The following commit has been merged into the x86/urgent branch of tip:

Commit-ID: 263e55949d8902a6a09bdb92a1ab6a3f67231abe Gitweb: https://git.kernel.org/tip/263e55949d8902a6a09bdb92a1ab6a3f67231abe Author: Sandipan Das sandipan.das@amd.com AuthorDate: Fri, 18 Apr 2025 11:49:40 +05:30 Committer: Ingo Molnar mingo@kernel.org CommitterDate: Fri, 18 Apr 2025 14:29:47 +02:00

x86/cpu/amd: Fix workaround for erratum 1054

Erratum 1054 affects AMD Zen processors that are a part of Family 17h Models 00-2Fh and the workaround is to not set HWCR[IRPerfEn]. However, when X86_FEATURE_ZEN1 was introduced, the condition to detect unaffected processors was incorrectly changed in a way that the IRPerfEn bit gets set only for unaffected Zen 1 processors.

Ensure that HWCR[IRPerfEn] is set for all unaffected processors. This includes a subset of Zen 1 (Family 17h Models 30h and above) and all later processors. Also clear X86_FEATURE_IRPERF on affected processors so that the IRPerfCount register is not used by other entities like the MSR PMU driver.

Fixes: 232afb557835 ("x86/CPU/AMD: Add X86_FEATURE_ZEN1") Signed-off-by: Sandipan Das sandipan.das@amd.com Signed-off-by: Ingo Molnar mingo@kernel.org Acked-by: Borislav Petkov bp@alien8.de Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/caa057a9d6f8ad579e2f1abaa71efbd5bd4eaf6d.174495646... --- arch/x86/kernel/cpu/amd.c | 19 ++++++++++++------- 1 file changed, 12 insertions(+), 7 deletions(-)

diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c index a839ff5..2b36379 100644 --- a/arch/x86/kernel/cpu/amd.c +++ b/arch/x86/kernel/cpu/amd.c @@ -869,6 +869,16 @@ static void init_amd_zen1(struct cpuinfo_x86 *c)

pr_notice_once("AMD Zen1 DIV0 bug detected. Disable SMT for full protection.\n"); setup_force_cpu_bug(X86_BUG_DIV0); + + /* + * Turn off the Instructions Retired free counter on machines that are + * susceptible to erratum #1054 "Instructions Retired Performance + * Counter May Be Inaccurate". + */ + if (c->x86_model < 0x30) { + msr_clear_bit(MSR_K7_HWCR, MSR_K7_HWCR_IRPERF_EN_BIT); + clear_cpu_cap(c, X86_FEATURE_IRPERF); + } }

static bool cpu_has_zenbleed_microcode(void) @@ -1052,13 +1062,8 @@ static void init_amd(struct cpuinfo_x86 *c) if (!cpu_feature_enabled(X86_FEATURE_XENPV)) set_cpu_bug(c, X86_BUG_SYSRET_SS_ATTRS);

- /* - * Turn on the Instructions Retired free counter on machines not - * susceptible to erratum #1054 "Instructions Retired Performance - * Counter May Be Inaccurate". - */ - if (cpu_has(c, X86_FEATURE_IRPERF) && - (boot_cpu_has(X86_FEATURE_ZEN1) && c->x86_model > 0x2f)) + /* Enable the Instructions Retired free counter */ + if (cpu_has(c, X86_FEATURE_IRPERF)) msr_set_bit(MSR_K7_HWCR, MSR_K7_HWCR_IRPERF_EN_BIT);

check_null_seg_clears_base(c);