linux-kernel - Re: [PATCH v4 4/4] x86/sev: Add SNP-specific unaccepted memory support

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Date:   Thu, 25 Aug 2022 15:10:52 -0700
From:   Dionna Amalie Glaze <dionnaglaze@...gle.com>
To:     Tom Lendacky <thomas.lendacky@....com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        "the arch/x86 maintainers" <x86@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "Kirill A. Shutemov" <kirill@...temov.name>,
        "H. Peter Anvin" <hpa@...or.com>,
        Michael Roth <michael.roth@....com>,
        Joerg Roedel <jroedel@...e.de>,
        Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v4 4/4] x86/sev: Add SNP-specific unaccepted memory support

>
> Add SNP-specific hooks to the unaccepted memory support in the boot
> path (__accept_memory()) and the core kernel (accept_memory()) in order
> to support booting SNP guests when unaccepted memory is present. Without
> this support, SNP guests will fail to boot and/or panic() when unaccepted
> memory is present in the EFI memory map.
>
> The process of accepting memory under SNP involves invoking the hypervisor
> to perform a page state change for the page to private memory and then
> issuing a PVALIDATE instruction to accept the page.

Thanks for this update! Tests show the boot performance shaves off a
good few seconds over eager acceptance, and it'll get better when we
have on-demand pinning.

The uncaught #VC exception is still there for 256GB machines and larger though.

-- 
-Dionna Glaze, PhD (she/her)