From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7E4872D46CE; Tue, 25 Aug 2026 16:01:31 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787673692; cv=none; b=W8AdVFXl7JMx4W/rlYYovVdF8BhpfMRPXA8nqOoBe6lAZJEEFFQeJSDrKXSZqJxzEIWfKDWEGJnyZ81jU1xEZwZmF9Kv+mMEA1PuGSwbwi67+m0VAXnjK2ma/0qcNbcmSTbiSY2X9NFgIRUuNqmfrUG00a2KtsxfJjmyqUphdos= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1787673692; c=relaxed/simple; bh=OK8qMkoBFUsKSDW1WXYaJvEYhrPVl7NXbf8oJ3V+T3w=; h=From:Date:Subject:MIME-Version:Content-Type:Message-Id:References: In-Reply-To:To:Cc; b=a/EoAqdXL0u3nmCsuhbMMNq+P5mSAQaL2vZ03Z+NXiDLSoMMrpBTXT7uKQKFmBOZtR2LHK/2Jp1sfgTXQP2LgSKEbrMQq6eCyxBb7c1noYJO5rcVG2J6Mx3lewREKdKiaUIG7Uiz6TLv4ajvLwGPf9QV5PumnThfzO7mx9/b+nc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=dHVqBfDS; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="dHVqBfDS" Received: by smtp.kernel.org (Postfix) with ESMTPSA id E1A1A1F00A3A; Tue, 25 Aug 2026 16:01:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1787673691; bh=2n/GT1zNcErOZDVCRG/HrutbSxrG2jWsh4QWz8aUK78=; h=From:Date:Subject:References:In-Reply-To:To:Cc; b=dHVqBfDStyFZhJftkYg6JAcTecPfldfshUIibfnQn0qeJVNaujjSLd6QcRAmlIRXf tTdHX3/a0nT8Hf2scWZ/o2rQ6nx/67V89ay+ONEXUq6aQ8Rm4AxNd3m0NwOk3UYgJm bVuEat7hL3MtjEf9FSh5iHr7SvtyvoQwT1X3z7olEPI7QlmA+rDexmL9ltF33TOOUD NNfdSnAfxZ/FwY0G3aq6lRTN4hdvcVD/dmrDytX67c9FAGK/UkHwS2bgvzhSH6/sHB Vl3QawoYBQfhM7anQ84gCbKoPubESoBoOX3vJukavt8xVf04nGHECoA8X8NeuIwjvk Sl/WWQKBAa1UA== From: "Lorenzo Stoakes (ARM)" Date: Tue, 25 Aug 2026 17:00:37 +0100 Subject: [PATCH 3/8] KVM: arm64: Propagate and use kvm_s2_fault_result on S2 fault Precedence: bulk X-Mailing-List: linux-doc@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Message-Id: <20260825-kvm-arm-prefault-v1-3-befe8947702e@kernel.org> References: <20260825-kvm-arm-prefault-v1-0-befe8947702e@kernel.org> In-Reply-To: <20260825-kvm-arm-prefault-v1-0-befe8947702e@kernel.org> To: Catalin Marinas , Will Deacon , Marc Zyngier , Oliver Upton , Fuad Tabba , Joey Gouly , Steffen Eiden , Suzuki K Poulose , Zenghui Yu , Paolo Bonzini , Jonathan Corbet Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kvmarm@lists.linux.dev, kvm@vger.kernel.org, linux-doc@vger.kernel.org, linux-kselftest@vger.kernel.org, Jack Thomson , Jack Thomson , Alexandru Elisei , Vincent Donnefort , "Aneesh Kumar K.V" , Sean Christopherson , Claudio Imbrenda , Leo Soares Passos , "Lorenzo Stoakes (ARM)" X-Mailer: b4 0.14.3 X-Developer-Signature: v=1; a=openpgp-sha256; l=4633; i=ljs@kernel.org; h=from:subject:message-id; bh=OK8qMkoBFUsKSDW1WXYaJvEYhrPVl7NXbf8oJ3V+T3w=; b=owGbwMvMwCV2fu7ZrsZH9SKMp9WSGLJ69zgdV7sdlbN67b4bp9Qnd+2ZwBXv6ZRSMyWBYafTD 6b1M/4+7ShlYRDjYpAVU2R5/kV8f5BI2LzOC/5uMHNYmUCGMHBxCsBE3kxnZHj/SLt2l/3/4Oen tq3p/dVhKHUs9ZhC9hflxkr29ZPaBBUZ/lmHSc57WP9DL7rR4+8NuSVptx/YJn6Purp10u1VqzY 9fs0AAA== X-Developer-Key: i=ljs@kernel.org; a=openpgp; fpr=E7F417BF5214569E89D04F46CF9DCD8A81E27F14 When stage 2 page tables fault the net result may either be that a page is mapped, an error occurred or the fault should be retried (-EAGAIN). When a fault succeeds it may be upgraded to a PMD size via transparent_hugepage_adjust(). In order to support KVM pre-faulting the outcome of the fault and the mapping size must be recorded. Track this in the new kvm_s2_fault_result struct, which is threaded through gmem_abort(), user_mem_abort() and kvm_s2_fault_map(). PKVM and SEA aren't relevant to synthetic pre-faulting so neither kvm_inject_sea() nor pkvm_mem_abort() are altered. Actual hardware faulting doesn't require this information, so kvm_handle_guest_abort() simply passes NULL kvm_s2_fault_result to gmem_abort() and user_mem_abort(). Faults are necessarily ephemeral and pre-faulting can't guarantee what may happen in parallel, so do not store the GFN or PFN in kvm_s2_fault_result. Pre-faulting only needs to know what was mapped in at the point of the fault. This struct could be replaced with a pointer to an unsigned long, however it's clearer to separate out the mapped flag and having a struct allows us to easily add additional fields in future as needed. No functional change intended. Suggested-by: Vincent Donnefort Signed-off-by: Lorenzo Stoakes (ARM) --- arch/arm64/kvm/mmu.c | 33 +++++++++++++++++++++++++++------ 1 file changed, 27 insertions(+), 6 deletions(-) diff --git a/arch/arm64/kvm/mmu.c b/arch/arm64/kvm/mmu.c index 80cb520e25b9..da15da4e40e6 100644 --- a/arch/arm64/kvm/mmu.c +++ b/arch/arm64/kvm/mmu.c @@ -1607,6 +1607,11 @@ struct kvm_s2_fault_desc { struct kvm_s2_mmu *mmu; }; +struct kvm_s2_fault_result { + unsigned long mapping_size; + bool mapped; +}; + static bool kvm_s2_fault_is_perm(const struct kvm_s2_fault_desc *s2fd) { return esr_fsc_is_permission_fault(s2fd->esr); @@ -1632,7 +1637,17 @@ static u64 kvm_s2_perm_fault_granule(const struct kvm_s2_fault_desc *s2fd) return BIT(ARM64_HW_PGTABLE_LEVEL_SHIFT(level)); } -static int gmem_abort(const struct kvm_s2_fault_desc *s2fd) +static void populate_fault_result(struct kvm_s2_fault_result *result, + unsigned long mapping_size) +{ + /* A THP upgrade may have altered mapping size. */ + result->mapping_size = mapping_size; + /* -EAGAIN is swallowed so be explicit when we actually map. */ + result->mapped = true; +} + +static int gmem_abort(const struct kvm_s2_fault_desc *s2fd, + struct kvm_s2_fault_result *result) { bool write_fault, exec_fault; const bool perm_fault = kvm_s2_fault_is_perm(s2fd); @@ -1714,6 +1729,8 @@ static int gmem_abort(const struct kvm_s2_fault_desc *s2fd) if ((prot & KVM_PGTABLE_PROT_W) && !ret) mark_page_dirty_in_slot(kvm, s2fd->memslot, gfn); + if (result && !ret) + populate_fault_result(result, PAGE_SIZE); return ret != -EAGAIN ? ret : 0; } @@ -2038,7 +2055,8 @@ static int kvm_s2_fault_compute_prot(const struct kvm_s2_fault_desc *s2fd, static int kvm_s2_fault_map(const struct kvm_s2_fault_desc *s2fd, const struct kvm_s2_fault_vma_info *s2vi, enum kvm_pgtable_prot prot, - void *memcache) + void *memcache, + struct kvm_s2_fault_result *result) { enum kvm_pgtable_walk_flags flags = KVM_PGTABLE_WALK_SHARED; bool writable = prot & KVM_PGTABLE_PROT_W; @@ -2117,12 +2135,15 @@ static int kvm_s2_fault_map(const struct kvm_s2_fault_desc *s2fd, mark_page_dirty_in_slot(kvm, s2fd->memslot, gpa_to_gfn(ipa)); } + if (result && !ret) + populate_fault_result(result, mapping_size); if (ret != -EAGAIN) return ret; return 0; } -static int user_mem_abort(const struct kvm_s2_fault_desc *s2fd) +static int user_mem_abort(const struct kvm_s2_fault_desc *s2fd, + struct kvm_s2_fault_result *result) { const bool perm_fault = kvm_s2_fault_is_perm(s2fd); struct kvm_s2_fault_vma_info s2vi = {}; @@ -2161,7 +2182,7 @@ static int user_mem_abort(const struct kvm_s2_fault_desc *s2fd) return ret; } - return kvm_s2_fault_map(s2fd, &s2vi, prot, memcache); + return kvm_s2_fault_map(s2fd, &s2vi, prot, memcache, result); } /* Resolve the access fault by making the page young again. */ @@ -2440,9 +2461,9 @@ int kvm_handle_guest_abort(struct kvm_vcpu *vcpu) !kvm_s2_fault_is_exec(&s2fd)); if (kvm_slot_has_gmem(memslot)) - ret = gmem_abort(&s2fd); + ret = gmem_abort(&s2fd, NULL); else - ret = user_mem_abort(&s2fd); + ret = user_mem_abort(&s2fd, NULL); } if (ret == 0) -- 2.55.0