diff options
Diffstat (limited to '0126-x86-spec-ctrl-Mitigate-IBPB-not-flushing-the-RSB-RAS.patch')
| -rw-r--r-- | 0126-x86-spec-ctrl-Mitigate-IBPB-not-flushing-the-RSB-RAS.patch | 113 |
1 files changed, 0 insertions, 113 deletions
diff --git a/0126-x86-spec-ctrl-Mitigate-IBPB-not-flushing-the-RSB-RAS.patch b/0126-x86-spec-ctrl-Mitigate-IBPB-not-flushing-the-RSB-RAS.patch deleted file mode 100644 index 2abb0f2..0000000 --- a/0126-x86-spec-ctrl-Mitigate-IBPB-not-flushing-the-RSB-RAS.patch +++ /dev/null @@ -1,113 +0,0 @@ -From 32445f23fea6a533fc1d7ade5871246d75210bf1 Mon Sep 17 00:00:00 2001 -From: Andrew Cooper <andrew.cooper3@citrix.com> -Date: Tue, 14 Jun 2022 16:18:36 +0100 -Subject: [PATCH 126/126] x86/spec-ctrl: Mitigate IBPB not flushing the RSB/RAS - -Introduce spec_ctrl_new_guest_context() to encapsulate all logic pertaining to -using MSR_PRED_CMD for a new guest context, even if it only has one user -presently. - -Introduce X86_BUG_IBPB_NO_RET, and use it extend spec_ctrl_new_guest_context() -with a manual fixup for hardware which mis-implements IBPB. - -This is part of XSA-422 / CVE-2022-23824. - -Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com> -Acked-by: Jan Beulich <jbeulich@suse.com> -(cherry picked from commit 2b27967fb89d7904a1571a2fb963b1c9cac548db) ---- - xen/arch/x86/asm-macros.c | 1 + - xen/arch/x86/domain.c | 2 +- - xen/arch/x86/spec_ctrl.c | 8 ++++++++ - xen/include/asm-x86/cpufeatures.h | 1 + - xen/include/asm-x86/spec_ctrl.h | 22 ++++++++++++++++++++++ - 5 files changed, 33 insertions(+), 1 deletion(-) - -diff --git a/xen/arch/x86/asm-macros.c b/xen/arch/x86/asm-macros.c -index 7e536b0d82f5..891d86c7655c 100644 ---- a/xen/arch/x86/asm-macros.c -+++ b/xen/arch/x86/asm-macros.c -@@ -1,2 +1,3 @@ - #include <asm/asm-defns.h> - #include <asm/alternative-asm.h> -+#include <asm/spec_ctrl_asm.h> -diff --git a/xen/arch/x86/domain.c b/xen/arch/x86/domain.c -index e9b8ed4c96c2..b82e18dd62d8 100644 ---- a/xen/arch/x86/domain.c -+++ b/xen/arch/x86/domain.c -@@ -2069,7 +2069,7 @@ void context_switch(struct vcpu *prev, struct vcpu *next) - */ - if ( *last_id != next_id ) - { -- wrmsrl(MSR_PRED_CMD, PRED_CMD_IBPB); -+ spec_ctrl_new_guest_context(); - *last_id = next_id; - } - } -diff --git a/xen/arch/x86/spec_ctrl.c b/xen/arch/x86/spec_ctrl.c -index 459c64d139b6..5636853aae6b 100644 ---- a/xen/arch/x86/spec_ctrl.c -+++ b/xen/arch/x86/spec_ctrl.c -@@ -775,6 +775,14 @@ static void __init ibpb_calculations(void) - return; - } - -+ /* -+ * AMD/Hygon CPUs to date (June 2022) don't flush the the RAS. Future -+ * CPUs are expected to enumerate IBPB_RET when this has been fixed. -+ * Until then, cover the difference with the software sequence. -+ */ -+ if ( boot_cpu_has(X86_FEATURE_IBPB) && !boot_cpu_has(X86_FEATURE_IBPB_RET) ) -+ setup_force_cpu_cap(X86_BUG_IBPB_NO_RET); -+ - /* - * IBPB-on-entry mitigations for Branch Type Confusion. - * -diff --git a/xen/include/asm-x86/cpufeatures.h b/xen/include/asm-x86/cpufeatures.h -index b233e5835fb5..bdb119a34c5d 100644 ---- a/xen/include/asm-x86/cpufeatures.h -+++ b/xen/include/asm-x86/cpufeatures.h -@@ -48,6 +48,7 @@ XEN_CPUFEATURE(IBPB_ENTRY_HVM, X86_SYNTH(29)) /* MSR_PRED_CMD used by Xen for - - #define X86_BUG_FPU_PTRS X86_BUG( 0) /* (F)X{SAVE,RSTOR} doesn't save/restore FOP/FIP/FDP. */ - #define X86_BUG_CLFLUSH_MFENCE X86_BUG( 2) /* MFENCE needed to serialise CLFLUSH */ -+#define X86_BUG_IBPB_NO_RET X86_BUG( 3) /* IBPB doesn't flush the RSB/RAS */ - - /* Total number of capability words, inc synth and bug words. */ - #define NCAPINTS (FSCAPINTS + X86_NR_SYNTH + X86_NR_BUG) /* N 32-bit words worth of info */ -diff --git a/xen/include/asm-x86/spec_ctrl.h b/xen/include/asm-x86/spec_ctrl.h -index 33e845991b0a..e400ff227391 100644 ---- a/xen/include/asm-x86/spec_ctrl.h -+++ b/xen/include/asm-x86/spec_ctrl.h -@@ -65,6 +65,28 @@ - void init_speculation_mitigations(void); - void spec_ctrl_init_domain(struct domain *d); - -+/* -+ * Switch to a new guest prediction context. -+ * -+ * This flushes all indirect branch predictors (BTB, RSB/RAS), so guest code -+ * which has previously run on this CPU can't attack subsequent guest code. -+ * -+ * As this flushes the RSB/RAS, it destroys the predictions of the calling -+ * context. For best performace, arrange for this to be used when we're going -+ * to jump out of the current context, e.g. with reset_stack_and_jump(). -+ * -+ * For hardware which mis-implements IBPB, fix up by flushing the RSB/RAS -+ * manually. -+ */ -+static always_inline void spec_ctrl_new_guest_context(void) -+{ -+ wrmsrl(MSR_PRED_CMD, PRED_CMD_IBPB); -+ -+ /* (ab)use alternative_input() to specify clobbers. */ -+ alternative_input("", "DO_OVERWRITE_RSB", X86_BUG_IBPB_NO_RET, -+ : "rax", "rcx"); -+} -+ - extern int8_t opt_ibpb_ctxt_switch; - extern bool opt_ssbd; - extern int8_t opt_eager_fpu; --- -2.37.4 - |