processor.cxxm

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/// SPDX-License-Identifier: Apache-2.0
/// @file arch/s390x/cpu/processor.cxxm
/// @brief some miscellaneous srtuff
 
export module arch.s390x.cpu.processor;
export import arch.s390x.cpu.types;
import zxfoundation.base.types;
import arch.s390x.cpu.ctlreg;
import arch.s390x.cpu.diag;
import lib.bit;
 
export {
 
namespace arch::s390x::cpu::processor {
 
    /// @brief cpuid structure (STIDP result).
    struct alignas(8) [[gnu::packed]] cpuid {
        u32 version:8;
        u32 ident:24;
        u32 machine:16;
        u32 unused:16;
    };
 
    auto get_cpuid(cpuid *id) -> void {
        __asm__ volatile("stidp %0" : "=m" (*id));
    }
 
    /// @brief Probe whether the kernel is running under a hypervisor.
    /// @return true if the kernel is running under a hypervisor.
    auto is_hypervisor() noexcept -> bool {
        cpuid id{};
        get_cpuid(&id);
        return id.version == 0xff;
    }
 
    /// @brief Read the current stack pointer (r15).
    [[nodiscard]] inline auto get_current_sp() noexcept -> u64 {
        u64 sp;
        __asm__ volatile ("stg %%r15, %0" : "=Q"(sp));
        return sp;
    }
 
    /// @brief Store Prefix (STPX) — returns the physical address in the Prefix Register.
    /// @return Physical base address of the current CPU's lowcore.
    [[deprecated("STPX is expensive — use lowcore::get_current() on the hot path")]]
    [[gnu::no_stack_protector]] auto get_prefix() noexcept -> u32 {
        u32 prefix;
        __asm__ volatile ("stpx %0" : "=Q"(prefix) : : "memory");
        return prefix;
    }
 
    /// @brief Set Prefix (SPX) — loads a new value into the Prefix Register.
    /// @param prefix  New physical base address (must be 4 KB aligned).
    auto set_prefix(const u32 prefix) noexcept -> void {
        __asm__ volatile ("spx %0" :: "m" (prefix) : "memory");
    }
 
    /// @brief Store CPU Address (STAP) — returns the hardware CPU address.
    /// @return The hardware CPU address used with SIGP instructions.
    auto cpu_addr() noexcept -> u16 {
        u16 addr;
        __asm__ volatile ("stap %0" : "=m" (addr));
        return addr;
    }
 
} // namespace arch::s390x::cpu::processor
 
} // end export