Merge tag 'kvm-x86-misc-6.19' of https://github.com/kvm-x86/linux into HEAD

KVM x86 misc changes for 6.19:

 - Fix an async #PF bug where KVM would clear the completion queue when the
   guest transitioned in and out of paging mode, e.g. when handling an SMI and
   then returning to paged mode via RSM.

 - Fix a bug where TDX would effectively corrupt user-return MSR values if the
   TDX Module rejects VP.ENTER and thus doesn't clobber host MSRs as expected.

 - Leave the user-return notifier used to restore MSRs registered when
   disabling virtualization, and instead pin kvm.ko.  Restoring host MSRs via
   IPI callback is either pointless (clean reboot) or dangerous (forced reboot)
   since KVM has no idea what code it's interrupting.

 - Use the checked version of {get,put}_user(), as Linus wants to kill them
   off, and they're measurably faster on modern CPUs due to the unchecked
   versions containing an LFENCE.

 - Fix a long-lurking bug where KVM's lack of catch-up logic for periodic APIC
   timers can result in a hard lockup in the host.

 - Revert the periodic kvmclock sync logic now that KVM doesn't use a
   clocksource that's subject to NPT corrections.

 - Clean up KVM's handling of MMIO Stale Data and L1TF, and bury the latter
   behind CONFIG_CPU_MITIGATIONS.

 - Context switch XCR0, XSS, and PKRU outside of the entry/exit fastpath as
   the only reason they were handled in the faspath was to paper of a bug in
   the core #MC code that has long since been fixed.

 - Add emulator support for AVX MOV instructions to play nice with emulated
   devices whose PCI BARs guest drivers like to access with large multi-byte
   instructions.

1 files changed, 9 insertions, 13 deletions

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index d7fa03bf51b4..70bb48ab46d7 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -192,14 +192,6 @@ EXPORT_SYMBOL_GPL(cpu_buf_idle_clear);
  */
 DEFINE_STATIC_KEY_FALSE(switch_mm_cond_l1d_flush);
 
-/*
- * Controls CPU Fill buffer clear before VMenter. This is a subset of
- * X86_FEATURE_CLEAR_CPU_BUF, and should only be enabled when KVM-only
- * mitigation is required.
- */
-DEFINE_STATIC_KEY_FALSE(cpu_buf_vm_clear);
-EXPORT_SYMBOL_GPL(cpu_buf_vm_clear);
-
 #undef pr_fmt
 #define pr_fmt(fmt)	"mitigations: " fmt
 
@@ -489,8 +481,8 @@ static enum rfds_mitigations rfds_mitigation __ro_after_init =
 	IS_ENABLED(CONFIG_MITIGATION_RFDS) ? RFDS_MITIGATION_AUTO : RFDS_MITIGATION_OFF;
 
 /*
- * Set if any of MDS/TAA/MMIO/RFDS are going to enable VERW clearing
- * through X86_FEATURE_CLEAR_CPU_BUF on kernel and guest entry.
+ * Set if any of MDS/TAA/MMIO/RFDS are going to enable VERW clearing on exit to
+ * userspace *and* on entry to KVM guests.
  */
 static bool verw_clear_cpu_buf_mitigation_selected __ro_after_init;
 
@@ -536,6 +528,7 @@ static void __init mds_apply_mitigation(void)
 	if (mds_mitigation == MDS_MITIGATION_FULL ||
 	    mds_mitigation == MDS_MITIGATION_VMWERV) {
 		setup_force_cpu_cap(X86_FEATURE_CLEAR_CPU_BUF);
+		setup_force_cpu_cap(X86_FEATURE_CLEAR_CPU_BUF_VM);
 		if (!boot_cpu_has(X86_BUG_MSBDS_ONLY) &&
 		    (mds_nosmt || smt_mitigations == SMT_MITIGATIONS_ON))
 			cpu_smt_disable(false);
@@ -647,6 +640,7 @@ static void __init taa_apply_mitigation(void)
 		 * present on host, enable the mitigation for UCODE_NEEDED as well.
 		 */
 		setup_force_cpu_cap(X86_FEATURE_CLEAR_CPU_BUF);
+		setup_force_cpu_cap(X86_FEATURE_CLEAR_CPU_BUF_VM);
 
 		if (taa_nosmt || smt_mitigations == SMT_MITIGATIONS_ON)
 			cpu_smt_disable(false);
@@ -748,9 +742,9 @@ static void __init mmio_apply_mitigation(void)
 	 */
 	if (verw_clear_cpu_buf_mitigation_selected) {
 		setup_force_cpu_cap(X86_FEATURE_CLEAR_CPU_BUF);
-		static_branch_disable(&cpu_buf_vm_clear);
+		setup_force_cpu_cap(X86_FEATURE_CLEAR_CPU_BUF_VM);
 	} else {
-		static_branch_enable(&cpu_buf_vm_clear);
+		setup_force_cpu_cap(X86_FEATURE_CLEAR_CPU_BUF_VM_MMIO);
 	}
 
 	/*
@@ -839,8 +833,10 @@ static void __init rfds_update_mitigation(void)
 
 static void __init rfds_apply_mitigation(void)
 {
-	if (rfds_mitigation == RFDS_MITIGATION_VERW)
+	if (rfds_mitigation == RFDS_MITIGATION_VERW) {
 		setup_force_cpu_cap(X86_FEATURE_CLEAR_CPU_BUF);
+		setup_force_cpu_cap(X86_FEATURE_CLEAR_CPU_BUF_VM);
+	}
 }
 
 static __init int rfds_parse_cmdline(char *str)