From mboxrd@z Thu Jan 1 00:00:00 1970 From: Borislav Petkov Subject: Re: [RFC PATCH v3 15/20] x86: Check for memory encryption on the APs Date: Tue, 22 Nov 2016 20:25:26 +0100 Message-ID: <20161122192526.vg63jjhwsbjwex7i@pd.tnic> References: <20161110003426.3280.2999.stgit@tlendack-t1.amdoffice.net> <20161110003740.3280.57300.stgit@tlendack-t1.amdoffice.net> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Return-path: Content-Disposition: inline In-Reply-To: <20161110003740.3280.57300.stgit@tlendack-t1.amdoffice.net> Sender: linux-doc-owner@vger.kernel.org To: Tom Lendacky Cc: linux-arch@vger.kernel.org, linux-efi@vger.kernel.org, kvm@vger.kernel.org, linux-doc@vger.kernel.org, x86@kernel.org, linux-kernel@vger.kernel.org, kasan-dev@googlegroups.com, linux-mm@kvack.org, iommu@lists.linux-foundation.org, Rik van Riel , Radim =?utf-8?B?S3LEjW3DocWZ?= , Arnd Bergmann , Jonathan Corbet , Matt Fleming , Joerg Roedel , Konrad Rzeszutek Wilk , Paolo Bonzini , Larry Woodman , Ingo Molnar , Andy Lutomirski , "H. Peter Anvin" , Andrey Ryabinin , Alexander Potapenko List-Id: linux-efi@vger.kernel.org On Wed, Nov 09, 2016 at 06:37:40PM -0600, Tom Lendacky wrote: > Add support to check if memory encryption is active in the kernel and that > it has been enabled on the AP. If memory encryption is active in the kernel > but has not been enabled on the AP then do not allow the AP to continue > start up. > > Signed-off-by: Tom Lendacky > --- > arch/x86/include/asm/realmode.h | 12 ++++++++++++ > arch/x86/realmode/init.c | 4 ++++ > arch/x86/realmode/rm/trampoline_64.S | 19 +++++++++++++++++++ > 3 files changed, 35 insertions(+) > > diff --git a/arch/x86/include/asm/realmode.h b/arch/x86/include/asm/realmode.h > index 230e190..850dbe0 100644 > --- a/arch/x86/include/asm/realmode.h > +++ b/arch/x86/include/asm/realmode.h > @@ -1,6 +1,15 @@ > #ifndef _ARCH_X86_REALMODE_H > #define _ARCH_X86_REALMODE_H > > +/* > + * Flag bit definitions for use with the flags field of the trampoline header > + * when configured for X86_64 Let's use kernel nomenclature: "... of the trampoline header in the CONFIG_X86_64 variant." > + */ > +#define TH_FLAGS_SME_ENABLE_BIT 0 > +#define TH_FLAGS_SME_ENABLE BIT_ULL(TH_FLAGS_SME_ENABLE_BIT) BIT() is the proper one for u32 flags variable. > + > +#ifndef __ASSEMBLY__ > + > #include > #include > > @@ -38,6 +47,7 @@ struct trampoline_header { > u64 start; > u64 efer; > u32 cr4; > + u32 flags; > #endif > }; > > @@ -69,4 +79,6 @@ static inline size_t real_mode_size_needed(void) > void set_real_mode_mem(phys_addr_t mem, size_t size); > void reserve_real_mode(void); > > +#endif /* __ASSEMBLY__ */ > + > #endif /* _ARCH_X86_REALMODE_H */ > diff --git a/arch/x86/realmode/init.c b/arch/x86/realmode/init.c > index 44ed32a..a8e7ebe 100644 > --- a/arch/x86/realmode/init.c > +++ b/arch/x86/realmode/init.c > @@ -101,6 +101,10 @@ static void __init setup_real_mode(void) > trampoline_cr4_features = &trampoline_header->cr4; > *trampoline_cr4_features = mmu_cr4_features; > > + trampoline_header->flags = 0; > + if (sme_me_mask) > + trampoline_header->flags |= TH_FLAGS_SME_ENABLE; > + > trampoline_pgd = (u64 *) __va(real_mode_header->trampoline_pgd); > trampoline_pgd[0] = trampoline_pgd_entry.pgd; > trampoline_pgd[511] = init_level4_pgt[511].pgd; > diff --git a/arch/x86/realmode/rm/trampoline_64.S b/arch/x86/realmode/rm/trampoline_64.S > index dac7b20..94e29f4 100644 > --- a/arch/x86/realmode/rm/trampoline_64.S > +++ b/arch/x86/realmode/rm/trampoline_64.S > @@ -30,6 +30,7 @@ > #include > #include > #include > +#include > #include "realmode.h" > > .text > @@ -92,6 +93,23 @@ ENTRY(startup_32) > movl %edx, %fs > movl %edx, %gs > > + /* Check for memory encryption support */ > + bt $TH_FLAGS_SME_ENABLE_BIT, pa_tr_flags > + jnc .Ldone > + movl $MSR_K8_SYSCFG, %ecx > + rdmsr > + bt $MSR_K8_SYSCFG_MEM_ENCRYPT_BIT, %eax > + jc .Ldone > + > + /* > + * Memory encryption is enabled but the MSR has not been set on this > + * CPU so we can't continue Can this ever happen? I mean, we set TH_FLAGS_SME_ENABLE when sme_me_mask is set and this would have happened only if the BSP has MSR_K8_SYSCFG[23] set. How is it possible that that bit won't be set on some of the APs but set on the BSP? I'd assume the BIOS is doing a consistent setting everywhere... -- Regards/Gruss, Boris. Good mailing practices for 400: avoid top-posting and trim the reply.