linux-kernel - Re: [PATCH v6 08/22] x86/sev: Pass SVSM calling area down to early page state change API

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Message-ID: <20250810203643.GLaJkC2wtmxtvrPbeT@fat_crate.local>
Date: Sun, 10 Aug 2025 22:36:43 +0200
From: Borislav Petkov <bp@...en8.de>
To: Ard Biesheuvel <ardb+git@...gle.com>
Cc: linux-kernel@...r.kernel.org, linux-efi@...r.kernel.org, x86@...nel.org,
	Ard Biesheuvel <ardb@...nel.org>, Ingo Molnar <mingo@...nel.org>,
	Kevin Loughlin <kevinloughlin@...gle.com>,
	Tom Lendacky <thomas.lendacky@....com>,
	Josh Poimboeuf <jpoimboe@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Nikunj A Dadhania <nikunj@....com>
Subject: Re: [PATCH v6 08/22] x86/sev: Pass SVSM calling area down to early
 page state change API

On Tue, Jul 22, 2025 at 09:27:17AM +0200, Ard Biesheuvel wrote:
> From: Ard Biesheuvel <ardb@...nel.org>
> 
> The early page state change API is mostly only used very early, when
> only the boot time SVSM calling area is in use. However, this API is
> also called by the kexec finishing code, which runs very late, and
> potentially from a different CPU (which uses a different calling area).
> 
> To avoid pulling the per-CPU SVSM calling area pointers and related SEV
> state into the startup code, refactor the page state change API so the
> SVSM calling area virtual and physical addresses can be provided by the
> caller.
> 
> No functional change intended.
> 
> Signed-off-by: Ard Biesheuvel <ardb@...nel.org>
> ---
>  arch/x86/boot/compressed/sev.c      | 12 +++++++++---
>  arch/x86/boot/startup/sev-shared.c  | 17 +++++++++--------
>  arch/x86/boot/startup/sev-startup.c | 11 +++++++----
>  arch/x86/coco/sev/core.c            |  3 ++-
>  arch/x86/include/asm/sev-internal.h |  3 ++-
>  5 files changed, 29 insertions(+), 17 deletions(-)
> 
> diff --git a/arch/x86/boot/compressed/sev.c b/arch/x86/boot/compressed/sev.c
> index f714235d3222..18b0ccf517eb 100644
> --- a/arch/x86/boot/compressed/sev.c
> +++ b/arch/x86/boot/compressed/sev.c
> @@ -65,7 +65,9 @@ void snp_set_page_private(unsigned long paddr)
>  	if (!sev_snp_enabled())
>  		return;
>  
> -	__page_state_change(paddr, paddr, SNP_PAGE_STATE_PRIVATE);
> +	__page_state_change(paddr, paddr, SNP_PAGE_STATE_PRIVATE,
> +			    (struct svsm_ca *)boot_svsm_caa_pa,
> +			    boot_svsm_caa_pa);

All those functions should probably get a

struct psc_desc *d;

where all those members are set to the current arguments so that we don't
marshall so many arguments back'n'forth.

-- 
Regards/Gruss,
    Boris.

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