Re: [PATCH 6.12 v2 4/8] KVM: arm64: Remove VHE host restore of CPACR_EL1.ZEN

[Sasha Levin <sashal@kernel.org>]

[ Sasha's backport helper bot ]

Hi,

✅ All tests passed successfully. No issues detected.
No action required from the submitter.

The upstream commit SHA1 provided is correct: 459f059be702056d91537b99a129994aa6ccdd35

WARNING: Author mismatch between patch and upstream commit:
Backport author: Mark Brown<broonie@kernel.org>
Commit author: Mark Rutland<mark.rutland@arm.com>

Status in newer kernel trees:
6.13.y | Present (different SHA1: 73882a98030a)

Note: The patch differs from the upstream commit:
---
1:  459f059be7020 ! 1:  416ce5863c885 KVM: arm64: Remove VHE host restore of CPACR_EL1.ZEN
    @@ Metadata
      ## Commit message ##
         KVM: arm64: Remove VHE host restore of CPACR_EL1.ZEN
     
    +    [ Upstream commit 459f059be702056d91537b99a129994aa6ccdd35 ]
    +
         When KVM is in VHE mode, the host kernel tries to save and restore the
         configuration of CPACR_EL1.ZEN (i.e. CPTR_EL2.ZEN when HCR_EL2.E2H=1)
         across kvm_arch_vcpu_load_fp() and kvm_arch_vcpu_put_fp(), since the
    @@ Commit message
         Reviewed-by: Oliver Upton <oliver.upton@linux.dev>
         Link: https://lore.kernel.org/r/20250210195226.1215254-4-mark.rutland@arm.com
         Signed-off-by: Marc Zyngier <maz@kernel.org>
    +    [Rework for refactoring of where the flags are stored -- broonie]
    +    Signed-off-by: Mark Brown <broonie@kernel.org>
     
      ## arch/arm64/include/asm/kvm_host.h ##
    -@@ arch/arm64/include/asm/kvm_host.h: struct cpu_sve_state {
    - struct kvm_host_data {
    - #define KVM_HOST_DATA_FLAG_HAS_SPE			0
    - #define KVM_HOST_DATA_FLAG_HAS_TRBE			1
    --#define KVM_HOST_DATA_FLAG_HOST_SVE_ENABLED		2
    - #define KVM_HOST_DATA_FLAG_HOST_SME_ENABLED		3
    - #define KVM_HOST_DATA_FLAG_TRBE_ENABLED			4
    - #define KVM_HOST_DATA_FLAG_EL1_TRACING_CONFIGURED	5
    +@@ arch/arm64/include/asm/kvm_host.h: struct kvm_vcpu_arch {
    + /* Save TRBE context if active  */
    + #define DEBUG_STATE_SAVE_TRBE	__vcpu_single_flag(iflags, BIT(6))
    + 
    +-/* SVE enabled for host EL0 */
    +-#define HOST_SVE_ENABLED	__vcpu_single_flag(sflags, BIT(0))
    + /* SME enabled for EL0 */
    + #define HOST_SME_ENABLED	__vcpu_single_flag(sflags, BIT(1))
    + /* Physical CPU not in supported_cpus */
     
      ## arch/arm64/kvm/fpsimd.c ##
     @@ arch/arm64/kvm/fpsimd.c: void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu)
      	fpsimd_save_and_flush_cpu_state();
      	*host_data_ptr(fp_owner) = FP_STATE_FREE;
      
    --	host_data_clear_flag(HOST_SVE_ENABLED);
    +-	vcpu_clear_flag(vcpu, HOST_SVE_ENABLED);
     -	if (read_sysreg(cpacr_el1) & CPACR_EL1_ZEN_EL0EN)
    --		host_data_set_flag(HOST_SVE_ENABLED);
    +-		vcpu_set_flag(vcpu, HOST_SVE_ENABLED);
     -
      	if (system_supports_sme()) {
    - 		host_data_clear_flag(HOST_SME_ENABLED);
    + 		vcpu_clear_flag(vcpu, HOST_SME_ENABLED);
      		if (read_sysreg(cpacr_el1) & CPACR_EL1_SMEN_EL0EN)
     @@ arch/arm64/kvm/fpsimd.c: void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu)
      		 * when needed.
    @@ arch/arm64/kvm/fpsimd.c: void kvm_arch_vcpu_put_fp(struct kvm_vcpu *vcpu)
     -		 * for EL0.  To avoid spurious traps, restore the trap state
     -		 * seen by kvm_arch_vcpu_load_fp():
     -		 */
    --		if (host_data_test_flag(HOST_SVE_ENABLED))
    +-		if (vcpu_get_flag(vcpu, HOST_SVE_ENABLED))
     -			sysreg_clear_set(CPACR_EL1, 0, CPACR_EL1_ZEN_EL0EN);
     -		else
     -			sysreg_clear_set(CPACR_EL1, CPACR_EL1_ZEN_EL0EN, 0);
---

Results of testing on various branches:

| Branch                    | Patch Apply | Build Test |
|---------------------------|-------------|------------|
| stable/linux-6.13.y       |  Success    |  Success   |