On Wed, 17 Jul 2019 17:06:36 +1000 Alexey Kardashevskiy <a...@ozlabs.ru> wrote:
> The pseries guests do not normally allocate PCI resources and rely on > the system firmware doing so. Furthermore at least at some point in > the past the pseries guests won't even allowed to change BARs, probably > it is still the case for phyp. So since the initial commit we have [1] > which prevents resource reallocation. > > This is not a problem until we want specific BAR alignments, for example, > PAGE_SIZE==64k to make sure we can still map MMIO BARs directly. For > the boot time devices we handle this in SLOF [2] but since QEMU's RTAS > does not allocate BARs, the guest does this instead and does not align > BARs even if Linux is given pci=resource_alignment=16@pci:0:0 as > PCI_PROBE_ONLY makes Linux ignore alignment requests. > > ARM folks added a dial to control PCI_PROBE_ONLY via the device tree [3]. > This makes use of the dial to advertise to the guest that we can handle > BAR reassignments. This limits the change to the latest pseries machine > to avoid old guests explosion. > > We do not remove the flag from [1] as pseries guests are still supported > under phyp so having that removed may cause problems. > > [1] > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/powerpc/platforms/pseries/setup.c?h=v5.1#n773 > [2] > https://git.qemu.org/?p=SLOF.git;a=blob;f=board-qemu/slof/pci-phb.fs;h=06729bcf77a0d4e900c527adcd9befe2a269f65d;hb=HEAD#l338 > [3] > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=f81c11af > Signed-off-by: Alexey Kardashevskiy <a...@ozlabs.ru> > --- > Changes: > v2: > * limited the change by a machine version > > --- > include/hw/ppc/spapr.h | 1 + > hw/ppc/spapr.c | 11 +++++++++++ > 2 files changed, 12 insertions(+) > > diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h > index 60553d32c4fa..11c8185b94a1 100644 > --- a/include/hw/ppc/spapr.h > +++ b/include/hw/ppc/spapr.h > @@ -120,6 +120,7 @@ struct SpaprMachineClass { > bool legacy_irq_allocation; > bool broken_host_serial_model; /* present real host info to the guest */ > bool pre_4_1_migration; /* don't migrate hpt-max-page-size */ > + bool linux_pci_probe; > > void (*phb_placement)(SpaprMachineState *spapr, uint32_t index, > uint64_t *buid, hwaddr *pio, > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c > index 8783b433960c..734d759d65b3 100644 > --- a/hw/ppc/spapr.c > +++ b/hw/ppc/spapr.c > @@ -1162,6 +1162,7 @@ static void > spapr_dt_ov5_platform_support(SpaprMachineState *spapr, void *fdt, > static void spapr_dt_chosen(SpaprMachineState *spapr, void *fdt) > { > MachineState *machine = MACHINE(spapr); > + SpaprMachineClass *smc = SPAPR_MACHINE_GET_CLASS(machine); > int chosen; > const char *boot_device = machine->boot_order; > char *stdout_path = spapr_vio_stdout_path(spapr->vio_bus); > @@ -1219,6 +1220,11 @@ static void spapr_dt_chosen(SpaprMachineState *spapr, > void *fdt) > _FDT(fdt_setprop_string(fdt, chosen, "stdout-path", stdout_path)); > } > > + /* We can deal with BAR reallocation just fine, advertise it to the > guest */ > + if (smc->linux_pci_probe) { > + _FDT(fdt_setprop_cell(fdt, chosen, "linux,pci-probe-only", 0)); > + } > + > spapr_dt_ov5_platform_support(spapr, fdt, chosen); > > g_free(stdout_path); > @@ -4432,6 +4438,9 @@ static const TypeInfo spapr_machine_info = { > static void spapr_machine_4_2_class_options(MachineClass *mc) > { > /* Defaults for the latest behaviour inherited from the base class */ > + SpaprMachineClass *smc = SPAPR_MACHINE_CLASS(mc); > + > + smc->linux_pci_probe = true; As written in the comment, defaults for the latest behavior belong to the base class, ie. this should go to spapr_machine_class_init(). > } > > DEFINE_SPAPR_MACHINE(4_2, "4.2", true); > @@ -4441,12 +4450,14 @@ DEFINE_SPAPR_MACHINE(4_2, "4.2", true); > */ > static void spapr_machine_4_1_class_options(MachineClass *mc) > { > + SpaprMachineClass *smc = SPAPR_MACHINE_CLASS(mc); > static GlobalProperty compat[] = { > /* Only allow 4kiB and 64kiB IOMMU pagesizes */ > { TYPE_SPAPR_PCI_HOST_BRIDGE, "pgsz", "0x11000" }, > }; > > spapr_machine_4_2_class_options(mc); > + smc->linux_pci_probe = false; > compat_props_add(mc->compat_props, compat, G_N_ELEMENTS(compat)); > } >
