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drivers/virt: pkvm: Add initial support for running as a protected guest
Implement a pKVM protected guest driver to probe the presence of pKVM and determine the memory protection granule using the HYP_MEMINFO hypercall. Acked-by: Marc Zyngier <maz@kernel.org> Link: https://lore.kernel.org/r/20240830130150.8568-3-will@kernel.org Signed-off-by: Will Deacon <will@kernel.org>
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‎Documentation/virt/kvm/arm/hypercalls.rst‎

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@@ -44,3 +44,25 @@ Provides a discovery mechanism for other KVM/arm64 hypercalls.
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----------------------------------------
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See ptp_kvm.rst
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``ARM_SMCCC_KVM_FUNC_HYP_MEMINFO``
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----------------------------------
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Query the memory protection parameters for a pKVM protected virtual machine.
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+---------------------+-------------------------------------------------------------+
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| Presence: | Optional; pKVM protected guests only. |
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+---------------------+-------------------------------------------------------------+
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| Calling convention: | HVC64 |
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+---------------------+----------+--------------------------------------------------+
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| Function ID: | (uint32) | 0xC6000002 |
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+---------------------+----------+----+---------------------------------------------+
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| Arguments: | (uint64) | R1 | Reserved / Must be zero |
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| +----------+----+---------------------------------------------+
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| | (uint64) | R2 | Reserved / Must be zero |
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| +----------+----+---------------------------------------------+
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| | (uint64) | R3 | Reserved / Must be zero |
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+---------------------+----------+----+---------------------------------------------+
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| Return Values: | (int64) | R0 | ``INVALID_PARAMETER (-3)`` on error, else |
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| | | | memory protection granule in bytes |
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+---------------------+----------+----+---------------------------------------------+

‎arch/arm64/include/asm/hypervisor.h‎

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void kvm_init_hyp_services(void);
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bool kvm_arm_hyp_service_available(u32 func_id);
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#ifdef CONFIG_ARM_PKVM_GUEST
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void pkvm_init_hyp_services(void);
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#else
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static inline void pkvm_init_hyp_services(void) { };
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#endif
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static inline void kvm_arch_init_hyp_services(void)
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{
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pkvm_init_hyp_services();
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};
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#endif

‎drivers/virt/coco/Kconfig‎

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source "drivers/virt/coco/efi_secret/Kconfig"
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source "drivers/virt/coco/pkvm-guest/Kconfig"
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source "drivers/virt/coco/sev-guest/Kconfig"
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source "drivers/virt/coco/tdx-guest/Kconfig"

‎drivers/virt/coco/Makefile‎

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#
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obj-$(CONFIG_TSM_REPORTS) += tsm.o
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obj-$(CONFIG_EFI_SECRET) += efi_secret/
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obj-$(CONFIG_ARM_PKVM_GUEST) += pkvm-guest/
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obj-$(CONFIG_SEV_GUEST) += sev-guest/
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obj-$(CONFIG_INTEL_TDX_GUEST) += tdx-guest/

‎drivers/virt/coco/pkvm-guest/Kconfig‎

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config ARM_PKVM_GUEST
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bool "Arm pKVM protected guest driver"
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depends on ARM64
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help
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Protected guests running under the pKVM hypervisor on arm64
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are isolated from the host and must issue hypercalls to enable
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interaction with virtual devices. This driver implements
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support for probing and issuing these hypercalls.
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If unsure, say 'N'.

‎drivers/virt/coco/pkvm-guest/Makefile‎

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# SPDX-License-Identifier: GPL-2.0-only
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obj-$(CONFIG_ARM_PKVM_GUEST) += arm-pkvm-guest.o

‎drivers/virt/coco/pkvm-guest/arm-pkvm-guest.c‎

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// SPDX-License-Identifier: GPL-2.0-only
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/*
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* Support for the hypercall interface exposed to protected guests by
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* pKVM.
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*
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* Author: Will Deacon <will@kernel.org>
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* Copyright (C) 2024 Google LLC
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*/
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#include <linux/arm-smccc.h>
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#include <linux/array_size.h>
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#include <linux/mm.h>
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#include <asm/hypervisor.h>
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static size_t pkvm_granule;
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void pkvm_init_hyp_services(void)
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{
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int i;
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struct arm_smccc_res res;
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const u32 funcs[] = {
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ARM_SMCCC_KVM_FUNC_HYP_MEMINFO,
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};
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for (i = 0; i < ARRAY_SIZE(funcs); ++i) {
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if (!kvm_arm_hyp_service_available(funcs[i]))
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return;
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}
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arm_smccc_1_1_invoke(ARM_SMCCC_VENDOR_HYP_KVM_HYP_MEMINFO_FUNC_ID,
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0, 0, 0, &res);
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if (res.a0 > PAGE_SIZE) /* Includes error codes */
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return;
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pkvm_granule = res.a0;
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}

‎include/linux/arm-smccc.h‎

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/* KVM "vendor specific" services */
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#define ARM_SMCCC_KVM_FUNC_FEATURES 0
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#define ARM_SMCCC_KVM_FUNC_PTP 1
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#define ARM_SMCCC_KVM_FUNC_HYP_MEMINFO 2
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#define ARM_SMCCC_KVM_FUNC_FEATURES_2 127
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#define ARM_SMCCC_KVM_NUM_FUNCS 128
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ARM_SMCCC_OWNER_VENDOR_HYP, \
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ARM_SMCCC_KVM_FUNC_PTP)
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#define ARM_SMCCC_VENDOR_HYP_KVM_HYP_MEMINFO_FUNC_ID \
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ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, \
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ARM_SMCCC_SMC_64, \
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ARM_SMCCC_OWNER_VENDOR_HYP, \
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ARM_SMCCC_KVM_FUNC_HYP_MEMINFO)
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/* ptp_kvm counter type ID */
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#define KVM_PTP_VIRT_COUNTER 0
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#define KVM_PTP_PHYS_COUNTER 1

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