This series implements support for SME use in non-protected KVM guests. Much of this is very similar to SVE, the main additional challenge that SME presents is that it introduces two new controls which change the registers seen by guests:
- PSTATE.ZA enables the ZA matrix register and, if SME2 is supported, the ZT0 LUT register. - PSTATE.SM enables streaming mode, a new floating point mode which uses the SVE register set with a separately configured vector length. In streaming mode implementation of the FFR register is optional.
It is also permitted to build systems which support SME without SVE, in this case when not in streaming mode no SVE registers or instructions are available. Further, there is no requirement that there be any overlap in the set of vector lengths supported by SVE and SME in a system, this is expected to be a common situation in practical systems.
Since there is a new vector length to configure we introduce a new feature parallel to the existing SVE one with a new pseudo register for the streaming mode vector length. Due to the overlap with SVE caused by streaming mode rather than finalising SME as a separate feature we use the existing SVE finalisation to also finalise SME, a new define KVM_ARM_VCPU_VEC is provided to help make user code clearer. Finalising SVE and SME separately would introduce complication with register access since finalising SVE makes the SVE regsiters writeable by userspace and doing multiple finalisations results in an error being reported. Dealing with a state where the SVE registers are writeable due to one of SVE or SME being finalised but may have their VL changed by the other being finalised seems like needless complexity with minimal practical utility, it seems clearer to just express directly that only one finalisation can be done in the ABI.
We represent the streaming mode registers to userspace by always using the existing SVE registers to access the floating point state, using the larger of the SME and (if enabled for the guest) SVE vector lengths.
There are a large number of subfeatures for SME, most of which only offer additional instructions but some of which (SME2 and FA64) add architectural state. The expectation is that these will be configured via the ID registers but since the mechanism for doing this is still unclear the current code enables SME2 and FA64 for the guest if the host supports them regardless of what the ID registers say.
Since we do not yet have support for SVE in protected guests and SME is very reliant on SVE this series does not implement support for SME in protected guests. This will be added separately once SVE support is merged into mainline (or along with merging that), there is code for protected guests using SVE in the Android tree.
The new KVM_ARM_VCPU_VEC feature and ZA and ZT0 registers have not been added to the get-reg-list selftest, the idea of supporting additional features there without restructuring the program to generate all possible feature combinations has been rejected. I will post a separate series which does that restructuring.
I am seeing some test failures currently which I've not got to the bottom of, at this point I'm reasonably sure these are preexisting issues in the kernel which are more apparent in a guest.
To: Marc Zyngier maz@kernel.org To: Oliver Upton oliver.upton@linux.dev To: James Morse james.morse@arm.com To: Suzuki K Poulose suzuki.poulose@arm.com To: Catalin Marinas catalin.marinas@arm.com To: Will Deacon will@kernel.org Cc: linux-arm-kernel@lists.infradead.org Cc: kvmarm@lists.linux.dev Cc: linux-kernel@vger.kernel.org To: Paolo Bonzini pbonzini@redhat.com To: Jonathan Corbet corbet@lwn.net Cc: kvm@vger.kernel.org Cc: linux-doc@vger.kernel.org To: Shuah Khan shuah@kernel.org Cc: linux-kselftest@vger.kernel.org Signed-off-by: Mark Brown broonie@kernel.org
Changes in v2: - Rebase onto v6.7-rc3. - Configure subfeatures based on host system only. - Complete nVHE support. - There was some snafu with sending v1 out, it didn't make it to the lists but in case it hit people's inboxes I'm sending as v2.
--- Mark Brown (22): KVM: arm64: Document why we trap SVE access from the host arm64/fpsimd: Make SVE<->FPSIMD rewriting available to KVM KVM: arm64: Move SVE state access macros after feature test macros KVM: arm64: Store vector lengths in an array KVM: arm64: Document the KVM ABI for SME KVM: arm64: Make FFR restore optional in __sve_restore_state() KVM: arm64: Define guest flags for SME KVM: arm64: Rename SVE finalization constants to be more general KVM: arm64: Basic SME system register descriptions KVM: arm64: Add support for TPIDR2_EL0 KVM: arm64: Make SMPRI_EL1 RES0 for SME guests KVM: arm64: Make SVCR a normal system register KVM: arm64: Context switch SME state for guest KVM: arm64: Manage and handle SME traps KVM: arm64: Implement SME vector length configuration KVM: arm64: Rename sve_state_reg_region KVM: arm64: Support userspace access to streaming mode SVE registers KVM: arm64: Expose ZA to userspace KVM: arm64: Provide userspace access to ZT0 KVM: arm64: Support SME version configuration via ID registers KVM: arm64: Provide userspace ABI for enabling SME KVM: arm64: selftests: Add SME system registers to get-reg-list
Documentation/virt/kvm/api.rst | 104 +++++--- arch/arm64/include/asm/fpsimd.h | 5 + arch/arm64/include/asm/kvm_emulate.h | 13 +- arch/arm64/include/asm/kvm_host.h | 99 +++++--- arch/arm64/include/asm/kvm_hyp.h | 3 +- arch/arm64/include/uapi/asm/kvm.h | 33 +++ arch/arm64/kernel/fpsimd.c | 51 +++- arch/arm64/kvm/arm.c | 16 +- arch/arm64/kvm/fpsimd.c | 266 ++++++++++++++++++--- arch/arm64/kvm/guest.c | 230 +++++++++++++++--- arch/arm64/kvm/handle_exit.c | 11 + arch/arm64/kvm/hyp/fpsimd.S | 11 +- arch/arm64/kvm/hyp/include/hyp/switch.h | 86 ++++++- arch/arm64/kvm/hyp/include/hyp/sysreg-sr.h | 16 ++ arch/arm64/kvm/hyp/nvhe/hyp-main.c | 60 ++++- arch/arm64/kvm/hyp/nvhe/switch.c | 13 +- arch/arm64/kvm/hyp/vhe/switch.c | 3 + arch/arm64/kvm/reset.c | 150 +++++++++--- arch/arm64/kvm/sys_regs.c | 67 +++++- include/uapi/linux/kvm.h | 1 + tools/testing/selftests/kvm/aarch64/get-reg-list.c | 32 ++- 21 files changed, 1063 insertions(+), 207 deletions(-) --- base-commit: 4ae6e89253b387476c2ba0202c3a80f2e1284e91 change-id: 20230301-kvm-arm64-sme-06a1246d3636
Best regards,