From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-182.mta1.migadu.com (out-182.mta1.migadu.com [95.215.58.182]) (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 7152F2DC76F for ; Thu, 11 Sep 2025 18:43:09 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.182 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757616193; cv=none; b=Y4KfAjwojp7EBZlJpBriS+Fdvekk1BOFTwNZDltARD2C88WP006/LBmm4HxARMYT2gxR2HdLvtX2oCwKTKmsXS/iC9X3/6481kke1jBZMo94BjXfslpJmO91oWXvc+toMGyo5Rf1OWDJ9kOM05lluTgl1b1pMo9jU7MUTIW7odo= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757616193; c=relaxed/simple; bh=EcEcABLK/dcKQ9JWVUCiNd/eISIFCjI2vQDwfd4qgsA=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=FhnSLeftjt2dRpXoCfzWfkXIM6V8Rp0f6OuMtj+bwgsDmLTJMEUtMu38yhCqvqv7opaEM2KgNxjqhXygZessP0AtvZ7YK6/cFRPVNYCH/R1neb+Tnye/UC+CwOvLrAo5aBT9wRzpEQ0J/2mTR3ltdkoSTS22C6dntgjWyFea9Z8= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=XXxdyqbW; arc=none smtp.client-ip=95.215.58.182 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="XXxdyqbW" Date: Thu, 11 Sep 2025 11:42:50 -0700 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1757616177; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=JKfsBIjjBs8pCarTDYZ380mGeD1i48PO8H8V6haIuBY=; b=XXxdyqbW2SGskkdgZ/rJMJue/1nScUY19rrTLrPPz4OVLJMvxhMn67kkpt+DVXOfnxcXwP rUi/hBVVpalMpFcdyXaIbMKbPeSzQCr05n2lwybhV8Vz3naZLTMdx2HAubQSlBd6dF78Ti 0kjk/i9g408ssx6NGLP8uPpZ436EaWs= X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: Oliver Upton To: Jack Thomson Cc: maz@kernel.org, pbonzini@redhat.com, joey.gouly@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, catalin.marinas@arm.com, will@kernel.org, shuah@kernel.org, linux-arm-kernel@lists.infradead.org, kvmarm@lists.linux.dev, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, isaku.yamahata@intel.com, roypat@amazon.co.uk, kalyazin@amazon.co.uk, jackabt@amazon.com Subject: Re: [PATCH 3/6] KVM: arm64: Add pre_fault_memory implementation Message-ID: References: <20250911134648.58945-1-jackabt.amazon@gmail.com> <20250911134648.58945-4-jackabt.amazon@gmail.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: <20250911134648.58945-4-jackabt.amazon@gmail.com> X-Migadu-Flow: FLOW_OUT On Thu, Sep 11, 2025 at 02:46:45PM +0100, Jack Thomson wrote: > @@ -1607,7 +1611,7 @@ static int __user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, > struct kvm_s2_trans *nested, > struct kvm_memory_slot *memslot, > long *page_size, unsigned long hva, > - bool fault_is_perm) > + bool fault_is_perm, bool pre_fault) > { > int ret = 0; > bool topup_memcache; > @@ -1631,10 +1635,13 @@ static int __user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa, > vm_flags_t vm_flags; > enum kvm_pgtable_walk_flags flags = KVM_PGTABLE_WALK_MEMABORT_FLAGS; > > + if (pre_fault) > + flags |= KVM_PGTABLE_WALK_PRE_FAULT; > + > if (fault_is_perm) > fault_granule = kvm_vcpu_trap_get_perm_fault_granule(vcpu); > - write_fault = kvm_is_write_fault(vcpu); > - exec_fault = kvm_vcpu_trap_is_exec_fault(vcpu); > + write_fault = !pre_fault && kvm_is_write_fault(vcpu); > + exec_fault = !pre_fault && kvm_vcpu_trap_is_exec_fault(vcpu); I'm not a fan of this. While user_mem_abort() is already a sloppy mess, one thing we could reliably assume is the presence of a valid fault context. Now we need to remember to special-case our interpretation of a fault on whether or not we're getting invoked for a pre-fault. I'd rather see the pre-fault infrastructure compose a synthetic fault context (HPFAR_EL2, ESR_EL2, etc.). It places the complexity where it belongs and the rest of the abort handling code should 'just work'. > +long kvm_arch_vcpu_pre_fault_memory(struct kvm_vcpu *vcpu, > + struct kvm_pre_fault_memory *range) > +{ > + int r; > + hva_t hva; > + phys_addr_t end; > + long page_size; > + struct kvm_memory_slot *memslot; > + phys_addr_t ipa = range->gpa; > + gfn_t gfn = gpa_to_gfn(range->gpa); > + > + while (true) { > + page_size = PAGE_SIZE; > + memslot = gfn_to_memslot(vcpu->kvm, gfn); > + if (!memslot) > + return -ENOENT; > + > + if (kvm_slot_has_gmem(memslot)) { > + r = __gmem_abort(vcpu, ipa, NULL, memslot, false, true); > + } else { > + hva = gfn_to_hva_memslot_prot(memslot, gfn, NULL); > + if (kvm_is_error_hva(hva)) > + return -EFAULT; > + r = __user_mem_abort(vcpu, ipa, NULL, memslot, &page_size, hva, false, > + true); > + } > + > + if (r != -EAGAIN) > + break; > + > + if (signal_pending(current)) > + return -EINTR; > + > + if (kvm_check_request(KVM_REQ_VM_DEAD, vcpu)) > + return -EIO; > + > + cond_resched(); > + }; Why do we need another retry loop? Looks like we've already got one in the arch-generic code. Thanks, Oliver