diff options
Diffstat (limited to '0021-x86-spec-ctrl-Mitigate-Branch-Type-Confusion-when-po.patch')
| -rw-r--r-- | 0021-x86-spec-ctrl-Mitigate-Branch-Type-Confusion-when-po.patch | 305 |
1 files changed, 0 insertions, 305 deletions
diff --git a/0021-x86-spec-ctrl-Mitigate-Branch-Type-Confusion-when-po.patch b/0021-x86-spec-ctrl-Mitigate-Branch-Type-Confusion-when-po.patch deleted file mode 100644 index 01be575..0000000 --- a/0021-x86-spec-ctrl-Mitigate-Branch-Type-Confusion-when-po.patch +++ /dev/null @@ -1,305 +0,0 @@ -From 35bf91d30f1a480dcf5bfd99b79384b2b283da7f Mon Sep 17 00:00:00 2001 -From: Andrew Cooper <andrew.cooper3@citrix.com> -Date: Mon, 27 Jun 2022 19:29:40 +0100 -Subject: [PATCH 021/126] x86/spec-ctrl: Mitigate Branch Type Confusion when - possible - -Branch Type Confusion affects AMD/Hygon CPUs on Zen2 and earlier. To -mitigate, we require SMT safety (STIBP on Zen2, no-SMT on Zen1), and to issue -an IBPB on each entry to Xen, to flush the BTB. - -Due to performance concerns, dom0 (which is trusted in most configurations) is -excluded from protections by default. - -Therefore: - * Use STIBP by default on Zen2 too, which now means we want it on by default - on all hardware supporting STIBP. - * Break the current IBPB logic out into a new function, extending it with - IBPB-at-entry logic. - * Change the existing IBPB-at-ctxt-switch boolean to be tristate, and disable - it by default when IBPB-at-entry is providing sufficient safety. - -If all PV guests on the system are trusted, then it is recommended to boot -with `spec-ctrl=ibpb-entry=no-pv`, as this will provide an additional marginal -perf improvement. - -This is part of XSA-407 / CVE-2022-23825. - -Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com> -Reviewed-by: Jan Beulich <jbeulich@suse.com> -(cherry picked from commit d8cb7e0f069e0f106d24941355b59b45a731eabe) ---- - docs/misc/xen-command-line.pandoc | 14 ++-- - xen/arch/x86/spec_ctrl.c | 113 ++++++++++++++++++++++++++---- - xen/include/asm-x86/spec_ctrl.h | 2 +- - 3 files changed, 112 insertions(+), 17 deletions(-) - -diff --git a/docs/misc/xen-command-line.pandoc b/docs/misc/xen-command-line.pandoc -index b06db5f654e5..b73c4a605011 100644 ---- a/docs/misc/xen-command-line.pandoc -+++ b/docs/misc/xen-command-line.pandoc -@@ -2170,7 +2170,7 @@ By default SSBD will be mitigated at runtime (i.e `ssbd=runtime`). - - ### spec-ctrl (x86) - > `= List of [ <bool>, xen=<bool>, {pv,hvm}=<bool>, --> {msr-sc,rsb,md-clear}=<bool>|{pv,hvm}=<bool>, -+> {msr-sc,rsb,md-clear,ibpb-entry}=<bool>|{pv,hvm}=<bool>, - > bti-thunk=retpoline|lfence|jmp, {ibrs,ibpb,ssbd,psfd, - > eager-fpu,l1d-flush,branch-harden,srb-lock, - > unpriv-mmio}=<bool> ]` -@@ -2195,9 +2195,10 @@ in place for guests to use. - - Use of a positive boolean value for either of these options is invalid. - --The `pv=`, `hvm=`, `msr-sc=`, `rsb=` and `md-clear=` options offer fine --grained control over the primitives by Xen. These impact Xen's ability to --protect itself, and/or Xen's ability to virtualise support for guests to use. -+The `pv=`, `hvm=`, `msr-sc=`, `rsb=`, `md-clear=` and `ibpb-entry=` options -+offer fine grained control over the primitives by Xen. These impact Xen's -+ability to protect itself, and/or Xen's ability to virtualise support for -+guests to use. - - * `pv=` and `hvm=` offer control over all suboptions for PV and HVM guests - respectively. -@@ -2216,6 +2217,11 @@ protect itself, and/or Xen's ability to virtualise support for guests to use. - compatibility with development versions of this fix, `mds=` is also accepted - on Xen 4.12 and earlier as an alias. Consult vendor documentation in - preference to here.* -+* `ibpb-entry=` offers control over whether IBPB (Indirect Branch Prediction -+ Barrier) is used on entry to Xen. This is used by default on hardware -+ vulnerable to Branch Type Confusion, but for performance reasons, dom0 is -+ unprotected by default. If it necessary to protect dom0 too, boot with -+ `spec-ctrl=ibpb-entry`. - - If Xen was compiled with INDIRECT_THUNK support, `bti-thunk=` can be used to - select which of the thunks gets patched into the `__x86_indirect_thunk_%reg` -diff --git a/xen/arch/x86/spec_ctrl.c b/xen/arch/x86/spec_ctrl.c -index 9f66c715516c..563519ce0e31 100644 ---- a/xen/arch/x86/spec_ctrl.c -+++ b/xen/arch/x86/spec_ctrl.c -@@ -39,6 +39,10 @@ static bool __initdata opt_rsb_hvm = true; - static int8_t __read_mostly opt_md_clear_pv = -1; - static int8_t __read_mostly opt_md_clear_hvm = -1; - -+static int8_t __read_mostly opt_ibpb_entry_pv = -1; -+static int8_t __read_mostly opt_ibpb_entry_hvm = -1; -+static bool __read_mostly opt_ibpb_entry_dom0; -+ - /* Cmdline controls for Xen's speculative settings. */ - static enum ind_thunk { - THUNK_DEFAULT, /* Decide which thunk to use at boot time. */ -@@ -54,7 +58,7 @@ int8_t __initdata opt_stibp = -1; - bool __read_mostly opt_ssbd; - int8_t __initdata opt_psfd = -1; - --bool __read_mostly opt_ibpb_ctxt_switch = true; -+int8_t __read_mostly opt_ibpb_ctxt_switch = -1; - int8_t __read_mostly opt_eager_fpu = -1; - int8_t __read_mostly opt_l1d_flush = -1; - bool __read_mostly opt_branch_harden = true; -@@ -114,6 +118,9 @@ static int __init parse_spec_ctrl(const char *s) - opt_rsb_hvm = false; - opt_md_clear_pv = 0; - opt_md_clear_hvm = 0; -+ opt_ibpb_entry_pv = 0; -+ opt_ibpb_entry_hvm = 0; -+ opt_ibpb_entry_dom0 = false; - - opt_thunk = THUNK_JMP; - opt_ibrs = 0; -@@ -140,12 +147,14 @@ static int __init parse_spec_ctrl(const char *s) - opt_msr_sc_pv = val; - opt_rsb_pv = val; - opt_md_clear_pv = val; -+ opt_ibpb_entry_pv = val; - } - else if ( (val = parse_boolean("hvm", s, ss)) >= 0 ) - { - opt_msr_sc_hvm = val; - opt_rsb_hvm = val; - opt_md_clear_hvm = val; -+ opt_ibpb_entry_hvm = val; - } - else if ( (val = parse_boolean("msr-sc", s, ss)) != -1 ) - { -@@ -210,6 +219,28 @@ static int __init parse_spec_ctrl(const char *s) - break; - } - } -+ else if ( (val = parse_boolean("ibpb-entry", s, ss)) != -1 ) -+ { -+ switch ( val ) -+ { -+ case 0: -+ case 1: -+ opt_ibpb_entry_pv = opt_ibpb_entry_hvm = -+ opt_ibpb_entry_dom0 = val; -+ break; -+ -+ case -2: -+ s += strlen("ibpb-entry="); -+ if ( (val = parse_boolean("pv", s, ss)) >= 0 ) -+ opt_ibpb_entry_pv = val; -+ else if ( (val = parse_boolean("hvm", s, ss)) >= 0 ) -+ opt_ibpb_entry_hvm = val; -+ else -+ default: -+ rc = -EINVAL; -+ break; -+ } -+ } - - /* Xen's speculative sidechannel mitigation settings. */ - else if ( !strncmp(s, "bti-thunk=", 10) ) -@@ -477,27 +508,31 @@ static void __init print_details(enum ind_thunk thunk, uint64_t caps) - * mitigation support for guests. - */ - #ifdef CONFIG_HVM -- printk(" Support for HVM VMs:%s%s%s%s%s\n", -+ printk(" Support for HVM VMs:%s%s%s%s%s%s\n", - (boot_cpu_has(X86_FEATURE_SC_MSR_HVM) || - boot_cpu_has(X86_FEATURE_SC_RSB_HVM) || - boot_cpu_has(X86_FEATURE_MD_CLEAR) || -+ boot_cpu_has(X86_FEATURE_IBPB_ENTRY_HVM) || - opt_eager_fpu) ? "" : " None", - boot_cpu_has(X86_FEATURE_SC_MSR_HVM) ? " MSR_SPEC_CTRL" : "", - boot_cpu_has(X86_FEATURE_SC_RSB_HVM) ? " RSB" : "", - opt_eager_fpu ? " EAGER_FPU" : "", -- boot_cpu_has(X86_FEATURE_MD_CLEAR) ? " MD_CLEAR" : ""); -+ boot_cpu_has(X86_FEATURE_MD_CLEAR) ? " MD_CLEAR" : "", -+ boot_cpu_has(X86_FEATURE_IBPB_ENTRY_HVM) ? " IBPB-entry" : ""); - - #endif - #ifdef CONFIG_PV -- printk(" Support for PV VMs:%s%s%s%s%s\n", -+ printk(" Support for PV VMs:%s%s%s%s%s%s\n", - (boot_cpu_has(X86_FEATURE_SC_MSR_PV) || - boot_cpu_has(X86_FEATURE_SC_RSB_PV) || - boot_cpu_has(X86_FEATURE_MD_CLEAR) || -+ boot_cpu_has(X86_FEATURE_IBPB_ENTRY_PV) || - opt_eager_fpu) ? "" : " None", - boot_cpu_has(X86_FEATURE_SC_MSR_PV) ? " MSR_SPEC_CTRL" : "", - boot_cpu_has(X86_FEATURE_SC_RSB_PV) ? " RSB" : "", - opt_eager_fpu ? " EAGER_FPU" : "", -- boot_cpu_has(X86_FEATURE_MD_CLEAR) ? " MD_CLEAR" : ""); -+ boot_cpu_has(X86_FEATURE_MD_CLEAR) ? " MD_CLEAR" : "", -+ boot_cpu_has(X86_FEATURE_IBPB_ENTRY_PV) ? " IBPB-entry" : ""); - - printk(" XPTI (64-bit PV only): Dom0 %s, DomU %s (with%s PCID)\n", - opt_xpti_hwdom ? "enabled" : "disabled", -@@ -730,6 +765,55 @@ static bool __init should_use_eager_fpu(void) - } - } - -+static void __init ibpb_calculations(void) -+{ -+ /* Check we have hardware IBPB support before using it... */ -+ if ( !boot_cpu_has(X86_FEATURE_IBRSB) && !boot_cpu_has(X86_FEATURE_IBPB) ) -+ { -+ opt_ibpb_entry_hvm = opt_ibpb_entry_pv = opt_ibpb_ctxt_switch = 0; -+ opt_ibpb_entry_dom0 = false; -+ return; -+ } -+ -+ /* -+ * IBPB-on-entry mitigations for Branch Type Confusion. -+ * -+ * IBPB && !BTC_NO selects all AMD/Hygon hardware, not known to be safe, -+ * that we can provide some form of mitigation on. -+ */ -+ if ( opt_ibpb_entry_pv == -1 ) -+ opt_ibpb_entry_pv = (IS_ENABLED(CONFIG_PV) && -+ boot_cpu_has(X86_FEATURE_IBPB) && -+ !boot_cpu_has(X86_FEATURE_BTC_NO)); -+ if ( opt_ibpb_entry_hvm == -1 ) -+ opt_ibpb_entry_hvm = (IS_ENABLED(CONFIG_HVM) && -+ boot_cpu_has(X86_FEATURE_IBPB) && -+ !boot_cpu_has(X86_FEATURE_BTC_NO)); -+ -+ if ( opt_ibpb_entry_pv ) -+ { -+ setup_force_cpu_cap(X86_FEATURE_IBPB_ENTRY_PV); -+ -+ /* -+ * We only need to flush in IST context if we're protecting against PV -+ * guests. HVM IBPB-on-entry protections are both atomic with -+ * NMI/#MC, so can't interrupt Xen ahead of having already flushed the -+ * BTB. -+ */ -+ default_spec_ctrl_flags |= SCF_ist_ibpb; -+ } -+ if ( opt_ibpb_entry_hvm ) -+ setup_force_cpu_cap(X86_FEATURE_IBPB_ENTRY_HVM); -+ -+ /* -+ * If we're using IBPB-on-entry to protect against PV and HVM guests -+ * (ignoring dom0 if trusted), then there's no need to also issue IBPB on -+ * context switch too. -+ */ -+ if ( opt_ibpb_ctxt_switch == -1 ) -+ opt_ibpb_ctxt_switch = !(opt_ibpb_entry_hvm && opt_ibpb_entry_pv); -+} -+ - /* Calculate whether this CPU is vulnerable to L1TF. */ - static __init void l1tf_calculations(uint64_t caps) - { -@@ -985,8 +1069,12 @@ void spec_ctrl_init_domain(struct domain *d) - bool verw = ((pv ? opt_md_clear_pv : opt_md_clear_hvm) || - (opt_fb_clear_mmio && is_iommu_enabled(d))); - -+ bool ibpb = ((pv ? opt_ibpb_entry_pv : opt_ibpb_entry_hvm) && -+ (d->domain_id != 0 || opt_ibpb_entry_dom0)); -+ - d->arch.spec_ctrl_flags = - (verw ? SCF_verw : 0) | -+ (ibpb ? SCF_entry_ibpb : 0) | - 0; - } - -@@ -1133,12 +1221,15 @@ void __init init_speculation_mitigations(void) - } - - /* -- * Use STIBP by default if the hardware hint is set. Otherwise, leave it -- * off as it a severe performance pentalty on pre-eIBRS Intel hardware -- * where it was retrofitted in microcode. -+ * Use STIBP by default on all AMD systems. Zen3 and later enumerate -+ * STIBP_ALWAYS, but STIBP is needed on Zen2 as part of the mitigations -+ * for Branch Type Confusion. -+ * -+ * Leave STIBP off by default on Intel. Pre-eIBRS systems suffer a -+ * substantial perf hit when it was implemented in microcode. - */ - if ( opt_stibp == -1 ) -- opt_stibp = !!boot_cpu_has(X86_FEATURE_STIBP_ALWAYS); -+ opt_stibp = !!boot_cpu_has(X86_FEATURE_AMD_STIBP); - - if ( opt_stibp && (boot_cpu_has(X86_FEATURE_STIBP) || - boot_cpu_has(X86_FEATURE_AMD_STIBP)) ) -@@ -1192,9 +1283,7 @@ void __init init_speculation_mitigations(void) - if ( opt_rsb_hvm ) - setup_force_cpu_cap(X86_FEATURE_SC_RSB_HVM); - -- /* Check we have hardware IBPB support before using it... */ -- if ( !boot_cpu_has(X86_FEATURE_IBRSB) && !boot_cpu_has(X86_FEATURE_IBPB) ) -- opt_ibpb_ctxt_switch = false; -+ ibpb_calculations(); - - /* Check whether Eager FPU should be enabled by default. */ - if ( opt_eager_fpu == -1 ) -diff --git a/xen/include/asm-x86/spec_ctrl.h b/xen/include/asm-x86/spec_ctrl.h -index 10cd0cd2518f..33e845991b0a 100644 ---- a/xen/include/asm-x86/spec_ctrl.h -+++ b/xen/include/asm-x86/spec_ctrl.h -@@ -65,7 +65,7 @@ - void init_speculation_mitigations(void); - void spec_ctrl_init_domain(struct domain *d); - --extern bool opt_ibpb_ctxt_switch; -+extern int8_t opt_ibpb_ctxt_switch; - extern bool opt_ssbd; - extern int8_t opt_eager_fpu; - extern int8_t opt_l1d_flush; --- -2.37.4 - |