> > On Fri, Mar 28, 2025 at 07:50:43PM +0200, Jarkko Sakkinen wrote: > > On Fri, Mar 28, 2025 at 02:57:41PM +0200, Elena Reshetova wrote: > > > SGX architecture introduced a new instruction called EUPDATESVN > > > to Ice Lake. It allows updating security SVN version, given that EPC > > > is completely empty. The latter is required for security reasons > > > in order to reason that enclave security posture is as secure as the > > > security SVN version of the TCB that created it. > > > > > > Additionally it is important to ensure that while ENCLS[EUPDATESVN] > > > runs, no concurrent page creation happens in EPC, because it might > > > result in #GP delivered to the creator. Legacy SW might not be prepared > > > to handle such unexpected #GPs and therefore this patch introduces > > > a locking mechanism to ensure no concurrent EPC allocations can happen. > > > > > > It is also ensured that ENCLS[EUPDATESVN] is not called when running > > > in a VM since it does not have a meaning in this context (microcode > > > updates application is limited to the host OS) and will create > > > unnecessary load. > > > > > > This patch is based on previous submision by Cathy Zhang > > > https://lore.kernel.org/all/20220520103904.1216-1- > cathy.zh...@intel.com/ > > > > > > Signed-off-by: Elena Reshetova <elena.reshet...@intel.com> > > > --- > > > arch/x86/include/asm/sgx.h | 41 +++++++++++++-------- > > > arch/x86/kernel/cpu/sgx/encls.h | 6 ++++ > > > arch/x86/kernel/cpu/sgx/main.c | 63 > ++++++++++++++++++++++++++++++++- > > > arch/x86/kernel/cpu/sgx/sgx.h | 1 + > > > 4 files changed, 95 insertions(+), 16 deletions(-) > > > > > > diff --git a/arch/x86/include/asm/sgx.h b/arch/x86/include/asm/sgx.h > > > index 6a0069761508..5caf5c31ebc6 100644 > > > --- a/arch/x86/include/asm/sgx.h > > > +++ b/arch/x86/include/asm/sgx.h > > > @@ -26,23 +26,26 @@ > > > #define SGX_CPUID_EPC_SECTION 0x1 > > > /* The bitmask for the EPC section type. */ > > > #define SGX_CPUID_EPC_MASK GENMASK(3, 0) > > > +/* EUPDATESVN presence indication */ > > > +#define SGX_CPUID_EUPDATESVN BIT(10) > > > > > > enum sgx_encls_function { > > > - ECREATE = 0x00, > > > - EADD = 0x01, > > > - EINIT = 0x02, > > > - EREMOVE = 0x03, > > > - EDGBRD = 0x04, > > > - EDGBWR = 0x05, > > > - EEXTEND = 0x06, > > > - ELDU = 0x08, > > > - EBLOCK = 0x09, > > > - EPA = 0x0A, > > > - EWB = 0x0B, > > > - ETRACK = 0x0C, > > > - EAUG = 0x0D, > > > - EMODPR = 0x0E, > > > - EMODT = 0x0F, > > > + ECREATE = 0x00, > > > + EADD = 0x01, > > > + EINIT = 0x02, > > > + EREMOVE = 0x03, > > > + EDGBRD = 0x04, > > > + EDGBWR = 0x05, > > > + EEXTEND = 0x06, > > > + ELDU = 0x08, > > > + EBLOCK = 0x09, > > > + EPA = 0x0A, > > > + EWB = 0x0B, > > > + ETRACK = 0x0C, > > > + EAUG = 0x0D, > > > + EMODPR = 0x0E, > > > + EMODT = 0x0F, > > > + EUPDATESVN = 0x18, > > > }; > > > > > > /** > > > @@ -73,6 +76,11 @@ enum sgx_encls_function { > > > * public key does not match > IA32_SGXLEPUBKEYHASH. > > > * %SGX_PAGE_NOT_MODIFIABLE: The EPC page cannot be modified > because it > > > * is in the PENDING or MODIFIED state. > > > + * %SGX_INSUFFICIENT_ENTROPY: Insufficient entropy in RNG. > > > + * %SGX_EPC_NOT_READY: EPC is not ready for SVN update. > > > + * %SGX_NO_UPDATE: EUPDATESVN was successful, but > CPUSVN was not > > > + * updated because current SVN was not > > > newer > than > > > + * CPUSVN. > > > * %SGX_UNMASKED_EVENT: An unmasked event, e.g. > INTR, was received > > > */ > > > enum sgx_return_code { > > > @@ -81,6 +89,9 @@ enum sgx_return_code { > > > SGX_CHILD_PRESENT = 13, > > > SGX_INVALID_EINITTOKEN = 16, > > > SGX_PAGE_NOT_MODIFIABLE = 20, > > > + SGX_INSUFFICIENT_ENTROPY = 29, > > > + SGX_EPC_NOT_READY = 30, > > > + SGX_NO_UPDATE = 31, > > > SGX_UNMASKED_EVENT = 128, > > > }; > > > > > > diff --git a/arch/x86/kernel/cpu/sgx/encls.h > b/arch/x86/kernel/cpu/sgx/encls.h > > > index 99004b02e2ed..3d83c76dc91f 100644 > > > --- a/arch/x86/kernel/cpu/sgx/encls.h > > > +++ b/arch/x86/kernel/cpu/sgx/encls.h > > > @@ -233,4 +233,10 @@ static inline int __eaug(struct sgx_pageinfo > *pginfo, void *addr) > > > return __encls_2(EAUG, pginfo, addr); > > > } > > > > > > +/* Update CPUSVN at runtime. */ > > > +static inline int __eupdatesvn(void) > > > +{ > > > + return __encls_ret_1(EUPDATESVN, ""); > > > +} > > > + > > > #endif /* _X86_ENCLS_H */ > > > diff --git a/arch/x86/kernel/cpu/sgx/main.c > b/arch/x86/kernel/cpu/sgx/main.c > > > index b61d3bad0446..24563110811d 100644 > > > --- a/arch/x86/kernel/cpu/sgx/main.c > > > +++ b/arch/x86/kernel/cpu/sgx/main.c > > > @@ -32,6 +32,11 @@ static DEFINE_XARRAY(sgx_epc_address_space); > > > static LIST_HEAD(sgx_active_page_list); > > > static DEFINE_SPINLOCK(sgx_reclaimer_lock); > > > > > > +/* This lock is held to prevent new EPC pages from being created > > > + * during the execution of ENCLS[EUPDATESVN]. > > > + */ > > > +static DEFINE_SPINLOCK(sgx_epc_eupdatesvn_lock); > > > + > > > static atomic_long_t sgx_nr_used_pages = ATOMIC_LONG_INIT(0); > > > static unsigned long sgx_nr_total_pages; > > > > > > @@ -457,7 +462,17 @@ static struct sgx_epc_page > *__sgx_alloc_epc_page_from_node(int nid) > > > page->flags = 0; > > > > > > spin_unlock(&node->lock); > > > - atomic_long_inc(&sgx_nr_used_pages); > > > + > > > + if (!atomic_long_inc_not_zero(&sgx_nr_used_pages)) { > > > + spin_lock(&sgx_epc_eupdatesvn_lock); > > > + /* Only call sgx_updatesvn() once the first enclave's > > > + * page is allocated from EPC > > > + */ > > > + if (atomic_long_read(&sgx_nr_used_pages) == 0) > > > + sgx_updatesvn(); > > > + atomic_long_inc(&sgx_nr_used_pages); > > > + spin_unlock(&sgx_epc_eupdatesvn_lock); > > > + } > > > > > > return page; > > > } > > > @@ -970,3 +985,49 @@ static int __init sgx_init(void) > > > } > > > > > > device_initcall(sgx_init); > > > + > > > +/** > > > + * sgx_updatesvn() - Issue ENCLS[EUPDATESVN] > > > + * If EPC is ready, this instruction will update CPUSVN to the currently > > > + * loaded microcode update SVN and generate new cryptographic assets. > > > + */ > > > +void sgx_updatesvn(void) > > > +{ > > > + int retry = 10; > > > + int ret; > > > + > > > + lockdep_assert_held(&sgx_epc_eupdatesvn_lock); > > > + > > > + if (!(cpuid_eax(SGX_CPUID) & SGX_CPUID_EUPDATESVN)) > > > + return; > > > + > > > + /* Do not execute ENCLS[EUPDATESVN] if running in a VM since > > > + * microcode updates are only meaningful to be applied on the host. > > > + */ > > > + if (boot_cpu_has(X86_FEATURE_HYPERVISOR)) > > > + return; > > > + > > > + do { > > > + ret = __eupdatesvn(); > > > + if (ret != SGX_INSUFFICIENT_ENTROPY) > > > + break; > > > + > > > + } while (--retry); > > > + > > > + switch (ret) { > > > + case 0: > > > + pr_info("EUPDATESVN: success\n"); > > > + break; > > > + case SGX_EPC_NOT_READY: > > > + case SGX_INSUFFICIENT_ENTROPY: > > > + case SGX_EPC_PAGE_CONFLICT: > > > + pr_err("EUPDATESVN: error %d\n", ret); > > > + break; > > > + case SGX_NO_UPDATE: > > > + break; > > > + default: > > > + pr_err("EUPDATESVN: unknown error %d\n", ret); > > > + break; > > > + } > > > > Overall, I think you're right in that "inversion" does make sense, > > now that other stuff is better aligned. > > > > At least when there is spurious error, I think ioctl's should stop > > responding and driver should not do anything useful anymore. I.e., > > it should go out-of-service. > > > > I don't think the driver should tear-down, just stop servicing > > VM's and responding ioctl's. > > > > Possibly thish should be also right action for other errors than > > "insufficient entropy" but I'm open for comments for this. > > Or actually actually I take one step back with my suggestions > because this really should be a question for which I don't have > the definitive answer. > > The current code works like this: if anything that we don't > like happens, we re-iterate. > > Should some of the "exceptional conditions" have a different > recovery or not?
None of these exceptional conditions are fatal or present an immediate danger to the system security. So, allowing the re-tries seems logical in this case. In case re-tries also fail, the system admin will have an option of gracefully shutting down all enclaves and doing either a full reboot (if SVN is the only concern) or other necessary actions like taking the physical node out of use, etc. Does this sound reasonable? Best Regards, Elena.
