Messages in this thread | | | Date | Wed, 17 Apr 2024 22:40:30 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH v3 03/14] x86/sev: Check for the presence of an SVSM in the SNP Secrets page |
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On Mon, Mar 25, 2024 at 05:26:22PM -0500, Tom Lendacky wrote: > During early boot phases, check for the presence of an SVSM when running > as an SEV-SNP guest. > > An SVSM is present if the 64-bit value at offset 0x148 into the secrets > page is non-zero. If an SVSM is present, save the SVSM Calling Area > address (CAA), located at offset 0x150 into the secrets page, and set > the VMPL level of the guest, which should be non-zero, to indicate the > presence of an SVSM.
Where are we pointing to the SVSM spec?
This is in the 0th message
https://www.amd.com/content/dam/amd/en/documents/epyc-technical-docs/specifications/58019.pdf
but pls add it to our documentation here:
Documentation/arch/x86/amd-memory-encryption.rst
> Signed-off-by: Tom Lendacky <thomas.lendacky@amd.com> > --- > arch/x86/boot/compressed/sev.c | 35 ++++++++--------- > arch/x86/include/asm/sev-common.h | 4 ++ > arch/x86/include/asm/sev.h | 25 +++++++++++- > arch/x86/kernel/sev-shared.c | 64 +++++++++++++++++++++++++++++++ > arch/x86/kernel/sev.c | 16 ++++++++ > 5 files changed, 125 insertions(+), 19 deletions(-) > > diff --git a/arch/x86/boot/compressed/sev.c b/arch/x86/boot/compressed/sev.c > index 49dc9661176d..fe61ff630c7e 100644 > --- a/arch/x86/boot/compressed/sev.c > +++ b/arch/x86/boot/compressed/sev.c > @@ -12,6 +12,7 @@ > */ > #include "misc.h" > > +#include <linux/mm.h> > #include <asm/bootparam.h> > #include <asm/pgtable_types.h> > #include <asm/sev.h> > @@ -29,6 +30,15 @@ > static struct ghcb boot_ghcb_page __aligned(PAGE_SIZE); > struct ghcb *boot_ghcb; > > +/* > + * SVSM related information: > + * When running under an SVSM, the VMPL that Linux is executing at must be > + * non-zero. The VMPL is therefore used to indicate the presence of an SVSM. > + */ > +static u8 vmpl __section(".data"); > +static u64 boot_svsm_caa_pa __section(".data"); > +static struct svsm_ca *boot_svsm_caa __section(".data");
Explain what those last 2 are in comments above it pls.
> /* > * SNP_FEATURES_IMPL_REQ is the mask of SNP features that will need > * guest side implementation for proper functioning of the guest. If any > @@ -480,6 +472,13 @@ static bool early_snp_init(struct boot_params *bp) > */ > setup_cpuid_table(cc_info); > > + /* > + * Record the SVSM Calling Area address (CAA) if the guest is not
Calling Area (CA) address
> + * running at VMPL0. The CA will be used to communicate with the
and then you can use "CA" here.
> + * SVSM to perform the SVSM services. > + */ > + setup_svsm_ca(cc_info); > + > /* > * Pass run-time kernel a pointer to CC info via boot_params so EFI > * config table doesn't need to be searched again during early startup > diff --git a/arch/x86/include/asm/sev-common.h b/arch/x86/include/asm/sev-common.h > index b463fcbd4b90..68a8cdf6fd6a 100644 > --- a/arch/x86/include/asm/sev-common.h > +++ b/arch/x86/include/asm/sev-common.h > @@ -159,6 +159,10 @@ struct snp_psc_desc { > #define GHCB_TERM_NOT_VMPL0 3 /* SNP guest is not running at VMPL-0 */ > #define GHCB_TERM_CPUID 4 /* CPUID-validation failure */ > #define GHCB_TERM_CPUID_HV 5 /* CPUID failure during hypervisor fallback */ > +#define GHCB_TERM_SECRETS_PAGE 6 /* Secrets page failure */ > +#define GHCB_TERM_NO_SVSM 7 /* SVSM is not advertised in the secrets page */ > +#define GHCB_TERM_SVSM_VMPL0 8 /* SVSM is present but has set VMPL to 0 */ > +#define GHCB_TERM_SVSM_CAA 9 /* SVSM is present but the CA is not page aligned */
"CAA" in the comment I guess. :)
> +/* > + * Maintain the GPA of the SVSM Calling Area (CA) in order to utilize the SVSM > + * services needed when not running in VMPL0. > + */ > +static void __head setup_svsm_ca(const struct cc_blob_sev_info *cc_info) > +{ > + struct snp_secrets_page_layout *secrets_page;
Why was that thing ever called "_layout" and not simply snp_secrets_page?
Fix it?
> + u64 caa; > + > + BUILD_BUG_ON(sizeof(*secrets_page) != PAGE_SIZE);
Put it in the header under the struct definition I guess.
> + /* > + * Use __pa() since this routine is running identity mapped when > + * called, both by the decompressor code and the early kernel code. > + */ > + if (running_at_vmpl0((void *)__pa(&boot_ghcb_page))) > + return; > + > + /* > + * Not running at VMPL0, ensure everything has been properly supplied > + * for running under an SVSM. > + */ > + if (!cc_info || !cc_info->secrets_phys || cc_info->secrets_len != PAGE_SIZE) > + sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_SECRETS_PAGE); > + > + secrets_page = (struct snp_secrets_page_layout *)cc_info->secrets_phys; > + if (!secrets_page->svsm_size) > + sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_NO_SVSM); > + > + if (!secrets_page->svsm_guest_vmpl) > + sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_SVSM_VMPL0); > + > + vmpl = secrets_page->svsm_guest_vmpl; > + > + caa = secrets_page->svsm_caa; > + if (!PAGE_ALIGNED(caa)) > + sev_es_terminate(SEV_TERM_SET_LINUX, GHCB_TERM_SVSM_CAA); > + > + /* > + * The CA is identity mapped when this routine is called, both by the > + * decompressor code and the early kernel code. > + */ > + boot_svsm_caa = (struct svsm_ca *)caa; > + boot_svsm_caa_pa = caa; > +} > diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c > index b59b09c2f284..64799a04feb4 100644 > --- a/arch/x86/kernel/sev.c > +++ b/arch/x86/kernel/sev.c > @@ -135,6 +135,15 @@ struct ghcb_state { > static DEFINE_PER_CPU(struct sev_es_runtime_data*, runtime_data); > static DEFINE_PER_CPU(struct sev_es_save_area *, sev_vmsa); > > +/* > + * SVSM related information: > + * When running under an SVSM, the VMPL that Linux is executing at must be > + * non-zero. The VMPL is therefore used to indicate the presence of an SVSM. > + */ > +static u8 vmpl __ro_after_init; > +static struct svsm_ca *boot_svsm_caa __ro_after_init; > +static u64 boot_svsm_caa_pa __ro_after_init;
Uff, duplication.
Let's put them in sev-shared.c pls and avoid that.
Thx.
-- Regards/Gruss, Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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