From: James Morse Date: Tue, 5 May 2026 16:52:03 +0000 (+0100) Subject: KVM: arm64: Work around C1-Pro erratum 4193714 for protected guests X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=1f7305d87aa23db2579df222eba504a333c2c978;p=thirdparty%2Flinux.git KVM: arm64: Work around C1-Pro erratum 4193714 for protected guests C1-Pro cores with SME have an erratum where TLBI+DSB does not complete all outstanding SME accesses. Instead a DSB needs to be executed on the affected CPUs. The implication is that pages cannot be unmapped from the host Stage 2 and then provided to a protected guest or to the hypervisor. Host SME accesses may still complete after this point. This erratum breaks pKVM's guarantees, and the workaround is hard to implement as EL2 and EL1 share a security state meaning EL1 can mask IPIs sent by EL2, leading to interrupt blackouts. Instead, do this in EL3. This has the advantage of a separate security state, meaning lower EL cannot mask the IPI. It is also simpler for EL3 to know about CPUs that are off or in PSCI's CPU_SUSPEND. Add the needed hook to host_stage2_set_owner_metadata_locked(). This covers the cases where the host loses access to a page: __pkvm_host_donate_guest() __pkvm_guest_unshare_host() host_stage2_set_owner_locked() when owner_id == PKVM_ID_HYP Since pKVM relies on the firmware call for correctness, check for the firmware counterpart during protected KVM initialisation and fail the pKVM initialisation if it is missing. Signed-off-by: James Morse Co-developed-by: Catalin Marinas Signed-off-by: Catalin Marinas Cc: Mark Rutland Cc: Marc Zyngier Cc: Oliver Upton Cc: Will Deacon Cc: Vincent Donnefort Cc: Lorenzo Pieralisi Cc: Sudeep Holla Link: https://patch.msgid.link/20260505165205.2690919-1-catalin.marinas@arm.com Signed-off-by: Marc Zyngier --- diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c index 8bb2c7422cc8..34c9950884d5 100644 --- a/arch/arm64/kvm/arm.c +++ b/arch/arm64/kvm/arm.c @@ -4,6 +4,7 @@ * Author: Christoffer Dall */ +#include #include #include #include @@ -2638,6 +2639,22 @@ static int init_pkvm_host_sve_state(void) return 0; } +static int pkvm_check_sme_dvmsync_fw_call(void) +{ + struct arm_smccc_res res; + + if (!cpus_have_final_cap(ARM64_WORKAROUND_4193714)) + return 0; + + arm_smccc_1_1_smc(ARM_SMCCC_CPU_WORKAROUND_4193714, &res); + if (res.a0) { + kvm_err("pKVM requires firmware support for C1-Pro erratum 4193714\n"); + return -ENODEV; + } + + return 0; +} + /* * Finalizes the initialization of hyp mode, once everything else is initialized * and the initialziation process cannot fail. @@ -2838,6 +2855,10 @@ static int __init init_hyp_mode(void) if (err) goto out_err; + err = pkvm_check_sme_dvmsync_fw_call(); + if (err) + goto out_err; + err = kvm_hyp_init_protection(hyp_va_bits); if (err) { kvm_err("Failed to init hyp memory protection\n"); diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c index 28a471d1927c..a3050e2b65b1 100644 --- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c +++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c @@ -5,6 +5,7 @@ */ #include + #include #include #include @@ -14,6 +15,7 @@ #include +#include #include #include #include @@ -29,6 +31,19 @@ static struct hyp_pool host_s2_pool; static DEFINE_PER_CPU(struct pkvm_hyp_vm *, __current_vm); #define current_vm (*this_cpu_ptr(&__current_vm)) +static void pkvm_sme_dvmsync_fw_call(void) +{ + if (alternative_has_cap_unlikely(ARM64_WORKAROUND_4193714)) { + struct arm_smccc_res res; + + /* + * Ignore the return value. Probing for the workaround + * availability took place in init_hyp_mode(). + */ + hyp_smccc_1_1_smc(ARM_SMCCC_CPU_WORKAROUND_4193714, &res); + } +} + static void guest_lock_component(struct pkvm_hyp_vm *vm) { hyp_spin_lock(&vm->lock); @@ -574,8 +589,14 @@ static int host_stage2_set_owner_metadata_locked(phys_addr_t addr, u64 size, ret = host_stage2_try(kvm_pgtable_stage2_annotate, &host_mmu.pgt, addr, size, &host_s2_pool, KVM_HOST_INVALID_PTE_TYPE_DONATION, annotation); - if (!ret) + if (!ret) { + /* + * After stage2 maintenance has happened, but before the page + * owner has changed. + */ + pkvm_sme_dvmsync_fw_call(); __host_update_page_state(addr, size, PKVM_NOPAGE); + } return ret; } diff --git a/include/linux/arm-smccc.h b/include/linux/arm-smccc.h index 50b47eba7d01..e7195750d21b 100644 --- a/include/linux/arm-smccc.h +++ b/include/linux/arm-smccc.h @@ -105,6 +105,12 @@ ARM_SMCCC_SMC_32, \ 0, 0x3fff) +/* C1-Pro erratum 4193714: SME DVMSync early acknowledgement */ +#define ARM_SMCCC_CPU_WORKAROUND_4193714 \ + ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, \ + ARM_SMCCC_SMC_32, \ + ARM_SMCCC_OWNER_CPU, 0x10) + #define ARM_SMCCC_VENDOR_HYP_CALL_UID_FUNC_ID \ ARM_SMCCC_CALL_VAL(ARM_SMCCC_FAST_CALL, \ ARM_SMCCC_SMC_32, \