On Thu, 12 Jan 2017 19:24:45 +0100 Laszlo Ersek <ler...@redhat.com> wrote:
> The generic edk2 SMM infrastructure prefers > EFI_SMM_CONTROL2_PROTOCOL.Trigger() to inject an SMI on each processor. If > Trigger() only brings the current processor into SMM, then edk2 handles it > in the following ways: > > (1) If Trigger() is executed by the BSP (which is guaranteed before > ExitBootServices(), but is not necessarily true at runtime), then: > > (a) If edk2 has been configured for "traditional" SMM synchronization, > then the BSP sends directed SMIs to the APs with APIC delivery, > bringing them into SMM individually. Then the BSP runs the SMI > handler / dispatcher. > > (b) If edk2 has been configured for "relaxed" SMM synchronization, > then the APs that are not already in SMM are not brought in, and > the BSP runs the SMI handler / dispatcher. > > (2) If Trigger() is executed by an AP (which is possible after > ExitBootServices(), and can be forced e.g. by "taskset -c 1 > efibootmgr"), then the AP in question brings in the BSP with a > directed SMI, and the BSP runs the SMI handler / dispatcher. > > The smaller problem with (1a) and (2) is that the BSP and AP > synchronization is slow. For example, the "taskset -c 1 efibootmgr" > command from (2) can take more than 3 seconds to complete, because > efibootmgr accesses non-volatile UEFI variables intensively. > > The larger problem is that QEMU's current behavior diverges from the > behavior usually seen on physical hardware, and that keeps exposing > obscure corner cases, race conditions and other instabilities in edk2, > which generally expects / prefers a software SMI to affect all CPUs at > once. > > Therefore introduce the "broadcast SMI" feature that causes QEMU to inject > the SMI on all VCPUs. > > While the original posting of this patch > <http://lists.nongnu.org/archive/html/qemu-devel/2015-10/msg05658.html> > only intended to speed up (2), based on our recent "stress testing" of SMM > this patch actually provides functional improvements. > > Cc: "Michael S. Tsirkin" <m...@redhat.com> > Cc: Gerd Hoffmann <kra...@redhat.com> > Cc: Igor Mammedov <imamm...@redhat.com> > Cc: Paolo Bonzini <pbonz...@redhat.com> > Signed-off-by: Laszlo Ersek <ler...@redhat.com> > Reviewed-by: Michael S. Tsirkin <m...@redhat.com> > --- > > Notes: > v6: > - no changes, pick up Michael's R-b > > v5: > - replace the ICH9_LPC_SMI_F_BROADCAST bit value with the > ICH9_LPC_SMI_F_BROADCAST_BIT bit position (necessary for > DEFINE_PROP_BIT() in the next patch) > > include/hw/i386/ich9.h | 3 +++ > hw/isa/lpc_ich9.c | 10 +++++++++- > 2 files changed, 12 insertions(+), 1 deletion(-) > > diff --git a/include/hw/i386/ich9.h b/include/hw/i386/ich9.h > index da1118727146..18dcca7ebcbf 100644 > --- a/include/hw/i386/ich9.h > +++ b/include/hw/i386/ich9.h > @@ -250,4 +250,7 @@ Object *ich9_lpc_find(void); > #define ICH9_SMB_HST_D1 0x06 > #define ICH9_SMB_HOST_BLOCK_DB 0x07 > > +/* bit positions used in fw_cfg SMI feature negotiation */ > +#define ICH9_LPC_SMI_F_BROADCAST_BIT 0 > + > #endif /* HW_ICH9_H */ > diff --git a/hw/isa/lpc_ich9.c b/hw/isa/lpc_ich9.c > index 376b7801a42c..ced6f803a4f2 100644 > --- a/hw/isa/lpc_ich9.c > +++ b/hw/isa/lpc_ich9.c > @@ -437,7 +437,15 @@ static void ich9_apm_ctrl_changed(uint32_t val, void > *arg) > > /* SMI_EN = PMBASE + 30. SMI control and enable register */ > if (lpc->pm.smi_en & ICH9_PMIO_SMI_EN_APMC_EN) { > - cpu_interrupt(current_cpu, CPU_INTERRUPT_SMI); > + if (lpc->smi_negotiated_features & > + (UINT64_C(1) << ICH9_LPC_SMI_F_BROADCAST_BIT)) { > + CPUState *cs; > + CPU_FOREACH(cs) { > + cpu_interrupt(cs, CPU_INTERRUPT_SMI); > + } Shouldn't CPUs with default SMI base be excluded from broadcast? > + } else { > + cpu_interrupt(current_cpu, CPU_INTERRUPT_SMI); > + } > } > } >