linux-kernel - Re: [PATCH v7 2/3] x86/boot/compressed: Skip Video Memory access in Decompressor for SEV-ES/SNP.

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Date: Wed, 5 Jun 2024 22:14:15 +0200
From: Borislav Petkov <bp@...en8.de>
To: Ashish Kalra <Ashish.Kalra@....com>
Cc: tglx@...utronix.de, mingo@...hat.com, dave.hansen@...ux.intel.com,
	x86@...nel.org, rafael@...nel.org, hpa@...or.com,
	peterz@...radead.org, adrian.hunter@...el.com,
	sathyanarayanan.kuppuswamy@...ux.intel.com, jun.nakajima@...el.com,
	rick.p.edgecombe@...el.com, thomas.lendacky@....com,
	michael.roth@....com, seanjc@...gle.com, kai.huang@...el.com,
	bhe@...hat.com, kirill.shutemov@...ux.intel.com, bdas@...hat.com,
	vkuznets@...hat.com, dionnaglaze@...gle.com, anisinha@...hat.com,
	jroedel@...e.de, ardb@...nel.org, kexec@...ts.infradead.org,
	linux-coco@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 2/3] x86/boot/compressed: Skip Video Memory access in
 Decompressor for SEV-ES/SNP.

On Thu, May 30, 2024 at 11:37:14PM +0000, Ashish Kalra wrote:
> -	lines = boot_params_ptr->screen_info.orig_video_lines;
> -	cols = boot_params_ptr->screen_info.orig_video_cols;
> +	if (!(sev_status & MSR_AMD64_SEV_ES_ENABLED)) {
> +		lines = boot_params_ptr->screen_info.orig_video_lines;
> +		cols = boot_params_ptr->screen_info.orig_video_cols;
> +	}

By now I get an allergic reaction from this sprinkling of "if sev..."
everywhere in the code.

>  	init_default_io_ops();

<--- right here there's a call to

	early_tdx_detect();

You can add a early_sev_detect() counterpart here and clear lines and
cols in it along with an explanation why it is being done.

This is at least a bit cleaner than this.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette