| Message ID | 20240126041126.1927228-11-michael.roth@amd.com |
|---|---|
| State | New |
| Headers | show |
| Series | Add AMD Secure Nested Paging (SEV-SNP) Initialization Support | expand |
On 26/01/2024 04:11, Michael Roth wrote: > From: Brijesh Singh <brijesh.singh@amd.com> > > The RMPUPDATE instruction updates the access restrictions for a page via > its corresponding entry in the RMP Table. The hypervisor will use the > instruction to enforce various access restrictions on pages used for > confidential guests and other specialized functionality. See APM3 for > details on the instruction operations. > > The PSMASH instruction expands a 2MB RMP entry in the RMP table into a > corresponding set of contiguous 4KB RMP entries while retaining the > state of the validated bit from the original 2MB RMP entry. The > hypervisor will use this instruction in cases where it needs to re-map a > page as 4K rather than 2MB in a guest's nested page table. > > Add helpers to make use of these instructions. > > Signed-off-by: Brijesh Singh <brijesh.singh@amd.com> > Signed-off-by: Ashish Kalra <ashish.kalra@amd.com> > [mdr: add RMPUPDATE retry logic for transient FAIL_OVERLAP errors] > Signed-off-by: Michael Roth <michael.roth@amd.com> > --- > arch/x86/include/asm/sev.h | 23 ++++++++++ > arch/x86/virt/svm/sev.c | 92 ++++++++++++++++++++++++++++++++++++++ > 2 files changed, 115 insertions(+) > > diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h > index 2c53e3de0b71..d3ccb7a0c7e9 100644 > --- a/arch/x86/include/asm/sev.h > +++ b/arch/x86/include/asm/sev.h > @@ -87,10 +87,23 @@ extern bool handle_vc_boot_ghcb(struct pt_regs *regs); > /* Software defined (when rFlags.CF = 1) */ > #define PVALIDATE_FAIL_NOUPDATE 255 > > +/* RMUPDATE detected 4K page and 2MB page overlap. */ > +#define RMPUPDATE_FAIL_OVERLAP 4 > + > /* RMP page size */ > #define RMP_PG_SIZE_4K 0 > #define RMP_PG_SIZE_2M 1 > #define RMP_TO_PG_LEVEL(level) (((level) == RMP_PG_SIZE_4K) ? PG_LEVEL_4K : PG_LEVEL_2M) > +#define PG_LEVEL_TO_RMP(level) (((level) == PG_LEVEL_4K) ? RMP_PG_SIZE_4K : RMP_PG_SIZE_2M) > + > +struct rmp_state { > + u64 gpa; > + u8 assigned; > + u8 pagesize; > + u8 immutable; > + u8 rsvd; > + u32 asid; > +} __packed; > > #define RMPADJUST_VMSA_PAGE_BIT BIT(16) > > @@ -248,10 +261,20 @@ static inline u64 sev_get_status(void) { return 0; } > bool snp_probe_rmptable_info(void); > int snp_lookup_rmpentry(u64 pfn, bool *assigned, int *level); > void snp_dump_hva_rmpentry(unsigned long address); > +int psmash(u64 pfn); > +int rmp_make_private(u64 pfn, u64 gpa, enum pg_level level, int asid, bool immutable); > +int rmp_make_shared(u64 pfn, enum pg_level level); > #else > static inline bool snp_probe_rmptable_info(void) { return false; } > static inline int snp_lookup_rmpentry(u64 pfn, bool *assigned, int *level) { return -ENODEV; } > static inline void snp_dump_hva_rmpentry(unsigned long address) {} > +static inline int psmash(u64 pfn) { return -ENODEV; } > +static inline int rmp_make_private(u64 pfn, u64 gpa, enum pg_level level, int asid, > + bool immutable) > +{ > + return -ENODEV; > +} > +static inline int rmp_make_shared(u64 pfn, enum pg_level level) { return -ENODEV; } > #endif > > #endif > diff --git a/arch/x86/virt/svm/sev.c b/arch/x86/virt/svm/sev.c > index c74266e039b2..16b3d8139649 100644 > --- a/arch/x86/virt/svm/sev.c > +++ b/arch/x86/virt/svm/sev.c > @@ -342,3 +342,95 @@ void snp_dump_hva_rmpentry(unsigned long hva) > paddr = PFN_PHYS(pte_pfn(*pte)) | (hva & ~page_level_mask(level)); > dump_rmpentry(PHYS_PFN(paddr)); > } > + > +/* > + * PSMASH a 2MB aligned page into 4K pages in the RMP table while preserving the > + * Validated bit. > + */ > +int psmash(u64 pfn) > +{ > + unsigned long paddr = pfn << PAGE_SHIFT; > + int ret; > + > + if (!cpu_feature_enabled(X86_FEATURE_SEV_SNP)) > + return -ENODEV; > + > + if (!pfn_valid(pfn)) > + return -EINVAL; > + > + /* Binutils version 2.36 supports the PSMASH mnemonic. */ > + asm volatile(".byte 0xF3, 0x0F, 0x01, 0xFF" > + : "=a" (ret) > + : "a" (paddr) > + : "memory", "cc"); > + > + return ret; > +} > +EXPORT_SYMBOL_GPL(psmash); > + > +/* > + * It is expected that those operations are seldom enough so that no mutual > + * exclusion of updaters is needed and thus the overlap error condition below > + * should happen very seldomly and would get resolved relatively quickly by > + * the firmware. > + * > + * If not, one could consider introducing a mutex or so here to sync concurrent > + * RMP updates and thus diminish the amount of cases where firmware needs to > + * lock 2M ranges to protect against concurrent updates. > + * > + * The optimal solution would be range locking to avoid locking disjoint > + * regions unnecessarily but there's no support for that yet. > + */ > +static int rmpupdate(u64 pfn, struct rmp_state *state) > +{ > + unsigned long paddr = pfn << PAGE_SHIFT; > + int ret; > + > + if (!cpu_feature_enabled(X86_FEATURE_SEV_SNP)) > + return -ENODEV; > + > + do { > + /* Binutils version 2.36 supports the RMPUPDATE mnemonic. */ > + asm volatile(".byte 0xF2, 0x0F, 0x01, 0xFE" > + : "=a" (ret) > + : "a" (paddr), "c" ((unsigned long)state) > + : "memory", "cc"); > + } while (ret == RMPUPDATE_FAIL_OVERLAP); > + > + if (ret) { > + pr_err("RMPUPDATE failed for PFN %llx, ret: %d\n", pfn, ret); > + dump_rmpentry(pfn); > + dump_stack(); > + return -EFAULT; > + } > + > + return 0; > +} > + > +/* Transition a page to guest-owned/private state in the RMP table. */ > +int rmp_make_private(u64 pfn, u64 gpa, enum pg_level level, int asid, bool immutable) asid is typically a u32 (or at least unsigned) - is it better to avoid potential conversion issues with an 'int'? Otherwise Reviewed-by: Liam Merwick <liam.merwick@oracle.com> > +{ > + struct rmp_state state; > + > + memset(&state, 0, sizeof(state)); > + state.assigned = 1; > + state.asid = asid > + state.immutable = immutable; > + state.gpa = gpa; > + state.pagesize = PG_LEVEL_TO_RMP(level); > + > + return rmpupdate(pfn, &state); > +} > +EXPORT_SYMBOL_GPL(rmp_make_private); > + > +/* Transition a page to hypervisor-owned/shared state in the RMP table. */ > +int rmp_make_shared(u64 pfn, enum pg_level level) > +{ > + struct rmp_state state; > + > + memset(&state, 0, sizeof(state)); > + state.pagesize = PG_LEVEL_TO_RMP(level); > + > + return rmpupdate(pfn, &state); > +} > +EXPORT_SYMBOL_GPL(rmp_make_shared);
On Mon, Jan 29, 2024 at 06:00:36PM +0000, Liam Merwick wrote: > asid is typically a u32 (or at least unsigned) - is it better to avoid > potential conversion issues with an 'int'? struct rmp_state.asid is already u32 but yeah, lemme fix that. > Otherwise > Reviewed-by: Liam Merwick <liam.merwick@oracle.com> Thx.
On Mon, Jan 29, 2024 at 08:28:20PM +0100, Borislav Petkov wrote: > On Mon, Jan 29, 2024 at 06:00:36PM +0000, Liam Merwick wrote: > > asid is typically a u32 (or at least unsigned) - is it better to avoid > > potential conversion issues with an 'int'? > > struct rmp_state.asid is already u32 but yeah, lemme fix that. Btw, static int sev_get_asid(struct kvm *kvm) { struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info; return sev->asid; } whereas struct kvm_sev_info { ... unsigned int asid; /* ASID used for this guest */ so that function needs fixing too. Thx.
diff --git a/arch/x86/include/asm/sev.h b/arch/x86/include/asm/sev.h index 2c53e3de0b71..d3ccb7a0c7e9 100644 --- a/arch/x86/include/asm/sev.h +++ b/arch/x86/include/asm/sev.h @@ -87,10 +87,23 @@ extern bool handle_vc_boot_ghcb(struct pt_regs *regs); /* Software defined (when rFlags.CF = 1) */ #define PVALIDATE_FAIL_NOUPDATE 255 +/* RMUPDATE detected 4K page and 2MB page overlap. */ +#define RMPUPDATE_FAIL_OVERLAP 4 + /* RMP page size */ #define RMP_PG_SIZE_4K 0 #define RMP_PG_SIZE_2M 1 #define RMP_TO_PG_LEVEL(level) (((level) == RMP_PG_SIZE_4K) ? PG_LEVEL_4K : PG_LEVEL_2M) +#define PG_LEVEL_TO_RMP(level) (((level) == PG_LEVEL_4K) ? RMP_PG_SIZE_4K : RMP_PG_SIZE_2M) + +struct rmp_state { + u64 gpa; + u8 assigned; + u8 pagesize; + u8 immutable; + u8 rsvd; + u32 asid; +} __packed; #define RMPADJUST_VMSA_PAGE_BIT BIT(16) @@ -248,10 +261,20 @@ static inline u64 sev_get_status(void) { return 0; } bool snp_probe_rmptable_info(void); int snp_lookup_rmpentry(u64 pfn, bool *assigned, int *level); void snp_dump_hva_rmpentry(unsigned long address); +int psmash(u64 pfn); +int rmp_make_private(u64 pfn, u64 gpa, enum pg_level level, int asid, bool immutable); +int rmp_make_shared(u64 pfn, enum pg_level level); #else static inline bool snp_probe_rmptable_info(void) { return false; } static inline int snp_lookup_rmpentry(u64 pfn, bool *assigned, int *level) { return -ENODEV; } static inline void snp_dump_hva_rmpentry(unsigned long address) {} +static inline int psmash(u64 pfn) { return -ENODEV; } +static inline int rmp_make_private(u64 pfn, u64 gpa, enum pg_level level, int asid, + bool immutable) +{ + return -ENODEV; +} +static inline int rmp_make_shared(u64 pfn, enum pg_level level) { return -ENODEV; } #endif #endif diff --git a/arch/x86/virt/svm/sev.c b/arch/x86/virt/svm/sev.c index c74266e039b2..16b3d8139649 100644 --- a/arch/x86/virt/svm/sev.c +++ b/arch/x86/virt/svm/sev.c @@ -342,3 +342,95 @@ void snp_dump_hva_rmpentry(unsigned long hva) paddr = PFN_PHYS(pte_pfn(*pte)) | (hva & ~page_level_mask(level)); dump_rmpentry(PHYS_PFN(paddr)); } + +/* + * PSMASH a 2MB aligned page into 4K pages in the RMP table while preserving the + * Validated bit. + */ +int psmash(u64 pfn) +{ + unsigned long paddr = pfn << PAGE_SHIFT; + int ret; + + if (!cpu_feature_enabled(X86_FEATURE_SEV_SNP)) + return -ENODEV; + + if (!pfn_valid(pfn)) + return -EINVAL; + + /* Binutils version 2.36 supports the PSMASH mnemonic. */ + asm volatile(".byte 0xF3, 0x0F, 0x01, 0xFF" + : "=a" (ret) + : "a" (paddr) + : "memory", "cc"); + + return ret; +} +EXPORT_SYMBOL_GPL(psmash); + +/* + * It is expected that those operations are seldom enough so that no mutual + * exclusion of updaters is needed and thus the overlap error condition below + * should happen very seldomly and would get resolved relatively quickly by + * the firmware. + * + * If not, one could consider introducing a mutex or so here to sync concurrent + * RMP updates and thus diminish the amount of cases where firmware needs to + * lock 2M ranges to protect against concurrent updates. + * + * The optimal solution would be range locking to avoid locking disjoint + * regions unnecessarily but there's no support for that yet. + */ +static int rmpupdate(u64 pfn, struct rmp_state *state) +{ + unsigned long paddr = pfn << PAGE_SHIFT; + int ret; + + if (!cpu_feature_enabled(X86_FEATURE_SEV_SNP)) + return -ENODEV; + + do { + /* Binutils version 2.36 supports the RMPUPDATE mnemonic. */ + asm volatile(".byte 0xF2, 0x0F, 0x01, 0xFE" + : "=a" (ret) + : "a" (paddr), "c" ((unsigned long)state) + : "memory", "cc"); + } while (ret == RMPUPDATE_FAIL_OVERLAP); + + if (ret) { + pr_err("RMPUPDATE failed for PFN %llx, ret: %d\n", pfn, ret); + dump_rmpentry(pfn); + dump_stack(); + return -EFAULT; + } + + return 0; +} + +/* Transition a page to guest-owned/private state in the RMP table. */ +int rmp_make_private(u64 pfn, u64 gpa, enum pg_level level, int asid, bool immutable) +{ + struct rmp_state state; + + memset(&state, 0, sizeof(state)); + state.assigned = 1; + state.asid = asid; + state.immutable = immutable; + state.gpa = gpa; + state.pagesize = PG_LEVEL_TO_RMP(level); + + return rmpupdate(pfn, &state); +} +EXPORT_SYMBOL_GPL(rmp_make_private); + +/* Transition a page to hypervisor-owned/shared state in the RMP table. */ +int rmp_make_shared(u64 pfn, enum pg_level level) +{ + struct rmp_state state; + + memset(&state, 0, sizeof(state)); + state.pagesize = PG_LEVEL_TO_RMP(level); + + return rmpupdate(pfn, &state); +} +EXPORT_SYMBOL_GPL(rmp_make_shared);