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| author | Marc Zyngier <maz@kernel.org> | 2021-10-27 11:18:00 +0100 |
|---|---|---|
| committer | Marc Zyngier <maz@kernel.org> | 2021-11-22 15:30:27 +0000 |
| commit | 8383741ab2e773a992f1f0f8acdca5e7a4687c49 (patch) | |
| tree | 65e8b49a1790d864984d178f3de9858a209b7b85 /arch/arm64/include | |
| parent | 892fd259cbf6b1dc16116611b84f7f164a11fe2e (diff) | |
| download | linux-8383741ab2e773a992f1f0f8acdca5e7a4687c49.tar.bz2 | |
KVM: arm64: Get rid of host SVE tracking/saving
The SVE host tracking in KVM is pretty involved. It relies on a
set of flags tracking the ownership of the SVE register, as well
as that of the EL0 access.
It is also pretty scary: __hyp_sve_save_host() computes
a thread_struct pointer and obtains a sve_state which gets directly
accessed without further ado, even on nVHE. How can this even work?
The answer to that is that it doesn't, and that this is mostly dead
code. Closer examination shows that on executing a syscall, userspace
loses its SVE state entirely. This is part of the ABI. Another
thing to notice is that although the kernel provides helpers such as
kernel_neon_begin()/end(), they only deal with the FP/NEON state,
and not SVE.
Given that you can only execute a guest as the result of a syscall,
and that the kernel cannot use SVE by itself, it becomes pretty
obvious that there is never any host SVE state to save, and that
this code is only there to increase confusion.
Get rid of the TIF_SVE tracking and host save infrastructure altogether.
Reviewed-by: Mark Brown <broonie@kernel.org>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Diffstat (limited to 'arch/arm64/include')
| -rw-r--r-- | arch/arm64/include/asm/kvm_host.h | 1 |
1 files changed, 0 insertions, 1 deletions
diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h index 3bfd30137ce2..3ccfc3e3e436 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -411,7 +411,6 @@ struct kvm_vcpu_arch { #define KVM_ARM64_DEBUG_DIRTY (1 << 0) #define KVM_ARM64_FP_ENABLED (1 << 1) /* guest FP regs loaded */ #define KVM_ARM64_FP_HOST (1 << 2) /* host FP regs loaded */ -#define KVM_ARM64_HOST_SVE_IN_USE (1 << 3) /* backup for host TIF_SVE */ #define KVM_ARM64_HOST_SVE_ENABLED (1 << 4) /* SVE enabled for EL0 */ #define KVM_ARM64_GUEST_HAS_SVE (1 << 5) /* SVE exposed to guest */ #define KVM_ARM64_VCPU_SVE_FINALIZED (1 << 6) /* SVE config completed */ |