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ANDROID: KVM: arm64: Create EL2 copy of __icache_flags for pKVM instead of alias

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Using an alias of the host's `__icache_flags` variable at EL2 for pKVM
is risky, as it provides the host with a mechanism to elide cache
maintenance of guest pages by causing functions such as icache_is_vpipt()
to erroneously return false.

Create a private copy of the __icache_flags variable at EL2 and
initialise it using the host's version during pKVM init.

Signed-off-by: Will Deacon <will@kernel.org>
Bug: 209580772
Change-Id: I595f11d1e336dadae0eb82222e4da79a1069012a
Signed-off-by: Will Deacon <willdeacon@google.com>
This commit is contained in:
Will Deacon
2022-01-05 16:20:21 +00:00
committed by Will Deacon
parent 870bcaf6e7
commit aebc0435b1
4 changed files with 5 additions and 3 deletions
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1
arch/arm64/include/asm/kvm_hyp.h
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@@ -123,4 +123,5 @@ extern u64 kvm_nvhe_sym(id_aa64mmfr0_el1_sys_val);
extern u64 kvm_nvhe_sym(id_aa64mmfr1_el1_sys_val);
extern u64 kvm_nvhe_sym(id_aa64mmfr2_el1_sys_val);
extern unsigned long kvm_nvhe_sym(__icache_flags);
#endif /* __ARM64_KVM_HYP_H__ */

3
arch/arm64/kernel/image-vars.h
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@@ -76,9 +76,6 @@ KVM_NVHE_ALIAS(nvhe_hyp_panic_handler);
/* Vectors installed by hyp-init on reset HVC. */
KVM_NVHE_ALIAS(__hyp_stub_vectors);
/* Kernel symbol used by icache_is_vpipt(). */
KVM_NVHE_ALIAS(__icache_flags);
/* Kernel symbols needed for cpus_have_final/const_caps checks. */
KVM_NVHE_ALIAS(arm64_const_caps_ready);
KVM_NVHE_ALIAS(cpu_hwcap_keys);

1
arch/arm64/kvm/arm.c
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@@ -2007,6 +2007,7 @@ static int kvm_hyp_init_protection(u32 hyp_va_bits)
kvm_nvhe_sym(id_aa64mmfr0_el1_sys_val) = read_sanitised_ftr_reg(SYS_ID_AA64MMFR0_EL1);
kvm_nvhe_sym(id_aa64mmfr1_el1_sys_val) = read_sanitised_ftr_reg(SYS_ID_AA64MMFR1_EL1);
kvm_nvhe_sym(id_aa64mmfr2_el1_sys_val) = read_sanitised_ftr_reg(SYS_ID_AA64MMFR2_EL1);
kvm_nvhe_sym(__icache_flags) = __icache_flags;
ret = create_hyp_mappings(addr, addr + hyp_mem_size, PAGE_HYP);
if (ret)

3
arch/arm64/kvm/hyp/nvhe/pkvm.c
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@@ -21,6 +21,9 @@
#include <nvhe/pkvm.h>
#include <nvhe/trap_handler.h>
/* Used by icache_is_vpipt(). */
unsigned long __icache_flags;
/*
* Set trap register values based on features in ID_AA64PFR0.
*/