git: 02904a06c76b - main - amd64: properly recalculate mitigations knobs after resume

The branch main has been updated by kib:

URL: https://cgit.FreeBSD.org/src/commit/?id=02904a06c76be857307b78184863654b9e7b88ab

commit 02904a06c76be857307b78184863654b9e7b88ab
Author:     Konstantin Belousov <kib@FreeBSD.org>
AuthorDate: 2023-03-17 13:02:03 +0000
Commit:     Konstantin Belousov <kib@FreeBSD.org>
CommitDate: 2023-03-18 15:40:05 +0000

    amd64: properly recalculate mitigations knobs after resume
    
    Revision r333125 AKA 986c4ca38772f72 forced clear cpu_stdext_feature3
    on suspend, since at that time microcode update was not reloaded
    early on resume. Then, revision 050f5a8405c63 started re-reading
    cpu_stdext_feature3 again. Since modern CPUs do not require mitigations
    from the Skylake era, this went unnoticed for some time.
    
    Keep zeroing cpu_stdext_feature3 on suspend, but re-read it in more
    controlled way on resume after microcode is reloaded, and recalculate
    active workarounds based on actual microcode capabilities.
    
    Reported and tested by: romain
    Reviewed by:    emaste, markj
    Sponsored by:   The FreeBSD Foundation
    MFC after:      1 week
    Differential revision:  https://reviews.freebsd.org/D39146
---
 sys/amd64/acpica/acpi_wakeup.c | 14 ++++++++++++++
 sys/amd64/amd64/initcpu.c      |  2 +-
 2 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/sys/amd64/acpica/acpi_wakeup.c b/sys/amd64/acpica/acpi_wakeup.c
index 9601a88e11a4..1afbdc3a3bec 100644
--- a/sys/amd64/acpica/acpi_wakeup.c
+++ b/sys/amd64/acpica/acpi_wakeup.c
@@ -288,6 +288,20 @@ acpi_wakeup_machdep(struct acpi_softc *sc, int state, int sleep_result,
 		if (!CPU_EMPTY(&suspcpus))
 			resume_cpus(suspcpus);
 #endif
+
+		/*
+		 * Re-read cpu_stdext_feature3, which was zeroed-out
+		 * in acpi_sleep_machdep, after the microcode was
+		 * reloaded.  Then recalculate the active mitigations
+		 * knobs that depend on the microcode and
+		 * cpu_stdext_feature3.
+		 */
+		identify_cpu_ext_features();
+		hw_ibrs_recalculate(true);
+		hw_ssb_recalculate(true);
+		amd64_syscall_ret_flush_l1d_recalc();
+		x86_rngds_mitg_recalculate(true);
+
 		mca_resume();
 		if (vmm_resume_p != NULL)
 			vmm_resume_p();
diff --git a/sys/amd64/amd64/initcpu.c b/sys/amd64/amd64/initcpu.c
index 16780a9e069b..8d4c9d9cbe64 100644
--- a/sys/amd64/amd64/initcpu.c
+++ b/sys/amd64/amd64/initcpu.c
@@ -313,7 +313,7 @@ initializecpu(void)
 	}
 	load_cr4(cr4);
 	/* Reload cpu ext features to reflect cr4 changes */
-	if (IS_BSP())
+	if (IS_BSP() && cold)
 		identify_cpu_ext_features();
 	if (IS_BSP() && (amd_feature & AMDID_NX) != 0) {
 		msr = rdmsr(MSR_EFER) | EFER_NXE;