[ Upstream commit 93ae6b01bafee8fa385aa25ee7ebdb40057f6abe ]
Since 8383741ab2e773a99 (KVM: arm64: Get rid of host SVE tracking/saving) KVM has not tracked the host SVE state, relying on the fact that we currently disable SVE whenever we perform a syscall. This may not be true in future since performance optimisation may result in us keeping SVE enabled in order to avoid needing to take access traps to reenable it. Handle this by clearing TIF_SVE and converting the stored task state to FPSIMD format when preparing to run the guest. This is done with a new call fpsimd_kvm_prepare() to keep the direct state manipulation functions internal to fpsimd.c.
Signed-off-by: Mark Brown broonie@kernel.org Reviewed-by: Catalin Marinas catalin.marinas@arm.com Reviewed-by: Marc Zyngier maz@kernel.org Link: https://lore.kernel.org/r/20221115094640.112848-2-broonie@kernel.org Signed-off-by: Will Deacon will@kernel.org [ Mark: trivial backport to v6.1 ] Signed-off-by: Mark Rutland mark.rutland@arm.com Signed-off-by: Mark Brown broonie@kernel.org --- arch/arm64/include/asm/fpsimd.h | 1 + arch/arm64/kernel/fpsimd.c | 23 +++++++++++++++++++++++ arch/arm64/kvm/fpsimd.c | 4 +++- 3 files changed, 27 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/include/asm/fpsimd.h b/arch/arm64/include/asm/fpsimd.h index 9a62884183e5..f7faf0f4507c 100644 --- a/arch/arm64/include/asm/fpsimd.h +++ b/arch/arm64/include/asm/fpsimd.h @@ -44,6 +44,7 @@ extern void fpsimd_signal_preserve_current_state(void); extern void fpsimd_preserve_current_state(void); extern void fpsimd_restore_current_state(void); extern void fpsimd_update_current_state(struct user_fpsimd_state const *state); +extern void fpsimd_kvm_prepare(void);
extern void fpsimd_bind_state_to_cpu(struct user_fpsimd_state *state, void *sve_state, unsigned int sve_vl); diff --git a/arch/arm64/kernel/fpsimd.c b/arch/arm64/kernel/fpsimd.c index e22571e57ae1..57e89361edcb 100644 --- a/arch/arm64/kernel/fpsimd.c +++ b/arch/arm64/kernel/fpsimd.c @@ -1108,6 +1108,29 @@ void fpsimd_signal_preserve_current_state(void) sve_to_fpsimd(current); }
+/* + * Called by KVM when entering the guest. + */ +void fpsimd_kvm_prepare(void) +{ + if (!system_supports_sve()) + return; + + /* + * KVM does not save host SVE state since we can only enter + * the guest from a syscall so the ABI means that only the + * non-saved SVE state needs to be saved. If we have left + * SVE enabled for performance reasons then update the task + * state to be FPSIMD only. + */ + get_cpu_fpsimd_context(); + + if (test_and_clear_thread_flag(TIF_SVE)) + sve_to_fpsimd(current); + + put_cpu_fpsimd_context(); +} + /* * Associate current's FPSIMD context with this cpu * The caller must have ownership of the cpu FPSIMD context before calling diff --git a/arch/arm64/kvm/fpsimd.c b/arch/arm64/kvm/fpsimd.c index 24734bfcfaa0..16e29f03dcbf 100644 --- a/arch/arm64/kvm/fpsimd.c +++ b/arch/arm64/kvm/fpsimd.c @@ -70,12 +70,14 @@ int kvm_arch_vcpu_run_map_fp(struct kvm_vcpu *vcpu) void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu) { BUG_ON(!current->mm); - BUG_ON(test_thread_flag(TIF_SVE));
vcpu->arch.flags &= ~KVM_ARM64_FP_ENABLED; vcpu->arch.flags |= KVM_ARM64_FP_HOST;
+ fpsimd_kvm_prepare(); + vcpu->arch.flags &= ~KVM_ARM64_HOST_SVE_ENABLED; + if (read_sysreg(cpacr_el1) & CPACR_EL1_ZEN_EL0EN) vcpu->arch.flags |= KVM_ARM64_HOST_SVE_ENABLED; }