Re: [PATCH v1 15/24] kvm: arm64: Bootstrap PSCI SMC handler in nVHE EL2

[Marc Zyngier <maz@kernel.org>]

On 2020-11-09 11:32, David Brazdil wrote:
> Add a handler of PSCI SMCs in nVHE hyp code. The handler is initialized
> with the version used by the host's PSCI driver and the function IDs it
> was configured with. If the SMC function ID matches one of the
> configured PSCI calls (for v0.1) or falls into the PSCI function ID
> range (for v0.2+), the SMC is handled by the PSCI handler. For now, all
> SMCs return PSCI_RET_NOT_SUPPORTED.
> 
> Signed-off-by: David Brazdil <dbrazdil@google.com>
> ---
>  arch/arm64/include/asm/kvm_hyp.h   |   4 ++
>  arch/arm64/kvm/arm.c               |  13 ++++
>  arch/arm64/kvm/hyp/nvhe/Makefile   |   2 +-
>  arch/arm64/kvm/hyp/nvhe/hyp-main.c |   4 ++
>  arch/arm64/kvm/hyp/nvhe/psci.c     | 102 +++++++++++++++++++++++++++++
>  include/uapi/linux/psci.h          |   1 +
>  6 files changed, 125 insertions(+), 1 deletion(-)
>  create mode 100644 arch/arm64/kvm/hyp/nvhe/psci.c
> 
> diff --git a/arch/arm64/include/asm/kvm_hyp.h 
> b/arch/arm64/include/asm/kvm_hyp.h
> index a3289071f3d8..95a2bbbcc7e1 100644
> --- a/arch/arm64/include/asm/kvm_hyp.h
> +++ b/arch/arm64/include/asm/kvm_hyp.h
> @@ -96,6 +96,10 @@ void deactivate_traps_vhe_put(void);
> 
>  u64 __guest_enter(struct kvm_vcpu *vcpu);
> 
> +#ifdef __KVM_NVHE_HYPERVISOR__
> +bool kvm_host_psci_handler(struct kvm_cpu_context *host_ctxt);
> +#endif
> +
>  void __noreturn hyp_panic(void);
>  #ifdef __KVM_NVHE_HYPERVISOR__
>  void __noreturn __hyp_do_panic(bool restore_host, u64 spsr, u64 elr, 
> u64 par);
> diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
> index 1a57b6025937..28e3bc056225 100644
> --- a/arch/arm64/kvm/arm.c
> +++ b/arch/arm64/kvm/arm.c
> @@ -19,6 +19,7 @@
>  #include <linux/kvm_irqfd.h>
>  #include <linux/irqbypass.h>
>  #include <linux/sched/stat.h>
> +#include <linux/psci.h>
>  #include <trace/events/kvm.h>
> 
>  #define CREATE_TRACE_POINTS
> @@ -1498,6 +1499,17 @@ static void init_cpu_logical_map(void)
>  		CHOOSE_NVHE_SYM(__cpu_logical_map)[cpu] = cpu_logical_map(cpu);
>  }
> 
> +static void init_psci(void)

nit: init_psci_relay?

> +{
> +	extern u32 kvm_nvhe_sym(kvm_host_psci_version);
> +	extern u32 kvm_nvhe_sym(kvm_host_psci_function_id)[PSCI_FN_MAX];
> +	int i;
> +
> +	CHOOSE_NVHE_SYM(kvm_host_psci_version) = psci_driver_version();
> +	for (i = 0; i < PSCI_FN_MAX; ++i)
> +		CHOOSE_NVHE_SYM(kvm_host_psci_function_id)[i] = 
> psci_get_function_id(i);
> +}
> +
>  static int init_common_resources(void)
>  {
>  	return kvm_set_ipa_limit();
> @@ -1677,6 +1689,7 @@ static int init_hyp_mode(void)
>  	}
> 
>  	init_cpu_logical_map();
> +	init_psci();
> 
>  	return 0;
> 
> diff --git a/arch/arm64/kvm/hyp/nvhe/Makefile 
> b/arch/arm64/kvm/hyp/nvhe/Makefile
> index c45f440cce51..647b63337a51 100644
> --- a/arch/arm64/kvm/hyp/nvhe/Makefile
> +++ b/arch/arm64/kvm/hyp/nvhe/Makefile
> @@ -7,7 +7,7 @@ asflags-y := -D__KVM_NVHE_HYPERVISOR__
>  ccflags-y := -D__KVM_NVHE_HYPERVISOR__
> 
>  obj-y := timer-sr.o sysreg-sr.o debug-sr.o switch.o tlb.o hyp-init.o 
> host.o \
> -	 hyp-main.o percpu.o
> +	 hyp-main.o percpu.o psci.o
>  obj-y += ../vgic-v3-sr.o ../aarch32.o ../vgic-v2-cpuif-proxy.o 
> ../entry.o \
>  	 ../fpsimd.o ../hyp-entry.o
> 
> diff --git a/arch/arm64/kvm/hyp/nvhe/hyp-main.c
> b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
> index 8661bc7deaa9..69f34d4f2773 100644
> --- a/arch/arm64/kvm/hyp/nvhe/hyp-main.c
> +++ b/arch/arm64/kvm/hyp/nvhe/hyp-main.c
> @@ -134,6 +134,10 @@ static void handle_host_smc(struct
> kvm_cpu_context *host_ctxt)
>  	 */
>  	skip_host_instruction();
> 
> +	/* Try to handle host's PSCI SMCs. */
> +	if (kvm_host_psci_handler(host_ctxt))
> +		return;
> +
>  	/* Forward SMC not handled in EL2 to EL3. */
>  	forward_host_smc(host_ctxt);
>  }
> diff --git a/arch/arm64/kvm/hyp/nvhe/psci.c 
> b/arch/arm64/kvm/hyp/nvhe/psci.c
> new file mode 100644
> index 000000000000..82d3b2c89658
> --- /dev/null
> +++ b/arch/arm64/kvm/hyp/nvhe/psci.c

nit: can we please name this psci-relay.c, or psci-proxy.c?
We already have a psci.c in the tree, and having the same file name 
messes
with my editor... ;-)

> @@ -0,0 +1,102 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (C) 2020 - Google LLC
> + * Author: David Brazdil <dbrazdil@google.com>
> + */
> +
> +#include <asm/kvm_asm.h>
> +#include <asm/kvm_hyp.h>
> +#include <asm/kvm_mmu.h>
> +#include <kvm/arm_hypercalls.h>
> +#include <linux/arm-smccc.h>
> +#include <linux/psci.h>
> +#include <kvm/arm_psci.h>
> +#include <uapi/linux/psci.h>
> +
> +/* Config options set by the host. */
> +u32 kvm_host_psci_version = PSCI_VERSION(0, 0);
> +u32 kvm_host_psci_function_id[PSCI_FN_MAX];
> +
> +static u64 get_psci_func_id(struct kvm_cpu_context *host_ctxt)
> +{
> +	return host_ctxt->regs.regs[0];
> +}
> +
> +static bool is_psci_0_1_call(u64 func_id)
> +{
> +	unsigned int i;
> +
> +	for (i = 0; i < ARRAY_SIZE(kvm_host_psci_function_id); ++i) {
> +		if (func_id == kvm_host_psci_function_id[i])
> +			return true;
> +	}
> +	return false;
> +}
> +
> +static bool is_psci_0_2_fn_call(u64 func_id)
> +{
> +	u64 base = func_id & ~PSCI_0_2_FN_ID_MASK;
> +
> +	return base == PSCI_0_2_FN_BASE || base == PSCI_0_2_FN64_BASE;

I couldn't spot in the spec where PSCI reserves 16bit worth of IDs in
each range.

> +}
> +
> +static bool is_psci_call(u64 func_id)
> +{
> +	if (kvm_host_psci_version == PSCI_VERSION(0, 0))
> +		return false;
> +	else if (kvm_host_psci_version == PSCI_VERSION(0, 1))
> +		return is_psci_0_1_call(func_id);
> +	else
> +		return is_psci_0_2_fn_call(func_id);

Consider using switch/case constructs for readability.

> +}
> +
> +static unsigned long psci_0_1_handler(u64 func_id, struct
> kvm_cpu_context *host_ctxt)
> +{
> +	return PSCI_RET_NOT_SUPPORTED;
> +}
> +
> +static unsigned long psci_0_2_handler(u64 func_id, struct
> kvm_cpu_context *host_ctxt)
> +{
> +	switch (func_id) {
> +	default:
> +		return PSCI_RET_NOT_SUPPORTED;
> +	}
> +}
> +
> +static unsigned long psci_1_0_handler(u64 func_id, struct
> kvm_cpu_context *host_ctxt)
> +{
> +	int ret;
> +
> +	ret = psci_0_2_handler(func_id, host_ctxt);
> +	if (ret != PSCI_RET_NOT_SUPPORTED)
> +		return ret;
> +
> +	switch (func_id) {
> +	default:
> +		return PSCI_RET_NOT_SUPPORTED;
> +	}

It would probably help to adopt the same structure as we have in the
KVM PSCI implementation:

	switch(psci_fn) {
	case PSCI_0_2_FN_PSCI_VERSION:
		val = KVM_ARM_PSCI_1_0;
		break;

         [...]
	default:
		return kvm_psci_0_2_call(vcpu);

which allows 1.0 to override some 0.2 functions, and otherwise leave
it to the 0.2 backend.

> +}
> +
> +bool kvm_host_psci_handler(struct kvm_cpu_context *host_ctxt)
> +{
> +	u64 func_id = get_psci_func_id(host_ctxt);
> +	unsigned long ret;
> +
> +	if (!is_psci_call(func_id))
> +		return false;
> +
> +	if (kvm_host_psci_version == PSCI_VERSION(0, 1))
> +		ret = psci_0_1_handler(func_id, host_ctxt);
> +	else if (kvm_host_psci_version == PSCI_VERSION(0, 2))
> +		ret = psci_0_2_handler(func_id, host_ctxt);
> +	else if (PSCI_VERSION_MAJOR(kvm_host_psci_version) >= 1)
> +		ret = psci_1_0_handler(func_id, host_ctxt);
> +	else
> +		ret = PSCI_RET_NOT_SUPPORTED;

Same remark about the use of switch/case.

> +
> +	host_ctxt->regs.regs[0] = ret;
> +	host_ctxt->regs.regs[1] = 0;
> +	host_ctxt->regs.regs[2] = 0;
> +	host_ctxt->regs.regs[3] = 0;
> +	return true;
> +}
> diff --git a/include/uapi/linux/psci.h b/include/uapi/linux/psci.h
> index 2fcad1dd0b0e..0d52b8dbe8c2 100644
> --- a/include/uapi/linux/psci.h
> +++ b/include/uapi/linux/psci.h
> @@ -29,6 +29,7 @@
>  #define PSCI_0_2_FN64_BASE			\
>  					(PSCI_0_2_FN_BASE + PSCI_0_2_64BIT)
>  #define PSCI_0_2_FN64(n)			(PSCI_0_2_FN64_BASE + (n))
> +#define PSCI_0_2_FN_ID_MASK			0xffff
> 
>  #define PSCI_0_2_FN_PSCI_VERSION		PSCI_0_2_FN(0)
>  #define PSCI_0_2_FN_CPU_SUSPEND			PSCI_0_2_FN(1)

Thanks,

         M.
-- 
Jazz is not dead. It just smells funny...