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D Scott PhillipsMarc Zyngier
D Scott Phillips
authored and
Marc Zyngier
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arm64: errata: Work around AmpereOne's erratum AC04_CPU_23
On AmpereOne AC04, updates to HCR_EL2 can rarely corrupt simultaneous translations for data addresses initiated by load/store instructions. Only instruction initiated translations are vulnerable, not translations from prefetches for example. A DSB before the store to HCR_EL2 is sufficient to prevent older instructions from hitting the window for corruption, and an ISB after is sufficient to prevent younger instructions from hitting the window for corruption. Signed-off-by: D Scott Phillips <scott@os.amperecomputing.com> Reviewed-by: Oliver Upton <oliver.upton@linux.dev> Acked-by: Catalin Marinas <catalin.marinas@arm.com> Link: https://lore.kernel.org/r/20250513184514.2678288-1-scott@os.amperecomputing.com Signed-off-by: Marc Zyngier <maz@kernel.org>
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‎Documentation/arch/arm64/silicon-errata.rst‎

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@@ -57,6 +57,8 @@ stable kernels.
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+----------------+-----------------+-----------------+-----------------------------+
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| Ampere | AmpereOne AC04 | AC04_CPU_10 | AMPERE_ERRATUM_AC03_CPU_38 |
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+----------------+-----------------+-----------------+-----------------------------+
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| Ampere | AmpereOne AC04 | AC04_CPU_23 | AMPERE_ERRATUM_AC04_CPU_23 |
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+----------------+-----------------+-----------------+-----------------------------+
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+----------------+-----------------+-----------------+-----------------------------+
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| ARM | Cortex-A510 | #2457168 | ARM64_ERRATUM_2457168 |
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+----------------+-----------------+-----------------+-----------------------------+

‎arch/arm64/Kconfig‎

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@@ -464,6 +464,23 @@ config AMPERE_ERRATUM_AC03_CPU_38
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If unsure, say Y.
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config AMPERE_ERRATUM_AC04_CPU_23
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bool "AmpereOne: AC04_CPU_23: Failure to synchronize writes to HCR_EL2 may corrupt address translations."
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default y
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help
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This option adds an alternative code sequence to work around Ampere
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errata AC04_CPU_23 on AmpereOne.
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Updates to HCR_EL2 can rarely corrupt simultaneous translations for
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data addresses initiated by load/store instructions. Only
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instruction initiated translations are vulnerable, not translations
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from prefetches for example. A DSB before the store to HCR_EL2 is
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sufficient to prevent older instructions from hitting the window
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for corruption, and an ISB after is sufficient to prevent younger
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instructions from hitting the window for corruption.
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If unsure, say Y.
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config ARM64_WORKAROUND_CLEAN_CACHE
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bool
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‎arch/arm64/include/asm/el2_setup.h‎

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@@ -38,7 +38,7 @@
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orr x0, x0, #HCR_E2H
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.LnVHE_\@:
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msr hcr_el2, x0
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msr_hcr_el2 x0
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isb
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.endm
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‎arch/arm64/include/asm/hardirq.h‎

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@@ -41,7 +41,7 @@ do { \
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\
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___hcr = read_sysreg(hcr_el2); \
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if (!(___hcr & HCR_TGE)) { \
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write_sysreg(___hcr | HCR_TGE, hcr_el2); \
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write_sysreg_hcr(___hcr | HCR_TGE); \
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isb(); \
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} \
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/* \
@@ -82,7 +82,7 @@ do { \
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*/ \
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barrier(); \
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if (!___ctx->cnt && !(___hcr & HCR_TGE)) \
85-
write_sysreg(___hcr, hcr_el2); \
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write_sysreg_hcr(___hcr); \
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} while (0)
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static inline void ack_bad_irq(unsigned int irq)

‎arch/arm64/include/asm/sysreg.h‎

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Original file line numberDiff line numberDiff line change
@@ -1091,6 +1091,15 @@
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__emit_inst(0xd5000000|(\sreg)|(.L__gpr_num_\rt))
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.endm
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1094+
.macro msr_hcr_el2, reg
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#if IS_ENABLED(CONFIG_AMPERE_ERRATUM_AC04_CPU_23)
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dsb nsh
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msr hcr_el2, \reg
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isb
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#else
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msr hcr_el2, \reg
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#endif
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.endm
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#else
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#include <linux/bitfield.h>
@@ -1178,13 +1187,31 @@
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write_sysreg(__scs_new, sysreg); \
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} while (0)
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#define sysreg_clear_set_hcr(clear, set) do { \
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u64 __scs_val = read_sysreg(hcr_el2); \
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u64 __scs_new = (__scs_val & ~(u64)(clear)) | (set); \
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if (__scs_new != __scs_val) \
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write_sysreg_hcr(__scs_new); \
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} while (0)
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#define sysreg_clear_set_s(sysreg, clear, set) do { \
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u64 __scs_val = read_sysreg_s(sysreg); \
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u64 __scs_new = (__scs_val & ~(u64)(clear)) | (set); \
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if (__scs_new != __scs_val) \
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write_sysreg_s(__scs_new, sysreg); \
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} while (0)
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1204+
#define write_sysreg_hcr(__val) do { \
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if (IS_ENABLED(CONFIG_AMPERE_ERRATUM_AC04_CPU_23) && \
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(!system_capabilities_finalized() || \
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alternative_has_cap_unlikely(ARM64_WORKAROUND_AMPERE_AC04_CPU_23))) \
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asm volatile("dsb nsh; msr hcr_el2, %x0; isb" \
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: : "rZ" (__val)); \
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else \
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asm volatile("msr hcr_el2, %x0" \
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: : "rZ" (__val)); \
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} while (0)
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#define read_sysreg_par() ({ \
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u64 par; \
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asm(ALTERNATIVE("nop", "dmb sy", ARM64_WORKAROUND_1508412)); \

‎arch/arm64/kernel/cpu_errata.c‎

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@@ -557,6 +557,13 @@ static const struct midr_range erratum_ac03_cpu_38_list[] = {
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};
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#endif
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#ifdef CONFIG_AMPERE_ERRATUM_AC04_CPU_23
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static const struct midr_range erratum_ac04_cpu_23_list[] = {
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MIDR_ALL_VERSIONS(MIDR_AMPERE1A),
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{},
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};
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#endif
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const struct arm64_cpu_capabilities arm64_errata[] = {
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#ifdef CONFIG_ARM64_WORKAROUND_CLEAN_CACHE
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{
@@ -875,6 +882,13 @@ const struct arm64_cpu_capabilities arm64_errata[] = {
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.capability = ARM64_WORKAROUND_AMPERE_AC03_CPU_38,
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ERRATA_MIDR_RANGE_LIST(erratum_ac03_cpu_38_list),
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},
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#endif
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#ifdef CONFIG_AMPERE_ERRATUM_AC04_CPU_23
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{
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.desc = "AmpereOne erratum AC04_CPU_23",
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.capability = ARM64_WORKAROUND_AMPERE_AC04_CPU_23,
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ERRATA_MIDR_RANGE_LIST(erratum_ac04_cpu_23_list),
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},
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#endif
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{
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.desc = "Broken CNTVOFF_EL2",

‎arch/arm64/kernel/hyp-stub.S‎

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@@ -97,7 +97,7 @@ SYM_CODE_START_LOCAL(__finalise_el2)
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2:
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// Engage the VHE magic!
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mov_q x0, HCR_HOST_VHE_FLAGS
100-
msr hcr_el2, x0
100+
msr_hcr_el2 x0
101101
isb
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103103
// Use the EL1 allocated stack, per-cpu offset

‎arch/arm64/kvm/at.c‎

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@@ -516,7 +516,7 @@ static void __mmu_config_save(struct mmu_config *config)
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517517
static void __mmu_config_restore(struct mmu_config *config)
518518
{
519-
write_sysreg(config->hcr, hcr_el2);
519+
write_sysreg_hcr(config->hcr);
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521521
/*
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* ARM errata 1165522 and 1530923 require TGE to be 1 before
@@ -1267,7 +1267,7 @@ static u64 __kvm_at_s1e01_fast(struct kvm_vcpu *vcpu, u32 op, u64 vaddr)
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skip_mmu_switch:
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/* Clear TGE, enable S2 translation, we're rolling */
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write_sysreg((config.hcr & ~HCR_TGE) | HCR_VM, hcr_el2);
1270+
write_sysreg_hcr((config.hcr & ~HCR_TGE) | HCR_VM);
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isb();
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switch (op) {
@@ -1350,7 +1350,7 @@ void __kvm_at_s1e2(struct kvm_vcpu *vcpu, u32 op, u64 vaddr)
13501350
if (!vcpu_el2_e2h_is_set(vcpu))
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val |= HCR_NV | HCR_NV1;
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1353-
write_sysreg(val, hcr_el2);
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write_sysreg_hcr(val);
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isb();
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par = SYS_PAR_EL1_F;
@@ -1375,7 +1375,7 @@ void __kvm_at_s1e2(struct kvm_vcpu *vcpu, u32 op, u64 vaddr)
13751375
if (!fail)
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par = read_sysreg_par();
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1378-
write_sysreg(hcr, hcr_el2);
1378+
write_sysreg_hcr(hcr);
13791379
isb();
13801380
}
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‎arch/arm64/kvm/hyp/include/hyp/switch.h‎

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@@ -301,7 +301,7 @@ static inline void ___activate_traps(struct kvm_vcpu *vcpu, u64 hcr)
301301
if (cpus_have_final_cap(ARM64_WORKAROUND_CAVIUM_TX2_219_TVM))
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hcr |= HCR_TVM;
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304-
write_sysreg(hcr, hcr_el2);
304+
write_sysreg_hcr(hcr);
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306306
if (cpus_have_final_cap(ARM64_HAS_RAS_EXTN) && (hcr & HCR_VSE))
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write_sysreg_s(vcpu->arch.vsesr_el2, SYS_VSESR_EL2);

‎arch/arm64/kvm/hyp/nvhe/host.S‎

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@@ -124,7 +124,7 @@ SYM_FUNC_START(__hyp_do_panic)
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/* Ensure host stage-2 is disabled */
125125
mrs x0, hcr_el2
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bic x0, x0, #HCR_VM
127-
msr hcr_el2, x0
127+
msr_hcr_el2 x0
128128
isb
129129
tlbi vmalls12e1
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dsb nsh

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