- 28 Apr, 2022 15 commits
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Mark Brown authored
Add test cases for the SME signal handing ABI patterned off the SVE tests. Due to the small size of the tests and the differences in ABI (especially around needing to account for both streaming SVE and ZA) there is some code duplication here. We currently cover: - Reporting of the vector length. - Lack of support for changing vector length. - Presence and size of register state for streaming SVE and ZA. As with the SVE tests we do not yet have any validation of register contents. Signed-off-by:
Mark Brown <broonie@kernel.org> Reviewed-by:
Shuah Khan <skhan@linuxfoundation.org> Acked-by:
Catalin Marinas <catalin.marinas@arm.com> Link: https://lore.kernel.org/r/20220419112247.711548-36-broonie@kernel.orgSigned-off-by:
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Mark Brown authored
Add a stress test for context switching of the ZA register state based on the similar tests Dave Martin wrote for FPSIMD and SVE registers. The test loops indefinitely writing a data pattern to ZA then reading it back and verifying that it's what was expected. Unlike the other tests we manually assemble the SME instructions since at present no released toolchain has SME support integrated. Signed-off-by:
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Mark Brown authored
As part of the generic code for signal handling test cases we parse all signal frames to make sure they have at least the basic form we expect and that there are no unexpected frames present in the signal context. Add coverage of the ZA signal frame to this code. Signed-off-by:
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Mark Brown authored
One of the features of SME is the addition of streaming mode, in which we have access to a set of streaming mode SVE registers at the SME vector length. Since these are accessed using the SVE instructions let's reuse the existing SVE stress test for testing with a compile time option for controlling the few small differences needed: - Enter streaming mode immediately on starting the program. - In streaming mode FFR is removed so skip reading and writing FFR. Signed-off-by:
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Mark Brown authored
Provide RDVL helpers for SME and extend the main vector configuration tests to cover SME. Signed-off-by:
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Mark Brown authored
The Scalable Matrix Extension adds a new system register TPIDR2 intended to be used by libc for its own thread specific use, add some kselftests which exercise the ABI for it. Since this test should with some adjustment work for TPIDR and any other similar registers added in future add tests for it in a separate directory rather than placing it with the other floating point tests, nothing existing looked suitable so I created a new test directory called "abi". Since this feature is intended to be used by libc the test is built as freestanding code using nolibc so we don't end up with the test program and libc both trying to manage the register simultaneously and distrupting each other. As a result of being written using nolibc rather than using hwcaps to identify if SME is available in the system we check for the default SME vector length configuration in proc, adding hwcap support to nolibc seems like disproportionate effort and didn't feel entirely idiomatic for what nolibc is trying to do. Signed-off-by:
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Mark Brown authored
The Scalable Matrix Extenions (SME) introduces additional register state with configurable vector lengths, similar to SVE but configured separately. Extend vlset to support configuring this state with a --sme or -s command line option. Signed-off-by:
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Mark Brown authored
As for the kernel so that we don't have ambitious toolchain requirements to build the tests manually encode some of the SVE instructions. Signed-off-by:
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Mark Brown authored
The current tests use the prctls for various things but there's no coverage of the edges of the interface so add some basics. This isn't hugely useful as it is (it originally had some coverage for the combinations with asymmetric mode but we removed the prctl() for that) but it might be a helpful starting point for future work, for example covering error handling. Signed-off-by:
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Mark Brown authored
Currently we just have a big if statement with a non-specific diagnostic checking both the mode and the tag. Since we'll need to dynamically check for asymmetric mode support in the system and to improve debugability split these checks out. Signed-off-by:
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Mark Brown authored
Help people figure out problems by printing a diagnostic when we get an unexpected asynchronous fault. Signed-off-by:
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Mark Brown authored
The MTE selftests have a helper evaluate_test() which translates a return code into a call to ksft_test_result_*(). Currently this only handles pass and fail, silently ignoring any other code. Update the helper to support skipped tests and log any unknown return codes as an error so we get at least some diagnostic if anything goes wrong. Signed-off-by:
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Mark Brown authored
Currently we validate that we can set the floating point state via the SVE regset and read the data via the FPSIMD regset but we do not valiate that the opposite case works as expected. Add a test that covers this case, noting that when reading via SVE regset the kernel has the option of returning either SVE or FPSIMD data so we need to accept both formats. Signed-off-by:
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Mark Brown authored
Currently the sve-ptrace test for setting and reading FPSIMD data assumes that the child will start off in FPSIMD only mode and that it can use this to read some FPSIMD mode SVE ptrace data, skipping the test if it can't. This isn't an assumption guaranteed by the ABI and also limits how we can use this testcase within the program. Instead skip the initial read and just generate a FPSIMD format buffer for the write part of the test, making the coverage more robust in the face of future kernel and test program changes. Signed-off-by:
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Mark Brown authored
The comment for ptrace_sve_get_fpsimd_data() doesn't describe what the test does at all, fix that. Signed-off-by:
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- 27 Apr, 2022 1 commit
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Mark Brown authored
We need to explicitly enumerate all the ID registers which we rely on for CPU capabilities in __read_sysreg_by_encoding(), ID_AA64SMFR0_EL1 was missed from this list so we trip a BUG() in paths which rely on that function such as CPU hotplug. Add the register. Reported-by:
Marek Szyprowski <m.szyprowski@samsung.com> Signed-off-by:
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- 22 Apr, 2022 24 commits
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Mark Brown authored
Now that basline support for the Scalable Matrix Extension (SME) is present introduce the Kconfig option allowing it to be built. While the feature registers don't impose a strong requirement for a system with SME to support SVE at runtime the support for streaming mode SVE is mostly shared with normal SVE so depend on SVE. Signed-off-by:
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Mark Brown authored
While we don't currently support SME in guests we do currently support it for the host system so we need to take care of SME's impact, including the floating point register state, when running guests. Simiarly to SVE we need to manage the traps in CPACR_RL1, what is new is the handling of streaming mode and ZA. Normally we defer any handling of the floating point register state until the guest first uses it however if the system is in streaming mode FPSIMD and SVE operations may generate SME traps which we would need to distinguish from actual attempts by the guest to use SME. Rather than do this for the time being if we are in streaming mode when entering the guest we force the floating point state to be saved immediately and exit streaming mode, meaning that the guest won't generate SME traps for supported operations. We could handle ZA in the access trap similarly to the FPSIMD/SVE state without the disruption caused by streaming mode but for simplicity handle it the same way as streaming mode for now. This will be revisited when we support SME for guests (hopefully before SME hardware becomes available), for now it will only incur additional cost on systems with SME and even there only if streaming mode or ZA are enabled. Signed-off-by:
Marc Zyngier <maz@kernel.org> Link: https://lore.kernel.org/r/20220419112247.711548-27-broonie@kernel.orgSigned-off-by:
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Mark Brown authored
SME defines two new traps which need to be enabled for guests to ensure that they can't use SME, one for the main SME operations which mirrors the traps for SVE and another for access to TPIDR2 in SCTLR_EL2. For VHE manage SMEN along with ZEN in activate_traps() and the FP state management callbacks, along with SCTLR_EL2.EnTPIDR2. There is no existing dynamic management of SCTLR_EL2. For nVHE manage TSM in activate_traps() along with the fine grained traps for TPIDR2 and SMPRI. There is no existing dynamic management of fine grained traps. Signed-off-by:
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Mark Brown authored
For the time being we do not support use of SME by KVM guests, support for this will be enabled in future. In order to prevent any side effects or side channels via the new system registers, including the EL0 read/write register TPIDR2, explicitly undefine all the system registers added by SME and mask out the SME bitfield in SYS_ID_AA64PFR1. Signed-off-by:
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Mark Brown authored
When saving and restoring the floating point state over an EFI runtime call ensure that we handle streaming mode, only handling FFR if we are not in streaming mode and ensuring that we are in normal mode over the call into runtime services. We currently assume that ZA will not be modified by runtime services, the specification is not yet finalised so this may need updating if that changes. Signed-off-by:
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Mark Brown authored
Both streaming mode and ZA may increase power consumption when they are enabled and streaming mode makes many FPSIMD and SVE instructions undefined which will cause problems for any kernel mode floating point so disable both when we flush the CPU state. This covers both kernel_neon_begin() and idle and after flushing the state a reload is always required anyway. Signed-off-by:
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Mark Brown authored
The ZA array can be read and written with the NT_ARM_ZA. Similarly to our interface for the SVE vector registers the regset consists of a header with information on the current vector length followed by an optional register data payload, represented as for signals as a series of horizontal vectors from 0 to VL/8 in the endianness independent format used for vectors. On get if ZA is enabled then register data will be provided, otherwise it will be omitted. On set if register data is provided then ZA is enabled and initialized using the provided data, otherwise it is disabled. Signed-off-by:
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Mark Brown authored
The streaming mode SVE registers are represented using the same data structures as for SVE but since the vector lengths supported and in use may not be the same as SVE we represent them with a new type NT_ARM_SSVE. Unfortunately we only have a single 16 bit reserved field available in the header so there is no space to fit the current and maximum vector length for both standard and streaming SVE mode without redefining the structure in a way the creates a complicatd and fragile ABI. Since FFR is not present in streaming mode it is read and written as zero. Setting NT_ARM_SSVE registers will put the task into streaming mode, similarly setting NT_ARM_SVE registers will exit it. Reads that do not correspond to the current mode of the task will return the header with no register data. For compatibility reasons on write setting no flag for the register type will be interpreted as setting SVE registers, though users can provide no register data as an alternative mechanism for doing so. Signed-off-by:
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Mark Brown authored
Implement support for ZA in signal handling in a very similar way to how we implement support for SVE registers, using a signal context structure with optional register state after it. Where present this register state stores the ZA matrix as a series of horizontal vectors numbered from 0 to VL/8 in the endinanness independent format used for vectors. As with SVE we do not allow changes in the vector length during signal return but we do allow ZA to be enabled or disabled. Signed-off-by:
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Mark Brown authored
When in streaming mode we have the same set of SVE registers as we do in regular SVE mode with the exception of FFR and the use of the SME vector length. Provide signal handling for these registers by taking one of the reserved words in the SVE signal context as a flags field and defining a flag which is set for streaming mode. When the flag is set the vector length is set to the streaming mode vector length and we save and restore streaming mode data. We support entering or leaving streaming mode based on the value of the flag but do not support changing the vector length, this is not currently supported SVE signal handling. We could instead allocate a separate record in the signal frame for the streaming mode SVE context but this inflates the size of the maximal signal frame required and adds complication when validating signal frames from userspace, especially given the current structure of the code. Any implementation of support for streaming mode vectors in signals will have some potential for causing issues for applications that attempt to handle SVE vectors in signals, use streaming mode but do not understand streaming mode in their signal handling code, it is hard to identify a case that is clearly better than any other - they all have cases where they could cause unexpected register corruption or faults. Signed-off-by:
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Mark Brown authored
The ABI requires that streaming mode and ZA are disabled when invoking signal handlers, do this in setup_return() when we prepare the task state for the signal handler. Signed-off-by:
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Mark Brown authored
By default all SME operations in userspace will trap. When this happens we allocate storage space for the SME register state, set up the SVE registers and disable traps. We do not need to initialize ZA since the architecture guarantees that it will be zeroed when enabled and when we trap ZA is disabled. On syscall we exit streaming mode if we were previously in it and ensure that all but the lower 128 bits of the registers are zeroed while preserving the state of ZA. This follows the aarch64 PCS for SME, ZA state is preserved over a function call and streaming mode is exited. Since the traps for SME do not distinguish between streaming mode SVE and ZA usage if ZA is in use rather than reenabling traps we instead zero the parts of the SVE registers not shared with FPSIMD and leave SME enabled, this simplifies handling SME traps. If ZA is not in use then we reenable SME traps and fall through to normal handling of SVE. Signed-off-by:
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Mark Brown authored
Allocate space for storing ZA on first access to SME and use that to save and restore ZA state when context switching. We do this by using the vector form of the LDR and STR ZA instructions, these do not require streaming mode and have implementation recommendations that they avoid contention issues in shared SMCU implementations. Since ZA is architecturally guaranteed to be zeroed when enabled we do not need to explicitly zero ZA, either we will be restoring from a saved copy or trapping on first use of SME so we know that ZA must be disabled. Signed-off-by:
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Mark Brown authored
When in streaming mode we need to save and restore the streaming mode SVE register state rather than the regular SVE register state. This uses the streaming mode vector length and omits FFR but is otherwise identical, if TIF_SVE is enabled when we are in streaming mode then streaming mode takes precedence. This does not handle use of streaming SVE state with KVM, ptrace or signals. This will be updated in further patches. Signed-off-by:
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Mark Brown authored
In SME the use of both streaming SVE mode and ZA are tracked through PSTATE.SM and PSTATE.ZA, visible through the system register SVCR. In order to context switch the floating point state for SME we need to context switch the contents of this register as part of context switching the floating point state. Since changing the vector length exits streaming SVE mode and disables ZA we also make sure we update SVCR appropriately when setting vector length, and similarly ensure that new threads have streaming SVE mode and ZA disabled. Signed-off-by:
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Mark Brown authored
The Scalable Matrix Extension introduces support for a new thread specific data register TPIDR2 intended for use by libc. The kernel must save the value of TPIDR2 on context switch and should ensure that all new threads start off with a default value of 0. Add a field to the thread_struct to store TPIDR2 and context switch it with the other thread specific data. In case there are future extensions which also use TPIDR2 we introduce system_supports_tpidr2() and use that rather than system_supports_sme() for TPIDR2 handling. Signed-off-by:
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Mark Brown authored
As for SVE provide a prctl() interface which allows processes to configure their SME vector length. Signed-off-by:
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Mark Brown authored
As for SVE provide a sysctl which allows the default SME vector length to be configured. Signed-off-by:
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Mark Brown authored
The vector lengths used for SME are controlled through a similar set of registers to those for SVE and enumerated using a similar algorithm with some slight differences due to the fact that unlike SVE there are no restrictions on which combinations of vector lengths can be supported nor any mandatory vector lengths which must be implemented. Add a new vector type and implement support for enumerating it. One slightly awkward feature is that we need to read the current vector length using a different instruction (or enter streaming mode which would have the same issue and be higher cost). Rather than add an ops structure we add special cases directly in the otherwise generic vec_probe_vqs() function, this is a bit inelegant but it's the only place where this is an issue. Signed-off-by:
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Mark Brown authored
This patch introduces basic cpufeature support for discovering the presence of the Scalable Matrix Extension. Signed-off-by:
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Mark Brown authored
SME requires similar setup to that for SVE: disable traps to EL2 and make sure that the maximum vector length is available to EL1, for SME we have two traps - one for SME itself and one for TPIDR2. In addition since we currently make no active use of priority control for SCMUs we map all SME priorities lower ELs may configure to 0, the architecture specified minimum priority, to ensure that nothing we manage is able to configure itself to consume excessive resources. This will need to be revisited should there be a need to manage SME priorities at runtime. Signed-off-by:
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Mark Brown authored
As with SVE rather than impose ambitious toolchain requirements for SME we manually encode the few instructions which we require in order to perform the work the kernel needs to do. The instructions used to save and restore context are provided as assembler macros while those for entering and leaving streaming mode are done in asm volatile blocks since they are expected to be used from C. We could do the SMSTART and SMSTOP operations with read/modify/write cycles on SVCR but using the aliases provided for individual field accesses should be slightly faster. These instructions are aliases for MSR but since our minimum toolchain requirements are old enough to mean that we can't use the sX_X_cX_cX_X form and they always use xzr rather than taking a value like write_sysreg_s() wants we just use .inst. Signed-off-by:
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Mark Brown authored
The arm64 Scalable Matrix Extension (SME) adds some new system registers, fields in existing system registers and exception syndromes. This patch adds definitions for these for use in future patches implementing support for this extension. Since SME will be the first user of FEAT_HCX in the kernel also include the definitions for enumerating it and the HCRX system register it adds. Signed-off-by:
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Mark Brown authored
Provide ABI documentation for SME similar to that for SVE. Due to the very large overlap around streaming SVE mode in both implementation and interfaces documentation for streaming mode SVE is added to the SVE document rather than the SME one. Signed-off-by:
Szabolcs Nagy <szabolcs.nagy@arm.com> Link: https://lore.kernel.org/r/20220419112247.711548-5-broonie@kernel.orgSigned-off-by:
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