From patchwork Tue Feb 11 13:52:11 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Joerg Roedel X-Patchwork-Id: 11375639 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 9EADE109A for ; Tue, 11 Feb 2020 13:58:16 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7A4772173E for ; Tue, 11 Feb 2020 13:58:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730050AbgBKN6I (ORCPT ); Tue, 11 Feb 2020 08:58:08 -0500 Received: from 8bytes.org ([81.169.241.247]:52122 "EHLO theia.8bytes.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729503AbgBKNxV (ORCPT ); Tue, 11 Feb 2020 08:53:21 -0500 Received: by theia.8bytes.org (Postfix, from userid 1000) id 33AF1CBB; Tue, 11 Feb 2020 14:53:10 +0100 (CET) From: Joerg Roedel To: x86@kernel.org Cc: hpa@zytor.com, Andy Lutomirski , Dave Hansen , Peter Zijlstra , Thomas Hellstrom , Jiri Slaby , Dan Williams , Tom Lendacky , Juergen Gross , Kees Cook , linux-kernel@vger.kernel.org, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, Joerg Roedel , Joerg Roedel Subject: [PATCH 17/62] x86/boot/compressed/64: Add function to map a page unencrypted Date: Tue, 11 Feb 2020 14:52:11 +0100 Message-Id: <20200211135256.24617-18-joro@8bytes.org> X-Mailer: git-send-email 2.17.1 In-Reply-To: <20200211135256.24617-1-joro@8bytes.org> References: <20200211135256.24617-1-joro@8bytes.org> Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org From: Joerg Roedel This function is needed to map the GHCB for SEV-ES guests. The GHCB is used for communication with the hypervisor, so its content must not be encrypted. Signed-off-by: Joerg Roedel --- arch/x86/boot/compressed/ident_map_64.c | 125 ++++++++++++++++++++++++ arch/x86/boot/compressed/misc.h | 1 + 2 files changed, 126 insertions(+) diff --git a/arch/x86/boot/compressed/ident_map_64.c b/arch/x86/boot/compressed/ident_map_64.c index feb180cced28..04a5ff4bda66 100644 --- a/arch/x86/boot/compressed/ident_map_64.c +++ b/arch/x86/boot/compressed/ident_map_64.c @@ -26,6 +26,7 @@ #include #include #include +#include /* Use the static base for this part of the boot process */ #undef __PAGE_OFFSET #define __PAGE_OFFSET __PAGE_OFFSET_BASE @@ -157,6 +158,130 @@ void initialize_identity_maps(void) write_cr3(top_level_pgt); } +static pte_t *split_large_pmd(struct x86_mapping_info *info, + pmd_t *pmdp, unsigned long __address) +{ + unsigned long page_flags; + unsigned long address; + pte_t *pte; + pmd_t pmd; + int i; + + pte = (pte_t *)info->alloc_pgt_page(info->context); + if (!pte) + return NULL; + + address = __address & PMD_MASK; + /* No large page - clear PSE flag */ + page_flags = info->page_flag & ~_PAGE_PSE; + + /* Populate the PTEs */ + for (i = 0; i < PTRS_PER_PMD; i++) { + set_pte(&pte[i], __pte(address | page_flags)); + address += PAGE_SIZE; + } + + /* + * Ideally we need to clear the large PMD first and do a TLB + * flush before we write the new PMD. But the 2M range of the + * PMD might contain the code we execute and/or the stack + * we are on, so we can't do that. But that should be safe here + * because we are going from large to small mappings and we are + * also the only user of the page-table, so there is no chance + * of a TLB multihit. + */ + pmd = __pmd((unsigned long)pte | info->kernpg_flag); + set_pmd(pmdp, pmd); + /* Flush TLB to establish the new PMD */ + write_cr3(top_level_pgt); + + return pte + pte_index(__address); +} + +static void clflush_page(unsigned long address) +{ + unsigned int flush_size; + char *cl, *start, *end; + + /* + * Hardcode cl-size to 64 - CPUID can't be used here because that might + * cause another #VC exception and the GHCB is not ready to use yet. + */ + flush_size = 64; + start = (char *)(address & PAGE_MASK); + end = start + PAGE_SIZE; + + /* + * First make sure there are no pending writes on the cache-lines to + * flush. + */ + asm volatile("mfence" : : : "memory"); + + for (cl = start; cl != end; cl += flush_size) + clflush(cl); +} + +static int __set_page_decrypted(struct x86_mapping_info *info, + unsigned long address) +{ + unsigned long scratch, *target; + pgd_t *pgdp = (pgd_t *)top_level_pgt; + p4d_t *p4dp; + pud_t *pudp; + pmd_t *pmdp; + pte_t *ptep, pte; + + /* + * First make sure there is a PMD mapping for 'address'. + * It should already exist, but keep things generic. + * + * To map the page just read from it and fault it in if there is no + * mapping yet. add_identity_map() can't be called here because that + * would unconditionally map the address on PMD level, destroying any + * PTE-level mappings that might already exist. Also do something + * useless with 'scratch' so the access won't be optimized away. + */ + target = (unsigned long *)address; + scratch = *target; + arch_cmpxchg(target, scratch, scratch); + + /* + * The page is mapped at least with PMD size - so skip checks and walk + * directly to the PMD. + */ + p4dp = p4d_offset(pgdp, address); + pudp = pud_offset(p4dp, address); + pmdp = pmd_offset(pudp, address); + + if (pmd_large(*pmdp)) + ptep = split_large_pmd(info, pmdp, address); + else + ptep = pte_offset_kernel(pmdp, address); + + if (!ptep) + return -ENOMEM; + + /* Clear encryption flag and write new pte */ + pte = pte_clear_flags(*ptep, _PAGE_ENC); + set_pte(ptep, pte); + + /* Flush TLB to map the page unencrypted */ + write_cr3(top_level_pgt); + + /* + * Changing encryption attributes of a page requires to flush it from + * the caches. + */ + clflush_page(address); + + return 0; +} + +int set_page_decrypted(unsigned long address) +{ + return __set_page_decrypted(&mapping_info, address); +} + static void pf_error(unsigned long error_code, unsigned long address, struct pt_regs *regs) { diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h index 0e3508c5c15c..42f68a858a35 100644 --- a/arch/x86/boot/compressed/misc.h +++ b/arch/x86/boot/compressed/misc.h @@ -98,6 +98,7 @@ static inline void choose_random_location(unsigned long input, #endif #ifdef CONFIG_X86_64 +extern int set_page_decrypted(unsigned long address); extern unsigned char _pgtable[]; #endif