linux-kernel - Re: [PATCH v2 05/31] EDAC/amd64: Add context struct

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Date:   Thu, 8 Jul 2021 15:53:34 -0400
From:   Yazen Ghannam <yazen.ghannam@....com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     linux-edac@...r.kernel.org, linux-kernel@...r.kernel.org,
        mchehab@...nel.org, tony.luck@...el.com,
        Smita.KoralahalliChannabasappa@....com
Subject: Re: [PATCH v2 05/31] EDAC/amd64: Add context struct

On Wed, Jun 30, 2021 at 07:17:41PM +0200, Borislav Petkov wrote:
> On Wed, Jun 23, 2021 at 07:19:36PM +0000, Yazen Ghannam wrote:
> > Define an address translation context struct. This will hold values that
> > will be passed between multiple functions.
> > 
> > Save return address, Node ID, and the Instance ID number to start.
> > Currently, we use the UMC number as the Instance ID, but future DF
> 
> Please use passive voice in your commit message: no "we" or "I", etc.
> 
> And this here is a perfect example: it sounds here like "we" is "AMD"
> but we use "we" mostly for the kernel. And there's the confusion.
> 
> So please teach yourself to formulate those commit messages properly -
> the future you will thank you, trust me!
> 
> :-)
>

Yeah, sorry I always seem to let it slip. :/

...

> > @@ -1097,6 +1100,16 @@ static int umc_normaddr_to_sysaddr(u64 norm_addr, u16 nid, u8 umc, u64 *sys_addr
> >  
> >  	struct df_reg reg;
> >  
> > +	struct addr_ctx ctx;
> 
> Those empty-lines spaced-out local vars look weird.
> 

Okay, I'll fix that.

...

> > @@ -1236,14 +1249,14 @@ static int umc_normaddr_to_sysaddr(u64 norm_addr, u16 nid, u8 umc, u64 *sys_addr
> >  		 * bits there are. "intlv_addr_bit" tells us how many "Y" bits
> >  		 * there are (where "I" starts).
> >  		 */
> > -		temp_addr_y = ret_addr & GENMASK_ULL(intlv_addr_bit-1, 0);
> > +		temp_addr_y = ctx.ret_addr & GENMASK_ULL(intlv_addr_bit - 1, 0);
> >  		temp_addr_i = (cs_id << intlv_addr_bit);
> > -		temp_addr_x = (ret_addr & GENMASK_ULL(63, intlv_addr_bit)) << num_intlv_bits;
> > -		ret_addr    = temp_addr_x | temp_addr_i | temp_addr_y;
> > +		temp_addr_x = (ctx.ret_addr & GENMASK_ULL(63, intlv_addr_bit)) << num_intlv_bits;
> > +		ctx.ret_addr    = temp_addr_x | temp_addr_i | temp_addr_y;
> 
> You want to align those vertically on the "=" for better readability.
> 

Most of this will be removed in later patches, so I didn't think to
change any more than is necessary to make sure the patch builds.

I'll check the end result to make sure things are aligned nicely.

> >  	}
> >  
> >  	/* Add dram base address */
> > -	ret_addr += dram_base_addr;
> > +	ctx.ret_addr += dram_base_addr;
> >  
> >  	/* If legacy MMIO hole enabled */
> >  	if (lgcy_mmio_hole_en) {
> > @@ -1251,29 +1264,29 @@ static int umc_normaddr_to_sysaddr(u64 norm_addr, u16 nid, u8 umc, u64 *sys_addr
> >  			goto out_err;
> >  
> >  		dram_hole_base = tmp & GENMASK(31, 24);
> > -		if (ret_addr >= dram_hole_base)
> > -			ret_addr += (BIT_ULL(32) - dram_hole_base);
> > +		if (ctx.ret_addr >= dram_hole_base)
> > +			ctx.ret_addr += (BIT_ULL(32) - dram_hole_base);
> >  	}
> >  
> >  	if (hash_enabled) {
> >  		/* Save some parentheses and grab ls-bit at the end. */
> > -		hashed_bit =	(ret_addr >> 12) ^
> > -				(ret_addr >> 18) ^
> > -				(ret_addr >> 21) ^
> > -				(ret_addr >> 30) ^
> > +		hashed_bit =	(ctx.ret_addr >> 12) ^
> > +				(ctx.ret_addr >> 18) ^
> > +				(ctx.ret_addr >> 21) ^
> > +				(ctx.ret_addr >> 30) ^
> >  				cs_id;
> >  
> >  		hashed_bit &= BIT(0);
> >  
> > -		if (hashed_bit != ((ret_addr >> intlv_addr_bit) & BIT(0)))
> > -			ret_addr ^= BIT(intlv_addr_bit);
> > +		if (hashed_bit != ((ctx.ret_addr >> intlv_addr_bit) & BIT(0)))
> > +			ctx.ret_addr ^= BIT(intlv_addr_bit);
> >  	}
> >  
> >  	/* Is calculated system address is above DRAM limit address? */
> > -	if (ret_addr > dram_limit_addr)
> > +	if (ctx.ret_addr > dram_limit_addr)
> >  		goto out_err;
> >  
> > -	*sys_addr = ret_addr;
> > +	*sys_addr = ctx.ret_addr;
> 
> So adding ctx to exchange data between functions - that was a good idea.
> 
> But what this patch does is pointless because you simply replace those
> variables with a local struct.
> 
> I guess the aha moment will come with the later patches when you start
> passing it around to functions.
> 
> /me waits to see.
>

That's true. I was trying to make each patch a single logical change, so
there are a few that have a lot of churn. I can squash some of the
patches together if that's okay.

Thanks,
Yazen