From 2bfc654b89c4dd1c372bb2cbba6b5a0eb578d214 Mon Sep 17 00:00:00 2001 From: Marc Zyngier Date: Thu, 9 Nov 2023 15:47:49 +0000 Subject: [PATCH] arm64: cpufeatures: Restrict NV support to FEAT_NV2 To anyone who has played with FEAT_NV, it is obvious that the level of performance is rather low due to the trap amplification that it imposes on the host hypervisor. FEAT_NV2 solves a number of the problems that FEAT_NV had. It also turns out that all the existing hardware that has FEAT_NV also has FEAT_NV2. Finally, it is now allowed by the architecture to build FEAT_NV2 *only* (as denoted by ID_AA64MMFR4_EL1.NV_frac), which effectively seals the fate of FEAT_NV. Restrict the NV support to NV2, and be done with it. Nobody will cry over the old crap. NV_frac will eventually be supported once the intrastructure is ready. Reviewed-by: Oliver Upton Signed-off-by: Marc Zyngier --- arch/arm64/kernel/cpufeature.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c index 646591c67e7a5..1329e974d187c 100644 --- a/arch/arm64/kernel/cpufeature.c +++ b/arch/arm64/kernel/cpufeature.c @@ -2339,7 +2339,7 @@ static const struct arm64_cpu_capabilities arm64_features[] = { .capability = ARM64_HAS_NESTED_VIRT, .type = ARM64_CPUCAP_SYSTEM_FEATURE, .matches = has_nested_virt_support, - ARM64_CPUID_FIELDS(ID_AA64MMFR2_EL1, NV, IMP) + ARM64_CPUID_FIELDS(ID_AA64MMFR2_EL1, NV, NV2) }, { .capability = ARM64_HAS_32BIT_EL0_DO_NOT_USE, -- 2.30.2