Re: [PATCH 5.15 v2 02/10] KVM: arm64: Discard any SVE state when entering KVM guests

[Sasha Levin <sashal@kernel.org>]

[ Sasha's backport helper bot ]

Hi,

Summary of potential issues:
ℹ️ This is part 02/10 of a series
⚠️ Found follow-up fixes in mainline

The upstream commit SHA1 provided is correct: 93ae6b01bafee8fa385aa25ee7ebdb40057f6abe

Status in newer kernel trees:
6.13.y | Present (exact SHA1)
6.12.y | Present (exact SHA1)
6.6.y | Present (exact SHA1)
6.1.y | Not found

Found fixes commits:
fbc7e61195e2 KVM: arm64: Unconditionally save+flush host FPSIMD/SVE/SME state

Note: The patch differs from the upstream commit:
---
1:  93ae6b01bafee ! 1:  710abf6eb6613 KVM: arm64: Discard any SVE state when entering KVM guests
    @@ Metadata
      ## Commit message ##
         KVM: arm64: Discard any SVE state when entering KVM guests
     
    +    [ 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
    @@ Commit message
         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 ##
     @@ arch/arm64/include/asm/fpsimd.h: extern void fpsimd_signal_preserve_current_state(void);
    @@ arch/arm64/include/asm/fpsimd.h: extern void fpsimd_signal_preserve_current_stat
     +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,
    + 				     void *sve_state, unsigned int sve_vl);
     
      ## arch/arm64/kernel/fpsimd.c ##
     @@ arch/arm64/kernel/fpsimd.c: void fpsimd_signal_preserve_current_state(void)
    @@ arch/arm64/kvm/fpsimd.c: int kvm_arch_vcpu_run_map_fp(struct kvm_vcpu *vcpu)
      	BUG_ON(!current->mm);
     -	BUG_ON(test_thread_flag(TIF_SVE));
      
    - 	if (!system_supports_fpsimd())
    - 		return;
    + 	vcpu->arch.flags &= ~KVM_ARM64_FP_ENABLED;
    + 	vcpu->arch.flags |= KVM_ARM64_FP_HOST;
      
     +	fpsimd_kvm_prepare();
     +
    - 	vcpu->arch.fp_state = FP_STATE_HOST_OWNED;
    - 
    - 	vcpu_clear_flag(vcpu, HOST_SVE_ENABLED);
    ++	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;
    + }
---

NOTE: These results are for this patch alone. Full series testing will be
performed when all parts are received.

Results of testing on various branches:

| Branch                    | Patch Apply | Build Test |
|---------------------------|-------------|------------|
| stable/linux-6.1.y        |  Success    |  Success   |