From mboxrd@z Thu Jan 1 00:00:00 1970 From: Joerg Roedel Subject: [PATCH v3 24/75] x86/boot/compressed/64: Unmap GHCB page before booting the kernel Date: Tue, 28 Apr 2020 17:16:34 +0200 Message-ID: <20200428151725.31091-25-joro@8bytes.org> References: <20200428151725.31091-1-joro@8bytes.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20200428151725.31091-1-joro@8bytes.org> List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: virtualization-bounces@lists.linux-foundation.org Sender: "Virtualization" To: x86@kernel.org Cc: Juergen Gross , Tom Lendacky , Thomas Hellstrom , Joerg Roedel , Mike Stunes , Kees Cook , kvm@vger.kernel.org, Peter Zijlstra , Cfir Cohen , Joerg Roedel , Dave Hansen , linux-kernel@vger.kernel.org, virtualization@lists.linux-foundation.org, Masami Hiramatsu , Andy Lutomirski , hpa@zytor.com, Erdem Aktas , David Rientjes , Dan Williams , Jiri Slaby List-Id: virtualization@lists.linuxfoundation.org From: Joerg Roedel Force a page-fault on any further accesses to the GHCB page when they shouldn't happen anymore. This will catch the bugs where a #VC exception is raised when no one is expected anymore. Signed-off-by: Joerg Roedel --- arch/x86/boot/compressed/ident_map_64.c | 23 +++++++++++++++++++---- arch/x86/boot/compressed/misc.h | 6 ++++++ arch/x86/boot/compressed/sev-es.c | 14 ++++++++++++++ 3 files changed, 39 insertions(+), 4 deletions(-) diff --git a/arch/x86/boot/compressed/ident_map_64.c b/arch/x86/boot/compressed/ident_map_64.c index bb68e9c9d87a..d3771d455249 100644 --- a/arch/x86/boot/compressed/ident_map_64.c +++ b/arch/x86/boot/compressed/ident_map_64.c @@ -291,10 +291,21 @@ int set_page_encrypted(unsigned long address) return set_clr_page_flags(&mapping_info, address, _PAGE_ENC, 0); } +int set_page_non_present(unsigned long address) +{ + return set_clr_page_flags(&mapping_info, address, 0, _PAGE_PRESENT); +} + void do_boot_page_fault(struct pt_regs *regs, unsigned long error_code) { - unsigned long address = native_read_cr2() & PMD_MASK; - unsigned long end = address + PMD_SIZE; + unsigned long address = native_read_cr2(); + unsigned long end; + bool ghcb_fault; + + ghcb_fault = sev_es_check_ghcb_fault(address); + + address &= PMD_MASK; + end = address + PMD_SIZE; /* * Check for unexpected error codes. Unexpected are: @@ -302,9 +313,13 @@ void do_boot_page_fault(struct pt_regs *regs, unsigned long error_code) * - User faults * - Reserved bits set */ - if (error_code & (X86_PF_PROT | X86_PF_USER | X86_PF_RSVD)) { + if (ghcb_fault || + error_code & (X86_PF_PROT | X86_PF_USER | X86_PF_RSVD)) { /* Print some information for debugging */ - error_putstr("Unexpected page-fault:"); + if (ghcb_fault) + error_putstr("Page-fault on GHCB page:"); + else + error_putstr("Unexpected page-fault:"); error_putstr("\nError Code: "); error_puthex(error_code); error_putstr("\nCR2: 0x"); diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h index 4d37a28370ed..2e5f82acc122 100644 --- a/arch/x86/boot/compressed/misc.h +++ b/arch/x86/boot/compressed/misc.h @@ -100,6 +100,7 @@ static inline void choose_random_location(unsigned long input, #ifdef CONFIG_X86_64 extern int set_page_decrypted(unsigned long address); extern int set_page_encrypted(unsigned long address); +extern int set_page_non_present(unsigned long address); extern unsigned char _pgtable[]; #endif @@ -117,8 +118,13 @@ void set_sev_encryption_mask(void); #ifdef CONFIG_AMD_MEM_ENCRYPT void sev_es_shutdown_ghcb(void); +extern bool sev_es_check_ghcb_fault(unsigned long address); #else static inline void sev_es_shutdown_ghcb(void) { } +static inline bool sev_es_check_ghcb_fault(unsigned long address) +{ + return false; +} #endif /* acpi.c */ diff --git a/arch/x86/boot/compressed/sev-es.c b/arch/x86/boot/compressed/sev-es.c index 940d72571fc9..1241697dd156 100644 --- a/arch/x86/boot/compressed/sev-es.c +++ b/arch/x86/boot/compressed/sev-es.c @@ -120,6 +120,20 @@ void sev_es_shutdown_ghcb(void) */ if (set_page_encrypted((unsigned long)&boot_ghcb_page)) error("Can't map GHCB page encrypted"); + + /* + * GHCB page is mapped encrypted again and flushed from the cache. + * Mark it non-present now to catch bugs when #VC exceptions trigger + * after this point. + */ + if (set_page_non_present((unsigned long)&boot_ghcb_page)) + error("Can't unmap GHCB page"); +} + +bool sev_es_check_ghcb_fault(unsigned long address) +{ + /* Check whether the fault was on the GHCB page */ + return ((address & PAGE_MASK) == (unsigned long)&boot_ghcb_page); } void do_boot_stage2_vc(struct pt_regs *regs, unsigned long exit_code) -- 2.17.1