Re: [PATCH v18 1/7] arm/arm64: Probe for the presence of KVM hypervisor

Steven Price
2021-02-10T16:08:56Z

On 08/02/2021 13:40, Marc Zyngier wrote:
> From: Will Deacon <will@kernel.org>
>
> Although the SMCCC specification provides some limited functionality for
> describing the presence of hypervisor and firmware services, this is
> generally applicable only to functions designated as "Arm Architecture
> Service Functions" and no portable discovery mechanism is provided for
> standard hypervisor services, despite having a designated range of
> function identifiers reserved by the specification.
>
> In an attempt to avoid the need for additional firmware changes every
> time a new function is added, introduce a UID to identify the service
> provider as being compatible with KVM. Once this has been established,
> additional services can be discovered via a feature bitmap.
>
> Signed-off-by: Will Deacon <will@kernel.org>
> Signed-off-by: Jianyong Wu <jianyong.wu@arm.com>
> [maz: move code to its own file, plug it into PSCI]
> Signed-off-by: Marc Zyngier <maz@kernel.org>
> Link: https://lore.kernel.org/r/20201209060932.212364-2-jianyong.wu@arm.com

Looks good to me, FWIW:

Reviewed-by: Steven Price <steven.price@arm.com>

> ---
> arch/arm/include/asm/hypervisor.h | 3 ++
> arch/arm64/include/asm/hypervisor.h | 3 ++
> drivers/firmware/psci/psci.c | 2 ++
> drivers/firmware/smccc/Makefile | 2 +-
> drivers/firmware/smccc/kvm_guest.c | 50 +++++++++++++++++++++++++++++
> drivers/firmware/smccc/smccc.c | 1 +
> include/linux/arm-smccc.h | 25 +++++++++++++++
> 7 files changed, 85 insertions(+), 1 deletion(-)
> create mode 100644 drivers/firmware/smccc/kvm_guest.c
>
> diff --git a/arch/arm/include/asm/hypervisor.h b/arch/arm/include/asm/hypervisor.h
> index df8524365637..bd61502b9715 100644
> --- a/arch/arm/include/asm/hypervisor.h
> +++ b/arch/arm/include/asm/hypervisor.h
> @@ -4,4 +4,7 @@
>
> #include <asm/xen/hypervisor.h>
>
> +void kvm_init_hyp_services(void);
> +bool kvm_arm_hyp_service_available(u32 func_id);
> +
> #endif
> diff --git a/arch/arm64/include/asm/hypervisor.h b/arch/arm64/include/asm/hypervisor.h
> index f9cc1d021791..0ae427f352c8 100644
> --- a/arch/arm64/include/asm/hypervisor.h
> +++ b/arch/arm64/include/asm/hypervisor.h
> @@ -4,4 +4,7 @@
>
> #include <asm/xen/hypervisor.h>
>
> +void kvm_init_hyp_services(void);
> +bool kvm_arm_hyp_service_available(u32 func_id);
> +
> #endif
> diff --git a/drivers/firmware/psci/psci.c b/drivers/firmware/psci/psci.c
> index f5fc429cae3f..69e296f02902 100644
> --- a/drivers/firmware/psci/psci.c
> +++ b/drivers/firmware/psci/psci.c
> @@ -23,6 +23,7 @@
>
> #include <asm/cpuidle.h>
> #include <asm/cputype.h>
> +#include <asm/hypervisor.h>
> #include <asm/system_misc.h>
> #include <asm/smp_plat.h>
> #include <asm/suspend.h>
> @@ -498,6 +499,7 @@ static int __init psci_probe(void)
> psci_init_cpu_suspend();
> psci_init_system_suspend();
> psci_init_system_reset2();
> + kvm_init_hyp_services();
> }
>
> return 0;
> diff --git a/drivers/firmware/smccc/Makefile b/drivers/firmware/smccc/Makefile
> index 72ab84042832..40d19144a860 100644
> --- a/drivers/firmware/smccc/Makefile
> +++ b/drivers/firmware/smccc/Makefile
> @@ -1,4 +1,4 @@
> # SPDX-License-Identifier: GPL-2.0
> #
> -obj-$(CONFIG_HAVE_ARM_SMCCC_DISCOVERY) += smccc.o
> +obj-$(CONFIG_HAVE_ARM_SMCCC_DISCOVERY) += smccc.o kvm_guest.o
> obj-$(CONFIG_ARM_SMCCC_SOC_ID) += soc_id.o
> diff --git a/drivers/firmware/smccc/kvm_guest.c b/drivers/firmware/smccc/kvm_guest.c
> new file mode 100644
> index 000000000000..08836f2f39ee
> --- /dev/null
> +++ b/drivers/firmware/smccc/kvm_guest.c
> @@ -0,0 +1,50 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#define pr_fmt(fmt) "smccc: KVM: " fmt
> +
> +#include <linux/arm-smccc.h>
> +#include <linux/bitmap.h>
> +#include <linux/kernel.h>
> +#include <linux/string.h>
> +
> +#include <asm/hypervisor.h>
> +
> +static DECLARE_BITMAP(__kvm_arm_hyp_services, ARM_SMCCC_KVM_NUM_FUNCS) __ro_after_init = { };
> +
> +void __init kvm_init_hyp_services(void)
> +{
> + struct arm_smccc_res res;
> + u32 val[4];
> +
> + if (arm_smccc_1_1_get_conduit() != SMCCC_CONDUIT_HVC)
> + return;
> +
> + arm_smccc_1_1_invoke(ARM_SMCCC_VENDOR_HYP_CALL_UID_FUNC_ID, &res);
> + if (res.a0 != ARM_SMCCC_VENDOR_HYP_UID_KVM_REG_0 ||
> + res.a1 != ARM_SMCCC_VENDOR_HYP_UID_KVM_REG_1 ||
> + res.a2 != ARM_SMCCC_VENDOR_HYP_UID_KVM_REG_2 ||
> + res.a3 != ARM_SMCCC_VENDOR_HYP_UID_KVM_REG_3)
> + return;
> +
> + memset(&res, 0, sizeof(res));
> + arm_smccc_1_1_invoke(ARM_SMCCC_VENDOR_HYP_KVM_FEATURES_FUNC_ID, &res);
> +
> + val[0] = lower_32_bits(res.a0);
> + val[1] = lower_32_bits(res.a1);
> + val[2] = lower_32_bits(res.a2);
> + val[3] = lower_32_bits(res.a3);
> +
> + bitmap_from_arr32(__kvm_arm_hyp_services, val, ARM_SMCCC_KVM_NUM_FUNCS);
> +
> + pr_info("hypervisor services detected (0x%08lx 0x%08lx 0x%08lx 0x%08lx)\n",
> + res.a3, res.a2, res.a1, res.a0);
> +}
> +
> +bool kvm_arm_hyp_service_available(u32 func_id)
> +{
> + if (func_id >= ARM_SMCCC_KVM_NUM_FUNCS)
> + return -EINVAL;
> +
> + return test_bit(func_id, __kvm_arm_hyp_services);
> +}
> +EXPORT_SYMBOL_GPL(kvm_arm_hyp_service_available);
> diff --git a/drivers/firmware/smccc/smccc.c b/drivers/firmware/smccc/smccc.c
> index 00c88b809c0c..94eca6ffda05 100644
> --- a/drivers/firmware/smccc/smccc.c
> +++ b/drivers/firmware/smccc/smccc.c
> @@ -7,6 +7,7 @@
>
> #include <linux/init.h>
> #include <linux/arm-smccc.h>
> +#include <linux/kernel.h>
>
> static u32 smccc_version = ARM_SMCCC_VERSION_1_0;
> static enum arm_smccc_conduit smccc_conduit = SMCCC_CONDUIT_NONE;
> diff --git a/include/linux/arm-smccc.h b/include/linux/arm-smccc.h
> index f860645f6512..74e90b65b489 100644
> --- a/include/linux/arm-smccc.h
> +++ b/include/linux/arm-smccc.h
> @@ -55,6 +55,8 @@
> #define ARM_SMCCC_OWNER_TRUSTED_OS 50
> #define ARM_SMCCC_OWNER_TRUSTED_OS_END 63
>
> +#define ARM_SMCCC_FUNC_QUERY_CALL_UID 0xff01
> +
> #define ARM_SMCCC_QUIRK_NONE 0
> #define ARM_SMCCC_QUIRK_QCOM_A6 1 /* Save/restore register a6 */
>
> @@ -87,6 +89,29 @@
> ARM_SMCCC_SMC_32, \
> 0, 0x7fff)
>
> +#define ARM_SMCCC_VENDOR_HYP_CALL_UID_FUNC_ID \
> + ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, \
> + ARM_SMCCC_SMC_32, \
> + ARM_SMCCC_OWNER_VENDOR_HYP, \
> + ARM_SMCCC_FUNC_QUERY_CALL_UID)
> +
> +/* KVM UID value: 28b46fb6-2ec5-11e9-a9ca-4b564d003a74 */
> +#define ARM_SMCCC_VENDOR_HYP_UID_KVM_REG_0 0xb66fb428U
> +#define ARM_SMCCC_VENDOR_HYP_UID_KVM_REG_1 0xe911c52eU
> +#define ARM_SMCCC_VENDOR_HYP_UID_KVM_REG_2 0x564bcaa9U
> +#define ARM_SMCCC_VENDOR_HYP_UID_KVM_REG_3 0x743a004dU
> +
> +/* KVM "vendor specific" services */
> +#define ARM_SMCCC_KVM_FUNC_FEATURES 0
> +#define ARM_SMCCC_KVM_FUNC_FEATURES_2 127
> +#define ARM_SMCCC_KVM_NUM_FUNCS 128
> +
> +#define ARM_SMCCC_VENDOR_HYP_KVM_FEATURES_FUNC_ID \
> + ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, \
> + ARM_SMCCC_SMC_32, \
> + ARM_SMCCC_OWNER_VENDOR_HYP, \
> + ARM_SMCCC_KVM_FUNC_FEATURES)
> +
> #define SMCCC_ARCH_WORKAROUND_RET_UNAFFECTED 1
>
> /* Paravirtualised time calls (defined by ARM DEN0057A) */
>