diff options
Diffstat (limited to '0037-x86-spec-ctrl-Knobs-for-STIBP-and-PSFD-and-follow-ha.patch')
| -rw-r--r-- | 0037-x86-spec-ctrl-Knobs-for-STIBP-and-PSFD-and-follow-ha.patch | 234 |
1 files changed, 0 insertions, 234 deletions
diff --git a/0037-x86-spec-ctrl-Knobs-for-STIBP-and-PSFD-and-follow-ha.patch b/0037-x86-spec-ctrl-Knobs-for-STIBP-and-PSFD-and-follow-ha.patch deleted file mode 100644 index 156aa58..0000000 --- a/0037-x86-spec-ctrl-Knobs-for-STIBP-and-PSFD-and-follow-ha.patch +++ /dev/null @@ -1,234 +0,0 @@ -From db6ca8176ccc4ff7dfe3c06969af9ebfab0d7b04 Mon Sep 17 00:00:00 2001 -From: Andrew Cooper <andrew.cooper3@citrix.com> -Date: Tue, 12 Jul 2022 11:13:33 +0200 -Subject: [PATCH 37/51] x86/spec-ctrl: Knobs for STIBP and PSFD, and follow - hardware STIBP hint -MIME-Version: 1.0 -Content-Type: text/plain; charset=UTF-8 -Content-Transfer-Encoding: 8bit - -STIBP and PSFD are slightly weird bits, because they're both implied by other -bits in MSR_SPEC_CTRL. Add fine grain controls for them, and take the -implications into account when setting IBRS/SSBD. - -Rearrange the IBPB text/variables/logic to keep all the MSR_SPEC_CTRL bits -together, for consistency. - -However, AMD have a hardware hint CPUID bit recommending that STIBP be set -unilaterally. This is advertised on Zen3, so follow the recommendation. -Furthermore, in such cases, set STIBP behind the guest's back for now. This -has negligible overhead for the guest, but saves a WRMSR on vmentry. This is -the only default change. - -Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com> -Reviewed-by: Jan Beulich <jbeulich@suse.com> -Reviewed-by: Roger Pau Monné <roger.pau@citrix.com> -master commit: fef244b179c06fcdfa581f7d57fa6e578c49ff50 -master date: 2022-06-30 18:07:13 +0100 ---- - docs/misc/xen-command-line.pandoc | 21 +++++++--- - xen/arch/x86/hvm/svm/vmcb.c | 9 +++++ - xen/arch/x86/spec_ctrl.c | 67 ++++++++++++++++++++++++++----- - 3 files changed, 82 insertions(+), 15 deletions(-) - -diff --git a/docs/misc/xen-command-line.pandoc b/docs/misc/xen-command-line.pandoc -index a642e43476a2..46e9c58d35cd 100644 ---- a/docs/misc/xen-command-line.pandoc -+++ b/docs/misc/xen-command-line.pandoc -@@ -2234,8 +2234,9 @@ By default SSBD will be mitigated at runtime (i.e `ssbd=runtime`). - - ### spec-ctrl (x86) - > `= List of [ <bool>, xen=<bool>, {pv,hvm,msr-sc,rsb,md-clear}=<bool>, --> bti-thunk=retpoline|lfence|jmp, {ibrs,ibpb,ssbd,eager-fpu, --> l1d-flush,branch-harden,srb-lock,unpriv-mmio}=<bool> ]` -+> bti-thunk=retpoline|lfence|jmp, {ibrs,ibpb,ssbd,psfd, -+> eager-fpu,l1d-flush,branch-harden,srb-lock, -+> unpriv-mmio}=<bool> ]` - - Controls for speculative execution sidechannel mitigations. By default, Xen - will pick the most appropriate mitigations based on compiled in support, -@@ -2285,9 +2286,10 @@ On hardware supporting IBRS (Indirect Branch Restricted Speculation), the - If Xen is not using IBRS itself, functionality is still set up so IBRS can be - virtualised for guests. - --On hardware supporting IBPB (Indirect Branch Prediction Barrier), the `ibpb=` --option can be used to force (the default) or prevent Xen from issuing branch --prediction barriers on vcpu context switches. -+On hardware supporting STIBP (Single Thread Indirect Branch Predictors), the -+`stibp=` option can be used to force or prevent Xen using the feature itself. -+By default, Xen will use STIBP when IBRS is in use (IBRS implies STIBP), and -+when hardware hints recommend using it as a blanket setting. - - On hardware supporting SSBD (Speculative Store Bypass Disable), the `ssbd=` - option can be used to force or prevent Xen using the feature itself. On AMD -@@ -2295,6 +2297,15 @@ hardware, this is a global option applied at boot, and not virtualised for - guest use. On Intel hardware, the feature is virtualised for guests, - independently of Xen's choice of setting. - -+On hardware supporting PSFD (Predictive Store Forwarding Disable), the `psfd=` -+option can be used to force or prevent Xen using the feature itself. By -+default, Xen will not use PSFD. PSFD is implied by SSBD, and SSBD is off by -+default. -+ -+On hardware supporting IBPB (Indirect Branch Prediction Barrier), the `ibpb=` -+option can be used to force (the default) or prevent Xen from issuing branch -+prediction barriers on vcpu context switches. -+ - On all hardware, the `eager-fpu=` option can be used to force or prevent Xen - from using fully eager FPU context switches. This is currently implemented as - a global control. By default, Xen will choose to use fully eager context -diff --git a/xen/arch/x86/hvm/svm/vmcb.c b/xen/arch/x86/hvm/svm/vmcb.c -index 565e997155f2..ef7224eb5dd7 100644 ---- a/xen/arch/x86/hvm/svm/vmcb.c -+++ b/xen/arch/x86/hvm/svm/vmcb.c -@@ -29,6 +29,7 @@ - #include <asm/hvm/support.h> - #include <asm/hvm/svm/svm.h> - #include <asm/hvm/svm/svmdebug.h> -+#include <asm/spec_ctrl.h> - - struct vmcb_struct *alloc_vmcb(void) - { -@@ -176,6 +177,14 @@ static int construct_vmcb(struct vcpu *v) - vmcb->_pause_filter_thresh = SVM_PAUSETHRESH_INIT; - } - -+ /* -+ * When default_xen_spec_ctrl simply SPEC_CTRL_STIBP, default this behind -+ * the back of the VM too. Our SMT topology isn't accurate, the overhead -+ * is neglegable, and doing this saves a WRMSR on the vmentry path. -+ */ -+ if ( default_xen_spec_ctrl == SPEC_CTRL_STIBP ) -+ v->arch.msrs->spec_ctrl.raw = SPEC_CTRL_STIBP; -+ - return 0; - } - -diff --git a/xen/arch/x86/spec_ctrl.c b/xen/arch/x86/spec_ctrl.c -index 1ed5ceda8b46..dfdd45c358c4 100644 ---- a/xen/arch/x86/spec_ctrl.c -+++ b/xen/arch/x86/spec_ctrl.c -@@ -48,9 +48,13 @@ static enum ind_thunk { - THUNK_LFENCE, - THUNK_JMP, - } opt_thunk __initdata = THUNK_DEFAULT; -+ - static int8_t __initdata opt_ibrs = -1; -+int8_t __initdata opt_stibp = -1; -+bool __read_mostly opt_ssbd; -+int8_t __initdata opt_psfd = -1; -+ - bool __read_mostly opt_ibpb = true; --bool __read_mostly opt_ssbd = false; - int8_t __read_mostly opt_eager_fpu = -1; - int8_t __read_mostly opt_l1d_flush = -1; - static bool __initdata opt_branch_harden = true; -@@ -172,12 +176,20 @@ static int __init parse_spec_ctrl(const char *s) - else - rc = -EINVAL; - } -+ -+ /* Bits in MSR_SPEC_CTRL. */ - else if ( (val = parse_boolean("ibrs", s, ss)) >= 0 ) - opt_ibrs = val; -- else if ( (val = parse_boolean("ibpb", s, ss)) >= 0 ) -- opt_ibpb = val; -+ else if ( (val = parse_boolean("stibp", s, ss)) >= 0 ) -+ opt_stibp = val; - else if ( (val = parse_boolean("ssbd", s, ss)) >= 0 ) - opt_ssbd = val; -+ else if ( (val = parse_boolean("psfd", s, ss)) >= 0 ) -+ opt_psfd = val; -+ -+ /* Misc settings. */ -+ else if ( (val = parse_boolean("ibpb", s, ss)) >= 0 ) -+ opt_ibpb = val; - else if ( (val = parse_boolean("eager-fpu", s, ss)) >= 0 ) - opt_eager_fpu = val; - else if ( (val = parse_boolean("l1d-flush", s, ss)) >= 0 ) -@@ -376,7 +388,7 @@ static void __init print_details(enum ind_thunk thunk, uint64_t caps) - "\n"); - - /* Settings for Xen's protection, irrespective of guests. */ -- printk(" Xen settings: BTI-Thunk %s, SPEC_CTRL: %s%s%s%s, Other:%s%s%s%s%s\n", -+ printk(" Xen settings: BTI-Thunk %s, SPEC_CTRL: %s%s%s%s%s, Other:%s%s%s%s%s\n", - thunk == THUNK_NONE ? "N/A" : - thunk == THUNK_RETPOLINE ? "RETPOLINE" : - thunk == THUNK_LFENCE ? "LFENCE" : -@@ -390,6 +402,9 @@ static void __init print_details(enum ind_thunk thunk, uint64_t caps) - (!boot_cpu_has(X86_FEATURE_SSBD) && - !boot_cpu_has(X86_FEATURE_AMD_SSBD)) ? "" : - (default_xen_spec_ctrl & SPEC_CTRL_SSBD) ? " SSBD+" : " SSBD-", -+ (!boot_cpu_has(X86_FEATURE_PSFD) && -+ !boot_cpu_has(X86_FEATURE_INTEL_PSFD)) ? "" : -+ (default_xen_spec_ctrl & SPEC_CTRL_PSFD) ? " PSFD+" : " PSFD-", - !(caps & ARCH_CAPS_TSX_CTRL) ? "" : - (opt_tsx & 1) ? " TSX+" : " TSX-", - !cpu_has_srbds_ctrl ? "" : -@@ -979,10 +994,7 @@ void __init init_speculation_mitigations(void) - if ( !has_spec_ctrl ) - printk(XENLOG_WARNING "?!? CET active, but no MSR_SPEC_CTRL?\n"); - else if ( opt_ibrs == -1 ) -- { - opt_ibrs = ibrs = true; -- default_xen_spec_ctrl |= SPEC_CTRL_IBRS | SPEC_CTRL_STIBP; -- } - - if ( opt_thunk == THUNK_DEFAULT || opt_thunk == THUNK_RETPOLINE ) - thunk = THUNK_JMP; -@@ -1086,14 +1098,49 @@ void __init init_speculation_mitigations(void) - setup_force_cpu_cap(X86_FEATURE_SC_MSR_HVM); - } - -- /* If we have IBRS available, see whether we should use it. */ -+ /* Figure out default_xen_spec_ctrl. */ - if ( has_spec_ctrl && ibrs ) -- default_xen_spec_ctrl |= SPEC_CTRL_IBRS; -+ { -+ /* IBRS implies STIBP. */ -+ if ( opt_stibp == -1 ) -+ opt_stibp = 1; -+ -+ default_xen_spec_ctrl |= SPEC_CTRL_IBRS; -+ } -+ -+ /* -+ * 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. -+ */ -+ if ( opt_stibp == -1 ) -+ opt_stibp = !!boot_cpu_has(X86_FEATURE_STIBP_ALWAYS); -+ -+ if ( opt_stibp && (boot_cpu_has(X86_FEATURE_STIBP) || -+ boot_cpu_has(X86_FEATURE_AMD_STIBP)) ) -+ default_xen_spec_ctrl |= SPEC_CTRL_STIBP; - -- /* If we have SSBD available, see whether we should use it. */ - if ( opt_ssbd && (boot_cpu_has(X86_FEATURE_SSBD) || - boot_cpu_has(X86_FEATURE_AMD_SSBD)) ) -+ { -+ /* SSBD implies PSFD */ -+ if ( opt_psfd == -1 ) -+ opt_psfd = 1; -+ - default_xen_spec_ctrl |= SPEC_CTRL_SSBD; -+ } -+ -+ /* -+ * Don't use PSFD by default. AMD designed the predictor to -+ * auto-clear on privilege change. PSFD is implied by SSBD, which is -+ * off by default. -+ */ -+ if ( opt_psfd == -1 ) -+ opt_psfd = 0; -+ -+ if ( opt_psfd && (boot_cpu_has(X86_FEATURE_PSFD) || -+ boot_cpu_has(X86_FEATURE_INTEL_PSFD)) ) -+ default_xen_spec_ctrl |= SPEC_CTRL_PSFD; - - /* - * PV guests can create RSB entries for any linear address they control, --- -2.35.1 - |