From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pf0-f199.google.com (mail-pf0-f199.google.com [209.85.192.199]) by kanga.kvack.org (Postfix) with ESMTP id BEAC76B0292 for ; Wed, 14 Jun 2017 15:49:12 -0400 (EDT) Received: by mail-pf0-f199.google.com with SMTP id b74so8253447pfj.5 for ; Wed, 14 Jun 2017 12:49:12 -0700 (PDT) Received: from NAM02-BL2-obe.outbound.protection.outlook.com (mail-bl2nam02on0045.outbound.protection.outlook.com. [104.47.38.45]) by mx.google.com with ESMTPS id d4si601561pgc.141.2017.06.14.12.49.11 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-SHA bits=128/128); Wed, 14 Jun 2017 12:49:11 -0700 (PDT) Subject: Re: [PATCH v6 25/34] swiotlb: Add warnings for use of bounce buffers with SME References: <20170607191309.28645.15241.stgit@tlendack-t1.amdoffice.net> <20170607191732.28645.42876.stgit@tlendack-t1.amdoffice.net> <20170614165052.fyn5t4gkq5leczcc@pd.tnic> From: Tom Lendacky Message-ID: <33d1debc-c684-cba1-7d95-493678f086d0@amd.com> Date: Wed, 14 Jun 2017 14:49:02 -0500 MIME-Version: 1.0 In-Reply-To: <20170614165052.fyn5t4gkq5leczcc@pd.tnic> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Borislav Petkov Cc: linux-arch@vger.kernel.org, linux-efi@vger.kernel.org, kvm@vger.kernel.org, linux-doc@vger.kernel.org, x86@kernel.org, kexec@lists.infradead.org, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, linux-mm@kvack.org, iommu@lists.linux-foundation.org, Rik van Riel , =?UTF-8?B?UmFkaW0gS3LEjW3DocWZ?= , Toshimitsu Kani , Arnd Bergmann , Jonathan Corbet , Matt Fleming , "Michael S. Tsirkin" , Joerg Roedel , Konrad Rzeszutek Wilk , Paolo Bonzini , Larry Woodman , Brijesh Singh , Ingo Molnar , Andy Lutomirski , "H. Peter Anvin" , Andrey Ryabinin , Alexander Potapenko , Dave Young , Thomas Gleixner , Dmitry Vyukov On 6/14/2017 11:50 AM, Borislav Petkov wrote: > On Wed, Jun 07, 2017 at 02:17:32PM -0500, Tom Lendacky wrote: >> Add warnings to let the user know when bounce buffers are being used for >> DMA when SME is active. Since the bounce buffers are not in encrypted >> memory, these notifications are to allow the user to determine some >> appropriate action - if necessary. >> >> Signed-off-by: Tom Lendacky >> --- >> arch/x86/include/asm/mem_encrypt.h | 8 ++++++++ >> include/asm-generic/mem_encrypt.h | 5 +++++ >> include/linux/dma-mapping.h | 9 +++++++++ >> lib/swiotlb.c | 3 +++ >> 4 files changed, 25 insertions(+) >> >> diff --git a/arch/x86/include/asm/mem_encrypt.h b/arch/x86/include/asm/mem_encrypt.h >> index f1215a4..c7a2525 100644 >> --- a/arch/x86/include/asm/mem_encrypt.h >> +++ b/arch/x86/include/asm/mem_encrypt.h >> @@ -69,6 +69,14 @@ static inline bool sme_active(void) >> return !!sme_me_mask; >> } >> >> +static inline u64 sme_dma_mask(void) >> +{ >> + if (!sme_me_mask) >> + return 0ULL; >> + >> + return ((u64)sme_me_mask << 1) - 1; >> +} >> + >> /* >> * The __sme_pa() and __sme_pa_nodebug() macros are meant for use when >> * writing to or comparing values from the cr3 register. Having the >> diff --git a/include/asm-generic/mem_encrypt.h b/include/asm-generic/mem_encrypt.h >> index b55c3f9..fb02ff0 100644 >> --- a/include/asm-generic/mem_encrypt.h >> +++ b/include/asm-generic/mem_encrypt.h >> @@ -22,6 +22,11 @@ static inline bool sme_active(void) >> return false; >> } >> >> +static inline u64 sme_dma_mask(void) >> +{ >> + return 0ULL; >> +} >> + >> /* >> * The __sme_set() and __sme_clr() macros are useful for adding or removing >> * the encryption mask from a value (e.g. when dealing with pagetable >> diff --git a/include/linux/dma-mapping.h b/include/linux/dma-mapping.h >> index 4f3eece..e2c5fda 100644 >> --- a/include/linux/dma-mapping.h >> +++ b/include/linux/dma-mapping.h >> @@ -10,6 +10,7 @@ >> #include >> #include >> #include >> +#include >> >> /** >> * List of possible attributes associated with a DMA mapping. The semantics >> @@ -577,6 +578,10 @@ static inline int dma_set_mask(struct device *dev, u64 mask) >> >> if (!dev->dma_mask || !dma_supported(dev, mask)) >> return -EIO; >> + >> + if (sme_active() && (mask < sme_dma_mask())) >> + dev_warn(dev, "SME is active, device will require DMA bounce buffers\n"); > > Something looks strange here: > > you're checking sme_active() before calling sme_dma_mask() and yet in > it, you're checking !sme_me_mask again. What gives? > I guess I don't need the sme_active() check since the second part of the if statement can only ever be true if SME is active (since mask is unsigned). Thanks, Tom > Why not move the sme_active() check into sme_dma_mask() and thus > simplify callers? > -- 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