| Message ID | 1535494377-25600-3-git-send-email-brijesh.singh@amd.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | x86: Fix SEV guest regression | expand |
On Tue, Aug 28, 2018 at 05:12:56PM -0500, Brijesh Singh wrote: > kvmclock defines few static variables which are shared with hypervisor ... with the hypervisor ... > during the kvmclock initialization. > > When SEV is active, memory is encrypted with a guest-specific key, and > if guest OS wants to share the memory region with hypervisor then it must > clear the C-bit before sharing it. Currently, we use > kernel_physical_mapping_init() to split large pages before clearing the > C-bit on shared pages. But the kernel_physical_mapping_init fails when "But it fails when... " > called from the kvmclock initialization (mainly because memblock allocator > was not ready). "... is not ready that early during boot)." > The '__decrypted' can be used to define a shared variable; the variables "Add a __decrypted section attribute which can be used when defining such shared variable. The so-defined variables will be placed..." > will be put in the .data.decryption section. This section is mapped with " ... in the .data..decrypted section." > C=0 early in the boot, we also ensure that the initialized values are "... early during boot, " > updated to match with C=0 (i.e perform an in-place decryption). The > .data..decrypted section is PMD aligned and sized so that we avoid the "... PMD-aligned ... " > need to split the large pages when mapping this section. > > The sme_encrypt_kernel() was used to perform the in-place encryption > of the Linux kernel and initrd when SME is active. The routine has been > enhanced to decrypt the .data..decryption section for both SME and SEV > cases. ".data..decrypted" > > While reusing the sme_populate_pgd() we found that the function does not > update the flags if the pte/pmd entry already exists. The patch updates > the function to take care of it. Change the tone to impartial: "While at it, fix sme_populate_pgd() to update page flags if the PMD/PTE entry already exists." And avoid using "This patch" - what this patch does, should be visible to the enlightened onlooker. > Signed-off-by: Brijesh Singh <brijesh.singh@amd.com> > Cc: stable@vger.kernel.org > Cc: Tom Lendacky <thomas.lendacky@amd.com> > Cc: kvm@vger.kernel.org > Cc: Thomas Gleixner <tglx@linutronix.de> > Cc: Borislav Petkov <bp@suse.de> > Cc: "H. Peter Anvin" <hpa@zytor.com> > Cc: linux-kernel@vger.kernel.org > Cc: Paolo Bonzini <pbonzini@redhat.com> > Cc: Sean Christopherson <sean.j.christopherson@intel.com> > Cc: kvm@vger.kernel.org > Cc: "Radim Krčmář" <rkrcmar@redhat.com> > --- > arch/x86/include/asm/mem_encrypt.h | 6 +++ > arch/x86/kernel/head64.c | 9 ++++ > arch/x86/kernel/vmlinux.lds.S | 17 +++++++ > arch/x86/mm/mem_encrypt_identity.c | 100 +++++++++++++++++++++++++++++-------- > 4 files changed, 112 insertions(+), 20 deletions(-) > > diff --git a/arch/x86/include/asm/mem_encrypt.h b/arch/x86/include/asm/mem_encrypt.h > index c064383..802b2eb 100644 > --- a/arch/x86/include/asm/mem_encrypt.h > +++ b/arch/x86/include/asm/mem_encrypt.h > @@ -52,6 +52,8 @@ void __init mem_encrypt_init(void); > bool sme_active(void); > bool sev_active(void); > > +#define __decrypted __attribute__((__section__(".data..decrypted"))) > + > #else /* !CONFIG_AMD_MEM_ENCRYPT */ > > #define sme_me_mask 0ULL > @@ -77,6 +79,8 @@ early_set_memory_decrypted(unsigned long vaddr, unsigned long size) { return 0; > static inline int __init > early_set_memory_encrypted(unsigned long vaddr, unsigned long size) { return 0; } > > +#define __decrypted > + > #endif /* CONFIG_AMD_MEM_ENCRYPT */ > > /* > @@ -88,6 +92,8 @@ early_set_memory_encrypted(unsigned long vaddr, unsigned long size) { return 0; > #define __sme_pa(x) (__pa(x) | sme_me_mask) > #define __sme_pa_nodebug(x) (__pa_nodebug(x) | sme_me_mask) > > +extern char __start_data_decrypted[], __end_data_decrypted[]; > + > #endif /* __ASSEMBLY__ */ > > #endif /* __X86_MEM_ENCRYPT_H__ */ > diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c > index 8047379..3e03129 100644 > --- a/arch/x86/kernel/head64.c > +++ b/arch/x86/kernel/head64.c > @@ -112,6 +112,7 @@ static bool __head check_la57_support(unsigned long physaddr) > unsigned long __head __startup_64(unsigned long physaddr, > struct boot_params *bp) > { > + unsigned long vaddr, vaddr_end; > unsigned long load_delta, *p; > unsigned long pgtable_flags; > pgdval_t *pgd; > @@ -234,6 +235,14 @@ unsigned long __head __startup_64(unsigned long physaddr, > /* Encrypt the kernel and related (if SME is active) */ > sme_encrypt_kernel(bp); > > + /* Clear the memory encryption mask from the decrypted section */ End sentences with a fullstop. > + vaddr = (unsigned long)__start_data_decrypted; > + vaddr_end = (unsigned long)__end_data_decrypted; > + for (; vaddr < vaddr_end; vaddr += PMD_SIZE) { > + i = pmd_index(vaddr); > + pmd[i] -= sme_get_me_mask(); > + } This needs to be no-op on !SME machines. Hint: if (sme_active())... > /* > * Return the SME encryption mask (if SME is active) to be used as a > * modifier for the initial pgdir entry programmed into CR3. > diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S > index 8bde0a4..0ef9320 100644 > --- a/arch/x86/kernel/vmlinux.lds.S > +++ b/arch/x86/kernel/vmlinux.lds.S > @@ -89,6 +89,21 @@ PHDRS { > note PT_NOTE FLAGS(0); /* ___ */ > } > > +/* > + * This section contains data which will be mapped as decrypted. Memory > + * encryption operates on a page basis. But we make this section a pmd "... make this section PMD-aligned ..." Also, avoid the "we" and formulate in passive voice. > + * aligned to avoid spliting the pages while mapping the section early. > + * > + * Note: We use a separate section so that only this section gets > + * decrypted to avoid exposing more than we wish. > + */ > +#define DATA_DECRYPTED_SECTION \ DATA_DECRYPTED is perfectly fine. > + . = ALIGN(PMD_SIZE); \ > + __start_data_decrypted = .; \ > + *(.data..decrypted); \ > + . = ALIGN(PMD_SIZE); \ > + __end_data_decrypted = .; \ > + > SECTIONS > { > #ifdef CONFIG_X86_32 > @@ -171,6 +186,8 @@ SECTIONS > /* rarely changed data like cpu maps */ > READ_MOSTLY_DATA(INTERNODE_CACHE_BYTES) > > + DATA_DECRYPTED_SECTION > + > /* End of data section */ > _edata = .; > } :data > diff --git a/arch/x86/mm/mem_encrypt_identity.c b/arch/x86/mm/mem_encrypt_identity.c > index bf6097e..88c1cce 100644 > --- a/arch/x86/mm/mem_encrypt_identity.c > +++ b/arch/x86/mm/mem_encrypt_identity.c > @@ -51,6 +51,8 @@ > (_PAGE_PAT | _PAGE_PWT)) > > #define PMD_FLAGS_ENC (PMD_FLAGS_LARGE | _PAGE_ENC) > +#define PMD_FLAGS_ENC_WP ((PMD_FLAGS_ENC & ~_PAGE_CACHE_MASK) | \ > + (_PAGE_PAT | _PAGE_PWT)) > > #define PTE_FLAGS (__PAGE_KERNEL_EXEC & ~_PAGE_GLOBAL) > > @@ -59,6 +61,8 @@ > (_PAGE_PAT | _PAGE_PWT)) > > #define PTE_FLAGS_ENC (PTE_FLAGS | _PAGE_ENC) > +#define PTE_FLAGS_ENC_WP ((PTE_FLAGS_ENC & ~_PAGE_CACHE_MASK) | \ > + (_PAGE_PAT | _PAGE_PWT)) > > struct sme_populate_pgd_data { > void *pgtable_area; > @@ -154,9 +158,6 @@ static void __init sme_populate_pgd_large(struct sme_populate_pgd_data *ppd) > return; > > pmd = pmd_offset(pud, ppd->vaddr); > - if (pmd_large(*pmd)) > - return; > - > set_pmd(pmd, __pmd(ppd->paddr | ppd->pmd_flags)); > } > > @@ -182,8 +183,7 @@ static void __init sme_populate_pgd(struct sme_populate_pgd_data *ppd) > return; > > pte = pte_offset_map(pmd, ppd->vaddr); > - if (pte_none(*pte)) > - set_pte(pte, __pte(ppd->paddr | ppd->pte_flags)); > + set_pte(pte, __pte(ppd->paddr | ppd->pte_flags)); > } > This looks like it belongs in a prepatch fix. > static void __init __sme_map_range_pmd(struct sme_populate_pgd_data *ppd) > @@ -235,6 +235,11 @@ static void __init sme_map_range_encrypted(struct sme_populate_pgd_data *ppd) > __sme_map_range(ppd, PMD_FLAGS_ENC, PTE_FLAGS_ENC); > } > > +static void __init sme_map_range_encrypted_wp(struct sme_populate_pgd_data *ppd) > +{ > + __sme_map_range(ppd, PMD_FLAGS_ENC_WP, PTE_FLAGS_ENC_WP); > +} > + > static void __init sme_map_range_decrypted(struct sme_populate_pgd_data *ppd) > { > __sme_map_range(ppd, PMD_FLAGS_DEC, PTE_FLAGS_DEC); These changes with the _WP flags and helper addition belong in a pre-patch. > @@ -382,7 +387,10 @@ static void __init build_workarea_map(struct boot_params *bp, > ppd->paddr = workarea_start; > ppd->vaddr = workarea_start; > ppd->vaddr_end = workarea_end; > - sme_map_range_decrypted(ppd); > + if (sev_active()) > + sme_map_range_encrypted(ppd); > + else > + sme_map_range_decrypted(ppd); > > /* Flush the TLB - no globals so cr3 is enough */ > native_write_cr3(__native_read_cr3()); > @@ -439,16 +447,27 @@ static void __init build_workarea_map(struct boot_params *bp, > sme_map_range_decrypted_wp(ppd); > } > > - /* Add decrypted workarea mappings to both kernel mappings */ > + /* > + * When SEV is active, kernel is already encrypted hence mapping > + * the initial workarea_start as encrypted. When SME is active, > + * the kernel is not encrypted hence add a decrypted workarea s/ a// > + * mappings to both kernel mappings. > + */ > ppd->paddr = workarea_start; > ppd->vaddr = workarea_start; > ppd->vaddr_end = workarea_end; > - sme_map_range_decrypted(ppd); > + if (sev_active()) > + sme_map_range_encrypted(ppd); > + else > + sme_map_range_decrypted(ppd); > > ppd->paddr = workarea_start; > ppd->vaddr = workarea_start + decrypted_base; > ppd->vaddr_end = workarea_end + decrypted_base; > - sme_map_range_decrypted(ppd); > + if (sev_active()) > + sme_map_range_encrypted(ppd); > + else > + sme_map_range_decrypted(ppd); > > wa->kernel_start = kernel_start; > wa->kernel_end = kernel_end; > @@ -491,28 +510,69 @@ static void __init remove_workarea_map(struct sme_workarea_data *wa, > native_write_cr3(__native_read_cr3()); > } > > +static void __init decrypt_data_decrypted_section(struct sme_workarea_data *wa, That function name could use some clarifying change... > + struct sme_populate_pgd_data *ppd) > +{ > + unsigned long decrypted_start, decrypted_end, decrypted_len; > + > + /* Physical addresses of decrypted data section */ > + decrypted_start = __pa_symbol(__start_data_decrypted); > + decrypted_end = ALIGN(__pa_symbol(__end_data_decrypted), PMD_PAGE_SIZE); > + decrypted_len = decrypted_end - decrypted_start; > + > + if (!decrypted_len) > + return; > + > + /* Add decrypted mapping for the section (identity) */ > + ppd->paddr = decrypted_start; > + ppd->vaddr = decrypted_start; > + ppd->vaddr_end = decrypted_end; > + sme_map_range_decrypted(ppd); > + > + /* Add encrypted-wp mapping for the section (non-identity) */ > + ppd->paddr = decrypted_start; > + ppd->vaddr = decrypted_start + wa->decrypted_base; > + ppd->vaddr_end = decrypted_end + wa->decrypted_base; > + sme_map_range_encrypted_wp(ppd); > + > + /* Perform in-place decryption */ > + sme_encrypt_execute(decrypted_start, > + decrypted_start + wa->decrypted_base, > + decrypted_len, wa->workarea_start, > + (unsigned long)ppd->pgd); > + > + ppd->vaddr = decrypted_start + wa->decrypted_base; > + ppd->vaddr_end = decrypted_end + wa->decrypted_base; > + sme_clear_pgd(ppd); > +} > + > void __init sme_encrypt_kernel(struct boot_params *bp) > { > struct sme_populate_pgd_data ppd; > struct sme_workarea_data wa; > > - if (!sme_active()) > + if (!mem_encrypt_active()) > return; > > build_workarea_map(bp, &wa, &ppd); > > - /* When SEV is active, encrypt kernel and initrd */ > - sme_encrypt_execute(wa.kernel_start, > - wa.kernel_start + wa.decrypted_base, > - wa.kernel_len, wa.workarea_start, > - (unsigned long)ppd.pgd); > - > - if (wa.initrd_len) > - sme_encrypt_execute(wa.initrd_start, > - wa.initrd_start + wa.decrypted_base, > - wa.initrd_len, wa.workarea_start, > + /* When SME is active, encrypt kernel and initrd */ > + if (sme_active()) { > + sme_encrypt_execute(wa.kernel_start, > + wa.kernel_start + wa.decrypted_base, > + wa.kernel_len, wa.workarea_start, > (unsigned long)ppd.pgd); > > + if (wa.initrd_len) > + sme_encrypt_execute(wa.initrd_start, > + wa.initrd_start + wa.decrypted_base, > + wa.initrd_len, wa.workarea_start, > + (unsigned long)ppd.pgd); > + } > + > + /* Decrypt the contents of .data..decrypted section */ > + decrypt_data_decrypted_section(&wa, &ppd); > + > remove_workarea_map(&wa, &ppd); > } > > -- > 2.7.4 >
On 08/29/2018 08:59 AM, Borislav Petkov wrote: > On Tue, Aug 28, 2018 at 05:12:56PM -0500, Brijesh Singh wrote: >> kvmclock defines few static variables which are shared with hypervisor > > ... with the hypervisor ... > >> during the kvmclock initialization. >> >> When SEV is active, memory is encrypted with a guest-specific key, and >> if guest OS wants to share the memory region with hypervisor then it must >> clear the C-bit before sharing it. Currently, we use >> kernel_physical_mapping_init() to split large pages before clearing the >> C-bit on shared pages. But the kernel_physical_mapping_init fails when > > "But it fails when..." > >> called from the kvmclock initialization (mainly because memblock allocator >> was not ready). > > "... is not ready that early during boot)." > >> The '__decrypted' can be used to define a shared variable; the variables > > "Add a __decrypted section attribute which can be used when defining > such shared variable. The so-defined variables will be placed..." > >> will be put in the .data.decryption section. This section is mapped with > > " ... in the .data..decrypted section." > >> C=0 early in the boot, we also ensure that the initialized values are > > "... early during boot," > >> updated to match with C=0 (i.e perform an in-place decryption). The >> .data..decrypted section is PMD aligned and sized so that we avoid the > > "... PMD-aligned ..." > >> need to split the large pages when mapping this section. >> >> The sme_encrypt_kernel() was used to perform the in-place encryption >> of the Linux kernel and initrd when SME is active. The routine has been >> enhanced to decrypt the .data..decryption section for both SME and SEV >> cases. > > ".data..decrypted" > >> >> While reusing the sme_populate_pgd() we found that the function does not >> update the flags if the pte/pmd entry already exists. The patch updates >> the function to take care of it. > > > Change the tone to impartial: > > "While at it, fix sme_populate_pgd() to update page flags if the PMD/PTE > entry already exists." > > And avoid using "This patch" - what this patch does, should be visible > to the enlightened onlooker. > Thanks Boris, I will incorporate your edits in commit message. >> Signed-off-by: Brijesh Singh <brijesh.singh@amd.com> >> Cc: stable@vger.kernel.org >> Cc: Tom Lendacky <thomas.lendacky@amd.com> >> Cc: kvm@vger.kernel.org >> Cc: Thomas Gleixner <tglx@linutronix.de> >> Cc: Borislav Petkov <bp@suse.de> >> Cc: "H. Peter Anvin" <hpa@zytor.com> >> Cc: linux-kernel@vger.kernel.org >> Cc: Paolo Bonzini <pbonzini@redhat.com> >> Cc: Sean Christopherson <sean.j.christopherson@intel.com> >> Cc: kvm@vger.kernel.org >> Cc: "Radim Krčmář" <rkrcmar@redhat.com> >> --- >> arch/x86/include/asm/mem_encrypt.h | 6 +++ >> arch/x86/kernel/head64.c | 9 ++++ >> arch/x86/kernel/vmlinux.lds.S | 17 +++++++ >> arch/x86/mm/mem_encrypt_identity.c | 100 +++++++++++++++++++++++++++++-------- >> 4 files changed, 112 insertions(+), 20 deletions(-) >> >> diff --git a/arch/x86/include/asm/mem_encrypt.h b/arch/x86/include/asm/mem_encrypt.h >> index c064383..802b2eb 100644 >> --- a/arch/x86/include/asm/mem_encrypt.h >> +++ b/arch/x86/include/asm/mem_encrypt.h >> @@ -52,6 +52,8 @@ void __init mem_encrypt_init(void); >> bool sme_active(void); >> bool sev_active(void); >> >> +#define __decrypted __attribute__((__section__(".data..decrypted"))) >> + >> #else /* !CONFIG_AMD_MEM_ENCRYPT */ >> >> #define sme_me_mask 0ULL >> @@ -77,6 +79,8 @@ early_set_memory_decrypted(unsigned long vaddr, unsigned long size) { return 0; >> static inline int __init >> early_set_memory_encrypted(unsigned long vaddr, unsigned long size) { return 0; } >> >> +#define __decrypted >> + >> #endif /* CONFIG_AMD_MEM_ENCRYPT */ >> >> /* >> @@ -88,6 +92,8 @@ early_set_memory_encrypted(unsigned long vaddr, unsigned long size) { return 0; >> #define __sme_pa(x) (__pa(x) | sme_me_mask) >> #define __sme_pa_nodebug(x) (__pa_nodebug(x) | sme_me_mask) >> >> +extern char __start_data_decrypted[], __end_data_decrypted[]; >> + >> #endif /* __ASSEMBLY__ */ >> >> #endif /* __X86_MEM_ENCRYPT_H__ */ >> diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c >> index 8047379..3e03129 100644 >> --- a/arch/x86/kernel/head64.c >> +++ b/arch/x86/kernel/head64.c >> @@ -112,6 +112,7 @@ static bool __head check_la57_support(unsigned long physaddr) >> unsigned long __head __startup_64(unsigned long physaddr, >> struct boot_params *bp) >> { >> + unsigned long vaddr, vaddr_end; >> unsigned long load_delta, *p; >> unsigned long pgtable_flags; >> pgdval_t *pgd; >> @@ -234,6 +235,14 @@ unsigned long __head __startup_64(unsigned long physaddr, >> /* Encrypt the kernel and related (if SME is active) */ >> sme_encrypt_kernel(bp); >> >> + /* Clear the memory encryption mask from the decrypted section */ > > End sentences with a fullstop. Noted. > >> + vaddr = (unsigned long)__start_data_decrypted; >> + vaddr_end = (unsigned long)__end_data_decrypted; >> + for (; vaddr < vaddr_end; vaddr += PMD_SIZE) { >> + i = pmd_index(vaddr); >> + pmd[i] -= sme_get_me_mask(); >> + } > > This needs to be no-op on !SME machines. Hint: if (sme_active())... Sure, I will add the check before calling this loop. > >> /* >> * Return the SME encryption mask (if SME is active) to be used as a >> * modifier for the initial pgdir entry programmed into CR3. >> diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S >> index 8bde0a4..0ef9320 100644 >> --- a/arch/x86/kernel/vmlinux.lds.S >> +++ b/arch/x86/kernel/vmlinux.lds.S >> @@ -89,6 +89,21 @@ PHDRS { >> note PT_NOTE FLAGS(0); /* ___ */ >> } >> >> +/* >> + * This section contains data which will be mapped as decrypted. Memory >> + * encryption operates on a page basis. But we make this section a pmd > > "... make this section PMD-aligned ..." > > Also, avoid the "we" and formulate in passive voic Noted. > >> + * aligned to avoid spliting the pages while mapping the section early. >> + * >> + * Note: We use a separate section so that only this section gets >> + * decrypted to avoid exposing more than we wish. >> + */ >> +#define DATA_DECRYPTED_SECTION \ > > DATA_DECRYPTED is perfectly fine. Noted. > >> + . = ALIGN(PMD_SIZE); \ >> + __start_data_decrypted = .; \ >> + *(.data..decrypted); \ >> + . = ALIGN(PMD_SIZE); \ >> + __end_data_decrypted = .; \ >> + >> SECTIONS >> { >> #ifdef CONFIG_X86_32 >> @@ -171,6 +186,8 @@ SECTIONS >> /* rarely changed data like cpu maps */ >> READ_MOSTLY_DATA(INTERNODE_CACHE_BYTES) >> >> + DATA_DECRYPTED_SECTION >> + >> /* End of data section */ >> _edata = .; >> } :data >> diff --git a/arch/x86/mm/mem_encrypt_identity.c b/arch/x86/mm/mem_encrypt_identity.c >> index bf6097e..88c1cce 100644 >> --- a/arch/x86/mm/mem_encrypt_identity.c >> +++ b/arch/x86/mm/mem_encrypt_identity.c >> @@ -51,6 +51,8 @@ >> (_PAGE_PAT | _PAGE_PWT)) >> >> #define PMD_FLAGS_ENC (PMD_FLAGS_LARGE | _PAGE_ENC) >> +#define PMD_FLAGS_ENC_WP ((PMD_FLAGS_ENC & ~_PAGE_CACHE_MASK) | \ >> + (_PAGE_PAT | _PAGE_PWT)) >> >> #define PTE_FLAGS (__PAGE_KERNEL_EXEC & ~_PAGE_GLOBAL) >> >> @@ -59,6 +61,8 @@ >> (_PAGE_PAT | _PAGE_PWT)) >> >> #define PTE_FLAGS_ENC (PTE_FLAGS | _PAGE_ENC) >> +#define PTE_FLAGS_ENC_WP ((PTE_FLAGS_ENC & ~_PAGE_CACHE_MASK) | \ >> + (_PAGE_PAT | _PAGE_PWT)) >> >> struct sme_populate_pgd_data { >> void *pgtable_area; >> @@ -154,9 +158,6 @@ static void __init sme_populate_pgd_large(struct sme_populate_pgd_data *ppd) >> return; >> >> pmd = pmd_offset(pud, ppd->vaddr); >> - if (pmd_large(*pmd)) >> - return; >> - >> set_pmd(pmd, __pmd(ppd->paddr | ppd->pmd_flags)); >> } >> >> @@ -182,8 +183,7 @@ static void __init sme_populate_pgd(struct sme_populate_pgd_data *ppd) >> return; >> >> pte = pte_offset_map(pmd, ppd->vaddr); >> - if (pte_none(*pte)) >> - set_pte(pte, __pte(ppd->paddr | ppd->pte_flags)); >> + set_pte(pte, __pte(ppd->paddr | ppd->pte_flags)); >> } >> > > This looks like it belongs in a prepatch fix. Sure, I can do a prepatch for this change. > >> static void __init __sme_map_range_pmd(struct sme_populate_pgd_data *ppd) >> @@ -235,6 +235,11 @@ static void __init sme_map_range_encrypted(struct sme_populate_pgd_data *ppd) >> __sme_map_range(ppd, PMD_FLAGS_ENC, PTE_FLAGS_ENC); >> } >> >> +static void __init sme_map_range_encrypted_wp(struct sme_populate_pgd_data *ppd) >> +{ >> + __sme_map_range(ppd, PMD_FLAGS_ENC_WP, PTE_FLAGS_ENC_WP); >> +} >> + >> static void __init sme_map_range_decrypted(struct sme_populate_pgd_data *ppd) >> { >> __sme_map_range(ppd, PMD_FLAGS_DEC, PTE_FLAGS_DEC); > > These changes with the _WP flags and helper addition belong in a pre-patch. > >> @@ -382,7 +387,10 @@ static void __init build_workarea_map(struct boot_params *bp, >> ppd->paddr = workarea_start; >> ppd->vaddr = workarea_start; >> ppd->vaddr_end = workarea_end; >> - sme_map_range_decrypted(ppd); >> + if (sev_active()) >> + sme_map_range_encrypted(ppd); >> + else >> + sme_map_range_decrypted(ppd); >> >> /* Flush the TLB - no globals so cr3 is enough */ >> native_write_cr3(__native_read_cr3()); >> @@ -439,16 +447,27 @@ static void __init build_workarea_map(struct boot_params *bp, >> sme_map_range_decrypted_wp(ppd); >> } >> >> - /* Add decrypted workarea mappings to both kernel mappings */ >> + /* >> + * When SEV is active, kernel is already encrypted hence mapping >> + * the initial workarea_start as encrypted. When SME is active, >> + * the kernel is not encrypted hence add a decrypted workarea > > s/ a// Noted. > >> + * mappings to both kernel mappings. >> + */ >> ppd->paddr = workarea_start; >> ppd->vaddr = workarea_start; >> ppd->vaddr_end = workarea_end; >> - sme_map_range_decrypted(ppd); >> + if (sev_active()) >> + sme_map_range_encrypted(ppd); >> + else >> + sme_map_range_decrypted(ppd); >> >> ppd->paddr = workarea_start; >> ppd->vaddr = workarea_start + decrypted_base; >> ppd->vaddr_end = workarea_end + decrypted_base; >> - sme_map_range_decrypted(ppd); >> + if (sev_active()) >> + sme_map_range_encrypted(ppd); >> + else >> + sme_map_range_decrypted(ppd); >> >> wa->kernel_start = kernel_start; >> wa->kernel_end = kernel_end; >> @@ -491,28 +510,69 @@ static void __init remove_workarea_map(struct sme_workarea_data *wa, >> native_write_cr3(__native_read_cr3()); >> } >> >> +static void __init decrypt_data_decrypted_section(struct sme_workarea_data *wa, > > That function name could use some clarifying change... How about decrypt_shared_data() ? > >> + struct sme_populate_pgd_data *ppd) >> +{ >> + unsigned long decrypted_start, decrypted_end, decrypted_len; >> + >> + /* Physical addresses of decrypted data section */ >> + decrypted_start = __pa_symbol(__start_data_decrypted); >> + decrypted_end = ALIGN(__pa_symbol(__end_data_decrypted), PMD_PAGE_SIZE); >> + decrypted_len = decrypted_end - decrypted_start; >> + >> + if (!decrypted_len) >> + return; >> + >> + /* Add decrypted mapping for the section (identity) */ >> + ppd->paddr = decrypted_start; >> + ppd->vaddr = decrypted_start; >> + ppd->vaddr_end = decrypted_end; >> + sme_map_range_decrypted(ppd); >> + >> + /* Add encrypted-wp mapping for the section (non-identity) */ >> + ppd->paddr = decrypted_start; >> + ppd->vaddr = decrypted_start + wa->decrypted_base; >> + ppd->vaddr_end = decrypted_end + wa->decrypted_base; >> + sme_map_range_encrypted_wp(ppd); >> + >> + /* Perform in-place decryption */ >> + sme_encrypt_execute(decrypted_start, >> + decrypted_start + wa->decrypted_base, >> + decrypted_len, wa->workarea_start, >> + (unsigned long)ppd->pgd); >> + >> + ppd->vaddr = decrypted_start + wa->decrypted_base; >> + ppd->vaddr_end = decrypted_end + wa->decrypted_base; >> + sme_clear_pgd(ppd); >> +} >> + >> void __init sme_encrypt_kernel(struct boot_params *bp) >> { >> struct sme_populate_pgd_data ppd; >> struct sme_workarea_data wa; >> >> - if (!sme_active()) >> + if (!mem_encrypt_active()) >> return; >> >> build_workarea_map(bp, &wa, &ppd); >> >> - /* When SEV is active, encrypt kernel and initrd */ >> - sme_encrypt_execute(wa.kernel_start, >> - wa.kernel_start + wa.decrypted_base, >> - wa.kernel_len, wa.workarea_start, >> - (unsigned long)ppd.pgd); >> - >> - if (wa.initrd_len) >> - sme_encrypt_execute(wa.initrd_start, >> - wa.initrd_start + wa.decrypted_base, >> - wa.initrd_len, wa.workarea_start, >> + /* When SME is active, encrypt kernel and initrd */ >> + if (sme_active()) { >> + sme_encrypt_execute(wa.kernel_start, >> + wa.kernel_start + wa.decrypted_base, >> + wa.kernel_len, wa.workarea_start, >> (unsigned long)ppd.pgd); >> >> + if (wa.initrd_len) >> + sme_encrypt_execute(wa.initrd_start, >> + wa.initrd_start + wa.decrypted_base, >> + wa.initrd_len, wa.workarea_start, >> + (unsigned long)ppd.pgd); >> + } >> + >> + /* Decrypt the contents of .data..decrypted section */ >> + decrypt_data_decrypted_section(&wa, &ppd); >> + >> remove_workarea_map(&wa, &ppd); >> } >> >> -- >> 2.7.4 >> >
On Tue, Aug 28, 2018 at 05:12:56PM -0500, Brijesh Singh wrote: > kvmclock defines few static variables which are shared with hypervisor > during the kvmclock initialization. > > When SEV is active, memory is encrypted with a guest-specific key, and > if guest OS wants to share the memory region with hypervisor then it must > clear the C-bit before sharing it. Currently, we use > kernel_physical_mapping_init() to split large pages before clearing the > C-bit on shared pages. But the kernel_physical_mapping_init fails when > called from the kvmclock initialization (mainly because memblock allocator > was not ready). > > The '__decrypted' can be used to define a shared variable; the variables > will be put in the .data.decryption section. This section is mapped with > C=0 early in the boot, we also ensure that the initialized values are > updated to match with C=0 (i.e perform an in-place decryption). The > .data..decrypted section is PMD aligned and sized so that we avoid the > need to split the large pages when mapping this section. What about naming the attribute (and section) '__unencrypted' instead of '__decrypted'? The attribute should be a property describing how the data must be accessed, it shouldn't imply anything regarding the history of the data. Decrypted implies that data was once encrypted, whereas unencrypted simply states that the data is stored in plain text. All data that has been decrypted is also unencrypted, but the reverse does not hold true.
On 08/29/2018 10:03 AM, Sean Christopherson wrote: > On Tue, Aug 28, 2018 at 05:12:56PM -0500, Brijesh Singh wrote: >> kvmclock defines few static variables which are shared with hypervisor >> during the kvmclock initialization. >> >> When SEV is active, memory is encrypted with a guest-specific key, and >> if guest OS wants to share the memory region with hypervisor then it must >> clear the C-bit before sharing it. Currently, we use >> kernel_physical_mapping_init() to split large pages before clearing the >> C-bit on shared pages. But the kernel_physical_mapping_init fails when >> called from the kvmclock initialization (mainly because memblock allocator >> was not ready). >> >> The '__decrypted' can be used to define a shared variable; the variables >> will be put in the .data.decryption section. This section is mapped with >> C=0 early in the boot, we also ensure that the initialized values are >> updated to match with C=0 (i.e perform an in-place decryption). The >> .data..decrypted section is PMD aligned and sized so that we avoid the >> need to split the large pages when mapping this section. > > What about naming the attribute (and section) '__unencrypted' instead > of '__decrypted'? The attribute should be a property describing how > the data must be accessed, it shouldn't imply anything regarding the > history of the data. Decrypted implies that data was once encrypted, > whereas unencrypted simply states that the data is stored in plain > text. All data that has been decrypted is also unencrypted, but the > reverse does not hold true. > During the initial SEV/SME patch review cycle we had some discussion about using decrypted vs unencrypted. At that time the consensus was that a memory range mapped with C=0 should be referred as 'decrypted'. Having said so, I do see your point and I am not oppose to calling it 'unencrypted' if others agrees to it. Tom and Boris, thoughts ?
Hi Boris, On 08/29/2018 08:59 AM, Borislav Petkov wrote: ... > >> static void __init __sme_map_range_pmd(struct sme_populate_pgd_data *ppd) >> @@ -235,6 +235,11 @@ static void __init sme_map_range_encrypted(struct sme_populate_pgd_data *ppd) >> __sme_map_range(ppd, PMD_FLAGS_ENC, PTE_FLAGS_ENC); >> } >> >> +static void __init sme_map_range_encrypted_wp(struct sme_populate_pgd_data *ppd) >> +{ >> + __sme_map_range(ppd, PMD_FLAGS_ENC_WP, PTE_FLAGS_ENC_WP); >> +} >> + >> static void __init sme_map_range_decrypted(struct sme_populate_pgd_data *ppd) >> { >> __sme_map_range(ppd, PMD_FLAGS_DEC, PTE_FLAGS_DEC); > > These changes with the _WP flags and helper addition belong in a pre-patch. > Please note that the _WP flags and helper functions are used by this patch only. Introducing a helper in a separate patch will cause a build warning. I am leaning to keep the helper in this patch but if you think it should be done in separate patch then let me know. -Brijesh
On Wed, Aug 29, 2018 at 09:37:46AM -0500, Brijesh Singh wrote: > > > @@ -491,28 +510,69 @@ static void __init remove_workarea_map(struct sme_workarea_data *wa, > > > native_write_cr3(__native_read_cr3()); > > > } > > > +static void __init decrypt_data_decrypted_section(struct sme_workarea_data *wa, > > > > That function name could use some clarifying change... > > > How about decrypt_shared_data() ? Much better. Thx.
On Wed, Aug 29, 2018 at 10:54:37AM -0500, Brijesh Singh wrote: > Please note that the _WP flags and helper functions are used by this > patch only. Introducing a helper in a separate patch will cause a build > warning. ... a build warning which goes away with the next patch, adding the users, right? > I am leaning to keep the helper in this patch but if you think > it should be done in separate patch then let me know. Well, if you're doing a bunch of different things in a single patch, it would be better, IMO, to have each thing in a separate patch. Thx.
dropping stable@ On Wed, Aug 29, 2018 at 10:33:24AM -0500, Brijesh Singh wrote: > During the initial SEV/SME patch review cycle we had some discussion about > using decrypted vs unencrypted. At that time the consensus was > that a memory range mapped with C=0 should be referred as 'decrypted'. Yes, the idea was to avoid having "unencrypted" *and* "decrypted" to mean pretty much the same thing for ease of understanding just by looking at the name. Also whether the data was initially unencrypted or was decrypted is immaterial - you only need to know how to access it. > Having said so, I do see your point and I am not oppose to calling it > 'unencrypted' if others agrees to it. No, please don't. Let's stick with "decrypted" for everything.
diff --git a/arch/x86/include/asm/mem_encrypt.h b/arch/x86/include/asm/mem_encrypt.h index c064383..802b2eb 100644 --- a/arch/x86/include/asm/mem_encrypt.h +++ b/arch/x86/include/asm/mem_encrypt.h @@ -52,6 +52,8 @@ void __init mem_encrypt_init(void); bool sme_active(void); bool sev_active(void); +#define __decrypted __attribute__((__section__(".data..decrypted"))) + #else /* !CONFIG_AMD_MEM_ENCRYPT */ #define sme_me_mask 0ULL @@ -77,6 +79,8 @@ early_set_memory_decrypted(unsigned long vaddr, unsigned long size) { return 0; static inline int __init early_set_memory_encrypted(unsigned long vaddr, unsigned long size) { return 0; } +#define __decrypted + #endif /* CONFIG_AMD_MEM_ENCRYPT */ /* @@ -88,6 +92,8 @@ early_set_memory_encrypted(unsigned long vaddr, unsigned long size) { return 0; #define __sme_pa(x) (__pa(x) | sme_me_mask) #define __sme_pa_nodebug(x) (__pa_nodebug(x) | sme_me_mask) +extern char __start_data_decrypted[], __end_data_decrypted[]; + #endif /* __ASSEMBLY__ */ #endif /* __X86_MEM_ENCRYPT_H__ */ diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c index 8047379..3e03129 100644 --- a/arch/x86/kernel/head64.c +++ b/arch/x86/kernel/head64.c @@ -112,6 +112,7 @@ static bool __head check_la57_support(unsigned long physaddr) unsigned long __head __startup_64(unsigned long physaddr, struct boot_params *bp) { + unsigned long vaddr, vaddr_end; unsigned long load_delta, *p; unsigned long pgtable_flags; pgdval_t *pgd; @@ -234,6 +235,14 @@ unsigned long __head __startup_64(unsigned long physaddr, /* Encrypt the kernel and related (if SME is active) */ sme_encrypt_kernel(bp); + /* Clear the memory encryption mask from the decrypted section */ + vaddr = (unsigned long)__start_data_decrypted; + vaddr_end = (unsigned long)__end_data_decrypted; + for (; vaddr < vaddr_end; vaddr += PMD_SIZE) { + i = pmd_index(vaddr); + pmd[i] -= sme_get_me_mask(); + } + /* * Return the SME encryption mask (if SME is active) to be used as a * modifier for the initial pgdir entry programmed into CR3. diff --git a/arch/x86/kernel/vmlinux.lds.S b/arch/x86/kernel/vmlinux.lds.S index 8bde0a4..0ef9320 100644 --- a/arch/x86/kernel/vmlinux.lds.S +++ b/arch/x86/kernel/vmlinux.lds.S @@ -89,6 +89,21 @@ PHDRS { note PT_NOTE FLAGS(0); /* ___ */ } +/* + * This section contains data which will be mapped as decrypted. Memory + * encryption operates on a page basis. But we make this section a pmd + * aligned to avoid spliting the pages while mapping the section early. + * + * Note: We use a separate section so that only this section gets + * decrypted to avoid exposing more than we wish. + */ +#define DATA_DECRYPTED_SECTION \ + . = ALIGN(PMD_SIZE); \ + __start_data_decrypted = .; \ + *(.data..decrypted); \ + . = ALIGN(PMD_SIZE); \ + __end_data_decrypted = .; \ + SECTIONS { #ifdef CONFIG_X86_32 @@ -171,6 +186,8 @@ SECTIONS /* rarely changed data like cpu maps */ READ_MOSTLY_DATA(INTERNODE_CACHE_BYTES) + DATA_DECRYPTED_SECTION + /* End of data section */ _edata = .; } :data diff --git a/arch/x86/mm/mem_encrypt_identity.c b/arch/x86/mm/mem_encrypt_identity.c index bf6097e..88c1cce 100644 --- a/arch/x86/mm/mem_encrypt_identity.c +++ b/arch/x86/mm/mem_encrypt_identity.c @@ -51,6 +51,8 @@ (_PAGE_PAT | _PAGE_PWT)) #define PMD_FLAGS_ENC (PMD_FLAGS_LARGE | _PAGE_ENC) +#define PMD_FLAGS_ENC_WP ((PMD_FLAGS_ENC & ~_PAGE_CACHE_MASK) | \ + (_PAGE_PAT | _PAGE_PWT)) #define PTE_FLAGS (__PAGE_KERNEL_EXEC & ~_PAGE_GLOBAL) @@ -59,6 +61,8 @@ (_PAGE_PAT | _PAGE_PWT)) #define PTE_FLAGS_ENC (PTE_FLAGS | _PAGE_ENC) +#define PTE_FLAGS_ENC_WP ((PTE_FLAGS_ENC & ~_PAGE_CACHE_MASK) | \ + (_PAGE_PAT | _PAGE_PWT)) struct sme_populate_pgd_data { void *pgtable_area; @@ -154,9 +158,6 @@ static void __init sme_populate_pgd_large(struct sme_populate_pgd_data *ppd) return; pmd = pmd_offset(pud, ppd->vaddr); - if (pmd_large(*pmd)) - return; - set_pmd(pmd, __pmd(ppd->paddr | ppd->pmd_flags)); } @@ -182,8 +183,7 @@ static void __init sme_populate_pgd(struct sme_populate_pgd_data *ppd) return; pte = pte_offset_map(pmd, ppd->vaddr); - if (pte_none(*pte)) - set_pte(pte, __pte(ppd->paddr | ppd->pte_flags)); + set_pte(pte, __pte(ppd->paddr | ppd->pte_flags)); } static void __init __sme_map_range_pmd(struct sme_populate_pgd_data *ppd) @@ -235,6 +235,11 @@ static void __init sme_map_range_encrypted(struct sme_populate_pgd_data *ppd) __sme_map_range(ppd, PMD_FLAGS_ENC, PTE_FLAGS_ENC); } +static void __init sme_map_range_encrypted_wp(struct sme_populate_pgd_data *ppd) +{ + __sme_map_range(ppd, PMD_FLAGS_ENC_WP, PTE_FLAGS_ENC_WP); +} + static void __init sme_map_range_decrypted(struct sme_populate_pgd_data *ppd) { __sme_map_range(ppd, PMD_FLAGS_DEC, PTE_FLAGS_DEC); @@ -382,7 +387,10 @@ static void __init build_workarea_map(struct boot_params *bp, ppd->paddr = workarea_start; ppd->vaddr = workarea_start; ppd->vaddr_end = workarea_end; - sme_map_range_decrypted(ppd); + if (sev_active()) + sme_map_range_encrypted(ppd); + else + sme_map_range_decrypted(ppd); /* Flush the TLB - no globals so cr3 is enough */ native_write_cr3(__native_read_cr3()); @@ -439,16 +447,27 @@ static void __init build_workarea_map(struct boot_params *bp, sme_map_range_decrypted_wp(ppd); } - /* Add decrypted workarea mappings to both kernel mappings */ + /* + * When SEV is active, kernel is already encrypted hence mapping + * the initial workarea_start as encrypted. When SME is active, + * the kernel is not encrypted hence add a decrypted workarea + * mappings to both kernel mappings. + */ ppd->paddr = workarea_start; ppd->vaddr = workarea_start; ppd->vaddr_end = workarea_end; - sme_map_range_decrypted(ppd); + if (sev_active()) + sme_map_range_encrypted(ppd); + else + sme_map_range_decrypted(ppd); ppd->paddr = workarea_start; ppd->vaddr = workarea_start + decrypted_base; ppd->vaddr_end = workarea_end + decrypted_base; - sme_map_range_decrypted(ppd); + if (sev_active()) + sme_map_range_encrypted(ppd); + else + sme_map_range_decrypted(ppd); wa->kernel_start = kernel_start; wa->kernel_end = kernel_end; @@ -491,28 +510,69 @@ static void __init remove_workarea_map(struct sme_workarea_data *wa, native_write_cr3(__native_read_cr3()); } +static void __init decrypt_data_decrypted_section(struct sme_workarea_data *wa, + struct sme_populate_pgd_data *ppd) +{ + unsigned long decrypted_start, decrypted_end, decrypted_len; + + /* Physical addresses of decrypted data section */ + decrypted_start = __pa_symbol(__start_data_decrypted); + decrypted_end = ALIGN(__pa_symbol(__end_data_decrypted), PMD_PAGE_SIZE); + decrypted_len = decrypted_end - decrypted_start; + + if (!decrypted_len) + return; + + /* Add decrypted mapping for the section (identity) */ + ppd->paddr = decrypted_start; + ppd->vaddr = decrypted_start; + ppd->vaddr_end = decrypted_end; + sme_map_range_decrypted(ppd); + + /* Add encrypted-wp mapping for the section (non-identity) */ + ppd->paddr = decrypted_start; + ppd->vaddr = decrypted_start + wa->decrypted_base; + ppd->vaddr_end = decrypted_end + wa->decrypted_base; + sme_map_range_encrypted_wp(ppd); + + /* Perform in-place decryption */ + sme_encrypt_execute(decrypted_start, + decrypted_start + wa->decrypted_base, + decrypted_len, wa->workarea_start, + (unsigned long)ppd->pgd); + + ppd->vaddr = decrypted_start + wa->decrypted_base; + ppd->vaddr_end = decrypted_end + wa->decrypted_base; + sme_clear_pgd(ppd); +} + void __init sme_encrypt_kernel(struct boot_params *bp) { struct sme_populate_pgd_data ppd; struct sme_workarea_data wa; - if (!sme_active()) + if (!mem_encrypt_active()) return; build_workarea_map(bp, &wa, &ppd); - /* When SEV is active, encrypt kernel and initrd */ - sme_encrypt_execute(wa.kernel_start, - wa.kernel_start + wa.decrypted_base, - wa.kernel_len, wa.workarea_start, - (unsigned long)ppd.pgd); - - if (wa.initrd_len) - sme_encrypt_execute(wa.initrd_start, - wa.initrd_start + wa.decrypted_base, - wa.initrd_len, wa.workarea_start, + /* When SME is active, encrypt kernel and initrd */ + if (sme_active()) { + sme_encrypt_execute(wa.kernel_start, + wa.kernel_start + wa.decrypted_base, + wa.kernel_len, wa.workarea_start, (unsigned long)ppd.pgd); + if (wa.initrd_len) + sme_encrypt_execute(wa.initrd_start, + wa.initrd_start + wa.decrypted_base, + wa.initrd_len, wa.workarea_start, + (unsigned long)ppd.pgd); + } + + /* Decrypt the contents of .data..decrypted section */ + decrypt_data_decrypted_section(&wa, &ppd); + remove_workarea_map(&wa, &ppd); }
kvmclock defines few static variables which are shared with hypervisor during the kvmclock initialization. When SEV is active, memory is encrypted with a guest-specific key, and if guest OS wants to share the memory region with hypervisor then it must clear the C-bit before sharing it. Currently, we use kernel_physical_mapping_init() to split large pages before clearing the C-bit on shared pages. But the kernel_physical_mapping_init fails when called from the kvmclock initialization (mainly because memblock allocator was not ready). The '__decrypted' can be used to define a shared variable; the variables will be put in the .data.decryption section. This section is mapped with C=0 early in the boot, we also ensure that the initialized values are updated to match with C=0 (i.e perform an in-place decryption). The .data..decrypted section is PMD aligned and sized so that we avoid the need to split the large pages when mapping this section. The sme_encrypt_kernel() was used to perform the in-place encryption of the Linux kernel and initrd when SME is active. The routine has been enhanced to decrypt the .data..decryption section for both SME and SEV cases. While reusing the sme_populate_pgd() we found that the function does not update the flags if the pte/pmd entry already exists. The patch updates the function to take care of it. Signed-off-by: Brijesh Singh <brijesh.singh@amd.com> Cc: stable@vger.kernel.org Cc: Tom Lendacky <thomas.lendacky@amd.com> Cc: kvm@vger.kernel.org Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Borislav Petkov <bp@suse.de> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: linux-kernel@vger.kernel.org Cc: Paolo Bonzini <pbonzini@redhat.com> Cc: Sean Christopherson <sean.j.christopherson@intel.com> Cc: kvm@vger.kernel.org Cc: "Radim Krčmář" <rkrcmar@redhat.com> --- arch/x86/include/asm/mem_encrypt.h | 6 +++ arch/x86/kernel/head64.c | 9 ++++ arch/x86/kernel/vmlinux.lds.S | 17 +++++++ arch/x86/mm/mem_encrypt_identity.c | 100 +++++++++++++++++++++++++++++-------- 4 files changed, 112 insertions(+), 20 deletions(-)