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    Subject[RFC PATCH 02/47] mm: asi: Add command-line parameter to enable/disable ASI
    From
    A parameter named "asi" is added, disabled by default. A feature flag
    X86_FEATURE_ASI is set if ASI is enabled.

    Signed-off-by: Junaid Shahid <junaids@google.com>


    ---
    arch/x86/include/asm/asi.h | 17 ++++++++++----
    arch/x86/include/asm/cpufeatures.h | 1 +
    arch/x86/include/asm/disabled-features.h | 8 ++++++-
    arch/x86/mm/asi.c | 29 ++++++++++++++++++++++++
    arch/x86/mm/init.c | 2 +-
    include/asm-generic/asi.h | 2 ++
    6 files changed, 53 insertions(+), 6 deletions(-)

    diff --git a/arch/x86/include/asm/asi.h b/arch/x86/include/asm/asi.h
    index f9fc928a555d..0a4af23ed0eb 100644
    --- a/arch/x86/include/asm/asi.h
    +++ b/arch/x86/include/asm/asi.h
    @@ -6,6 +6,7 @@

    #include <asm/pgtable_types.h>
    #include <asm/percpu.h>
    +#include <asm/cpufeature.h>

    #ifdef CONFIG_ADDRESS_SPACE_ISOLATION

    @@ -52,18 +53,24 @@ void asi_exit(void);

    static inline void asi_set_target_unrestricted(void)
    {
    - barrier();
    - this_cpu_write(asi_cpu_state.target_asi, NULL);
    + if (static_cpu_has(X86_FEATURE_ASI)) {
    + barrier();
    + this_cpu_write(asi_cpu_state.target_asi, NULL);
    + }
    }

    static inline struct asi *asi_get_current(void)
    {
    - return this_cpu_read(asi_cpu_state.curr_asi);
    + return static_cpu_has(X86_FEATURE_ASI)
    + ? this_cpu_read(asi_cpu_state.curr_asi)
    + : NULL;
    }

    static inline struct asi *asi_get_target(void)
    {
    - return this_cpu_read(asi_cpu_state.target_asi);
    + return static_cpu_has(X86_FEATURE_ASI)
    + ? this_cpu_read(asi_cpu_state.target_asi)
    + : NULL;
    }

    static inline bool is_asi_active(void)
    @@ -76,6 +83,8 @@ static inline bool asi_is_target_unrestricted(void)
    return !asi_get_target();
    }

    +#define static_asi_enabled() cpu_feature_enabled(X86_FEATURE_ASI)
    +
    #endif /* CONFIG_ADDRESS_SPACE_ISOLATION */

    #endif
    diff --git a/arch/x86/include/asm/cpufeatures.h b/arch/x86/include/asm/cpufeatures.h
    index d5b5f2ab87a0..0b0ead3cdd48 100644
    --- a/arch/x86/include/asm/cpufeatures.h
    +++ b/arch/x86/include/asm/cpufeatures.h
    @@ -295,6 +295,7 @@
    #define X86_FEATURE_PER_THREAD_MBA (11*32+ 7) /* "" Per-thread Memory Bandwidth Allocation */
    #define X86_FEATURE_SGX1 (11*32+ 8) /* "" Basic SGX */
    #define X86_FEATURE_SGX2 (11*32+ 9) /* "" SGX Enclave Dynamic Memory Management (EDMM) */
    +#define X86_FEATURE_ASI (11*32+10) /* Kernel Address Space Isolation */

    /* Intel-defined CPU features, CPUID level 0x00000007:1 (EAX), word 12 */
    #define X86_FEATURE_AVX_VNNI (12*32+ 4) /* AVX VNNI instructions */
    diff --git a/arch/x86/include/asm/disabled-features.h b/arch/x86/include/asm/disabled-features.h
    index 8f28fafa98b3..9659cd9f867d 100644
    --- a/arch/x86/include/asm/disabled-features.h
    +++ b/arch/x86/include/asm/disabled-features.h
    @@ -56,6 +56,12 @@
    # define DISABLE_PTI (1 << (X86_FEATURE_PTI & 31))
    #endif

    +#ifdef CONFIG_ADDRESS_SPACE_ISOLATION
    +# define DISABLE_ASI 0
    +#else
    +# define DISABLE_ASI (1 << (X86_FEATURE_ASI & 31))
    +#endif
    +
    /* Force disable because it's broken beyond repair */
    #define DISABLE_ENQCMD (1 << (X86_FEATURE_ENQCMD & 31))

    @@ -79,7 +85,7 @@
    #define DISABLED_MASK8 0
    #define DISABLED_MASK9 (DISABLE_SMAP|DISABLE_SGX)
    #define DISABLED_MASK10 0
    -#define DISABLED_MASK11 0
    +#define DISABLED_MASK11 (DISABLE_ASI)
    #define DISABLED_MASK12 0
    #define DISABLED_MASK13 0
    #define DISABLED_MASK14 0
    diff --git a/arch/x86/mm/asi.c b/arch/x86/mm/asi.c
    index 9928325f3787..d274c86f89b7 100644
    --- a/arch/x86/mm/asi.c
    +++ b/arch/x86/mm/asi.c
    @@ -1,5 +1,7 @@
    // SPDX-License-Identifier: GPL-2.0

    +#include <linux/init.h>
    +
    #include <asm/asi.h>
    #include <asm/pgalloc.h>
    #include <asm/mmu_context.h>
    @@ -18,6 +20,9 @@ int asi_register_class(const char *name, uint flags,
    {
    int i;

    + if (!boot_cpu_has(X86_FEATURE_ASI))
    + return 0;
    +
    VM_BUG_ON(name == NULL);

    spin_lock(&asi_class_lock);
    @@ -43,6 +48,9 @@ EXPORT_SYMBOL_GPL(asi_register_class);

    void asi_unregister_class(int index)
    {
    + if (!boot_cpu_has(X86_FEATURE_ASI))
    + return;
    +
    spin_lock(&asi_class_lock);

    WARN_ON(asi_class[index].name == NULL);
    @@ -52,10 +60,22 @@ void asi_unregister_class(int index)
    }
    EXPORT_SYMBOL_GPL(asi_unregister_class);

    +static int __init set_asi_param(char *str)
    +{
    + if (strcmp(str, "on") == 0)
    + setup_force_cpu_cap(X86_FEATURE_ASI);
    +
    + return 0;
    +}
    +early_param("asi", set_asi_param);
    +
    int asi_init(struct mm_struct *mm, int asi_index)
    {
    struct asi *asi = &mm->asi[asi_index];

    + if (!boot_cpu_has(X86_FEATURE_ASI))
    + return 0;
    +
    /* Index 0 is reserved for special purposes. */
    WARN_ON(asi_index == 0 || asi_index >= ASI_MAX_NUM);
    WARN_ON(asi->pgd != NULL);
    @@ -79,6 +99,9 @@ EXPORT_SYMBOL_GPL(asi_init);

    void asi_destroy(struct asi *asi)
    {
    + if (!boot_cpu_has(X86_FEATURE_ASI))
    + return;
    +
    free_pages((ulong)asi->pgd, PGD_ALLOCATION_ORDER);
    memset(asi, 0, sizeof(struct asi));
    }
    @@ -109,6 +132,9 @@ static void __asi_enter(void)

    void asi_enter(struct asi *asi)
    {
    + if (!static_cpu_has(X86_FEATURE_ASI))
    + return;
    +
    VM_WARN_ON_ONCE(!asi);

    this_cpu_write(asi_cpu_state.target_asi, asi);
    @@ -123,6 +149,9 @@ void asi_exit(void)
    u64 unrestricted_cr3;
    struct asi *asi;

    + if (!static_cpu_has(X86_FEATURE_ASI))
    + return;
    +
    preempt_disable();

    VM_BUG_ON(this_cpu_read(cpu_tlbstate.loaded_mm) ==
    diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c
    index 000cbe5315f5..dfff17363365 100644
    --- a/arch/x86/mm/init.c
    +++ b/arch/x86/mm/init.c
    @@ -240,7 +240,7 @@ static void __init probe_page_size_mask(void)
    __default_kernel_pte_mask = __supported_pte_mask;
    /* Except when with PTI or ASI where the kernel is mostly non-Global: */
    if (cpu_feature_enabled(X86_FEATURE_PTI) ||
    - IS_ENABLED(CONFIG_ADDRESS_SPACE_ISOLATION))
    + cpu_feature_enabled(X86_FEATURE_ASI))
    __default_kernel_pte_mask &= ~_PAGE_GLOBAL;

    /* Enable 1 GB linear kernel mappings if available: */
    diff --git a/include/asm-generic/asi.h b/include/asm-generic/asi.h
    index e5ba51d30b90..dae1403ee1d0 100644
    --- a/include/asm-generic/asi.h
    +++ b/include/asm-generic/asi.h
    @@ -44,6 +44,8 @@ static inline struct asi *asi_get_target(void) { return NULL; }

    static inline struct asi *asi_get_current(void) { return NULL; }

    +#define static_asi_enabled() false
    +
    #endif /* !_ASSEMBLY_ */

    #endif /* !CONFIG_ADDRESS_SPACE_ISOLATION */
    --
    2.35.1.473.g83b2b277ed-goog
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