From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wm1-f45.google.com (mail-wm1-f45.google.com [209.85.128.45]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 0BDE13FA5FC for ; Thu, 23 Jul 2026 15:29:43 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.45 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784820586; cv=none; b=DUSIjFBowsadvrXKsRMeciVBmAopSq/dYo5xCXBfxWG+Jq6iLRex5dPOMavMfdraTkwfvOJDQa6qwycihprN9eHbOufvTbiOuc8Wh3yBjEnDbrNZQiYif6KQq6TxsA1EL7eriF0S7htFi1Pe9goqjx4/OMqJsl35mzzVpG6nAyE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1784820586; c=relaxed/simple; bh=b+Dy8uMnMtF4EY2uXcTzTNWGbKJO4obdHHaMV4tsUV0=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=YtGJpBvkBnrkvqCNvcQeEttvHOPVWg1IiLZb2TNJBlZPmg48mdjqEeBZpKOh99m7EGPRm/kh+eWRzufIqSXjZ+0J3DrvOvKun/RQrpiw5uQhzW+6e38tqvT7cyB7kVPrl8YKlMfVxvn4VrBFYr3w8H6dpbEcVL75UXv1rSAk378= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=lcV5HmRZ; arc=none smtp.client-ip=209.85.128.45 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="lcV5HmRZ" Received: by mail-wm1-f45.google.com with SMTP id 5b1f17b1804b1-4954bb689dfso46985e9.1 for ; Thu, 23 Jul 2026 08:29:43 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1784820582; x=1785425382; darn=vger.kernel.org; h=in-reply-to:content-disposition:content-type:mime-version :references:message-id:subject:cc:to:from:date:from:to:cc:subject :date:message-id:reply-to:content-type; bh=az69NFcHQRpQtQpk0RYT0bOWRtpe4QIe7DhS238fcTI=; b=lcV5HmRZTQYO6HQcOG16U+EM99f4h/pdnAlDhHVtls6WV0BCWufe45eB2nzNC5Tt0y zhFxq0aThdt0z7KB33x083eFbdmzfgoCJrYv1EV7VhcyW2HBXyazS1fTZjLrBvGQleGc Dr/ycFnraSgW9RE8Sq/xQXl7+ds480rZtVdlDd7W7nnuHO5vqDO93v2U5Mr03ItJGF+/ 8e13nAPUJX7VYgJlD9UDY3//xdXLDDyAoOmwSuRcM5tF9pYJbb0vddEVQhgRH08fRBut xHUfqit7zJrvgFc2bwo7gfy3KIGhlyc/DuB+LFcmZtz2Mz7rnK9WT03IiwtQW6/8oxWl BqFA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1784820582; x=1785425382; h=in-reply-to:content-disposition:content-type:mime-version :references:message-id:subject:cc:to:from:date:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to :content-type; bh=az69NFcHQRpQtQpk0RYT0bOWRtpe4QIe7DhS238fcTI=; b=bE41NW0xzbuALp8Q6ODAFMk5yxWQOmQU/avXgQLx9/yTjwcNDNGSgqd647aao5T+Gw 7u9psL/ZKv/MhNHhJ5cC80GjddFTHYhXfX2b8VLFWc4fViBPGe5IYPY8iZgpgXFe0/y6 q6Im7gGy+PU++sUj53yaq0zB9kPqv53VZz2vd5ROFAqkE01gOpTgYQh7nbFjBMrrxj95 0G+y3XkX0pANrjE5O9QfK/r7nuIAbDGtjI3YqgHpqXXgxtlAJ4fPFIMb0Hgd62Une9KK c+WAgbsiluu9KHoyFiWpDOsPihogVDjgicwNNbQCyyhdA6UZFHobCvJWcb61wVCSRK5Q CrrA== X-Forwarded-Encrypted: i=1; AHgh+Rp2zRjV/le2h6UnckQsAIF6vQin1htQXh4/K9ruVTI7P5i96zpzrayx/85jFt8hr9Jkw8/OUW6jYBwsOQA=@vger.kernel.org X-Gm-Message-State: AOJu0YxKW6gcgEoCeJrBAUZM7NozEZPE64lUCYtlwbz1tC/BWzF3Ms42 XZFD2zGqcKlebMf/G7ur9DxVFFNU3oPV1sEVe0tJJSn/5Ev3LlOT76cAJ2XoF1bSXg== X-Gm-Gg: AR+sD12Zpyj86EetOuKdTLgOZ7nyapBYwch1JPEmBG+BC4j75oTP5KQB90MlF/3Jhoe P1TqVjvn5T8gfFAPPFs4PfQtv7BmGNZkDsBwE5Wv/o6gF9QMfFaEr1ZsttN+MktaZJJ9h4mHFeL gSBMvxfaoPrkbeUmAu2hpm71po/8Tp5odEsLypsP6swsrGqf/iN8sXhZM0bO4aEDFMJoPurg8W9 v9LExSnfmSW81AiPCfSaLc6lv+DeHZUFWlq+jTH1X6+TgpbsAk88oMdJjtFlU6fD1dOGEAnJaUj tmQhYDnjOTlRIrA/MfK2tFsya+aAK8urdYRqwbDgvuDyZ4+mcvvgkYwHn+sSuGhGrxD3umhgKQa 6wjLRQ/dEJG2kxsd3DwRdJFjpFR/FOxi91PV4lslq+8boJQ1ImDljECovkDV1hZG9raa57g/9Vg s1o4LmixslPswRH9lpcAksayxOLLES2ZKrhqzWPGIjKZg= X-Received: by 2002:a05:600c:25a:b0:495:4593:616c with SMTP id 5b1f17b1804b1-49573dbe5f0mr1298465e9.1.1784820581451; Thu, 23 Jul 2026 08:29:41 -0700 (PDT) Received: from google.com (145.16.38.34.bc.googleusercontent.com. [34.38.16.145]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-47f85c531afsm15860709f8f.24.2026.07.23.08.29.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 23 Jul 2026 08:29:40 -0700 (PDT) Date: Thu, 23 Jul 2026 15:29:37 +0000 From: Sebastian Ene To: Mostafa Saleh Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kvmarm@lists.linux.dev, iommu@lists.linux.dev, catalin.marinas@arm.com, will@kernel.org, maz@kernel.org, oliver.upton@linux.dev, joey.gouly@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, joro@8bytes.org, jgg@ziepe.ca, mark.rutland@arm.com, qperret@google.com, tabba@google.com, vdonnefort@google.com, keirf@google.com Subject: Re: [PATCH v7 07/24] KVM: arm64: iommu: Shadow host stage-2 page table Message-ID: References: <20260715115906.2664882-1-smostafa@google.com> <20260715115906.2664882-8-smostafa@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260715115906.2664882-8-smostafa@google.com> On Wed, Jul 15, 2026 at 11:58:48AM +0000, Mostafa Saleh wrote: > Create a page-table for the IOMMU that shadows the host CPU stage-2 > to establish DMA isolation. > > An initial snapshot is created after the driver init, then > on every permission change a callback would be called for > the IOMMU driver to update the page table. > > There are 3 different ways to add the callback: > 1) In the high level memory transitions: (__pkvm_host_donate_hyp(), > __pkvm_host_donate_guest()... > > 2) In Lower level functions covering all transitions > - host_stage2_set_owner_metadata_locked() which covers: > - __pkvm_host_donate_hyp() > - __pkvm_host_donate_guest() > - __pkvm_host_donate_hyp() > - __pkvm_guest_unshare_host() > - host_stage2_set_owner_locked() only for ID_HOST which covers: > - __pkvm_hyp_donate_host() > - __pkvm_host_force_reclaim_page_guest() > - __pkvm_host_reclaim_page_guest() > - __pkvm_guest_share_host() > > 3) In the lowest level function __host_update_page_state(), which > requires only one callback. However, in that case the page state > is not enough as we might need to know the old state also. > > Option #2 was implemented here. > > For some cases, an SMMUv3 may be able to share the same page-table > used with the host CPU stage-2 directly. > > However, this is too strict and requires changes to the core hypervisor > page-table code, plus it would require the hypervisor to handle IOMMU > page-faults. This can be added later as an optimization for SMMUV3. > > Signed-off-by: Mostafa Saleh > --- > arch/arm64/kvm/hyp/include/nvhe/iommu.h | 4 + > arch/arm64/kvm/hyp/include/nvhe/mem_protect.h | 1 + > arch/arm64/kvm/hyp/nvhe/iommu.c | 129 +++++++++++++++++- > arch/arm64/kvm/hyp/nvhe/mem_protect.c | 27 ++-- > 4 files changed, 145 insertions(+), 16 deletions(-) > > diff --git a/arch/arm64/kvm/hyp/include/nvhe/iommu.h b/arch/arm64/kvm/hyp/include/nvhe/iommu.h > index df3d0cc5d4db..857d7dd2ebc3 100644 > --- a/arch/arm64/kvm/hyp/include/nvhe/iommu.h > +++ b/arch/arm64/kvm/hyp/include/nvhe/iommu.h > @@ -3,11 +3,15 @@ > #define __ARM64_KVM_NVHE_IOMMU_H__ > > #include > +#include > > struct pkvm_iommu_ops { > int (*init)(void); > + int (*host_stage2_idmap)(phys_addr_t start, phys_addr_t end, int prot); Hi Mostafa, Maybe host_stage2_idmap_locked, since it is invoked while the host stage-2 lock is acquired ? > }; > > int pkvm_iommu_init(void); > > +int pkvm_iommu_host_stage2_idmap(phys_addr_t start, phys_addr_t end, > + enum kvm_pgtable_prot prot); > #endif /* __ARM64_KVM_NVHE_IOMMU_H__ */ > diff --git a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h > index 51b0eb3844a9..99b821b3cf65 100644 > --- a/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h > +++ b/arch/arm64/kvm/hyp/include/nvhe/mem_protect.h > @@ -59,6 +59,7 @@ int __pkvm_host_test_clear_young_guest(u64 gfn, u64 nr_pages, bool mkold, struct > int __pkvm_host_mkyoung_guest(u64 gfn, struct pkvm_hyp_vcpu *vcpu); > > bool addr_is_memory(phys_addr_t phys); > + > int host_stage2_idmap_locked(phys_addr_t addr, u64 size, enum kvm_pgtable_prot prot); > int host_stage2_set_owner_locked(phys_addr_t addr, u64 size, u8 owner_id); > int kvm_host_prepare_stage2(void *pgt_pool_base); > diff --git a/arch/arm64/kvm/hyp/nvhe/iommu.c b/arch/arm64/kvm/hyp/nvhe/iommu.c > index ef456eff42d2..08009609ec59 100644 > --- a/arch/arm64/kvm/hyp/nvhe/iommu.c > +++ b/arch/arm64/kvm/hyp/nvhe/iommu.c > @@ -4,16 +4,137 @@ > * > * Copyright (C) 2022 Linaro Ltd. > */ > +#include > +#include > + > #include > +#include > +#include > > /* Only one set of ops supported */ > struct pkvm_iommu_ops *pkvm_iommu_ops; > > -int pkvm_iommu_init(void) > +/* Protected by host_mmu.lock */ > +static bool pkvm_idmap_initialized; > + > +static inline int pkvm_to_iommu_prot(enum kvm_pgtable_prot prot) > { > - /* Keep DMA isolation optional. */ > - if (!pkvm_iommu_ops || !pkvm_iommu_ops->init) > + int iommu_prot = 0; > + > + if (prot & KVM_PGTABLE_PROT_R) > + iommu_prot |= IOMMU_READ; > + if (prot & KVM_PGTABLE_PROT_W) > + iommu_prot |= IOMMU_WRITE; > + > + /* We don't understand that, might be dangerous. */ > + WARN_ON(prot & ~PKVM_HOST_MEM_PROT); > + return iommu_prot; > +} > + > +/* > + * IOMMU page tables are shadowed and not shared, that is mainly because: > + * - Possible inconsistency between IOMMU and CPU features or format. > + * - KVM relies on handling in page faults (BBM, lazy mapping). > + */ > +static int __snapshot_host_stage2(const struct kvm_pgtable_visit_ctx *ctx, > + enum kvm_pgtable_walk_flags visit) > +{ > + u64 start = ctx->addr; > + u64 block_end = ALIGN_DOWN(ctx->addr, kvm_granule_size(ctx->level)) + > + kvm_granule_size(ctx->level); > + u64 end = min(ctx->end, block_end); > + kvm_pte_t pte = *ctx->ptep; > + bool is_memory = *(bool *)ctx->arg; > + int prot; > + > + /* > + * Keep annotated PTEs unmapped, and map everything else even lazily > + * mapped PTEs(0), as the IOMMU can't handle page faults. > + * That maps the whole address space which can be large, but that doesn't > + * use a lot of memory as it will be mostly large block (1 GB with 4kb pages) > + */ > + if (pte && !kvm_pte_valid(pte)) > return 0; > > - return pkvm_iommu_ops->init(); > + if (kvm_pte_valid(pte)) > + prot = pkvm_to_iommu_prot(kvm_pgtable_stage2_pte_prot(pte)); > + else > + prot = IOMMU_READ | IOMMU_WRITE; If it's invalid in the host stage-2 why do you make it read/write in the IOMMU ? Shouldn't it be an invalid descriptor in the IOMMU pagetables as well ? > + > + if (!is_memory) > + prot |= IOMMU_MMIO; > + > + return pkvm_iommu_ops->host_stage2_idmap(start, end, prot); > +} > + > +static int pkvm_iommu_snapshot_host_stage2(void) > +{ > + struct kvm_pgtable *pgt = &host_mmu.pgt; > + bool is_memory; > + struct kvm_pgtable_walker walker = { > + .cb = __snapshot_host_stage2, > + .flags = KVM_PGTABLE_WALK_LEAF, > + .arg = &is_memory, > + }; > + int ret = 0, i; > + u64 start = 0; > + > + hyp_spin_lock(&host_mmu.lock); > + for (i = 0; i < hyp_memblock_nr; i++) { > + struct memblock_region *reg = &hyp_memory[i]; > + > + if (start < reg->base) { > + is_memory = false; > + ret = kvm_pgtable_walk(pgt, start, reg->base - start, &walker); > + if (ret) > + goto out_unlock; > + } > + > + is_memory = true; > + ret = kvm_pgtable_walk(pgt, reg->base, reg->size, &walker); > + if (ret) > + goto out_unlock; > + > + start = reg->base + reg->size; > + } > + > + if (start < BIT(pgt->ia_bits)) { > + is_memory = false; > + ret = kvm_pgtable_walk(pgt, start, BIT(pgt->ia_bits) - start, &walker); > + if (ret) > + goto out_unlock; > + } > + > + pkvm_idmap_initialized = true; > + > +out_unlock: > + hyp_spin_unlock(&host_mmu.lock); > + return ret; > +} > + > +int pkvm_iommu_init(void) > +{ > + int ret; > + > + /* Keep DMA isolation optional. */ > + if (!pkvm_iommu_ops || !pkvm_iommu_ops->init || > + !pkvm_iommu_ops->host_stage2_idmap) > + return 0; Shouldn't this scream or return not supported ? > + > + ret = pkvm_iommu_ops->init(); > + if (ret) > + return ret; > + > + return pkvm_iommu_snapshot_host_stage2(); If pkvm_iommu_snapshot_host_stage2() fails would you have to provide a ->deinit() corresponding callback ? > +} > + > +int pkvm_iommu_host_stage2_idmap(phys_addr_t start, phys_addr_t end, > + enum kvm_pgtable_prot prot) > +{ > + hyp_assert_lock_held(&host_mmu.lock); > + > + if (!pkvm_idmap_initialized) > + return 0; > + > + return pkvm_iommu_ops->host_stage2_idmap(start, end, pkvm_to_iommu_prot(prot)); > } > diff --git a/arch/arm64/kvm/hyp/nvhe/mem_protect.c b/arch/arm64/kvm/hyp/nvhe/mem_protect.c > index d803b3dd4cb4..ce610274bda0 100644 > --- a/arch/arm64/kvm/hyp/nvhe/mem_protect.c > +++ b/arch/arm64/kvm/hyp/nvhe/mem_protect.c > @@ -17,6 +17,7 @@ > > #include > #include > +#include > #include > #include > #include > @@ -596,16 +597,15 @@ 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) { > - /* > - * 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; > + if (ret) > + return 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 pkvm_iommu_host_stage2_idmap(addr, addr + size, 0); > } > > int host_stage2_set_owner_locked(phys_addr_t addr, u64 size, u8 owner_id) > @@ -618,8 +618,10 @@ int host_stage2_set_owner_locked(phys_addr_t addr, u64 size, u8 owner_id) > return -EPERM; > > ret = host_stage2_idmap_locked(addr, size, PKVM_HOST_MEM_PROT); > - if (!ret) > - __host_update_page_state(addr, size, PKVM_PAGE_OWNED); > + if (ret) > + break; > + __host_update_page_state(addr, size, PKVM_PAGE_OWNED); > + ret = pkvm_iommu_host_stage2_idmap(addr, addr + size, PKVM_HOST_MEM_PROT); > break; > case PKVM_ID_HYP: > ret = host_stage2_set_owner_metadata_locked(addr, size, > @@ -1022,6 +1024,7 @@ int __pkvm_guest_share_host(struct pkvm_hyp_vcpu *vcpu, u64 gfn) > pkvm_mkstate(KVM_PGTABLE_PROT_RWX, PKVM_PAGE_SHARED_OWNED), > &vcpu->vcpu.arch.pkvm_memcache, 0)); > WARN_ON(__host_set_page_state_range(phys, PAGE_SIZE, PKVM_PAGE_SHARED_BORROWED)); > + WARN_ON(pkvm_iommu_host_stage2_idmap(phys, phys + PAGE_SIZE, PKVM_HOST_MEM_PROT)); > unlock: > guest_unlock_component(vm); > host_unlock_component(); > -- > 2.55.0.141.g00534a21ce-goog >