Re: [PATCH v9 04/27] virt: gunyah: Add hypercalls to identify Gunyah

Elliot Berman
2023-01-30T19:05:52Z

On 1/30/2023 2:01 AM, Greg Kroah-Hartman wrote:
> On Fri, Jan 20, 2023 at 02:46:03PM -0800, 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@quicinc.com>
>> ---
>> MAINTAINERS | 2 +
>> arch/arm64/Kbuild | 1 +
>> arch/arm64/gunyah/Makefile | 3 ++
>> arch/arm64/gunyah/gunyah_hypercall.c | 75 ++++++++++++++++++++++++++++
>> drivers/virt/Kconfig | 2 +
>> drivers/virt/gunyah/Kconfig | 14 ++++++
>> include/linux/gunyah.h | 33 ++++++++++++
>> 7 files changed, 130 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 f1e07e39b2f5..fe19e71efc6d 100644
>> --- a/MAINTAINERS
>> +++ b/MAINTAINERS
>> @@ -9048,6 +9048,8 @@ L: linux-arm-msm@vger.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..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..ffed4b71641f
>> --- /dev/null
>> +++ b/arch/arm64/gunyah/gunyah_hypercall.c
>> @@ -0,0 +1,75 @@
>> +// 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] = {
>
> uint32_t is not a kernel type, please use sane ones, like u32.
>
>> + {0x19bd54bd, 0x0b37571b, 0x946f609b, 0x54539de6}, /* QC_HYP (Qualcomm's build) */
>> + {0x673d5f14, 0x9265ce36, 0xa4535fdb, 0xc1d58fcd}, /* GUNYAH (open source build) */
>
> And why not use the kernel uuid type here? Why create your own?
>
>> +};
>> +
>> +#define GH_HYPERCALL_HYP_IDENTIFY GH_HYPERCALL(0x0000)
>> +
>> +/**
>> + * 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.
>> + */
>> +void gh_hypercall_get_uid(u32 uid[4])
>> +{
>> + struct arm_smccc_res res;
>> + u32 uid[4];
>
> How does this work when you have a local variable the same name as the
> parameter to the function? What shadows what and how? The compiler
> didn't complain about this?
>
>> + 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);
>
> How can a function that returns void actually return anything?
>
> This obviously was never compiled. I'm stopping here in my review.
>

Fell victim to trusting automatic git commit --fixup tools here. I'll
send out v10 with proper bisectability.