Subject: Re: [PATCH 1/6] kvm: arm64: Prevent use of invalid PSCI v0.1 function IDs

From: Marc Zyngier <[email-masked]>
Date: Tue, 22 Dec 2020 16:05:35 +0000

On Tue, 08 Dec 2020 17:26:28 +0000,
Mark Rutland <[email-masked]> wrote:
> 
> On Tue, Dec 08, 2020 at 03:56:39PM +0000, Marc Zyngier wrote:
> > On 2020-12-08 14:24, David Brazdil wrote:
> > > PSCI driver exposes a struct containing the PSCI v0.1 function IDs
> > > configured in the DT. However, the struct does not convey the
> > > information whether these were set from DT or contain the default value
> > > zero. This could be a problem for PSCI proxy in KVM protected mode.
> > > 
> > > Extend config passed to KVM with a bit mask with individual bits set
> > > depending on whether the corresponding function pointer in psci_ops is
> > > set, eg. set bit for PSCI_CPU_SUSPEND if psci_ops.cpu_suspend != NULL.
> > > 
> > > Previously config was split into multiple global variables. Put
> > > everything into a single struct for convenience.
> > > 
> > > Reported-by: Mark Rutland <[email-masked]>
> > > Signed-off-by: David Brazdil <[email-masked]>
> > > ---
> > >  arch/arm64/include/asm/kvm_host.h    | 20 +++++++++++
> > >  arch/arm64/kvm/arm.c                 | 14 +++++---
> > >  arch/arm64/kvm/hyp/nvhe/psci-relay.c | 53 +++++++++++++++++++++-------
> > >  3 files changed, 70 insertions(+), 17 deletions(-)
> > > 
> > > diff --git a/arch/arm64/include/asm/kvm_host.h
> > > b/arch/arm64/include/asm/kvm_host.h
> > > index 11beda85ee7e..828d50d40dc2 100644
> > > --- a/arch/arm64/include/asm/kvm_host.h
> > > +++ b/arch/arm64/include/asm/kvm_host.h
> > > @@ -17,6 +17,7 @@
> > >  #include <linux/jump_label.h>
> > >  #include <linux/kvm_types.h>
> > >  #include <linux/percpu.h>
> > > +#include <linux/psci.h>
> > >  #include <asm/arch_gicv3.h>
> > >  #include <asm/barrier.h>
> > >  #include <asm/cpufeature.h>
> > > @@ -240,6 +241,25 @@ struct kvm_host_data {
> > >  	struct kvm_pmu_events pmu_events;
> > >  };
> > > 
> > > +#define KVM_HOST_PSCI_0_1_CPU_SUSPEND	BIT(0)
> > > +#define KVM_HOST_PSCI_0_1_CPU_ON	BIT(1)
> > > +#define KVM_HOST_PSCI_0_1_CPU_OFF	BIT(2)
> > > +#define KVM_HOST_PSCI_0_1_MIGRATE	BIT(3)
> > > +
> > > +struct kvm_host_psci_config {
> > > +	/* PSCI version used by host. */
> > > +	u32 version;
> > > +
> > > +	/* Function IDs used by host if version is v0.1. */
> > > +	struct psci_0_1_function_ids function_ids_0_1;
> > > +
> > > +	/* Bitmask of functions enabled for v0.1, bits KVM_HOST_PSCI_0_1_*. */
> > > +	unsigned int enabled_functions_0_1;
> > 
> > Nit: the conventional type for bitmaps is 'unsigned long'.
> > Also, "enabled" seems odd. Isn't it actually "available"?
> 
> Sure, that or "implemented" works here.
> 
> Since there are only 4 functions here, it might make sense to use
> independent bools rather than a bitmap, which might make this a bit
> simpler...
> 
> > > get_psci_0_1_function_ids();
> > > +	kvm_host_psci_config.version = psci_ops.get_version();
> > > +
> > > +	if (kvm_host_psci_config.version == PSCI_VERSION(0, 1)) {
> > > +		kvm_host_psci_config.function_ids_0_1 = get_psci_0_1_function_ids();
> > > +		kvm_host_psci_config.enabled_functions_0_1 =
> > > +			(psci_ops.cpu_suspend ? KVM_HOST_PSCI_0_1_CPU_SUSPEND : 0) |
> > > +			(psci_ops.cpu_off ? KVM_HOST_PSCI_0_1_CPU_OFF : 0) |
> > > +			(psci_ops.cpu_on ? KVM_HOST_PSCI_0_1_CPU_ON : 0) |
> > > +			(psci_ops.migrate ? KVM_HOST_PSCI_0_1_MIGRATE : 0);
> 
> ... since e.g. this could be roughly:
> 
> 	kvm_host_psci_config.cpu_suspend_implemented = psci_ops.cpu_suspend;
> 	kvm_host_psci_config.cpu_off_implemented = psci_ops.cpu_off;
> 	kvm_host_psci_config.cpu_on_implemented = psci_ops.cpu_on;
> 	kvm_host_psci_config.migrate_implemented = psci_ops.migrate;
> 
> > > +static inline bool is_psci_0_1_cpu_suspend(u64 func_id)
> > > +{
> > > +	return is_psci_0_1_function_enabled(KVM_HOST_PSCI_0_1_CPU_SUSPEND) &&
> > > +	       (func_id == kvm_host_psci_config.function_ids_0_1.cpu_suspend);
> > > +}
> 
> ...and similarly:
> 
> 	return  kvm_host_psci_config.cpu_suspend_implemented &&
> 		func_id == kvm_host_psci_config.function_ids_0_1.cpu_suspend)
> 
> > Otherwise looks OK. Don't bother respinning the series for my
> > comments, I can tidy things up as I apply it if there are no other
> > issues.
> 
> FWIW, I'm happy with whatever choose to do here, so don't feel like you
> have to follow my suggestions above.

FWIW, I've queued the following patch on top of the series, using the
above suggestions and some creative use of macros, allowing some
cleanup.

	M.

>From 767c973f2e4a9264a4f159c9fad5ca8acdb9915e Mon Sep 17 00:00:00 2001
From: Marc Zyngier <[email-masked]>
Date: Tue, 22 Dec 2020 12:46:41 +0000
Subject: [PATCH] KVM: arm64: Declutter host PSCI 0.1 handling

Although there is nothing wrong with the current host PSCI relay
implementation, we can clean it up and remove some of the helpers
that do not improve the overall readability of the legacy PSCI 0.1
handling.

Opportunity is taken to turn the bitmap into a set of booleans,
and creative use of preprocessor macros make init and check
more concise/readable.

Suggested-by: Mark Rutland <[email-masked]>
Signed-off-by: Marc Zyngier <[email-masked]>
---
 arch/arm64/include/asm/kvm_host.h    | 11 ++--
 arch/arm64/kvm/arm.c                 | 12 +++--
 arch/arm64/kvm/hyp/nvhe/psci-relay.c | 77 +++++++---------------------
 3 files changed, 30 insertions(+), 70 deletions(-)

diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h
index bce2452b305c..8fcfab0c2567 100644
--- a/arch/arm64/include/asm/kvm_host.h
+++ b/arch/arm64/include/asm/kvm_host.h
@@ -241,11 +241,6 @@ struct kvm_host_data {
 	struct kvm_pmu_events pmu_events;
 };
 
-#define KVM_HOST_PSCI_0_1_CPU_SUSPEND	BIT(0)
-#define KVM_HOST_PSCI_0_1_CPU_ON	BIT(1)
-#define KVM_HOST_PSCI_0_1_CPU_OFF	BIT(2)
-#define KVM_HOST_PSCI_0_1_MIGRATE	BIT(3)
-
 struct kvm_host_psci_config {
 	/* PSCI version used by host. */
 	u32 version;
@@ -253,8 +248,10 @@ struct kvm_host_psci_config {
 	/* Function IDs used by host if version is v0.1. */
 	struct psci_0_1_function_ids function_ids_0_1;
 
-	/* Bitmask of functions enabled for v0.1, bits KVM_HOST_PSCI_0_1_*. */
-	unsigned int enabled_functions_0_1;
+	bool psci_0_1_cpu_suspend_implemented;
+	bool psci_0_1_cpu_on_implemented;
+	bool psci_0_1_cpu_off_implemented;
+	bool psci_0_1_migrate_implemented;
 };
 
 extern struct kvm_host_psci_config kvm_nvhe_sym(kvm_host_psci_config);
diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c
index 836ca763b91d..e207e4541f55 100644
--- a/arch/arm64/kvm/arm.c
+++ b/arch/arm64/kvm/arm.c
@@ -1603,6 +1603,9 @@ static void init_cpu_logical_map(void)
 		hyp_cpu_logical_map[cpu] = cpu_logical_map(cpu);
 }
 
+#define init_psci_0_1_impl_state(config, what)	\
+	config.psci_0_1_ ## what ## _implemented = psci_ops.what
+
 static bool init_psci_relay(void)
 {
 	/*
@@ -1618,11 +1621,10 @@ static bool init_psci_relay(void)
 
 	if (kvm_host_psci_config.version == PSCI_VERSION(0, 1)) {
 		kvm_host_psci_config.function_ids_0_1 = get_psci_0_1_function_ids();
-		kvm_host_psci_config.enabled_functions_0_1 =
-			(psci_ops.cpu_suspend ? KVM_HOST_PSCI_0_1_CPU_SUSPEND : 0) |
-			(psci_ops.cpu_off ? KVM_HOST_PSCI_0_1_CPU_OFF : 0) |
-			(psci_ops.cpu_on ? KVM_HOST_PSCI_0_1_CPU_ON : 0) |
-			(psci_ops.migrate ? KVM_HOST_PSCI_0_1_MIGRATE : 0);
+		init_psci_0_1_impl_state(kvm_host_psci_config, cpu_suspend);
+		init_psci_0_1_impl_state(kvm_host_psci_config, cpu_on);
+		init_psci_0_1_impl_state(kvm_host_psci_config, cpu_off);
+		init_psci_0_1_impl_state(kvm_host_psci_config, migrate);
 	}
 	return true;
 }
diff --git a/arch/arm64/kvm/hyp/nvhe/psci-relay.c b/arch/arm64/kvm/hyp/nvhe/psci-relay.c
index 1f7237e45148..e3947846ffcb 100644
--- a/arch/arm64/kvm/hyp/nvhe/psci-relay.c
+++ b/arch/arm64/kvm/hyp/nvhe/psci-relay.c
@@ -43,48 +43,16 @@ struct psci_boot_args {
 static DEFINE_PER_CPU(struct psci_boot_args, cpu_on_args) = PSCI_BOOT_ARGS_INIT;
 static DEFINE_PER_CPU(struct psci_boot_args, suspend_args) = PSCI_BOOT_ARGS_INIT;
 
-static u64 get_psci_func_id(struct kvm_cpu_context *host_ctxt)
-{
-	DECLARE_REG(u64, func_id, host_ctxt, 0);
-
-	return func_id;
-}
-
-static inline bool is_psci_0_1_function_enabled(unsigned int fn_bit)
-{
-	return kvm_host_psci_config.enabled_functions_0_1 & fn_bit;
-}
-
-static inline bool is_psci_0_1_cpu_suspend(u64 func_id)
-{
-	return is_psci_0_1_function_enabled(KVM_HOST_PSCI_0_1_CPU_SUSPEND) &&
-	       (func_id == kvm_host_psci_config.function_ids_0_1.cpu_suspend);
-}
-
-static inline bool is_psci_0_1_cpu_on(u64 func_id)
-{
-	return is_psci_0_1_function_enabled(KVM_HOST_PSCI_0_1_CPU_ON) &&
-	       (func_id == kvm_host_psci_config.function_ids_0_1.cpu_on);
-}
-
-static inline bool is_psci_0_1_cpu_off(u64 func_id)
-{
-	return is_psci_0_1_function_enabled(KVM_HOST_PSCI_0_1_CPU_OFF) &&
-	       (func_id == kvm_host_psci_config.function_ids_0_1.cpu_off);
-}
-
-static inline bool is_psci_0_1_migrate(u64 func_id)
-{
-	return is_psci_0_1_function_enabled(KVM_HOST_PSCI_0_1_MIGRATE) &&
-	       (func_id == kvm_host_psci_config.function_ids_0_1.migrate);
-}
+#define	is_psci_0_1(what, func_id)					\
+	(kvm_host_psci_config.psci_0_1_ ## what ## _implemented &&	\
+	 (func_id) == kvm_host_psci_config.function_ids_0_1.what)
 
 static bool is_psci_0_1_call(u64 func_id)
 {
-	return is_psci_0_1_cpu_suspend(func_id) ||
-	       is_psci_0_1_cpu_on(func_id) ||
-	       is_psci_0_1_cpu_off(func_id) ||
-	       is_psci_0_1_migrate(func_id);
+	return (is_psci_0_1(cpu_suspend, func_id) ||
+		is_psci_0_1(cpu_on, func_id) ||
+		is_psci_0_1(cpu_off, func_id) ||
+		is_psci_0_1(migrate, func_id));
 }
 
 static bool is_psci_0_2_call(u64 func_id)
@@ -94,16 +62,6 @@ static bool is_psci_0_2_call(u64 func_id)
 	       (PSCI_0_2_FN64(0) <= func_id && func_id <= PSCI_0_2_FN64(31));
 }
 
-static bool is_psci_call(u64 func_id)
-{
-	switch (kvm_host_psci_config.version) {
-	case PSCI_VERSION(0, 1):
-		return is_psci_0_1_call(func_id);
-	default:
-		return is_psci_0_2_call(func_id);
-	}
-}
-
 static unsigned long psci_call(unsigned long fn, unsigned long arg0,
 			       unsigned long arg1, unsigned long arg2)
 {
@@ -273,14 +231,14 @@ asmlinkage void __noreturn kvm_host_psci_cpu_entry(bool is_cpu_on)
 
 static unsigned long psci_0_1_handler(u64 func_id, struct kvm_cpu_context *host_ctxt)
 {
-	if (is_psci_0_1_cpu_off(func_id) || is_psci_0_1_migrate(func_id))
+	if (is_psci_0_1(cpu_off, func_id) || is_psci_0_1(migrate, func_id))
 		return psci_forward(host_ctxt);
-	else if (is_psci_0_1_cpu_on(func_id))
+	if (is_psci_0_1(cpu_on, func_id))
 		return psci_cpu_on(func_id, host_ctxt);
-	else if (is_psci_0_1_cpu_suspend(func_id))
+	if (is_psci_0_1(cpu_suspend, func_id))
 		return psci_cpu_suspend(func_id, host_ctxt);
-	else
-		return PSCI_RET_NOT_SUPPORTED;
+
+	return PSCI_RET_NOT_SUPPORTED;
 }
 
 static unsigned long psci_0_2_handler(u64 func_id, struct kvm_cpu_context *host_ctxt)
@@ -322,20 +280,23 @@ static unsigned long psci_1_0_handler(u64 func_id, struct kvm_cpu_context *host_
 
 bool kvm_host_psci_handler(struct kvm_cpu_context *host_ctxt)
 {
-	u64 func_id = get_psci_func_id(host_ctxt);
+	DECLARE_REG(u64, func_id, host_ctxt, 0);
 	unsigned long ret;
 
-	if (!is_psci_call(func_id))
-		return false;
-
 	switch (kvm_host_psci_config.version) {
 	case PSCI_VERSION(0, 1):
+		if (!is_psci_0_1_call(func_id))
+			return false;
 		ret = psci_0_1_handler(func_id, host_ctxt);
 		break;
 	case PSCI_VERSION(0, 2):
+		if (!is_psci_0_2_call(func_id))
+			return false;
 		ret = psci_0_2_handler(func_id, host_ctxt);
 		break;
 	default:
+		if (!is_psci_0_2_call(func_id))
+			return false;
 		ret = psci_1_0_handler(func_id, host_ctxt);
 		break;
 	}
-- 
2.29.2

-- 
Without deviation from the norm, progress is not possible.

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