From: Brijesh Singh <brijesh.singh@xxxxxxx> The snp_lookup_rmpentry() can be used by the host to read the RMP entry for a given page. The RMP entry format is documented in AMD PPR, see https://bugzilla.kernel.org/attachment.cgi?id=296015. Co-developed-by: Ashish Kalra <ashish.kalra@xxxxxxx> Signed-off-by: Ashish Kalra <ashish.kalra@xxxxxxx> Signed-off-by: Brijesh Singh <brijesh.singh@xxxxxxx> Signed-off-by: Michael Roth <michael.roth@xxxxxxx> --- arch/x86/include/asm/sev.h | 4 +- arch/x86/kernel/sev.c | 83 ++++++++++++++++++++++++++++++++++++++ 2 files changed, 86 insertions(+), 1 deletion(-) diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h index ebc271bb6d8e..8d3ce2ad27da 100644 --- a/arch/x86/include/asm/sev.h +++ b/arch/x86/include/asm/sev.h @@ -83,7 +83,7 @@ extern bool handle_vc_boot_ghcb(struct pt_regs *regs); /* RMP page size */ #define RMP_PG_SIZE_4K 0 - +#define RMP_TO_X86_PG_LEVEL(level) (((level) == RMP_PG_SIZE_4K) ? PG_LEVEL_4K : PG_LEVEL_2M) #define RMPADJUST_VMSA_PAGE_BIT BIT(16) /* SNP Guest message request */ @@ -197,6 +197,7 @@ void snp_set_wakeup_secondary_cpu(void); bool snp_init(struct boot_params *bp); void __init __noreturn snp_abort(void); int snp_issue_guest_request(u64 exit_code, struct snp_req_data *input, unsigned long *fw_err); +int snp_lookup_rmpentry(u64 pfn, int *level); #else static inline void sev_es_ist_enter(struct pt_regs *regs) { } static inline void sev_es_ist_exit(void) { } @@ -221,6 +222,7 @@ static inline int snp_issue_guest_request(u64 exit_code, struct snp_req_data *in { return -ENOTTY; } +static inline int snp_lookup_rmpentry(u64 pfn, int *level) { return 0; } #endif #endif diff --git a/arch/x86/kernel/sev.c b/arch/x86/kernel/sev.c index 687a91284506..706675561f49 100644 --- a/arch/x86/kernel/sev.c +++ b/arch/x86/kernel/sev.c @@ -61,11 +61,35 @@ #define AP_INIT_CR0_DEFAULT 0x60000010 #define AP_INIT_MXCSR_DEFAULT 0x1f80 +/* + * The RMP entry format is not architectural. The format is defined in PPR + * Family 19h Model 01h, Rev B1 processor. + */ +struct rmpentry { + union { + struct { + u64 assigned : 1, + pagesize : 1, + immutable : 1, + rsvd1 : 9, + gpa : 39, + asid : 10, + vmsa : 1, + validated : 1, + rsvd2 : 1; + } info; + u64 low; + }; + u64 high; +} __packed; + /* * The first 16KB from the RMP_BASE is used by the processor for the * bookkeeping, the range needs to be added during the RMP entry lookup. */ #define RMPTABLE_CPU_BOOKKEEPING_SZ 0x4000 +#define RMPENTRY_SHIFT 8 +#define rmptable_page_offset(x) (RMPTABLE_CPU_BOOKKEEPING_SZ + (((unsigned long)x) >> RMPENTRY_SHIFT)) /* For early boot hypervisor communication in SEV-ES enabled guests */ static struct ghcb boot_ghcb_page __bss_decrypted __aligned(PAGE_SIZE); @@ -2440,3 +2464,62 @@ static int __init snp_rmptable_init(void) * the page(s) used for DMA are hypervisor owned. */ fs_initcall(snp_rmptable_init); + +static inline unsigned int rmpentry_assigned(struct rmpentry *e) +{ + return e->info.assigned; +} + +static inline unsigned int rmpentry_pagesize(struct rmpentry *e) +{ + return e->info.pagesize; +} + +static struct rmpentry *rmptable_entry(unsigned long paddr) +{ + unsigned long vaddr; + + vaddr = rmptable_start + rmptable_page_offset(paddr); + if (unlikely(vaddr > rmptable_end)) + return ERR_PTR(-EFAULT); + + return (struct rmpentry *)vaddr; +} + +static struct rmpentry *__snp_lookup_rmpentry(u64 pfn, int *level) +{ + unsigned long paddr = pfn << PAGE_SHIFT; + struct rmpentry *entry, *large_entry; + + if (!cpu_feature_enabled(X86_FEATURE_SEV_SNP)) + return ERR_PTR(-ENXIO); + + if (!pfn_valid(pfn)) + return ERR_PTR(-EINVAL); + + entry = rmptable_entry(paddr); + if (IS_ERR(entry)) + return entry; + + /* Read a large RMP entry to get the correct page level used in RMP entry. */ + large_entry = rmptable_entry(paddr & PMD_MASK); + *level = RMP_TO_X86_PG_LEVEL(rmpentry_pagesize(large_entry)); + + return entry; +} + +/* + * Return 1 if the RMP entry is assigned, 0 if it exists but is not assigned, + * and -errno if there is no corresponding RMP entry. + */ +int snp_lookup_rmpentry(u64 pfn, int *level) +{ + struct rmpentry *e; + + e = __snp_lookup_rmpentry(pfn, level); + if (IS_ERR(e)) + return PTR_ERR(e); + + return !!rmpentry_assigned(e); +} +EXPORT_SYMBOL_GPL(snp_lookup_rmpentry); -- 2.25.1
