Add the arm64 variant of mshv_vtl_return_call() to support the MSHV_VTL driver on arm64. This function enables the transition between Virtual Trust Levels (VTLs) in MSHV_VTL when the kernel acts as a paravisor.
Signed-off-by: Roman Kisel <[email protected]> Reviewed-by: Roman Kisel <[email protected]> Signed-off-by: Naman Jain <[email protected]> --- arch/arm64/hyperv/Makefile | 1 + arch/arm64/hyperv/hv_vtl.c | 158 ++++++++++++++++++++++++++++++ arch/arm64/include/asm/mshyperv.h | 13 +++ arch/x86/include/asm/mshyperv.h | 2 - drivers/hv/mshv_vtl.h | 3 + include/asm-generic/mshyperv.h | 2 + 6 files changed, 177 insertions(+), 2 deletions(-) create mode 100644 arch/arm64/hyperv/hv_vtl.c diff --git a/arch/arm64/hyperv/Makefile b/arch/arm64/hyperv/Makefile index 87c31c001da9..9701a837a6e1 100644 --- a/arch/arm64/hyperv/Makefile +++ b/arch/arm64/hyperv/Makefile @@ -1,2 +1,3 @@ # SPDX-License-Identifier: GPL-2.0 obj-y := hv_core.o mshyperv.o +obj-$(CONFIG_HYPERV_VTL_MODE) += hv_vtl.o diff --git a/arch/arm64/hyperv/hv_vtl.c b/arch/arm64/hyperv/hv_vtl.c new file mode 100644 index 000000000000..59cbeb74e7b9 --- /dev/null +++ b/arch/arm64/hyperv/hv_vtl.c @@ -0,0 +1,158 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (C) 2026, Microsoft, Inc. + * + * Authors: + * Roman Kisel <[email protected]> + * Naman Jain <[email protected]> + */ + +#include <asm/mshyperv.h> +#include <asm/neon.h> +#include <linux/export.h> + +void mshv_vtl_return_call(struct mshv_vtl_cpu_context *vtl0) +{ + struct user_fpsimd_state fpsimd_state; + u64 base_ptr = (u64)vtl0->x; + + /* + * Obtain the CPU FPSIMD registers for VTL context switch. + * This saves the current task's FP/NEON state and allows us to + * safely load VTL0's FP/NEON context for the hypercall. + */ + kernel_neon_begin(&fpsimd_state); + + /* + * VTL switch for ARM64 platform - managing VTL0's CPU context. + * We explicitly use the stack to save the base pointer, and use x16 + * as our working register for accessing the context structure. + * + * Register Handling: + * - X0-X17: Saved/restored (general-purpose, shared for VTL communication) + * - X18: NOT touched - hypervisor-managed per-VTL (platform register) + * - X19-X30: Saved/restored (part of VTL0's execution context) + * - Q0-Q31: Saved/restored (128-bit NEON/floating-point registers, shared) + * - SP: Not in structure, hypervisor-managed per-VTL + * + * X29 (FP) and X30 (LR) are in the structure and must be saved/restored + * as part of VTL0's complete execution state. + */ + asm __volatile__ ( + /* Save base pointer to stack explicitly, then load into x16 */ + "str %0, [sp, #-16]!\n\t" /* Push base pointer onto stack */ + "mov x16, %0\n\t" /* Load base pointer into x16 */ + /* Volatile registers (Windows ARM64 ABI: x0-x17) */ + "ldp x0, x1, [x16]\n\t" + "ldp x2, x3, [x16, #(2*8)]\n\t" + "ldp x4, x5, [x16, #(4*8)]\n\t" + "ldp x6, x7, [x16, #(6*8)]\n\t" + "ldp x8, x9, [x16, #(8*8)]\n\t" + "ldp x10, x11, [x16, #(10*8)]\n\t" + "ldp x12, x13, [x16, #(12*8)]\n\t" + "ldp x14, x15, [x16, #(14*8)]\n\t" + /* x16 will be loaded last, after saving base pointer */ + "ldr x17, [x16, #(17*8)]\n\t" + /* x18 is hypervisor-managed per-VTL - DO NOT LOAD */ + + /* General-purpose registers: x19-x30 */ + "ldp x19, x20, [x16, #(19*8)]\n\t" + "ldp x21, x22, [x16, #(21*8)]\n\t" + "ldp x23, x24, [x16, #(23*8)]\n\t" + "ldp x25, x26, [x16, #(25*8)]\n\t" + "ldp x27, x28, [x16, #(27*8)]\n\t" + + /* Frame pointer and link register */ + "ldp x29, x30, [x16, #(29*8)]\n\t" + + /* Shared NEON/FP registers: Q0-Q31 (128-bit) */ + "ldp q0, q1, [x16, #(32*8)]\n\t" + "ldp q2, q3, [x16, #(32*8 + 2*16)]\n\t" + "ldp q4, q5, [x16, #(32*8 + 4*16)]\n\t" + "ldp q6, q7, [x16, #(32*8 + 6*16)]\n\t" + "ldp q8, q9, [x16, #(32*8 + 8*16)]\n\t" + "ldp q10, q11, [x16, #(32*8 + 10*16)]\n\t" + "ldp q12, q13, [x16, #(32*8 + 12*16)]\n\t" + "ldp q14, q15, [x16, #(32*8 + 14*16)]\n\t" + "ldp q16, q17, [x16, #(32*8 + 16*16)]\n\t" + "ldp q18, q19, [x16, #(32*8 + 18*16)]\n\t" + "ldp q20, q21, [x16, #(32*8 + 20*16)]\n\t" + "ldp q22, q23, [x16, #(32*8 + 22*16)]\n\t" + "ldp q24, q25, [x16, #(32*8 + 24*16)]\n\t" + "ldp q26, q27, [x16, #(32*8 + 26*16)]\n\t" + "ldp q28, q29, [x16, #(32*8 + 28*16)]\n\t" + "ldp q30, q31, [x16, #(32*8 + 30*16)]\n\t" + + /* Now load x16 itself */ + "ldr x16, [x16, #(16*8)]\n\t" + + /* Return to the lower VTL */ + "hvc #3\n\t" + + /* Save context after return - reload base pointer from stack */ + "stp x16, x17, [sp, #-16]!\n\t" /* Save x16, x17 temporarily */ + "ldr x16, [sp, #16]\n\t" /* Reload base pointer (skip saved x16,x17) */ + + /* Volatile registers */ + "stp x0, x1, [x16]\n\t" + "stp x2, x3, [x16, #(2*8)]\n\t" + "stp x4, x5, [x16, #(4*8)]\n\t" + "stp x6, x7, [x16, #(6*8)]\n\t" + "stp x8, x9, [x16, #(8*8)]\n\t" + "stp x10, x11, [x16, #(10*8)]\n\t" + "stp x12, x13, [x16, #(12*8)]\n\t" + "stp x14, x15, [x16, #(14*8)]\n\t" + "ldp x0, x1, [sp], #16\n\t" /* Recover saved x16, x17 */ + "stp x0, x1, [x16, #(16*8)]\n\t" + /* x18 is hypervisor-managed - DO NOT SAVE */ + + /* General-purpose registers: x19-x30 */ + "stp x19, x20, [x16, #(19*8)]\n\t" + "stp x21, x22, [x16, #(21*8)]\n\t" + "stp x23, x24, [x16, #(23*8)]\n\t" + "stp x25, x26, [x16, #(25*8)]\n\t" + "stp x27, x28, [x16, #(27*8)]\n\t" + "stp x29, x30, [x16, #(29*8)]\n\t" /* Frame pointer and link register */ + + /* Shared NEON/FP registers: Q0-Q31 (128-bit) */ + "stp q0, q1, [x16, #(32*8)]\n\t" + "stp q2, q3, [x16, #(32*8 + 2*16)]\n\t" + "stp q4, q5, [x16, #(32*8 + 4*16)]\n\t" + "stp q6, q7, [x16, #(32*8 + 6*16)]\n\t" + "stp q8, q9, [x16, #(32*8 + 8*16)]\n\t" + "stp q10, q11, [x16, #(32*8 + 10*16)]\n\t" + "stp q12, q13, [x16, #(32*8 + 12*16)]\n\t" + "stp q14, q15, [x16, #(32*8 + 14*16)]\n\t" + "stp q16, q17, [x16, #(32*8 + 16*16)]\n\t" + "stp q18, q19, [x16, #(32*8 + 18*16)]\n\t" + "stp q20, q21, [x16, #(32*8 + 20*16)]\n\t" + "stp q22, q23, [x16, #(32*8 + 22*16)]\n\t" + "stp q24, q25, [x16, #(32*8 + 24*16)]\n\t" + "stp q26, q27, [x16, #(32*8 + 26*16)]\n\t" + "stp q28, q29, [x16, #(32*8 + 28*16)]\n\t" + "stp q30, q31, [x16, #(32*8 + 30*16)]\n\t" + + /* Clean up stack - pop base pointer */ + "add sp, sp, #16\n\t" + + : /* No outputs */ + : /* Input */ "r"(base_ptr) + : /* Clobber list - x16 used as base, x18 is hypervisor-managed (not touched) */ + "memory", "cc", + "x0", "x1", "x2", "x3", "x4", "x5", + "x6", "x7", "x8", "x9", "x10", "x11", "x12", "x13", + "x14", "x15", "x16", "x17", "x19", "x20", "x21", + "x22", "x23", "x24", "x25", "x26", "x27", "x28", + "x29", "x30", + "v0", "v1", "v2", "v3", "v4", "v5", "v6", "v7", + "v8", "v9", "v10", "v11", "v12", "v13", "v14", "v15", + "v16", "v17", "v18", "v19", "v20", "v21", "v22", "v23", + "v24", "v25", "v26", "v27", "v28", "v29", "v30", "v31"); + + /* + * Restore the task's FP/SIMD state and return CPU FPSIMD registers + * back to normal kernel use. + */ + kernel_neon_end(&fpsimd_state); +} +EXPORT_SYMBOL(mshv_vtl_return_call); diff --git a/arch/arm64/include/asm/mshyperv.h b/arch/arm64/include/asm/mshyperv.h index 585b23a26f1b..9eb0e5999f29 100644 --- a/arch/arm64/include/asm/mshyperv.h +++ b/arch/arm64/include/asm/mshyperv.h @@ -60,6 +60,18 @@ static inline u64 hv_get_non_nested_msr(unsigned int reg) ARM_SMCCC_SMC_64, \ ARM_SMCCC_OWNER_VENDOR_HYP, \ HV_SMCCC_FUNC_NUMBER) + +struct mshv_vtl_cpu_context { +/* + * x18 is managed by the hypervisor. It won't be reloaded from this array. + * It is included here for convenience in array indexing. + * 'rsvd' field serves as alignment padding so q[] starts at offset 32*8=256. + */ + __u64 x[31]; + __u64 rsvd; + __uint128_t q[32]; +}; + #ifdef CONFIG_HYPERV_VTL_MODE /* * Get/Set the register. If the function returns `1`, that must be done via @@ -69,6 +81,7 @@ static inline int hv_vtl_get_set_reg(struct hv_register_assoc *regs, bool set, b { return 1; } + #endif #include <asm-generic/mshyperv.h> diff --git a/arch/x86/include/asm/mshyperv.h b/arch/x86/include/asm/mshyperv.h index 08278547b84c..b4d80c9a673a 100644 --- a/arch/x86/include/asm/mshyperv.h +++ b/arch/x86/include/asm/mshyperv.h @@ -286,7 +286,6 @@ struct mshv_vtl_cpu_context { #ifdef CONFIG_HYPERV_VTL_MODE void __init hv_vtl_init_platform(void); int __init hv_vtl_early_init(void); -void mshv_vtl_return_call(struct mshv_vtl_cpu_context *vtl0); void mshv_vtl_return_call_init(u64 vtl_return_offset); void mshv_vtl_return_hypercall(void); void __mshv_vtl_return_call(struct mshv_vtl_cpu_context *vtl0); @@ -294,7 +293,6 @@ int hv_vtl_get_set_reg(struct hv_register_assoc *regs, bool set, bool shared); #else static inline void __init hv_vtl_init_platform(void) {} static inline int __init hv_vtl_early_init(void) { return 0; } -static inline void mshv_vtl_return_call(struct mshv_vtl_cpu_context *vtl0) {} static inline void mshv_vtl_return_call_init(u64 vtl_return_offset) {} static inline void mshv_vtl_return_hypercall(void) {} static inline void __mshv_vtl_return_call(struct mshv_vtl_cpu_context *vtl0) {} diff --git a/drivers/hv/mshv_vtl.h b/drivers/hv/mshv_vtl.h index a6eea52f7aa2..103f07371f3f 100644 --- a/drivers/hv/mshv_vtl.h +++ b/drivers/hv/mshv_vtl.h @@ -22,4 +22,7 @@ struct mshv_vtl_run { char vtl_ret_actions[MSHV_MAX_RUN_MSG_SIZE]; }; +static_assert(sizeof(struct mshv_vtl_cpu_context) <= 1024, + "struct mshv_vtl_cpu_context exceeds reserved space in struct mshv_vtl_run"); + #endif /* _MSHV_VTL_H */ diff --git a/include/asm-generic/mshyperv.h b/include/asm-generic/mshyperv.h index db183c8cfb95..8cdf2a9fbdfb 100644 --- a/include/asm-generic/mshyperv.h +++ b/include/asm-generic/mshyperv.h @@ -396,8 +396,10 @@ static inline int hv_deposit_memory(u64 partition_id, u64 status) #if IS_ENABLED(CONFIG_HYPERV_VTL_MODE) u8 __init get_vtl(void); +void mshv_vtl_return_call(struct mshv_vtl_cpu_context *vtl0); #else static inline u8 get_vtl(void) { return 0; } +static inline void mshv_vtl_return_call(struct mshv_vtl_cpu_context *vtl0) {} #endif #endif -- 2.43.0
