The following commit has been merged into the x86/seves branch of tip:
Commit-ID: 69add17a7c1992593a7cf775a66e0256ad4b3ef8
Gitweb: https://git.kernel.org/tip/69add17a7c1992593a7cf775a66e0256ad4b3ef8
Author: Joerg Roedel <jroedel@xxxxxxx>
AuthorDate: Mon, 07 Sep 2020 15:15:25 +02:00
Committer: Borislav Petkov <bp@xxxxxxx>
CommitterDate: Mon, 07 Sep 2020 19:45:26 +02:00
x86/boot/compressed/64: Unmap GHCB page before booting the kernel
Force a page-fault on any further accesses to the GHCB page when they
shouldn't happen anymore. This will catch any bugs where a #VC exception
is raised even though none is expected anymore.
Signed-off-by: Joerg Roedel <jroedel@xxxxxxx>
Signed-off-by: Borislav Petkov <bp@xxxxxxx>
Link: https://lkml.kernel.org/r/20200907131613.12703-25-joro@xxxxxxxxxx
---
arch/x86/boot/compressed/ident_map_64.c | 17 +++++++++++++++--
arch/x86/boot/compressed/misc.h | 6 ++++++
arch/x86/boot/compressed/sev-es.c | 14 ++++++++++++++
3 files changed, 35 insertions(+), 2 deletions(-)
diff --git a/arch/x86/boot/compressed/ident_map_64.c b/arch/x86/boot/compressed/ident_map_64.c
index 05742f6..063a60e 100644
--- a/arch/x86/boot/compressed/ident_map_64.c
+++ b/arch/x86/boot/compressed/ident_map_64.c
@@ -298,6 +298,11 @@ 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);
+}
+
static void do_pf_error(const char *msg, unsigned long error_code,
unsigned long address, unsigned long ip)
{
@@ -316,8 +321,14 @@ static void do_pf_error(const char *msg, unsigned long error_code,
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:
@@ -327,6 +338,8 @@ void do_boot_page_fault(struct pt_regs *regs, unsigned long error_code)
*/
if (error_code & (X86_PF_PROT | X86_PF_USER | X86_PF_RSVD))
do_pf_error("Unexpected page-fault:", error_code, address, regs->ip);
+ else if (ghcb_fault)
+ do_pf_error("Page-fault on GHCB page:", error_code, address, regs->ip);
/*
* Error code is sane - now identity map the 2M region around
diff --git a/arch/x86/boot/compressed/misc.h b/arch/x86/boot/compressed/misc.h
index 9995c70..c0e0ffe 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 fa62af7..1e1fab5 100644
--- a/arch/x86/boot/compressed/sev-es.c
+++ b/arch/x86/boot/compressed/sev-es.c
@@ -121,6 +121,20 @@ 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)
|