Re: [kvm-unit-tests v2 06/10] powerpc/sprs: Specify SPRs with data rather than code

[Thomas Huth <thuth@redhat.com>]

On 20/03/2023 08.03, Nicholas Piggin wrote:
> A significant rework that builds an array of 'struct spr', where each
> element describes an SPR. This makes various metadata about the SPR
> like name and access type easier to carry and use.
> 
> Hypervisor privileged registers are described despite not being used
> at the moment for completeness, but also the code might one day be
> reused for a hypervisor-privileged test.
> 
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
> 
> This ended up a little over-engineered perhaps, but there are lots of
> SPRs, lots of access types, lots of changes between processor and ISA
> versions, and lots of places they are implemented and used, so lots of
> room for mistakes. There is not a good system in place to easily
> see that userspace, supervisor, etc., switches perform all the right
> SPR context switching so this is a nice test case to have. The sprs test
> quickly caught a few QEMU TCG SPR bugs which really motivated me to
> improve the SPR coverage.
> ---
>   powerpc/sprs.c | 589 +++++++++++++++++++++++++++++++++----------------
>   1 file changed, 394 insertions(+), 195 deletions(-)
> 
> diff --git a/powerpc/sprs.c b/powerpc/sprs.c
> index db341a9..dd83dac 100644
> --- a/powerpc/sprs.c
> +++ b/powerpc/sprs.c
> @@ -82,231 +82,407 @@ static void mtspr(unsigned spr, uint64_t val)
>   	: "lr", "ctr", "xer");
>   }
>   
> -uint64_t before[1024], after[1024];
> +static uint64_t before[1024], after[1024];
>   
> -/* Common SPRs for all PowerPC CPUs */
> -static void set_sprs_common(uint64_t val)
> -{
> -	// mtspr(9, val);	/* CTR */ /* Used by mfspr/mtspr */
> -	// mtspr(273, val);	/* SPRG1 */  /* Used by our exception handler */
> -	mtspr(274, val);	/* SPRG2 */
> -	mtspr(275, val);	/* SPRG3 */
> -}
> +#define SPR_PR_READ	0x0001
> +#define SPR_PR_WRITE	0x0002
> +#define SPR_OS_READ	0x0010
> +#define SPR_OS_WRITE	0x0020
> +#define SPR_HV_READ	0x0100
> +#define SPR_HV_WRITE	0x0200
> +
> +#define RW		0x333
> +#define RO		0x111
> +#define WO		0x222
> +#define OS_RW		0x330
> +#define OS_RO		0x110
> +#define OS_WO		0x220
> +#define HV_RW		0x300
> +#define HV_RO		0x100
> +#define HV_WO		0x200
> +
> +#define SPR_ASYNC	0x1000	/* May be updated asynchronously */
> +#define SPR_INT		0x2000	/* May be updated by synchronous interrupt */
> +#define SPR_HARNESS	0x4000	/* Test harness uses the register */
> +
> +struct spr {
> +	const char	*name;
> +	uint8_t		width;
> +	uint16_t	access;
> +	uint16_t	type;
> +};
> +
> +/* SPRs common denominator back to PowerPC Operating Environment Architecture */
> +static const struct spr sprs_common[1024] = {
> +  [1] = {"XER",		64,	RW,		SPR_HARNESS, }, /* Compiler */
> +  [8] = {"LR", 		64,	RW,		SPR_HARNESS, }, /* Compiler, mfspr/mtspr */
> +  [9] = {"CTR",		64,	RW,		SPR_HARNESS, }, /* Compiler, mfspr/mtspr */
> + [18] = {"DSISR",	32,	OS_RW,		SPR_INT, },
> + [19] = {"DAR",		64,	OS_RW,		SPR_INT, },
> + [26] = {"SRR0",	64,	OS_RW,		SPR_INT, },
> + [27] = {"SRR1",	64,	OS_RW,		SPR_INT, },
> +[268] = {"TB",		64,	RO	,	SPR_ASYNC, },
> +[269] = {"TBU",		32,	RO,		SPR_ASYNC, },
> +[272] = {"SPRG0",	64,	OS_RW,		SPR_HARNESS, }, /* Int stack */
> +[273] = {"SPRG1",	64,	OS_RW,		SPR_HARNESS, }, /* Scratch */
> +[274] = {"SPRG2",	64,	OS_RW, },
> +[275] = {"SPRG3",	64,	OS_RW, },
> +[287] = {"PVR",		32,	OS_RO, },
> +};

Using a size of 1024 for each of these arrays looks weird. Why don't you add 
a "nr" field to struct spr and specify the register number via that field 
instead of using the index into the array as register number?

  Thomas