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KVM: arm64: Flush hyp bss section after initialization of variables in bss

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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: 6c30bfb18d ("KVM: arm64: Add handlers for protected VM System Registers")
Suggested-by: Fuad Tabba <tabba@google.com>
Signed-off-by: Lokesh Vutla <lokeshvutla@google.com>
Link: https://lore.kernel.org/r/20250121044016.2219256-1-lokeshvutla@google.com
Signed-off-by: Marc Zyngier <maz@kernel.org>
This commit is contained in:
Lokesh Vutla 2025-01-21 04:40:16 +00:00 • committed by Marc Zyngier
parent 01009b06a6
commit 9bcbb6104a
1 changed files with 7 additions and 0 deletions
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7
arch/arm64/kvm/arm.c
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@ -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)