From 28a99e95f55c61855983d36a88c05c178d966bb7 Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Mon, 18 Jul 2022 13:41:37 +0200 Subject: x86/amd: Use IBPB for firmware calls On AMD IBRS does not prevent Retbleed; as such use IBPB before a firmware call to flush the branch history state. And because in order to do an EFI call, the kernel maps a whole lot of the kernel page table into the EFI page table, do an IBPB just in case in order to prevent the scenario of poisoning the BTB and causing an EFI call using the unprotected RET there. [ bp: Massage. ] Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Borislav Petkov Link: https://lore.kernel.org/r/20220715194550.793957-1-cascardo@canonical.com --- arch/x86/kernel/cpu/bugs.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) (limited to 'arch/x86/kernel') diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c index aa34f908c39f..78c9082242a9 100644 --- a/arch/x86/kernel/cpu/bugs.c +++ b/arch/x86/kernel/cpu/bugs.c @@ -1516,7 +1516,16 @@ static void __init spectre_v2_select_mitigation(void) * the CPU supports Enhanced IBRS, kernel might un-intentionally not * enable IBRS around firmware calls. */ - if (boot_cpu_has(X86_FEATURE_IBRS) && !spectre_v2_in_ibrs_mode(mode)) { + if (boot_cpu_has_bug(X86_BUG_RETBLEED) && + (boot_cpu_data.x86_vendor == X86_VENDOR_AMD || + boot_cpu_data.x86_vendor == X86_VENDOR_HYGON)) { + + if (retbleed_cmd != RETBLEED_CMD_IBPB) { + setup_force_cpu_cap(X86_FEATURE_USE_IBPB_FW); + pr_info("Enabling Speculation Barrier for firmware calls\n"); + } + + } else if (boot_cpu_has(X86_FEATURE_IBRS) && !spectre_v2_in_ibrs_mode(mode)) { setup_force_cpu_cap(X86_FEATURE_USE_IBRS_FW); pr_info("Enabling Restricted Speculation for firmware calls\n"); } -- cgit