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    Subject[RFC 2/3] Allow saving of individual states in fpu_xsave().
    Date
    Add a feature mask argument to fpu_xsave(). Introduce XCNTXT_DEFAULT
    to specify which feature states are to be saved/restored by default at
    context switches. Rename XCNTXT_MASK to XCNTXT_SUPPORTED to make clear
    what it really is.

    Signed-off-by: Hans Rosenfeld <hans.rosenfeld@amd.com>
    ---
    arch/x86/include/asm/i387.h | 4 ++--
    arch/x86/include/asm/xsave.h | 14 +++++++++++---
    arch/x86/kernel/xsave.c | 2 +-
    3 files changed, 14 insertions(+), 6 deletions(-)

    diff --git a/arch/x86/include/asm/i387.h b/arch/x86/include/asm/i387.h
    index de8593b..33600d3 100644
    --- a/arch/x86/include/asm/i387.h
    +++ b/arch/x86/include/asm/i387.h
    @@ -201,7 +201,7 @@ static inline void fpu_save_init(struct fpu *fpu)
    if (use_xsave()) {
    struct xsave_struct *xstate = &fpu->state->xsave;

    - fpu_xsave(xstate);
    + fpu_xsave(xstate, XCNTXT_DEFAULT);

    /*
    * xsave header may indicate the init state of the FP.
    @@ -239,7 +239,7 @@ static inline void __save_init_fpu(struct task_struct *tsk)
    static inline int fpu_restore_checking(struct fpu *fpu)
    {
    if (use_xsave())
    - return xrstor_checking(&fpu->state->xsave, -1);
    + return xrstor_checking(&fpu->state->xsave, XCNTXT_DEFAULT);
    else
    return fxrstor_checking(&fpu->state->fxsave);
    }
    diff --git a/arch/x86/include/asm/xsave.h b/arch/x86/include/asm/xsave.h
    index 8bcbbce..8820b57 100644
    --- a/arch/x86/include/asm/xsave.h
    +++ b/arch/x86/include/asm/xsave.h
    @@ -23,7 +23,12 @@
    /*
    * These are the features that the OS can handle currently.
    */
    -#define XCNTXT_MASK (XSTATE_FP | XSTATE_SSE | XSTATE_YMM)
    +#define XCNTXT_SUPPORTED (XSTATE_FP | XSTATE_SSE | XSTATE_YMM)
    +
    +/*
    + * These are the features that the OS saves/restores by default.
    + */
    +#define XCNTXT_DEFAULT (-1)

    #ifdef CONFIG_X86_64
    #define REX_PREFIX "0x48, "
    @@ -113,15 +118,18 @@ static inline void xsave_state(struct xsave_struct *fx, u64 mask)
    : "memory");
    }

    -static inline void fpu_xsave(struct xsave_struct *fx)
    +static inline void fpu_xsave(struct xsave_struct *fx, u64 mask)
    {
    + u32 lmask = mask;
    + u32 hmask = mask >> 32;
    +
    /* This, however, we can work around by forcing the compiler to select
    an addressing mode that doesn't require extended registers. */
    alternative_input(
    ".byte " REX_PREFIX "0x0f,0xae,0x27",
    ".byte " REX_PREFIX "0x0f,0xae,0x37",
    X86_FEATURE_XSAVEOPT,
    - [fx] "D" (fx), "a" (-1), "d" (-1) :
    + [fx] "D" (fx), "a" (lmask), "d" (hmask) :
    "memory");
    }
    #endif
    diff --git a/arch/x86/kernel/xsave.c b/arch/x86/kernel/xsave.c
    index 5eb15d4..11c3445 100644
    --- a/arch/x86/kernel/xsave.c
    +++ b/arch/x86/kernel/xsave.c
    @@ -434,7 +434,7 @@ static void __init xstate_enable_boot_cpu(void)
    /*
    * Support only the state known to OS.
    */
    - pcntxt_mask = pcntxt_mask & XCNTXT_MASK;
    + pcntxt_mask = pcntxt_mask & XCNTXT_SUPPORTED;

    xstate_enable();

    --
    1.5.6.5



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