
> +static hyp_alternate_select(__deactivate_traps_arch,
> +			    __deactivate_traps_nvhe, __deactivate_traps_vhe,
> +			    ARM64_HAS_VIRT_HOST_EXTN);
> +
> +static void __hyp_text __deactivate_traps(struct kvm_vcpu *vcpu)
> +{
> +	__deactivate_traps_arch()();
>  	write_sysreg(0, hstr_el2);
>  	write_sysreg(read_sysreg(mdcr_el2) & MDCR_EL2_HPMN_MASK, mdcr_el2);
> -	write_sysreg(0, cptr_el2);
>  }
>  
>  static void __hyp_text __activate_vm(struct kvm_vcpu *vcpu)
> -- 
> 2.1.4
> 

Otherwise looks good.

-Christoffer