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Message-ID: <63bbc640-9b0c-95af-3d35-291da0323db3@linaro.org>
Date: Mon, 9 Jan 2023 15:34:25 -0600
From: Alex Elder <elder@...aro.org>
To: Elliot Berman <quic_eberman@...cinc.com>,
Bjorn Andersson <quic_bjorande@...cinc.com>,
Catalin Marinas <catalin.marinas@....com>,
Will Deacon <will@...nel.org>,
Murali Nalajala <quic_mnalajal@...cinc.com>
Cc: Trilok Soni <quic_tsoni@...cinc.com>,
Srivatsa Vaddagiri <quic_svaddagi@...cinc.com>,
Carl van Schaik <quic_cvanscha@...cinc.com>,
Prakruthi Deepak Heragu <quic_pheragu@...cinc.com>,
Arnd Bergmann <arnd@...db.de>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Rob Herring <robh+dt@...nel.org>,
Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
Jonathan Corbet <corbet@....net>,
Bagas Sanjaya <bagasdotme@...il.com>,
Jassi Brar <jassisinghbrar@...il.com>,
Sudeep Holla <sudeep.holla@....com>,
Mark Rutland <mark.rutland@....com>,
Lorenzo Pieralisi <lpieralisi@...nel.org>,
Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
linux-arm-msm@...r.kernel.org, devicetree@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org, linux-acpi@...r.kernel.org
Subject: Re: [PATCH v8 05/28] virt: gunyah: Add hypercalls to identify Gunyah
On 12/19/22 4:58 PM, Elliot Berman wrote:
> Add hypercalls to identify when Linux is running a virtual machine under
> Gunyah.
>
> There are two calls to help identify Gunyah:
>
> 1. gh_hypercall_get_uid() returns a UID when running under a Gunyah
> hypervisor.
> 2. gh_hypercall_hyp_identify() returns build information and a set of
> feature flags that are supported by Gunyah.
The first is a "service", while the second is a "hypercall".
Can you explain the distinction? The sentence at the top
refers to both as "hypercalls".
>
> Signed-off-by: Elliot Berman <quic_eberman@...cinc.com>
> ---
> MAINTAINERS | 2 +
> arch/arm64/Kbuild | 1 +
> arch/arm64/gunyah/Makefile | 1 +
> arch/arm64/gunyah/gunyah_hypercall.c | 69 ++++++++++++++++++++++++++++
> drivers/virt/Kconfig | 1 +
> drivers/virt/gunyah/Kconfig | 12 +++++
> include/linux/gunyah.h | 25 ++++++++++
> 7 files changed, 111 insertions(+)
> create mode 100644 arch/arm64/gunyah/Makefile
> create mode 100644 arch/arm64/gunyah/gunyah_hypercall.c
> create mode 100644 drivers/virt/gunyah/Kconfig
>
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 74e76e0ab14d..36698df6b0e5 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -8941,6 +8941,8 @@ L: linux-arm-msm@...r.kernel.org
> S: Supported
> F: Documentation/devicetree/bindings/firmware/gunyah-hypervisor.yaml
> F: Documentation/virt/gunyah/
> +F: arch/arm64/gunyah/
> +F: drivers/virt/gunyah/
> F: include/linux/gunyah.h
>
> HABANALABS PCI DRIVER
> diff --git a/arch/arm64/Kbuild b/arch/arm64/Kbuild
> index 5bfbf7d79c99..e4847ba0e3c9 100644
> --- a/arch/arm64/Kbuild
> +++ b/arch/arm64/Kbuild
> @@ -3,6 +3,7 @@ obj-y += kernel/ mm/ net/
> obj-$(CONFIG_KVM) += kvm/
> obj-$(CONFIG_XEN) += xen/
> obj-$(subst m,y,$(CONFIG_HYPERV)) += hyperv/
> +obj-$(CONFIG_GUNYAH) += gunyah/
> obj-$(CONFIG_CRYPTO) += crypto/
>
> # for cleaning
> diff --git a/arch/arm64/gunyah/Makefile b/arch/arm64/gunyah/Makefile
> new file mode 100644
> index 000000000000..9fbc720b6fb6
> --- /dev/null
> +++ b/arch/arm64/gunyah/Makefile
> @@ -0,0 +1 @@
> +obj-$(CONFIG_GUNYAH) += gunyah_hypercall.o
> diff --git a/arch/arm64/gunyah/gunyah_hypercall.c b/arch/arm64/gunyah/gunyah_hypercall.c
> new file mode 100644
> index 000000000000..0beb3123d650
> --- /dev/null
> +++ b/arch/arm64/gunyah/gunyah_hypercall.c
> @@ -0,0 +1,69 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * Copyright (c) 2022 Qualcomm Innovation Center, Inc. All rights reserved.
> + */
> +
> +#include <linux/arm-smccc.h>
> +#include <linux/module.h>
> +#include <linux/gunyah.h>
> +
> +#define GH_CALL_TYPE_PLATFORM_CALL 0
> +#define GH_CALL_TYPE_HYPERCALL 2
> +#define GH_CALL_TYPE_SERVICE 3
> +#define GH_CALL_TYPE_SHIFT 14
> +#define GH_CALL_FUNCTION_NUM_MASK 0x3fff
A FN_ID is a 32-bit value. Are all 18 high-order bits considered
part of the call type? It might be good to specify that explicitly
by defining a mask for it.
> +
> +#define GH_FN_ID(type, num) ((type) << GH_CALL_TYPE_SHIFT | ((num) & GH_CALL_FUNCTION_NUM_MASK))
> +
Is there any need for the endianness of these values to be specified?
Does Gunyah operate with a well-defined endianness? Is there any
chance a VM can run with an endianness different from Gunyah? I
see that the arm_smcc_* structures are defined without endianness.
(Sorry if these are dumb questions.)
> +#define GH_SERVICE(fn) ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, ARM_SMCCC_SMC_32, \
> + ARM_SMCCC_OWNER_VENDOR_HYP, \
> + GH_FN_ID(GH_CALL_TYPE_SERVICE, fn))
> +
> +#define GH_HYPERCALL_CALL_UID GH_SERVICE(0x3f01)
Perhaps 0x3f01 could be defined symbolically.
However if this is the only place it's ever used, doing so
doesn't add much value (meaning, just do it the way you did).
> +
> +#define GH_HYPERCALL(fn) ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, ARM_SMCCC_SMC_64, \
> + ARM_SMCCC_OWNER_VENDOR_HYP, \
> + GH_FN_ID(GH_CALL_TYPE_HYPERCALL, fn))
> +
> +#define GH_HYPERCALL_HYP_IDENTIFY GH_HYPERCALL(0x0000)
Will there be a growing set of well-known hypervisor call functions?
Perhaps 0x0000 should be defined symbolically. (Or not if it's only
used here.)
> +
> +/**
> + * gh_hypercall_get_uid() - Returns a UID when running under a Gunyah hypervisor
> + * @uid: An array of 4 u32's (u32 uid[4];)
> + *
> + * Caller should compare the resulting UID to a list of known Gunyah UIDs to
> + * confirm that Linux is running as a guest of Gunyah.
I presume that, if the returned UID isn't well-known, then no other
Gunyah-related calls are meaningful. Is that correct?
> + */
> +void gh_hypercall_get_uid(u32 uid[4])
> +{
> + struct arm_smccc_res res;
> +
> + arm_smccc_1_1_hvc(GH_HYPERCALL_CALL_UID, &res);
> +
> + uid[0] = res.a0;
> + uid[1] = res.a1;
> + uid[2] = res.a2;
> + uid[3] = res.a3;
I see in the definition of struct arm_smccc_res that the four
fields are unsigned long values. That differs from the u32
array passed as argument. Are the resource IDs guaranteed to
be four 32-bit values? I personally prefer being explicit
about the upper 32-bits being discarded (though some don't
agree with that convention).
> +}
> +EXPORT_SYMBOL_GPL(gh_hypercall_get_uid);
> +
> +/**
> + * gh_hypercall_hyp_identify() - Returns build information and feature flags
> + * supported by Gunyah.
> + * @hyp_identity: filled by the hypercall with the API info and feature flags.
> + */
> +void gh_hypercall_hyp_identify(struct gh_hypercall_hyp_identify_resp *hyp_identity)
> +{
> + struct arm_smccc_res res;
> +
> + arm_smccc_1_1_hvc(GH_HYPERCALL_HYP_IDENTIFY, &res);
> +
> + hyp_identity->api_info = res.a0;
> + hyp_identity->flags[0] = res.a1;
> + hyp_identity->flags[1] = res.a2;
> + hyp_identity->flags[2] = res.a3;
> +}
> +EXPORT_SYMBOL_GPL(gh_hypercall_hyp_identify);
> +
> +MODULE_LICENSE("GPL");
> +MODULE_DESCRIPTION("Gunyah Hypervisor Hypercalls");
> diff --git a/drivers/virt/Kconfig b/drivers/virt/Kconfig
> index 87ef258cec64..259dc2be6cad 100644
> --- a/drivers/virt/Kconfig
> +++ b/drivers/virt/Kconfig
> @@ -52,4 +52,5 @@ source "drivers/virt/coco/efi_secret/Kconfig"
>
> source "drivers/virt/coco/sev-guest/Kconfig"
>
> +source "drivers/virt/gunyah/Kconfig"
> endif
> diff --git a/drivers/virt/gunyah/Kconfig b/drivers/virt/gunyah/Kconfig
> new file mode 100644
> index 000000000000..127156a678a6
> --- /dev/null
> +++ b/drivers/virt/gunyah/Kconfig
> @@ -0,0 +1,12 @@
> +# SPDX-License-Identifier: GPL-2.0-only
> +
> +config GUNYAH
Maybe config QCOM_GUNYAH? Will this ever run on hardware
other than Qualcomm's?
> + tristate "Gunyah Virtualization drivers"
> + depends on ARM64
> + help
> + The Gunyah drivers are the helper interfaces that runs in a guest VM
s/runs/run/
> + such as basic inter-VM IPC and signaling mechanisms, and higher level
> + services such as memory/device sharing, IRQ sharing, and so on.
> +
> + Say Y/M here to enable the drivers needed to interact in a Gunyah
> + virtual environment.
> diff --git a/include/linux/gunyah.h b/include/linux/gunyah.h
> index 824e20a11d27..2765d2b40198 100644
> --- a/include/linux/gunyah.h
> +++ b/include/linux/gunyah.h
> @@ -6,6 +6,7 @@
> #ifndef _GUNYAH_H
> #define _GUNYAH_H
>
> +#include <linux/bitfield.h>
> #include <linux/types.h>
> #include <linux/errno.h>
>
> @@ -71,4 +72,28 @@ static inline int gh_remap_error(int gh_error)
> }
> }
>
> +#define GUNYAH_API_V1 1
> +
> +#define GH_API_INFO_API_VERSION_MASK GENMASK_ULL(13, 0)
> +#define GH_API_INFO_BIG_ENDIAN BIT_ULL(14)
> +#define GH_API_INFO_IS_64BIT BIT_ULL(15)
> +#define GH_API_INFO_VARIANT_MASK GENMASK_ULL(63, 56)
> +
How are the GH_IDENTIFY bits below used? Are they encoded
in the three 64-bit flags fields in the response structure?
Does that mean only the first of those three is (currently)
used?
> +#define GH_IDENTIFY_PARTITION_CSPACE BIT_ULL(0)
> +#define GH_IDENTIFY_DOORBELL BIT_ULL(1)
> +#define GH_IDENTIFY_MSGQUEUE BIT_ULL(2)
> +#define GH_IDENTIFY_VIC BIT_ULL(3)
> +#define GH_IDENTIFY_VPM BIT_ULL(4)
> +#define GH_IDENTIFY_VCPU BIT_ULL(5)
> +#define GH_IDENTIFY_MEMEXTENT BIT_ULL(6)
> +#define GH_IDENTIFY_TRACE_CTRL BIT_ULL(7)
> +
> +struct gh_hypercall_hyp_identify_resp {
> + u64 api_info;
> + u64 flags[3];
> +};
Again I'll ask about endianness. This is a response coming *from*
Gunyah. Is it guaranteed to use the same byte order convention as
the running operating system (Linux) guest?
-Alex
> +
> +void gh_hypercall_get_uid(u32 uid[4]);
> +void gh_hypercall_hyp_identify(struct gh_hypercall_hyp_identify_resp *hyp_identity);
> +
> #endif
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