From: Lokesh Vutla Date: Tue, 21 Jan 2025 04:40:16 +0000 (+0000) Subject: KVM: arm64: Flush hyp bss section after initialization of variables in bss X-Git-Tag: v6.14-rc2~3^2~3^2~6 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=9bcbb6104a344d3526e185ee1e7b985509914e90;p=thirdparty%2Flinux.git KVM: arm64: Flush hyp bss section after initialization of variables in bss To determine CPU features during initialization, the nVHE hypervisor utilizes sanitized values of the host's CPU features registers. These values, stored in u64 idaa64*_el1_sys_val variables are updated by the kvm_hyp_init_symbols() function at EL1. To ensure EL2 visibility with the MMU off, the data cache needs to be flushed after these updates. However, individually flushing each variable using kvm_flush_dcache_to_poc() is inefficient. These cpu feature variables would be part of the bss section of the hypervisor. Hence, flush the entire bss section of hypervisor once the initialization is complete. Fixes: 6c30bfb18d0b ("KVM: arm64: Add handlers for protected VM System Registers") Suggested-by: Fuad Tabba Signed-off-by: Lokesh Vutla Link: https://lore.kernel.org/r/20250121044016.2219256-1-lokeshvutla@google.com Signed-off-by: Marc Zyngier --- diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c index bcc4f7e926349..0725a0b50a3e9 100644 --- a/arch/arm64/kvm/arm.c +++ b/arch/arm64/kvm/arm.c @@ -2400,6 +2400,13 @@ static void kvm_hyp_init_symbols(void) kvm_nvhe_sym(id_aa64smfr0_el1_sys_val) = read_sanitised_ftr_reg(SYS_ID_AA64SMFR0_EL1); kvm_nvhe_sym(__icache_flags) = __icache_flags; kvm_nvhe_sym(kvm_arm_vmid_bits) = kvm_arm_vmid_bits; + + /* + * Flush entire BSS since part of its data containing init symbols is read + * while the MMU is off. + */ + kvm_flush_dcache_to_poc(kvm_ksym_ref(__hyp_bss_start), + kvm_ksym_ref(__hyp_bss_end) - kvm_ksym_ref(__hyp_bss_start)); } static int __init kvm_hyp_init_protection(u32 hyp_va_bits)