From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wr0-f200.google.com (mail-wr0-f200.google.com [209.85.128.200]) by kanga.kvack.org (Postfix) with ESMTP id 055066B0387 for ; Tue, 7 Mar 2017 10:00:19 -0500 (EST) Received: by mail-wr0-f200.google.com with SMTP id w37so1381307wrc.2 for ; Tue, 07 Mar 2017 07:00:18 -0800 (PST) Received: from mx2.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id i21si847599wmc.94.2017.03.07.07.00.17 for (version=TLS1 cipher=AES128-SHA bits=128/128); Tue, 07 Mar 2017 07:00:17 -0800 (PST) Date: Tue, 7 Mar 2017 15:59:54 +0100 From: Borislav Petkov Subject: Re: [RFC PATCH v2 08/32] x86: Use PAGE_KERNEL protection for ioremap of memory page Message-ID: <20170307145954.l2fqy5s5h65wbtyz@pd.tnic> References: <148846752022.2349.13667498174822419498.stgit@brijesh-build-machine> <148846761276.2349.4899767672892365544.stgit@brijesh-build-machine> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <148846761276.2349.4899767672892365544.stgit@brijesh-build-machine> Sender: owner-linux-mm@kvack.org List-ID: To: Brijesh Singh Cc: simon.guinot@sequanux.org, linux-efi@vger.kernel.org, kvm@vger.kernel.org, rkrcmar@redhat.com, matt@codeblueprint.co.uk, linux-pci@vger.kernel.org, linus.walleij@linaro.org, gary.hook@amd.com, linux-mm@kvack.org, paul.gortmaker@windriver.com, hpa@zytor.com, cl@linux.com, dan.j.williams@intel.com, aarcange@redhat.com, sfr@canb.auug.org.au, andriy.shevchenko@linux.intel.com, herbert@gondor.apana.org.au, bhe@redhat.com, xemul@parallels.com, joro@8bytes.org, x86@kernel.org, peterz@infradead.org, piotr.luc@intel.com, mingo@redhat.com, msalter@redhat.com, ross.zwisler@linux.intel.com, dyoung@redhat.com, thomas.lendacky@amd.com, jroedel@suse.de, keescook@chromium.org, arnd@arndb.de, toshi.kani@hpe.com, mathieu.desnoyers@efficios.com, luto@kernel.org, devel@linuxdriverproject.org, bhelgaas@google.com, tglx@linutronix.de, mchehab@kernel.org, iamjoonsoo.kim@lge.com, labbott@fedoraproject.org, tony.luck@intel.com, alexandre.bounine@idt.com, kuleshovmail@gmail.com, linux-kernel@vger.kernel.org, mcgrof@kernel.org, mst@redhat.com, linux-crypto@vger.kernel.org, tj@kernel.org, pbonzini@redhat.com, akpm@linux-foundation.org, davem@davemloft.net On Thu, Mar 02, 2017 at 10:13:32AM -0500, Brijesh Singh wrote: > From: Tom Lendacky > > In order for memory pages to be properly mapped when SEV is active, we > need to use the PAGE_KERNEL protection attribute as the base protection. > This will insure that memory mapping of, e.g. ACPI tables, receives the > proper mapping attributes. > > Signed-off-by: Tom Lendacky > --- > diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c > index c400ab5..481c999 100644 > --- a/arch/x86/mm/ioremap.c > +++ b/arch/x86/mm/ioremap.c > @@ -151,7 +151,15 @@ static void __iomem *__ioremap_caller(resource_size_t phys_addr, > pcm = new_pcm; > } > > + /* > + * If the page being mapped is in memory and SEV is active then > + * make sure the memory encryption attribute is enabled in the > + * resulting mapping. > + */ > prot = PAGE_KERNEL_IO; > + if (sev_active() && page_is_mem(pfn)) Hmm, a resource tree walk per ioremap call. This could get expensive for ioremap-heavy workloads. __ioremap_caller() gets called here during boot 55 times so not a whole lot but I wouldn't be surprised if there were some nasty use cases which ioremap a lot. ... > diff --git a/kernel/resource.c b/kernel/resource.c > index 9b5f044..db56ba3 100644 > --- a/kernel/resource.c > +++ b/kernel/resource.c > @@ -518,6 +518,46 @@ int __weak page_is_ram(unsigned long pfn) > } > EXPORT_SYMBOL_GPL(page_is_ram); > > +/* > + * This function returns true if the target memory is marked as > + * IORESOURCE_MEM and IORESOUCE_BUSY and described as other than > + * IORES_DESC_NONE (e.g. IORES_DESC_ACPI_TABLES). > + */ > +static int walk_mem_range(unsigned long start_pfn, unsigned long nr_pages) > +{ > + struct resource res; > + unsigned long pfn, end_pfn; > + u64 orig_end; > + int ret = -1; > + > + res.start = (u64) start_pfn << PAGE_SHIFT; > + res.end = ((u64)(start_pfn + nr_pages) << PAGE_SHIFT) - 1; > + res.flags = IORESOURCE_MEM | IORESOURCE_BUSY; > + orig_end = res.end; > + while ((res.start < res.end) && > + (find_next_iomem_res(&res, IORES_DESC_NONE, true) >= 0)) { > + pfn = (res.start + PAGE_SIZE - 1) >> PAGE_SHIFT; > + end_pfn = (res.end + 1) >> PAGE_SHIFT; > + if (end_pfn > pfn) > + ret = (res.desc != IORES_DESC_NONE) ? 1 : 0; > + if (ret) > + break; > + res.start = res.end + 1; > + res.end = orig_end; > + } > + return ret; > +} So the relevant difference between this one and walk_system_ram_range() is this: - ret = (*func)(pfn, end_pfn - pfn, arg); + ret = (res.desc != IORES_DESC_NONE) ? 1 : 0; so it seems to me you can have your own *func() pointer which does that IORES_DESC_NONE comparison. And then you can define your own workhorse __walk_memory_range() which gets called by both walk_mem_range() and walk_system_ram_range() instead of almost duplicating them. And looking at walk_system_ram_res(), that one looks similar too except the pfn computation. But AFAICT the pfn/end_pfn things are computed from res.start and res.end so it looks to me like all those three functions are crying for unification... -- Regards/Gruss, Boris. SUSE Linux GmbH, GF: Felix ImendA?rffer, Jane Smithard, Graham Norton, HRB 21284 (AG NA 1/4 rnberg) -- -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org