diff options
Diffstat (limited to '0036-x86-spec-ctrl-Only-adjust-MSR_SPEC_CTRL-for-idle-wit.patch')
| -rw-r--r-- | 0036-x86-spec-ctrl-Only-adjust-MSR_SPEC_CTRL-for-idle-wit.patch | 93 |
1 files changed, 0 insertions, 93 deletions
diff --git a/0036-x86-spec-ctrl-Only-adjust-MSR_SPEC_CTRL-for-idle-wit.patch b/0036-x86-spec-ctrl-Only-adjust-MSR_SPEC_CTRL-for-idle-wit.patch deleted file mode 100644 index 8bc0768..0000000 --- a/0036-x86-spec-ctrl-Only-adjust-MSR_SPEC_CTRL-for-idle-wit.patch +++ /dev/null @@ -1,93 +0,0 @@ -From 09d533f4c80b7eaf9fb4e36ebba8259580857a9d Mon Sep 17 00:00:00 2001 -From: Andrew Cooper <andrew.cooper3@citrix.com> -Date: Tue, 12 Jul 2022 11:12:46 +0200 -Subject: [PATCH 36/51] x86/spec-ctrl: Only adjust MSR_SPEC_CTRL for idle with - legacy IBRS -MIME-Version: 1.0 -Content-Type: text/plain; charset=UTF-8 -Content-Transfer-Encoding: 8bit - -Back at the time of the original Spectre-v2 fixes, it was recommended to clear -MSR_SPEC_CTRL when going idle. This is because of the side effects on the -sibling thread caused by the microcode IBRS and STIBP implementations which -were retrofitted to existing CPUs. - -However, there are no relevant cross-thread impacts for the hardware -IBRS/STIBP implementations, so this logic should not be used on Intel CPUs -supporting eIBRS, or any AMD CPUs; doing so only adds unnecessary latency to -the idle path. - -Furthermore, there's no point playing with MSR_SPEC_CTRL in the idle paths if -SMT is disabled for other reasons. - -Fixes: 8d03080d2a33 ("x86/spec-ctrl: Cease using thunk=lfence on AMD") -Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com> -Reviewed-by: Roger Pau Monné <roger.pau@citrix.com> -master commit: ffc7694e0c99eea158c32aa164b7d1e1bb1dc46b -master date: 2022-06-30 18:07:13 +0100 ---- - xen/arch/x86/spec_ctrl.c | 10 ++++++++-- - xen/include/asm-x86/cpufeatures.h | 2 +- - xen/include/asm-x86/spec_ctrl.h | 5 +++-- - 3 files changed, 12 insertions(+), 5 deletions(-) - -diff --git a/xen/arch/x86/spec_ctrl.c b/xen/arch/x86/spec_ctrl.c -index 099113ba41e6..1ed5ceda8b46 100644 ---- a/xen/arch/x86/spec_ctrl.c -+++ b/xen/arch/x86/spec_ctrl.c -@@ -1150,8 +1150,14 @@ void __init init_speculation_mitigations(void) - /* (Re)init BSP state now that default_spec_ctrl_flags has been calculated. */ - init_shadow_spec_ctrl_state(); - -- /* If Xen is using any MSR_SPEC_CTRL settings, adjust the idle path. */ -- if ( default_xen_spec_ctrl ) -+ /* -+ * For microcoded IBRS only (i.e. Intel, pre eIBRS), it is recommended to -+ * clear MSR_SPEC_CTRL before going idle, to avoid impacting sibling -+ * threads. Activate this if SMT is enabled, and Xen is using a non-zero -+ * MSR_SPEC_CTRL setting. -+ */ -+ if ( boot_cpu_has(X86_FEATURE_IBRSB) && !(caps & ARCH_CAPS_IBRS_ALL) && -+ hw_smt_enabled && default_xen_spec_ctrl ) - setup_force_cpu_cap(X86_FEATURE_SC_MSR_IDLE); - - xpti_init_default(caps); -diff --git a/xen/include/asm-x86/cpufeatures.h b/xen/include/asm-x86/cpufeatures.h -index bd45a144ee78..493d338a085e 100644 ---- a/xen/include/asm-x86/cpufeatures.h -+++ b/xen/include/asm-x86/cpufeatures.h -@@ -33,7 +33,7 @@ XEN_CPUFEATURE(SC_MSR_HVM, X86_SYNTH(17)) /* MSR_SPEC_CTRL used by Xen fo - XEN_CPUFEATURE(SC_RSB_PV, X86_SYNTH(18)) /* RSB overwrite needed for PV */ - XEN_CPUFEATURE(SC_RSB_HVM, X86_SYNTH(19)) /* RSB overwrite needed for HVM */ - XEN_CPUFEATURE(XEN_SELFSNOOP, X86_SYNTH(20)) /* SELFSNOOP gets used by Xen itself */ --XEN_CPUFEATURE(SC_MSR_IDLE, X86_SYNTH(21)) /* (SC_MSR_PV || SC_MSR_HVM) && default_xen_spec_ctrl */ -+XEN_CPUFEATURE(SC_MSR_IDLE, X86_SYNTH(21)) /* Clear MSR_SPEC_CTRL on idle */ - XEN_CPUFEATURE(XEN_LBR, X86_SYNTH(22)) /* Xen uses MSR_DEBUGCTL.LBR */ - /* Bits 23,24 unused. */ - XEN_CPUFEATURE(SC_VERW_IDLE, X86_SYNTH(25)) /* VERW used by Xen for idle */ -diff --git a/xen/include/asm-x86/spec_ctrl.h b/xen/include/asm-x86/spec_ctrl.h -index 751355f471f4..7e83e0179fb9 100644 ---- a/xen/include/asm-x86/spec_ctrl.h -+++ b/xen/include/asm-x86/spec_ctrl.h -@@ -78,7 +78,8 @@ static always_inline void spec_ctrl_enter_idle(struct cpu_info *info) - uint32_t val = 0; - - /* -- * Branch Target Injection: -+ * It is recommended in some cases to clear MSR_SPEC_CTRL when going idle, -+ * to avoid impacting sibling threads. - * - * Latch the new shadow value, then enable shadowing, then update the MSR. - * There are no SMP issues here; only local processor ordering concerns. -@@ -114,7 +115,7 @@ static always_inline void spec_ctrl_exit_idle(struct cpu_info *info) - uint32_t val = info->xen_spec_ctrl; - - /* -- * Branch Target Injection: -+ * Restore MSR_SPEC_CTRL on exit from idle. - * - * Disable shadowing before updating the MSR. There are no SMP issues - * here; only local processor ordering concerns. --- -2.35.1 - |