From 105485a182dc6ba32e55db46839af756c105afae Mon Sep 17 00:00:00 2001 From: Marc Zyngier Date: Tue, 1 Jul 2025 15:02:58 +0100 Subject: [PATCH 1/2] KVM: arm64: Fix handling of FEAT_GTG for unimplemented granule sizes Booting an EL2 guest on a system only supporting a subset of the possible page sizes leads to interesting situations. For example, on a system that only supports 4kB and 64kB, and is booted with a 4kB kernel, we end-up advertising 16kB support at stage-2, which is pretty weird. That's because we consider that any S2 bigger than our base granule is fair game, irrespective of what the HW actually supports. While this is not impossible to support (KVM would happily handle it), it is likely to be confusing for the guest. Add new checks that will verify that this granule size is actually supported before publishing it to the guest. Fixes: e7ef6ed4583ea ("KVM: arm64: Enforce NV limits on a per-idregs basis") Reviewed-by: Oliver Upton Signed-off-by: Marc Zyngier --- arch/arm64/kvm/nested.c | 26 +++++++++++++++++++++++--- 1 file changed, 23 insertions(+), 3 deletions(-) diff --git a/arch/arm64/kvm/nested.c b/arch/arm64/kvm/nested.c index 5b191f4dc566..dc1d26559bfa 100644 --- a/arch/arm64/kvm/nested.c +++ b/arch/arm64/kvm/nested.c @@ -1402,6 +1402,21 @@ static void kvm_map_l1_vncr(struct kvm_vcpu *vcpu) } } +#define has_tgran_2(__r, __sz) \ + ({ \ + u64 _s1, _s2, _mmfr0 = __r; \ + \ + _s2 = SYS_FIELD_GET(ID_AA64MMFR0_EL1, \ + TGRAN##__sz##_2, _mmfr0); \ + \ + _s1 = SYS_FIELD_GET(ID_AA64MMFR0_EL1, \ + TGRAN##__sz, _mmfr0); \ + \ + ((_s2 != ID_AA64MMFR0_EL1_TGRAN##__sz##_2_NI && \ + _s2 != ID_AA64MMFR0_EL1_TGRAN##__sz##_2_TGRAN##__sz) || \ + (_s2 == ID_AA64MMFR0_EL1_TGRAN##__sz##_2_TGRAN##__sz && \ + _s1 != ID_AA64MMFR0_EL1_TGRAN##__sz##_NI)); \ + }) /* * Our emulated CPU doesn't support all the possible features. For the * sake of simplicity (and probably mental sanity), wipe out a number @@ -1411,6 +1426,8 @@ static void kvm_map_l1_vncr(struct kvm_vcpu *vcpu) */ u64 limit_nv_id_reg(struct kvm *kvm, u32 reg, u64 val) { + u64 orig_val = val; + switch (reg) { case SYS_ID_AA64ISAR0_EL1: /* Support everything but TME */ @@ -1480,13 +1497,16 @@ u64 limit_nv_id_reg(struct kvm *kvm, u32 reg, u64 val) */ switch (PAGE_SIZE) { case SZ_4K: - val |= SYS_FIELD_PREP_ENUM(ID_AA64MMFR0_EL1, TGRAN4_2, IMP); + if (has_tgran_2(orig_val, 4)) + val |= SYS_FIELD_PREP_ENUM(ID_AA64MMFR0_EL1, TGRAN4_2, IMP); fallthrough; case SZ_16K: - val |= SYS_FIELD_PREP_ENUM(ID_AA64MMFR0_EL1, TGRAN16_2, IMP); + if (has_tgran_2(orig_val, 16)) + val |= SYS_FIELD_PREP_ENUM(ID_AA64MMFR0_EL1, TGRAN16_2, IMP); fallthrough; case SZ_64K: - val |= SYS_FIELD_PREP_ENUM(ID_AA64MMFR0_EL1, TGRAN64_2, IMP); + if (has_tgran_2(orig_val, 64)) + val |= SYS_FIELD_PREP_ENUM(ID_AA64MMFR0_EL1, TGRAN64_2, IMP); break; } From 42ce432522a17685f5a84529de49e555477c0a1f Mon Sep 17 00:00:00 2001 From: Mark Rutland Date: Thu, 19 Jun 2025 14:48:17 +0100 Subject: [PATCH 2/2] KVM: arm64: Remove kvm_arch_vcpu_run_map_fp() Historically KVM hyp code saved the host's FPSIMD state into the hosts's fpsimd_state memory, and so it was necessary to map this into the hyp Stage-1 mappings before running a vCPU. This is no longer necessary as of commits: * fbc7e61195e2 ("KVM: arm64: Unconditionally save+flush host FPSIMD/SVE/SME state") * 8eca7f6d5100 ("KVM: arm64: Remove host FPSIMD saving for non-protected KVM") Since those commits, we eagerly save the host's FPSIMD state before calling into hyp to run a vCPU, and hyp code never reads nor writes the host's fpsimd_state memory. There's no longer any need to map the host's fpsimd_state memory into the hyp Stage-1, and kvm_arch_vcpu_run_map_fp() is unnecessary but benign. Remove kvm_arch_vcpu_run_map_fp(). Currently there is no code to perform a corresponding unmap, and we never mapped the host's SVE or SME state into the hyp Stage-1, so no other code needs to be removed. Signed-off-by: Mark Rutland Cc: Catalin Marinas Cc: Fuad Tabba Cc: Marc Zyngier Cc: Mark Brown Cc: Oliver Upton Cc: Will Deacon Cc: kvmarm@lists.linux.dev Reviewed-by: Mark Brown Tested-by: Fuad Tabba Reviewed-by: Fuad Tabba Link: https://lore.kernel.org/r/20250619134817.4075340-1-mark.rutland@arm.com Signed-off-by: Marc Zyngier --- arch/arm64/include/asm/kvm_host.h | 1 - arch/arm64/kvm/arm.c | 4 ---- arch/arm64/kvm/fpsimd.c | 26 -------------------------- 3 files changed, 31 deletions(-) diff --git a/arch/arm64/include/asm/kvm_host.h b/arch/arm64/include/asm/kvm_host.h index d27079968341..3e41a880b062 100644 --- a/arch/arm64/include/asm/kvm_host.h +++ b/arch/arm64/include/asm/kvm_host.h @@ -1480,7 +1480,6 @@ int kvm_vm_ioctl_get_reg_writable_masks(struct kvm *kvm, struct reg_mask_range *range); /* Guest/host FPSIMD coordination helpers */ -int kvm_arch_vcpu_run_map_fp(struct kvm_vcpu *vcpu); void kvm_arch_vcpu_load_fp(struct kvm_vcpu *vcpu); void kvm_arch_vcpu_ctxflush_fp(struct kvm_vcpu *vcpu); void kvm_arch_vcpu_ctxsync_fp(struct kvm_vcpu *vcpu); diff --git a/arch/arm64/kvm/arm.c b/arch/arm64/kvm/arm.c index b223d21c063c..23dd3f3fc3eb 100644 --- a/arch/arm64/kvm/arm.c +++ b/arch/arm64/kvm/arm.c @@ -825,10 +825,6 @@ int kvm_arch_vcpu_run_pid_change(struct kvm_vcpu *vcpu) if (!kvm_arm_vcpu_is_finalized(vcpu)) return -EPERM; - ret = kvm_arch_vcpu_run_map_fp(vcpu); - if (ret) - return ret; - if (likely(vcpu_has_run_once(vcpu))) return 0; diff --git a/arch/arm64/kvm/fpsimd.c b/arch/arm64/kvm/fpsimd.c index 8f6c8f57c6b9..15e17aca1dec 100644 --- a/arch/arm64/kvm/fpsimd.c +++ b/arch/arm64/kvm/fpsimd.c @@ -14,32 +14,6 @@ #include #include -/* - * Called on entry to KVM_RUN unless this vcpu previously ran at least - * once and the most recent prior KVM_RUN for this vcpu was called from - * the same task as current (highly likely). - * - * This is guaranteed to execute before kvm_arch_vcpu_load_fp(vcpu), - * such that on entering hyp the relevant parts of current are already - * mapped. - */ -int kvm_arch_vcpu_run_map_fp(struct kvm_vcpu *vcpu) -{ - struct user_fpsimd_state *fpsimd = ¤t->thread.uw.fpsimd_state; - int ret; - - /* pKVM has its own tracking of the host fpsimd state. */ - if (is_protected_kvm_enabled()) - return 0; - - /* Make sure the host task fpsimd state is visible to hyp: */ - ret = kvm_share_hyp(fpsimd, fpsimd + 1); - if (ret) - return ret; - - return 0; -} - /* * Prepare vcpu for saving the host's FPSIMD state and loading the guest's. * The actual loading is done by the FPSIMD access trap taken to hyp.