[PATCH 2/9] arm64: alternatives: kvm: prepare for cap changes

Mark Rutland
2022-09-01T15:15:21Z

The KVM patching callbacks use cpus_have_final_cap() internally within
has_vhe(), and subsequent patches will make it invalid to call
cpus_have_final_cap() before alternatives patching has completed, and
will mean that cpus_have_const_cap() will always fall back to dynamic
checks prior to alternatives patching.

In preparation for said change, this patch modifies the KVM patching
callbacks to use cpus_have_cap() directly. This is not subject to
patching, and will dynamically check the cpu_hwcaps array, which is
functionally equivalent to the existing behaviour.

There should be no functional change as a result of this patch.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: James Morse <james.morse@arm.com>
Cc: Joey Gouly <joey.gouly@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Will Deacon <will@kernel.org>
---
arch/arm64/kvm/va_layout.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kvm/va_layout.c b/arch/arm64/kvm/va_layout.c
index acdb7b3cc97d6..91b22a014610b 100644
--- a/arch/arm64/kvm/va_layout.c
+++ b/arch/arm64/kvm/va_layout.c
@@ -169,7 +169,7 @@ void __init kvm_update_va_mask(struct alt_instr *alt,
* dictates it and we don't have any spare bits in the
* address), NOP everything after masking the kernel VA.
*/
- if (has_vhe() || (!tag_val && i > 0)) {
+ if (cpus_have_cap(ARM64_HAS_VIRT_HOST_EXTN) || (!tag_val && i > 0)) {
updptr[i] = cpu_to_le32(aarch64_insn_gen_nop());
continue;
}
@@ -193,7 +193,8 @@ void kvm_patch_vector_branch(struct alt_instr *alt,

BUG_ON(nr_inst != 4);

- if (!cpus_have_const_cap(ARM64_SPECTRE_V3A) || WARN_ON_ONCE(has_vhe()))
+ if (!cpus_have_cap(ARM64_SPECTRE_V3A) ||
+ WARN_ON_ONCE(cpus_have_cap(ARM64_HAS_VIRT_HOST_EXTN)))
return;

/*