From 3f9cd0ca848413fd368278310d2cdd6c2bef48b2 Mon Sep 17 00:00:00 2001 From: Jing Zhang Date: Tue, 3 Oct 2023 23:03:57 +0000 Subject: KVM: arm64: Allow userspace to get the writable masks for feature ID registers While the Feature ID range is well defined and pretty large, it isn't inconceivable that the architecture will eventually grow some other ranges that will need to similarly be described to userspace. Add a VM ioctl to allow userspace to get writable masks for feature ID registers in below system register space: op0 = 3, op1 = {0, 1, 3}, CRn = 0, CRm = {0 - 7}, op2 = {0 - 7} This is used to support mix-and-match userspace and kernels for writable ID registers, where userspace may want to know upfront whether it can actually tweak the contents of an idreg or not. Add a new capability (KVM_CAP_ARM_SUPPORTED_FEATURE_ID_RANGES) that returns a bitmap of the valid ranges, which can subsequently be retrieved, one at a time by setting the index of the set bit as the range identifier. Suggested-by: Marc Zyngier Suggested-by: Cornelia Huck Signed-off-by: Jing Zhang Reviewed-by: Cornelia Huck Reviewed-by: Marc Zyngier Link: https://lore.kernel.org/r/20231003230408.3405722-2-oliver.upton@linux.dev Signed-off-by: Oliver Upton --- arch/arm64/include/uapi/asm/kvm.h | 32 ++++++++++++++++++++++++++++++++ 1 file changed, 32 insertions(+) (limited to 'arch/arm64/include/uapi') diff --git a/arch/arm64/include/uapi/asm/kvm.h b/arch/arm64/include/uapi/asm/kvm.h index f7ddd73a8c0f..89d2fc872d9f 100644 --- a/arch/arm64/include/uapi/asm/kvm.h +++ b/arch/arm64/include/uapi/asm/kvm.h @@ -505,6 +505,38 @@ struct kvm_smccc_filter { #define KVM_HYPERCALL_EXIT_SMC (1U << 0) #define KVM_HYPERCALL_EXIT_16BIT (1U << 1) +/* + * Get feature ID registers userspace writable mask. + * + * From DDI0487J.a, D19.2.66 ("ID_AA64MMFR2_EL1, AArch64 Memory Model + * Feature Register 2"): + * + * "The Feature ID space is defined as the System register space in + * AArch64 with op0==3, op1=={0, 1, 3}, CRn==0, CRm=={0-7}, + * op2=={0-7}." + * + * This covers all currently known R/O registers that indicate + * anything useful feature wise, including the ID registers. + * + * If we ever need to introduce a new range, it will be described as + * such in the range field. + */ +#define KVM_ARM_FEATURE_ID_RANGE_IDX(op0, op1, crn, crm, op2) \ + ({ \ + __u64 __op1 = (op1) & 3; \ + __op1 -= (__op1 == 3); \ + (__op1 << 6 | ((crm) & 7) << 3 | (op2)); \ + }) + +#define KVM_ARM_FEATURE_ID_RANGE 0 +#define KVM_ARM_FEATURE_ID_RANGE_SIZE (3 * 8 * 8) + +struct reg_mask_range { + __u64 addr; /* Pointer to mask array */ + __u32 range; /* Requested range */ + __u32 reserved[13]; +}; + #endif #endif /* __ARM_KVM_H__ */ -- cgit v1.2.3