On Mon, 16 Oct 2023, Arnd Bergmann <arnd@xxxxxxxxxx> wrote:
> From: Arnd Bergmann <arnd@xxxxxxxx>
>
> The newly added memset() causes a warning for some reason I could not figure out:
>
> In file included from arch/x86/include/asm/string.h:3,
> from drivers/gpu/drm/i915/gt/intel_rc6.c:6:
> In function 'rc6_res_reg_init',
> inlined from 'intel_rc6_init' at drivers/gpu/drm/i915/gt/intel_rc6.c:610:2:
> arch/x86/include/asm/string_32.h:195:29: error: '__builtin_memset' writing 16 bytes into a region of size 0 overflows the destination [-Werror=stringop-overflow=]
> 195 | #define memset(s, c, count) __builtin_memset(s, c, count)
> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/gpu/drm/i915/gt/intel_rc6.c:584:9: note: in expansion of macro 'memset'
> 584 | memset(rc6->res_reg, INVALID_MMIO_REG.reg, sizeof(rc6->res_reg));
> | ^~~~~~
> In function 'intel_rc6_init':
>
> Change it to an normal initializer and an added memcpy() that does not have
> this problem.
>
> Fixes: 4bb9ca7ee0745 ("drm/i915/mtl: C6 residency and C state type for MTL SAMedia")
> Signed-off-by: Arnd Bergmann <arnd@xxxxxxxx>
> ---
> drivers/gpu/drm/i915/gt/intel_rc6.c | 16 ++++++++++------
> 1 file changed, 10 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/intel_rc6.c b/drivers/gpu/drm/i915/gt/intel_rc6.c
> index 8b67abd720be8..7090e4be29cb6 100644
> --- a/drivers/gpu/drm/i915/gt/intel_rc6.c
> +++ b/drivers/gpu/drm/i915/gt/intel_rc6.c
> @@ -581,19 +581,23 @@ static void __intel_rc6_disable(struct intel_rc6 *rc6)
>
> static void rc6_res_reg_init(struct intel_rc6 *rc6)
> {
> - memset(rc6->res_reg, INVALID_MMIO_REG.reg, sizeof(rc6->res_reg));
That's just bollocks. memset() is byte granularity, while
INVALID_MMIO_REG.reg is u32. If the value was anything other than 0,
this would break.
And you're not supposed to look at the guts of i915_reg_t to begin with,
that's why it's a typedef. Basically any code that accesses the members
of i915_reg_t outside of its implementation are doing it wrong.
Reviewed-by: Jani Nikula <jani.nikula@xxxxxxxxx>
> + i915_reg_t res_reg[INTEL_RC6_RES_MAX] = {
> + [0 ... INTEL_RC6_RES_MAX - 1] = INVALID_MMIO_REG,
> + };
>
> switch (rc6_to_gt(rc6)->type) {
> case GT_MEDIA:
> - rc6->res_reg[INTEL_RC6_RES_RC6] = MTL_MEDIA_MC6;
> + res_reg[INTEL_RC6_RES_RC6] = MTL_MEDIA_MC6;
> break;
> default:
> - rc6->res_reg[INTEL_RC6_RES_RC6_LOCKED] = GEN6_GT_GFX_RC6_LOCKED;
> - rc6->res_reg[INTEL_RC6_RES_RC6] = GEN6_GT_GFX_RC6;
> - rc6->res_reg[INTEL_RC6_RES_RC6p] = GEN6_GT_GFX_RC6p;
> - rc6->res_reg[INTEL_RC6_RES_RC6pp] = GEN6_GT_GFX_RC6pp;
> + res_reg[INTEL_RC6_RES_RC6_LOCKED] = GEN6_GT_GFX_RC6_LOCKED;
> + res_reg[INTEL_RC6_RES_RC6] = GEN6_GT_GFX_RC6;
> + res_reg[INTEL_RC6_RES_RC6p] = GEN6_GT_GFX_RC6p;
> + res_reg[INTEL_RC6_RES_RC6pp] = GEN6_GT_GFX_RC6pp;
> break;
> }
> +
> + memcpy(rc6->res_reg, res_reg, sizeof(res_reg));
> }
>
> void intel_rc6_init(struct intel_rc6 *rc6)
--
Jani Nikula, Intel
