From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1AD01C25B6B for ; Fri, 27 Oct 2023 00:55:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1345060AbjJ0AzA (ORCPT ); Thu, 26 Oct 2023 20:55:00 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38046 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1345018AbjJ0Ay7 (ORCPT ); Thu, 26 Oct 2023 20:54:59 -0400 Received: from mail-yb1-xb4a.google.com (mail-yb1-xb4a.google.com [IPv6:2607:f8b0:4864:20::b4a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 543311B5 for ; Thu, 26 Oct 2023 17:54:57 -0700 (PDT) Received: by mail-yb1-xb4a.google.com with SMTP id 3f1490d57ef6-d9ab79816a9so1243606276.3 for ; Thu, 26 Oct 2023 17:54:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1698368096; x=1698972896; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=bkuZQVHnF0aSkP/dIjheAABr7DI7ra4xf7ceUlIhIOA=; b=N5vy/BojceYcyZsXOErv9zlqMz1YHVjjgIddiN4EzVvc+LKvh7WUmN6EwF9jycZquG +Mb1ojPiJFciP1PWnyLDQc60VyVp/soJDRKccS60oDKonDjLxB1zQPDqEvPyuWsxjpoQ utzhW01A6U9is1aAtx7IY4OAsJyAan2JMlz5fw/9TMUpY8T68GIf8f3ckH1zqsB5NVfQ 6jcbk+Tf6i1jO4DmdPwR1NXu431HnoR3DeUcI0bzulPOv5RbkCvRXjMKxU5JSL1yuS7/ ghitgYvgvmA5SIdscnxFNL2YmWU8V23TDUqPrvIdzjy8GevIxVV5IFJ0SP2cUdytMiAq pldQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1698368096; x=1698972896; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=bkuZQVHnF0aSkP/dIjheAABr7DI7ra4xf7ceUlIhIOA=; b=AZnmuAbzAb+RS3Qm7CCRpdfXf77aewArR0xBmdjUIbVqiLM/FseFramHZNwKeU8DVc MrR4xvxhEEAPmau8HoMU5h9jinO6Z+Zu24MxEyMCiotSERcQu7mI3TSxduUU+g5/I0UV Rm8bpoyRKZKHjW68zVjh9YvE4e7klY7RxQNI6/GNord91CmMvLmtxpaKEMOb/FwUBNmV IodjbXAVuP98qqUYE0jcteGNym3Wk8Ict1AeVclzbN+ajh0/1tcJ/CRVKmkBibJaiLNA SsUldsaIsn39OtbX6bW6yJJ/jEiT8MizEbp/VsisYSAe5uq0p6EucF90kOi+sjUVTqcR YFEg== X-Gm-Message-State: AOJu0YxiERnutmUu8rVU/ZvI0kEgnIB+zxDH9lSFpIfdEIqKnl69UxIT oXemH3qvDYTkmWPJ2C3yxa14MvhHZAs= X-Google-Smtp-Source: AGHT+IFzmJoqDgYO9QXDRmkYoxqCR+kjdKTksziWrDJdDTfTH+RScme8Nu0cffkwjhcLtTaBByM2IWGLXsM= X-Received: from zagreus.c.googlers.com ([fda3:e722:ac3:cc00:7f:e700:c0a8:5c37]) (user=seanjc job=sendgmr) by 2002:a25:494:0:b0:d13:856b:c10a with SMTP id 142-20020a250494000000b00d13856bc10amr22985ybe.3.1698368096547; Thu, 26 Oct 2023 17:54:56 -0700 (PDT) Date: Thu, 26 Oct 2023 17:54:54 -0700 In-Reply-To: Mime-Version: 1.0 References: Message-ID: Subject: Re: Run user level code in guest in a new KVM selftest From: Sean Christopherson To: Xin Li Cc: kvm@vger.kernel.org Content-Type: text/plain; charset="us-ascii" Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Thu, Oct 26, 2023, Xin Li wrote: > Hi Sean, > > I'm adding a nested exception selftest for FRED, which needs to run > user level code in guest. I have to add the following hack for that: > > diff --git a/tools/testing/selftests/kvm/lib/x86_64/processor.c > b/tools/testing/selftests/kvm/lib/x86_64/processor.c > index d8288374078e..72928c07ccbe 100644 > --- a/tools/testing/selftests/kvm/lib/x86_64/processor.c > +++ b/tools/testing/selftests/kvm/lib/x86_64/processor.c > @@ -159,6 +159,7 @@ static uint64_t *virt_create_upper_pte(struct kvm_vm > *vm, > > if (!(*pte & PTE_PRESENT_MASK)) { > *pte = PTE_PRESENT_MASK | PTE_WRITABLE_MASK; > + *pte |= PTE_USER_MASK; > if (current_level == target_level) > *pte |= PTE_LARGE_MASK | (paddr & > PHYSICAL_PAGE_MASK); > else > @@ -222,6 +223,7 @@ void __virt_pg_map(struct kvm_vm *vm, uint64_t vaddr, > uint64_t paddr, int level) > TEST_ASSERT(!(*pte & PTE_PRESENT_MASK), > "PTE already present for 4k page at vaddr: 0x%lx\n", > vaddr); > *pte = PTE_PRESENT_MASK | PTE_WRITABLE_MASK | (paddr & > PHYSICAL_PAGE_MASK); > + *pte |= PTE_USER_MASK; > } > > void virt_arch_pg_map(struct kvm_vm *vm, uint64_t vaddr, uint64_t paddr) > > > Is there an exiting selftest running user level code in guest? Nope, not that I know of. > It seems there is none as the USER bit in PTEs is never set, what have I > missed? Nothing. > If such a facility doesn't exist, we probably need to find a > clean solution to add the USER bit in user level page table mappings > (which seems not yet clearly defined yet). Yes, being able to run usercode would be very nice indeed. It should be a lot simpler than KUT since we can stuff guest state directly. The big hiccup is SMEP and SMAP, e.g. we can't just set PTE_USER_MASK blindly :-( My best off-the-top-of-my-head idea is to play games with "enum vm_guest_mode" so that we know from time zero that the guest will be run in user mode, e.g. so that loading the initial guest_code can map it for user.