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| author | Marc Zyngier <maz@kernel.org> | 2024-04-19 11:29:35 +0100 |
|---|---|---|
| committer | Marc Zyngier <maz@kernel.org> | 2024-04-20 12:42:51 +0100 |
| commit | 814ad8f96e929fa9c60bd360d2f7bccfc1df0111 (patch) | |
| tree | 9e48cb0ea141dbcc4ae187363b209ea4ab78f088 /arch/arm64/include/asm | |
| parent | f4f6a95bac49144c0d507c24af9905bb999a4579 (diff) | |
| download | linux-stable-814ad8f96e929fa9c60bd360d2f7bccfc1df0111.tar.gz linux-stable-814ad8f96e929fa9c60bd360d2f7bccfc1df0111.tar.bz2 linux-stable-814ad8f96e929fa9c60bd360d2f7bccfc1df0111.zip | |
KVM: arm64: Drop trapping of PAuth instructions/keys
We currently insist on disabling PAuth on vcpu_load(), and get to
enable it on first guest use of an instruction or a key (ignoring
the NV case for now).
It isn't clear at all what this is trying to achieve: guests tend
to use PAuth when available, and nothing forces you to expose it
to the guest if you don't want to. This also isn't totally free:
we take a full GPR save/restore between host and guest, only to
write ten 64bit registers. The "value proposition" escapes me.
So let's forget this stuff and enable PAuth eagerly if exposed to
the guest. This results in much simpler code. Performance wise,
that's not bad either (tested on M2 Pro running a fully automated
Debian installer as the workload):
- On a non-NV guest, I can see reduction of 0.24% in the number
of cycles (measured with perf over 10 consecutive runs)
- On a NV guest (L2), I see a 2% reduction in wall-clock time
(measured with 'time', as M2 doesn't have a PMUv3 and NV
doesn't support it either)
So overall, a much reduced complexity and a (small) performance
improvement.
Reviewed-by: Oliver Upton <oliver.upton@linux.dev>
Link: https://lore.kernel.org/r/20240419102935.1935571-16-maz@kernel.org
Signed-off-by: Marc Zyngier <maz@kernel.org>
Diffstat (limited to 'arch/arm64/include/asm')
| -rw-r--r-- | arch/arm64/include/asm/kvm_emulate.h | 5 | ||||
| -rw-r--r-- | arch/arm64/include/asm/kvm_ptrauth.h | 21 |
2 files changed, 21 insertions, 5 deletions
diff --git a/arch/arm64/include/asm/kvm_emulate.h b/arch/arm64/include/asm/kvm_emulate.h index 87f2c31f3206..382164d791f4 100644 --- a/arch/arm64/include/asm/kvm_emulate.h +++ b/arch/arm64/include/asm/kvm_emulate.h @@ -125,11 +125,6 @@ static inline void vcpu_set_wfx_traps(struct kvm_vcpu *vcpu) vcpu->arch.hcr_el2 |= HCR_TWI; } -static inline void vcpu_ptrauth_disable(struct kvm_vcpu *vcpu) -{ - vcpu->arch.hcr_el2 &= ~(HCR_API | HCR_APK); -} - static inline unsigned long vcpu_get_vsesr(struct kvm_vcpu *vcpu) { return vcpu->arch.vsesr_el2; diff --git a/arch/arm64/include/asm/kvm_ptrauth.h b/arch/arm64/include/asm/kvm_ptrauth.h index 0cd0965255d2..d81bac256abc 100644 --- a/arch/arm64/include/asm/kvm_ptrauth.h +++ b/arch/arm64/include/asm/kvm_ptrauth.h @@ -99,5 +99,26 @@ alternative_else_nop_endif .macro ptrauth_switch_to_hyp g_ctxt, h_ctxt, reg1, reg2, reg3 .endm #endif /* CONFIG_ARM64_PTR_AUTH */ + +#else /* !__ASSEMBLY */ + +#define __ptrauth_save_key(ctxt, key) \ + do { \ + u64 __val; \ + __val = read_sysreg_s(SYS_ ## key ## KEYLO_EL1); \ + ctxt_sys_reg(ctxt, key ## KEYLO_EL1) = __val; \ + __val = read_sysreg_s(SYS_ ## key ## KEYHI_EL1); \ + ctxt_sys_reg(ctxt, key ## KEYHI_EL1) = __val; \ + } while(0) + +#define ptrauth_save_keys(ctxt) \ + do { \ + __ptrauth_save_key(ctxt, APIA); \ + __ptrauth_save_key(ctxt, APIB); \ + __ptrauth_save_key(ctxt, APDA); \ + __ptrauth_save_key(ctxt, APDB); \ + __ptrauth_save_key(ctxt, APGA); \ + } while(0) + #endif /* __ASSEMBLY__ */ #endif /* __ASM_KVM_PTRAUTH_H */ |