[PATCH v4 7/8] KVM: PPC: Ultravisor: Enter a secure guest

[Nicholas Piggin]

Claudio Carvalho's on June 29, 2019 6:08 am:
> From: Sukadev Bhattiprolu <sukadev at linux.vnet.ibm.com>
> 
> To enter a secure guest, we have to go through the ultravisor, therefore
> we do a ucall when we are entering a secure guest.
> 
> This change is needed for any sort of entry to the secure guest from the
> hypervisor, whether it is a return from an hcall, a return from a
> hypervisor interrupt, or the first time that a secure guest vCPU is run.
> 
> If we are returning from an hcall, the results are already in the
> appropriate registers R3:12, except for R3, R6 and R7. R3 has the status
> of the reflected hcall, therefore we move it to R0 for the ultravisor and
> set R3 to the UV_RETURN ucall number. R6,7 were used as temporary
> registers, hence we restore them.
> 
> Have fast_guest_return check the kvm_arch.secure_guest field so that a
> new CPU enters UV when started (in response to a RTAS start-cpu call).
> 
> Thanks to input from Paul Mackerras, Ram Pai and Mike Anderson.
> 
> Signed-off-by: Sukadev Bhattiprolu <sukadev at linux.vnet.ibm.com>
> [ Pass SRR1 in r11 for UV_RETURN, fix kvmppc_msr_interrupt to preserve
>   the MSR_S bit ]
> Signed-off-by: Paul Mackerras <paulus at ozlabs.org>
> [ Fix UV_RETURN ucall number and arch.secure_guest check ]
> Signed-off-by: Ram Pai <linuxram at us.ibm.com>
> [ Save the actual R3 in R0 for the ultravisor and use R3 for the
>   UV_RETURN ucall number. Update commit message and ret_to_ultra comment ]
> Signed-off-by: Claudio Carvalho <cclaudio at linux.ibm.com>
> ---
>  arch/powerpc/include/asm/kvm_host.h       |  1 +
>  arch/powerpc/include/asm/ultravisor-api.h |  1 +
>  arch/powerpc/kernel/asm-offsets.c         |  1 +
>  arch/powerpc/kvm/book3s_hv_rmhandlers.S   | 40 +++++++++++++++++++----
>  4 files changed, 37 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/powerpc/include/asm/kvm_host.h b/arch/powerpc/include/asm/kvm_host.h
> index 013c76a0a03e..184becb62ea4 100644
> --- a/arch/powerpc/include/asm/kvm_host.h
> +++ b/arch/powerpc/include/asm/kvm_host.h
> @@ -294,6 +294,7 @@ struct kvm_arch {
>  	cpumask_t cpu_in_guest;
>  	u8 radix;
>  	u8 fwnmi_enabled;
> +	u8 secure_guest;
>  	bool threads_indep;
>  	bool nested_enable;
>  	pgd_t *pgtable;
> diff --git a/arch/powerpc/include/asm/ultravisor-api.h b/arch/powerpc/include/asm/ultravisor-api.h
> index 141940771add..7c4d0b4ced12 100644
> --- a/arch/powerpc/include/asm/ultravisor-api.h
> +++ b/arch/powerpc/include/asm/ultravisor-api.h
> @@ -19,5 +19,6 @@
>  
>  /* opcodes */
>  #define UV_WRITE_PATE			0xF104
> +#define UV_RETURN			0xF11C
>  
>  #endif /* _ASM_POWERPC_ULTRAVISOR_API_H */
> diff --git a/arch/powerpc/kernel/asm-offsets.c b/arch/powerpc/kernel/asm-offsets.c
> index 8e02444e9d3d..44742724513e 100644
> --- a/arch/powerpc/kernel/asm-offsets.c
> +++ b/arch/powerpc/kernel/asm-offsets.c
> @@ -508,6 +508,7 @@ int main(void)
>  	OFFSET(KVM_VRMA_SLB_V, kvm, arch.vrma_slb_v);
>  	OFFSET(KVM_RADIX, kvm, arch.radix);
>  	OFFSET(KVM_FWNMI, kvm, arch.fwnmi_enabled);
> +	OFFSET(KVM_SECURE_GUEST, kvm, arch.secure_guest);
>  	OFFSET(VCPU_DSISR, kvm_vcpu, arch.shregs.dsisr);
>  	OFFSET(VCPU_DAR, kvm_vcpu, arch.shregs.dar);
>  	OFFSET(VCPU_VPA, kvm_vcpu, arch.vpa.pinned_addr);
> diff --git a/arch/powerpc/kvm/book3s_hv_rmhandlers.S b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
> index cffb365d9d02..89813ca987c2 100644
> --- a/arch/powerpc/kvm/book3s_hv_rmhandlers.S
> +++ b/arch/powerpc/kvm/book3s_hv_rmhandlers.S
> @@ -36,6 +36,7 @@
>  #include <asm/asm-compat.h>
>  #include <asm/feature-fixups.h>
>  #include <asm/cpuidle.h>
> +#include <asm/ultravisor-api.h>
>  
>  /* Sign-extend HDEC if not on POWER9 */
>  #define EXTEND_HDEC(reg)			\
> @@ -1092,16 +1093,12 @@ BEGIN_FTR_SECTION
>  END_FTR_SECTION_IFSET(CPU_FTR_HAS_PPR)
>  
>  	ld	r5, VCPU_LR(r4)
> -	ld	r6, VCPU_CR(r4)
>  	mtlr	r5
> -	mtcr	r6
>  
>  	ld	r1, VCPU_GPR(R1)(r4)
>  	ld	r2, VCPU_GPR(R2)(r4)
>  	ld	r3, VCPU_GPR(R3)(r4)
>  	ld	r5, VCPU_GPR(R5)(r4)
> -	ld	r6, VCPU_GPR(R6)(r4)
> -	ld	r7, VCPU_GPR(R7)(r4)
>  	ld	r8, VCPU_GPR(R8)(r4)
>  	ld	r9, VCPU_GPR(R9)(r4)
>  	ld	r10, VCPU_GPR(R10)(r4)

Just to try to be less arbitrary about things, could you use regs
adjacent to r4? Generally good because then it has a chance to get
our loads paired up (which may not help some CPUs).

Thanks,
Nick