Re: [PATCH v10 04/26] virt: gunyah: Add hypercalls to identify Gunyah

From: Alex Elder
Date: Thu Feb 23 2023 - 19:09:24 EST

On 2/14/23 3:12 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.

Signed-off-by: Elliot Berman <quic_eberman@xxxxxxxxxxx>
---
arch/arm64/Kbuild | 1 +
arch/arm64/gunyah/Makefile | 3 ++
arch/arm64/gunyah/gunyah_hypercall.c | 61 ++++++++++++++++++++++++++++
drivers/virt/Kconfig | 2 +
drivers/virt/gunyah/Kconfig | 13 ++++++
include/linux/gunyah.h | 33 +++++++++++++++
6 files changed, 113 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/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..84f1e38cafb1
--- /dev/null
+++ b/arch/arm64/gunyah/Makefile
@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: GPL-2.0
+
+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..f30d06ee80cf
--- /dev/null
+++ b/arch/arm64/gunyah/gunyah_hypercall.c
@@ -0,0 +1,61 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2022-2023 Qualcomm Innovation Center, Inc. All rights reserved.
+ */
+
+#include <linux/arm-smccc.h>
+#include <linux/module.h>
+#include <linux/gunyah.h>
+
+static const uint32_t gunyah_known_uuids[][4] = {
+ {0x19bd54bd, 0x0b37571b, 0x946f609b, 0x54539de6}, /* QC_HYP (Qualcomm's build) */
+ {0x673d5f14, 0x9265ce36, 0xa4535fdb, 0xc1d58fcd}, /* GUNYAH (open source build) */
+};

Are these really UUIDs? Standard ones? Define them using
the standard Linux way of doing it. See <linux/uuid.h>.

+
+bool arch_is_gunyah_guest(void)
+{
+ struct arm_smccc_res res;
+ u32 uid[4];
+ int i;
+
+ arm_smccc_1_1_hvc(ARM_SMCCC_VENDOR_HYP_CALL_UID_FUNC_ID, &res);
+
+ uid[0] = lower_32_bits(res.a0);
+ uid[1] = lower_32_bits(res.a1);
+ uid[2] = lower_32_bits(res.a2);
+ uid[3] = lower_32_bits(res.a3);
+
+ for (i = 0; i < ARRAY_SIZE(gunyah_known_uuids); i++)
+ if (!memcmp(uid, gunyah_known_uuids[i], sizeof(uid)))
+ break;
+
+ return i != ARRAY_SIZE(gunyah_known_uuids);
+}
+EXPORT_SYMBOL_GPL(arch_is_gunyah_guest);
+
+#define GH_HYPERCALL(fn) ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, ARM_SMCCC_SMC_64, \
+ ARM_SMCCC_OWNER_VENDOR_HYP, \
+ fn)
+
+#define GH_HYPERCALL_HYP_IDENTIFY GH_HYPERCALL(0x8000)
+
+/**
+ * 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 f79ab13a5c28..85bd6626ffc9 100644
--- a/drivers/virt/Kconfig
+++ b/drivers/virt/Kconfig
@@ -54,4 +54,6 @@ source "drivers/virt/coco/sev-guest/Kconfig"
source "drivers/virt/coco/tdx-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..1a737694c333
--- /dev/null
+++ b/drivers/virt/gunyah/Kconfig
@@ -0,0 +1,13 @@
+# SPDX-License-Identifier: GPL-2.0-only
+
+config GUNYAH
+ tristate "Gunyah Virtualization drivers"
+ depends on ARM64
+ depends on MAILBOX
+ help
+ The Gunyah drivers are the helper interfaces that run in a guest VM
+ 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 59ef4c735ae8..3fef2854c5e1 100644
--- a/include/linux/gunyah.h
+++ b/include/linux/gunyah.h
@@ -6,8 +6,10 @@
#ifndef _LINUX_GUNYAH_H
#define _LINUX_GUNYAH_H
+#include <linux/bitfield.h>
#include <linux/errno.h>
#include <linux/limits.h>
+#include <linux/types.h>
/******************************************************************************/
/* Common arch-independent definitions for Gunyah hypercalls */
@@ -79,4 +81,35 @@ static inline int gh_remap_error(enum gh_error gh_error)
}
}
+enum gh_api_feature {
+ GH_API_FEATURE_DOORBELL,
+ GH_API_FEATURE_MSGQUEUE,
+ GH_API_FEATURE_VCPU,
+ GH_API_FEATURE_MEMEXTENT,
+};

Can't you reuse these symbols, so that the same set
represents the feature and the identify response?

I'm not sure what a good naming scheme would be, but
you could easily do:
enum gh_api_feature {
GH_FEATURE_DOORBELL = 1,
GH_FEATURE_MSGQUEUE = 2,
GH_FEATURE_VCPU = 5,
GH_FEATURE_MEMEXTENT = 6,
};

And then you could do:

bool gh_api_has_feature(enum gh_api_feature feature)
{
switch (feature) {
case GH_FEATURE_DOORBELL:
case GH_FEATURES_MSGQUEUE:
case GH_FEATURE_VCPU:
case GH_FEATURE_MEMEXTENT:
return !!(gunyah_api.flags[0] & BIT_ULL(feature));

default:
return false;
}
}

+
+bool arch_is_gunyah_guest(void);
+
+u16 gh_api_version(void);
+bool gh_api_has_feature(enum gh_api_feature feature);
+
+#define GUNYAH_API_V1 1
+

Rather than _INFO_ here, maybe _IDENTIFY_?

Why is "API_" needed in these symbol names?

+#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)
+
+#define GH_IDENTIFY_DOORBELL BIT_ULL(1)
+#define GH_IDENTIFY_MSGQUEUE BIT_ULL(2)
+#define GH_IDENTIFY_VCPU BIT_ULL(5)
+#define GH_IDENTIFY_MEMEXTENT BIT_ULL(6)
+
+struct gh_hypercall_hyp_identify_resp {
+ u64 api_info;
+ u64 flags[3];
+};
+
+void gh_hypercall_hyp_identify(struct gh_hypercall_hyp_identify_resp *hyp_identity);

Since this is a user space API, you *could* consider having
this function return an int. Just in case there's a future
reason that a failure could occur, or that you want to
supply some other information. If this truly doesn't make
sense, it's fine as-is...

+
#endif