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Message-ID: <Yxm3clMvSK8uLKju@jpiotrowski-Surface-Book-3>
Date: Thu, 8 Sep 2022 11:35:46 +0200
From: Jeremi Piotrowski <jpiotrowski@...ux.microsoft.com>
To: Michael Roth <michael.roth@....com>
Cc: NOMURA JUNICHI(野村 淳一)
<junichi.nomura@....com>, LKML <linux-kernel@...r.kernel.org>,
"x86@...nel.org" <x86@...nel.org>, "bp@...e.de" <bp@...e.de>
Subject: Re: [Regression v5.19-rc1] kernel fails to boot, no console output
(Re: [PATCH v12 38/46] x86/sev: Add SEV-SNP feature detection/setup)
On Mon, Aug 22, 2022 at 11:39:33AM -0500, Michael Roth wrote:
> On Wed, Aug 17, 2022 at 10:40:40AM +0200, Jeremi Piotrowski wrote:
> > On Tue, Aug 16, 2022 at 10:06:37AM -0500, Michael Roth wrote:
> > > And if that does not avoid the issue, can you retry with the below change
> > > (without the above change in place)?
> > >
> > > diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c
> > > index 7b668f91c9ab..0b430f98e053 100644
> > > --- a/arch/x86/kernel/sev.c
> > > +++ b/arch/x86/kernel/sev.c
> > > @@ -2073,10 +2073,12 @@ static __init struct cc_blob_sev_info *find_cc_blob(struct boot_params *bp)
> > > struct cc_blob_sev_info *cc_info;
> > >
> > > /* Boot kernel would have passed the CC blob via boot_params. */
> > > +#if 0
> > > if (bp->cc_blob_address) {
> > > cc_info = (struct cc_blob_sev_info *)(unsigned long)bp->cc_blob_address;
> > > goto found_cc_info;
> > > }
> > > +#endif
> > >
> > > /*
> > > * If kernel was booted directly, without the use of the
> > > @@ -2087,7 +2089,7 @@ static __init struct cc_blob_sev_info *find_cc_blob(struct boot_params *bp)
> > > if (!cc_info)
> > > return NULL;
> > >
> > > -found_cc_info:
> > > +//found_cc_info:
> > > if (cc_info->magic != CC_BLOB_SEV_HDR_MAGIC)
> > > snp_abort();
> > >
> > > Trying to see if you're hitting a separate issue or not.
> >
> > This version boots correctly.
>
> Hi Jeremi,
>
> Still haven't been able to reproduce this on my systems, but it looks like
> it's either an issue dereferencing boot_params, or bp->cc_blob_address is
> pointing to garbage, so the cc_info->magic check fails. The latter seems
> more likely, since sme_enable() previously made use of the same boot_params
> pointer without any issues.
>
> To confirm, please give the below fix a try:
>
>
> diff --git a/arch/x86/boot/compressed/sev.c b/arch/x86/boot/compressed/sev.c
> index 52f989f6acc2..dd6cd0d7c740 100644
> --- a/arch/x86/boot/compressed/sev.c
> +++ b/arch/x86/boot/compressed/sev.c
> @@ -392,6 +392,13 @@ bool snp_init(struct boot_params *bp)
> if (!bp)
> return false;
>
> + /*
> + * bp->cc_blob_address should only be set by boot/compressed kernel.
> + * Initialize it to 0 to ensure that uninitialized values from
> + * buggy bootloaders aren't propagated.
> + */
> + bp->cc_blob_address = 0;
> +
> cc_info = find_cc_blob(bp);
> if (!cc_info)
> return false;
>
Sorry, couldn't get back to you sooner.
I tested the patch https://lore.kernel.org/lkml/20220823160734.89036-1-michael.roth@amd.com/
and it solves the issue.
Thanks for looking into this
Jeremi
> Thanks!
>
> -Mike
>
> >
> > >
> > > Thanks,
> > >
> > > Mike
> > >
> > >
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