Re: [PATCH v2 08/16] arm/arm64: KVM: Advertise SMCCC v1.1 - Russell King

From: Russell King - ARM Linux <linux@armlinux.org.uk>
To: Marc Zyngier <marc.zyngier@arm.com>
Cc: linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	kvmarm@lists.cs.columbia.edu, Mark Rutland <mark.rutland@arm.com>,
	Peter Maydell <peter.maydell@linaro.org>,
	Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>,
	Ard Biesheuvel <ard.biesheuvel@linaro.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Will Deacon <will.deacon@arm.com>, Jon Masters <jcm@redhat.com>,
	Robin Murphy <robin.murphy@arm.com>,
	Christoffer Dall <christoffer.dall@linaro.org>
Subject: Re: [PATCH v2 08/16] arm/arm64: KVM: Advertise SMCCC v1.1
Date: Tue, 30 Jan 2018 00:23:28 +0000	[thread overview]
Message-ID: <20180130002328.GB9418@n2100.armlinux.org.uk> (raw)
In-Reply-To: <20180129174559.1866-9-marc.zyngier@arm.com>

On Mon, Jan 29, 2018 at 05:45:51PM +0000, Marc Zyngier wrote:
> The new SMC Calling Convention (v1.1) allows for a reduced overhead
> when calling into the firmware, and provides a new feature discovery
> mechanism.
> 
> Make it visible to KVM guests.
> 
> Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
> ---
>  Documentation/virtual/kvm/arm/psci.txt | 12 +++++++-----
>  arch/arm/kvm/handle_exit.c             |  2 +-
>  arch/arm64/kvm/handle_exit.c           |  2 +-
>  include/kvm/arm_psci.h                 |  2 +-
>  include/linux/arm-smccc.h              | 13 +++++++++++++
>  virt/kvm/arm/psci.c                    | 24 +++++++++++++++++++++++-
>  6 files changed, 46 insertions(+), 9 deletions(-)
> 
> diff --git a/Documentation/virtual/kvm/arm/psci.txt b/Documentation/virtual/kvm/arm/psci.txt
> index 2e49a4e9f084..aafdab887b04 100644
> --- a/Documentation/virtual/kvm/arm/psci.txt
> +++ b/Documentation/virtual/kvm/arm/psci.txt
> @@ -13,7 +13,7 @@ a migration causes a different PSCI version to be exposed out of the
>  blue to an unsuspecting guest.
>  
>  In order to remedy this situation, KVM exposes a set of "firmware
> -pseuodo-registers" that can be manipulated using the GET/SET_ONE_REG
> +pseudo-registers" that can be manipulated using the GET/SET_ONE_REG

This should surely be in patch 7?

>  interface. These registers can be saved/restored by userspace, and set
>  to a convenient value if required.
>  
> @@ -21,8 +21,10 @@ The following register is defined:
>  
>  * KVM_REG_ARM_PSCI_VERSION:
>  
> -  - Only valid if the vcpu has KVM_ARM_VCPU_PSCI_0_2 feature set
> -  - Returns the current PSCI version on GET_ONE_REG
> -  - Allows any supported PSCI version compatible with v0.2 to be set
> -    with SET_ONE_REG
> +  - Only valid if the vcpu has the KVM_ARM_VCPU_PSCI_0_2 feature set
> +    (and thus has already been initialized)
> +  - Returns the current PSCI version on GET_ONE_REG (defaulting to the
> +    highest PSCI version implemented by KVM and compatible with v0.2)
> +  - Allows any PSCI version implemented by KVM and compatible with
> +    v0.2 to be set with SET_ONE_REG
>    - Affects the whole VM (even if the register view is per-vcpu)
> diff --git a/arch/arm/kvm/handle_exit.c b/arch/arm/kvm/handle_exit.c
> index e020cc82c4b1..a4520c7118d2 100644
> --- a/arch/arm/kvm/handle_exit.c
> +++ b/arch/arm/kvm/handle_exit.c
> @@ -36,7 +36,7 @@ static int handle_hvc(struct kvm_vcpu *vcpu, struct kvm_run *run)
>  		      kvm_vcpu_hvc_get_imm(vcpu));
>  	vcpu->stat.hvc_exit_stat++;
>  
> -	ret = kvm_psci_call(vcpu);
> +	ret = kvm_hvc_call_handler(vcpu);
>  	if (ret < 0) {
>  		vcpu_set_reg(vcpu, 0, ~0UL);
>  		return 1;
> diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
> index 97e8d64a203d..bb6e1518d819 100644
> --- a/arch/arm64/kvm/handle_exit.c
> +++ b/arch/arm64/kvm/handle_exit.c
> @@ -52,7 +52,7 @@ static int handle_hvc(struct kvm_vcpu *vcpu, struct kvm_run *run)
>  			    kvm_vcpu_hvc_get_imm(vcpu));
>  	vcpu->stat.hvc_exit_stat++;
>  
> -	ret = kvm_psci_call(vcpu);
> +	ret = kvm_hvc_call_handler(vcpu);
>  	if (ret < 0) {
>  		vcpu_set_reg(vcpu, 0, ~0UL);
>  		return 1;
> diff --git a/include/kvm/arm_psci.h b/include/kvm/arm_psci.h
> index f2fa7d752c4e..4876bfac2195 100644
> --- a/include/kvm/arm_psci.h
> +++ b/include/kvm/arm_psci.h
> @@ -26,7 +26,7 @@
>  #define KVM_ARM_PSCI_LATEST	KVM_ARM_PSCI_1_0
>  
>  int kvm_psci_version(struct kvm_vcpu *vcpu);
> -int kvm_psci_call(struct kvm_vcpu *vcpu);
> +int kvm_hvc_call_handler(struct kvm_vcpu *vcpu);
>  
>  struct kvm_one_reg;
>  
> diff --git a/include/linux/arm-smccc.h b/include/linux/arm-smccc.h
> index 4c5bca38c653..dc68aa5a7261 100644
> --- a/include/linux/arm-smccc.h
> +++ b/include/linux/arm-smccc.h
> @@ -60,6 +60,19 @@
>  #define ARM_SMCCC_QUIRK_NONE		0
>  #define ARM_SMCCC_QUIRK_QCOM_A6		1 /* Save/restore register a6 */
>  
> +#define ARM_SMCCC_VERSION_1_0		0x10000
> +#define ARM_SMCCC_VERSION_1_1		0x10001
> +
> +#define ARM_SMCCC_VERSION_FUNC_ID					\
> +	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL,				\
> +			   ARM_SMCCC_SMC_32,				\
> +			   0, 0)
> +
> +#define ARM_SMCCC_ARCH_FEATURES_FUNC_ID					\
> +	ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL,				\
> +			   ARM_SMCCC_SMC_32,				\
> +			   0, 1)
> +
>  #ifndef __ASSEMBLY__
>  
>  #include <linux/linkage.h>
> diff --git a/virt/kvm/arm/psci.c b/virt/kvm/arm/psci.c
> index 682f9be6264b..3bb336ac7d7d 100644
> --- a/virt/kvm/arm/psci.c
> +++ b/virt/kvm/arm/psci.c
> @@ -15,6 +15,7 @@
>   * along with this program.  If not, see <http://www.gnu.org/licenses/>.
>   */
>  
> +#include <linux/arm-smccc.h>
>  #include <linux/preempt.h>
>  #include <linux/kvm_host.h>
>  #include <linux/uaccess.h>
> @@ -353,6 +354,7 @@ static int kvm_psci_1_0_call(struct kvm_vcpu *vcpu)
>  		case PSCI_0_2_FN_SYSTEM_OFF:
>  		case PSCI_0_2_FN_SYSTEM_RESET:
>  		case PSCI_1_0_FN_PSCI_FEATURES:
> +		case ARM_SMCCC_VERSION_FUNC_ID:
>  			val = 0;
>  			break;
>  		default:
> @@ -407,7 +409,7 @@ static int kvm_psci_0_1_call(struct kvm_vcpu *vcpu)
>   * Errors:
>   * -EINVAL: Unrecognized PSCI function
>   */
> -int kvm_psci_call(struct kvm_vcpu *vcpu)
> +static int kvm_psci_call(struct kvm_vcpu *vcpu)
>  {
>  	switch (kvm_psci_version(vcpu)) {
>  	case KVM_ARM_PSCI_1_0:
> @@ -421,6 +423,26 @@ int kvm_psci_call(struct kvm_vcpu *vcpu)
>  	};
>  }
>  
> +int kvm_hvc_call_handler(struct kvm_vcpu *vcpu)
> +{
> +	u32 func_id = smccc_get_function(vcpu);
> +	u32 val;
> +
> +	switch (func_id) {
> +	case ARM_SMCCC_VERSION_FUNC_ID:
> +		val = ARM_SMCCC_VERSION_1_1;
> +		break;
> +	case ARM_SMCCC_ARCH_FEATURES_FUNC_ID:
> +		val = -1;	/* Nothing supported yet */
> +		break;
> +	default:
> +		return kvm_psci_call(vcpu);
> +	}
> +
> +	smccc_set_retval(vcpu, val, 0, 0, 0);
> +	return 1;
> +}
> +
>  int kvm_arm_get_fw_num_regs(struct kvm_vcpu *vcpu)
>  {
>  	return 1;		/* PSCI version */
> -- 
> 2.14.2
> 
> 
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> linux-arm-kernel@lists.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

-- 
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