Messages in this thread Patch in this message | | | From | Tom Lendacky <> | Subject | [PATCH v3 03/14] x86/sev: Check for the presence of an SVSM in the SNP Secrets page | Date | Mon, 25 Mar 2024 17:26:22 -0500 |
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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.
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"); + /* * Copy a version of this function here - insn-eval.c can't be used in * pre-decompression code. @@ -335,24 +345,6 @@ void do_boot_stage2_vc(struct pt_regs *regs, unsigned long exit_code) sev_es_terminate(SEV_TERM_SET_GEN, GHCB_SEV_ES_GEN_REQ); } -static bool running_at_vmpl0(void *va) -{ - u64 attrs; - - /* - * RMPADJUST modifies RMP permissions of a lesser-privileged (numerically - * higher) privilege level. Here, clear the VMPL1 permission mask of the - * GHCB page. If the guest is not running at VMPL0, this will fail. - * - * If the guest is running at VMPL0, it will succeed. Even if that operation - * modifies permission bits, it is still ok to do so currently because Linux - * SNP guests running at VMPL0 only run at VMPL0, so VMPL1 or higher - * permission mask changes are a don't-care. - */ - attrs = 1; - return !rmpadjust((unsigned long)va, RMP_PG_SIZE_4K, attrs); -} - /* * 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 + * running at VMPL0. The CA will be used to communicate with the + * 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 */ #define GHCB_RESP_CODE(v) ((v) & GHCB_MSR_INFO_MASK) diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h index 9477b4053bce..891e7d9a1f66 100644 --- a/arch/x86/include/asm/sev.h +++ b/arch/x86/include/asm/sev.h @@ -152,9 +152,32 @@ struct snp_secrets_page_layout { u8 vmpck2[VMPCK_KEY_LEN]; u8 vmpck3[VMPCK_KEY_LEN]; struct secrets_os_area os_area; - u8 rsvd3[3840]; + + u8 vmsa_tweak_bitmap[64]; + + /* SVSM fields */ + u64 svsm_base; + u64 svsm_size; + u64 svsm_caa; + u32 svsm_max_version; + u8 svsm_guest_vmpl; + u8 rsvd3[3]; + + /* Remainder of page */ + u8 rsvd4[3744]; } __packed; +/* + * The SVSM Calling Area (CA) related structures. + */ +struct svsm_ca { + u8 call_pending; + u8 mem_available; + u8 rsvd1[6]; + + u8 svsm_buffer[PAGE_SIZE - 8]; +}; + #ifdef CONFIG_AMD_MEM_ENCRYPT extern void __sev_es_ist_enter(struct pt_regs *regs); extern void __sev_es_ist_exit(void); diff --git a/arch/x86/kernel/sev-shared.c b/arch/x86/kernel/sev-shared.c index 8b04958da5e7..66d33292eb78 100644 --- a/arch/x86/kernel/sev-shared.c +++ b/arch/x86/kernel/sev-shared.c @@ -111,6 +111,24 @@ sev_es_terminate(unsigned int set, unsigned int reason) asm volatile("hlt\n" : : : "memory"); } +static bool running_at_vmpl0(void *va) +{ + u64 attrs; + + /* + * RMPADJUST modifies RMP permissions of a lesser-privileged (numerically + * higher) privilege level. Here, clear the VMPL1 permission mask of the + * GHCB page. If the guest is not running at VMPL0, this will fail. + * + * If the guest is running at VMPL0, it will succeed. Even if that operation + * modifies permission bits, it is still ok to do so currently because Linux + * SNP guests running at VMPL0 only run at VMPL0, so VMPL1 or higher + * permission mask changes are a don't-care. + */ + attrs = 1; + return !rmpadjust((unsigned long)va, RMP_PG_SIZE_4K, attrs); +} + /* * The hypervisor features are available from GHCB version 2 onward. */ @@ -1267,3 +1285,49 @@ static enum es_result vc_check_opcode_bytes(struct es_em_ctxt *ctxt, return ES_UNSUPPORTED; } + +/* + * 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; + u64 caa; + + BUILD_BUG_ON(sizeof(*secrets_page) != PAGE_SIZE); + + /* + * 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; + struct sev_config { __u64 debug : 1, @@ -2122,6 +2131,13 @@ bool __head snp_init(struct boot_params *bp) setup_cpuid_table(cc_info); + /* + * Record the SVSM Calling Area address (CAA) if the guest is not + * running at VMPL0. The CA will be used to communicate with the + * SVSM to perform the SVSM services. + */ + setup_svsm_ca(cc_info); + /* * The CC blob will be used later to access the secrets page. Cache * it here like the boot kernel does. -- 2.43.2
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