On Tue, 11 Dec 2018 14:53:32 +1100 Alexey Kardashevskiy <a...@ozlabs.ru> wrote:
> On 10/12/2018 20:30, Greg Kurz wrote: > > On Mon, 10 Dec 2018 17:20:43 +1100 > > David Gibson <da...@gibson.dropbear.id.au> wrote: > > > >> On Mon, Nov 12, 2018 at 03:12:26PM +1100, Alexey Kardashevskiy wrote: > >>> > >>> > >>> On 12/11/2018 05:10, Greg Kurz wrote: > >>>> Hi Alexey, > >>>> > >>>> Just a few remarks. See below. > >>>> > >>>> On Thu, 8 Nov 2018 12:44:06 +1100 > >>>> Alexey Kardashevskiy <a...@ozlabs.ru> wrote: > >>>> > >>>>> SLOF receives a device tree and updates it with various properties > >>>>> before switching to the guest kernel and QEMU is not aware of any > >>>>> changes > >>>>> made by SLOF. Since there is no real RTAS (QEMU implements it), it makes > >>>>> sense to pass the SLOF final device tree to QEMU to let it implement > >>>>> RTAS related tasks better, such as PCI host bus adapter hotplug. > >>>>> > >>>>> Specifially, now QEMU can find out the actual XICS phandle (for PHB > >>>>> hotplug) and the RTAS linux,rtas-entry/base properties (for firmware > >>>>> assisted NMI - FWNMI). > >>>>> > >>>>> This stores the initial DT blob in the sPAPR machine and replaces it > >>>>> in the KVMPPC_H_UPDATE_DT (new private hypercall) handler. > >>>>> > >>>>> This adds an @update_dt_enabled machine property to allow backward > >>>>> migration. > >>>>> > >>>>> SLOF already has a hypercall since > >>>>> https://github.com/aik/SLOF/commit/e6fc84652c9c0073f9183 > >>>>> > >>>>> Signed-off-by: Alexey Kardashevskiy <a...@ozlabs.ru> > >>>>> --- > >>>>> include/hw/ppc/spapr.h | 7 ++++++- > >>>>> hw/ppc/spapr.c | 29 ++++++++++++++++++++++++++++- > >>>>> hw/ppc/spapr_hcall.c | 32 ++++++++++++++++++++++++++++++++ > >>>>> hw/ppc/trace-events | 2 ++ > >>>>> 4 files changed, 68 insertions(+), 2 deletions(-) > >>>>> > >>>>> diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h > >>>>> index ad4d7cfd97..f5dcaf44cb 100644 > >>>>> --- a/include/hw/ppc/spapr.h > >>>>> +++ b/include/hw/ppc/spapr.h > >>>>> @@ -100,6 +100,7 @@ struct sPAPRMachineClass { > >>>>> > >>>>> /*< public >*/ > >>>>> bool dr_lmb_enabled; /* enable dynamic-reconfig/hotplug of > >>>>> LMBs */ > >>>>> + bool update_dt_enabled; /* enable KVMPPC_H_UPDATE_DT */ > >>>>> bool use_ohci_by_default; /* use USB-OHCI instead of XHCI */ > >>>>> bool pre_2_10_has_unused_icps; > >>>>> bool legacy_irq_allocation; > >>>>> @@ -136,6 +137,9 @@ struct sPAPRMachineState { > >>>>> int vrma_adjust; > >>>>> ssize_t rtas_size; > >>>>> void *rtas_blob; > >>>>> + uint32_t fdt_size; > >>>>> + uint32_t fdt_initial_size; > >>>> > >>>> I don't quite see the purpose of fdt_initial_size... it seems to be only > >>>> used to print a trace. > >>> > >>> > >>> Ah, lost in rebase. The purpose was to test if the new device tree has > >>> not grown too much. > >>> > >>> > >>> > >>>> > >>>>> + void *fdt_blob; > >>>>> long kernel_size; > >>>>> bool kernel_le; > >>>>> uint32_t initrd_base; > >>>>> @@ -462,7 +466,8 @@ struct sPAPRMachineState { > >>>>> #define KVMPPC_H_LOGICAL_MEMOP (KVMPPC_HCALL_BASE + 0x1) > >>>>> /* Client Architecture support */ > >>>>> #define KVMPPC_H_CAS (KVMPPC_HCALL_BASE + 0x2) > >>>>> -#define KVMPPC_HCALL_MAX KVMPPC_H_CAS > >>>>> +#define KVMPPC_H_UPDATE_DT (KVMPPC_HCALL_BASE + 0x3) > >>>>> +#define KVMPPC_HCALL_MAX KVMPPC_H_UPDATE_DT > >>>>> > >>>>> typedef struct sPAPRDeviceTreeUpdateHeader { > >>>>> uint32_t version_id; > >>>>> diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c > >>>>> index c08130facb..5e2d4d211c 100644 > >>>>> --- a/hw/ppc/spapr.c > >>>>> +++ b/hw/ppc/spapr.c > >>>>> @@ -1633,7 +1633,10 @@ static void spapr_machine_reset(void) > >>>>> /* Load the fdt */ > >>>>> qemu_fdt_dumpdtb(fdt, fdt_totalsize(fdt)); > >>>>> cpu_physical_memory_write(fdt_addr, fdt, fdt_totalsize(fdt)); > >>>>> - g_free(fdt); > >>>>> + g_free(spapr->fdt_blob); > >>>>> + spapr->fdt_size = fdt_totalsize(fdt); > >>>>> + spapr->fdt_initial_size = spapr->fdt_size; > >>>>> + spapr->fdt_blob = fdt; > >>>> > >>>> Hmm... It looks weird to store state in a reset handler. I'd rather zeroe > >>>> both fdt_blob and fdt_size here. > >>> > >>> The device tree is built from the reset handler and the idea is that we > >>> want to always have some tree in the machine. > >> > >> Yes, I think the approach here is fine. Otherwise when we want to > >> look up the current fdt state in RTAS calls or whatever we'd always > >> have to do > >> if (fdt_blob) > >> look up that > >> else > >> look up qemu created fdt. > >> > > > > No. We only have one fdt blob: the initial one, I'd rather > > call reset time one, or the updated one. > > There is one fdt in the machine, always. Either initial or from cas. > Yeah, reset time fdt is either the initial one, either cas... and I'm now wandering what happens if migration occurs between cas that sets cas_reboot and the corresponding reset. With the current code base, I have the impression that the destination will redo the full cas+cas_reboot cycle after restart or am I missing something ? > > > >> Incidentally 'fdt' and 'fdt_blob' names do a terrible job of > >> distinguishing what the difference is. Renaming fdt to fdt_initial > >> (to match fdt_initial_size) and fdt_blob to fdt should make that > >> clearer. > >> > > > > As mentioned earlier in this thread, spapr->fdt_initial_size is only used > > for tracing if the received fdt blob fails fdt_check_full()... > > > > $ git grep -H fdt_initial_size > > hw/ppc/spapr.c: spapr->fdt_initial_size = spapr->fdt_size; > > hw/ppc/spapr.c: VMSTATE_UINT32(fdt_initial_size, sPAPRMachineState), > > hw/ppc/spapr_hcall.c: > > trace_spapr_update_dt_failed(spapr->fdt_initial_size, cb, > > include/hw/ppc/spapr.h: uint32_t fdt_initial_size; > > > > Not sure it is helpful, and anyway, it is expected to be the same in source > > and destination, so why put it in the migration stream ? > > > Well, we do build the fdt anyway even when receive migration but we do > not have to and yes we can expect the fdt on the destination to be of > the same size since it is the same command line, it is just guessing and > expecting vs. knowing and I prefer the latter as the reset time fdt and > migration source fdt might have different size because of > host-model/host-serial/slot-label/similar properties. > Right but I still don't see the usefulness of fdt_initial_size... > > > The only case where we want to migrate something is when h_update_dt() has > > succeeded, ie, the guest passed a valid DT blob. This implies that its > > size isn't 0, otherwise fdt_check_full() would return -FDT_ERR_TRUNCATED. > > > > I would suggest rather to: > > > > - completely drop spapr->fdt_initial_size > > - clear spapr->fdt_size at machine reset > > - migrate if spapr->fdt_size is not zero > > > > Also, I've just realized another problem... nothing prevents a malicious > > guest to pass an insanely great size to h_update_dt, which would cause > > g_malloc0() to abort... The passed size should be checked against > > FDT_MAX_SIZE. > > Good point. Just noticed - as posted, the checker actually checks the > reset time tree, not the updated one, my bad :) > > >
