Re: [PATCH v2 1/2] Fetch XSAVE area component offsets and sizes when initializing x86 CPU

[Paul Goyette <paul%whooppee.com@localhost>]

Are there any userland programs that use cpu.h?  Or any kernel modules?

If so, these changes would create a change in the kernel API and would 
therefore require a kernel version bump.


On Wed, 5 Jun 2019, MichaÅ~B Górny wrote:

> Introduce two new arrays, x86_xsave_offsets and x86_xsave_sizes,
> and initialize them with XSAVE area component offsets and sizes queried
> via CPUID.  This will be needed to implement getters and setters for
> additional register types.
>
> While at it, add XSAVE_* constants corresponding to specific XSAVE
> components.
> ---
> sys/arch/x86/include/cpu.h        |  2 ++
> sys/arch/x86/include/specialreg.h | 20 ++++++++++++++++++++
> sys/arch/x86/x86/identcpu.c       | 12 ++++++++++++
> 3 files changed, 34 insertions(+)
>
> diff --git a/sys/arch/x86/include/cpu.h b/sys/arch/x86/include/cpu.h
> index 143ae3c5c5ec..589f179ce758 100644
> --- a/sys/arch/x86/include/cpu.h
> +++ b/sys/arch/x86/include/cpu.h
> @@ -459,6 +459,8 @@ extern int x86_fpu_save;
> #define	FPU_SAVE_XSAVEOPT	3
> extern unsigned int x86_fpu_save_size;
> extern uint64_t x86_xsave_features;
> +extern size_t x86_xsave_offsets[];
> +extern size_t x86_xsave_sizes[];
> extern uint32_t x86_fpu_mxcsr_mask;
> extern bool x86_fpu_eager;
>
> diff --git a/sys/arch/x86/include/specialreg.h b/sys/arch/x86/include/specialreg.h
> index 4f8c4cca6db7..1c0e8c972b07 100644
> --- a/sys/arch/x86/include/specialreg.h
> +++ b/sys/arch/x86/include/specialreg.h
> @@ -146,6 +146,26 @@
> #define XCR0_FPU	(XCR0_X87 | XCR0_SSE | XCR0_YMM_Hi128 | \
> 			 XCR0_Opmask | XCR0_ZMM_Hi256 | XCR0_Hi16_ZMM)
>
> +/*
> + * XSAVE component indices.
> + */
> +#define XSAVE_X87	0
> +#define XSAVE_SSE	1
> +#define XSAVE_YMM_Hi128	2
> +#define XSAVE_BNDREGS	3
> +#define XSAVE_BNDCSR	4
> +#define XSAVE_Opmask	5
> +#define XSAVE_ZMM_Hi256	6
> +#define XSAVE_Hi16_ZMM	7
> +#define XSAVE_PT	8
> +#define XSAVE_PKRU	9
> +#define XSAVE_HDC	10
> +
> +/*
> + * Highest XSAVE component enabled by XCR0_FPU.
> + */
> +#define XSAVE_MAX_COMPONENT XSAVE_Hi16_ZMM
> +
> /*
>  * CPUID "features" bits
>  */
> diff --git a/sys/arch/x86/x86/identcpu.c b/sys/arch/x86/x86/identcpu.c
> index 9037fb2673fd..9714865bfb43 100644
> --- a/sys/arch/x86/x86/identcpu.c
> +++ b/sys/arch/x86/x86/identcpu.c
> @@ -74,6 +74,8 @@ char cpu_brand_string[49];
> int x86_fpu_save __read_mostly;
> unsigned int x86_fpu_save_size __read_mostly = sizeof(struct save87);
> uint64_t x86_xsave_features __read_mostly = 0;
> +size_t x86_xsave_offsets[XSAVE_MAX_COMPONENT] __read_mostly;
> +size_t x86_xsave_sizes[XSAVE_MAX_COMPONENT] __read_mostly;
>
> /*
>  * Note: these are just the ones that may not have a cpuid instruction.
> @@ -755,6 +757,7 @@ static void
> cpu_probe_fpu(struct cpu_info *ci)
> {
> 	u_int descs[4];
> +	int i;
>
> 	x86_fpu_eager = true;
> 	x86_fpu_save = FPU_SAVE_FSAVE;
> @@ -816,6 +819,15 @@ cpu_probe_fpu(struct cpu_info *ci)
> 		x86_fpu_save_size = descs[2];
>
> 	x86_xsave_features = (uint64_t)descs[3] << 32 | descs[0];
> +
> +	/* Get component offsets and sizes for the save area */
> +	for (i = XSAVE_YMM_Hi128; i < __arraycount(x86_xsave_offsets); i++) {
> +		if (x86_xsave_features & ((uint64_t)1 << i)) {
> +			x86_cpuid2(0xd, i, descs);
> +			x86_xsave_offsets[i] = descs[1];
> +			x86_xsave_sizes[i] = descs[0];
> +		}
> +	}
> }
>
> void
> --
> 2.22.0.rc3
>
>
> !DSPAM:5cf7db2f272681658520559!

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