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Re: [PATCH v2] ppc/spapr: Add support for implement support for H_SCM_HE
From: |
Greg Kurz |
Subject: |
Re: [PATCH v2] ppc/spapr: Add support for implement support for H_SCM_HEALTH |
Date: |
Thu, 1 Apr 2021 07:51:55 +0200 |
On Thu, 1 Apr 2021 13:26:11 +1100
David Gibson <david@gibson.dropbear.id.au> wrote:
> On Thu, Apr 01, 2021 at 06:35:19AM +0530, Vaibhav Jain wrote:
> > Add support for H_SCM_HEALTH hcall described at [1] for spapr
> > nvdimms. This enables guest to detect the 'unarmed' status of a
> > specific spapr nvdimm identified by its DRC and if its unarmed, mark
> > the region backed by the nvdimm as read-only.
> >
> > The patch adds h_scm_health() to handle the H_SCM_HEALTH hcall which
> > returns two 64-bit bitmaps (health bitmap, health bitmap mask) derived
> > from 'struct nvdimm->unarmed' member.
> >
> > Linux kernel side changes to enable handling of 'unarmed' nvdimms for
> > ppc64 are proposed at [2].
> >
> > References:
> > [1] "Hypercall Op-codes (hcalls)"
> >
> > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/powerpc/papr_hcalls.rst#n220
> > [2] "powerpc/papr_scm: Mark nvdimm as unarmed if needed during probe"
> >
> > https://lore.kernel.org/linux-nvdimm/20210329113103.476760-1-vaibhav@linux.ibm.com/
> >
> > Signed-off-by: Vaibhav Jain <vaibhav@linux.ibm.com>
>
> As well as the handful of comments below, this will definitely need to
> wait for ppc-6.1 at this point.
>
> > ---
> > Changelog
> >
> > v2:
> > * Added a check for drc->dev to ensure that the dimm is plugged in
> > when servicing H_SCM_HEALTH. [ Shiva ]
> > * Instead of accessing the 'nvdimm->unarmed' member directly use the
> > object_property_get_bool accessor to fetch it. [ Shiva ]
> > * Update the usage of PAPR_PMEM_UNARMED* macros [ Greg ]
> > * Updated patch description reference#1 to point appropriate section
> > in the documentation. [ Greg ]
> > ---
> > hw/ppc/spapr_nvdimm.c | 38 ++++++++++++++++++++++++++++++++++++++
> > include/hw/ppc/spapr.h | 3 ++-
> > 2 files changed, 40 insertions(+), 1 deletion(-)
> >
> > diff --git a/hw/ppc/spapr_nvdimm.c b/hw/ppc/spapr_nvdimm.c
> > index b46c36917c..34096e4718 100644
> > --- a/hw/ppc/spapr_nvdimm.c
> > +++ b/hw/ppc/spapr_nvdimm.c
> > @@ -31,6 +31,13 @@
> > #include "qemu/range.h"
> > #include "hw/ppc/spapr_numa.h"
> >
> > +/* DIMM health bitmap bitmap indicators. Taken from kernel's papr_scm.c */
> > +/* SCM device is unable to persist memory contents */
> > +#define PAPR_PMEM_UNARMED (1ULL << (63 - 0))
>
> You can use PPC_BIT() for more clarity here.
>
I had already suggested PPC_BIT(0) but since this macro was copied
from the kernel source, I've let Vaibhav decide whether to use
PPC_BIT() or keep the macro and comment it comes from the kernel.
I agree I prefer PPC_BIT(0) :-)
> > +/* Bits status indicators for health bitmap indicating unarmed dimm */
> > +#define PAPR_PMEM_UNARMED_MASK (PAPR_PMEM_UNARMED)
>
> I'm not sure why you want two equal #defines here.
>
Especially, this define doesn't make sense for the hypervisor IMHO.
It is _just_ the mask of bits for the "unarmed" state in the kernel.
> > +
> > bool spapr_nvdimm_validate(HotplugHandler *hotplug_dev, NVDIMMDevice
> > *nvdimm,
> > uint64_t size, Error **errp)
> > {
> > @@ -467,6 +474,36 @@ static target_ulong h_scm_unbind_all(PowerPCCPU *cpu,
> > SpaprMachineState *spapr,
> > return H_SUCCESS;
> > }
> >
> > +static target_ulong h_scm_health(PowerPCCPU *cpu, SpaprMachineState *spapr,
> > + target_ulong opcode, target_ulong *args)
> > +{
> > + uint32_t drc_index = args[0];
> > + SpaprDrc *drc = spapr_drc_by_index(drc_index);
> > + NVDIMMDevice *nvdimm;
> > +
> > + if (drc && spapr_drc_type(drc) != SPAPR_DR_CONNECTOR_TYPE_PMEM) {
>
> This will fail badly if !drc (given index is way out of bounds). I'm
> pretty sure you want
> if (!drc || spapr_drc_type(drc) != SPAPR_DR_CONNECTOR_TYPE_PMEM) {
>
>
> > + return H_PARAMETER;
> > + }
> > +
> > + /* Ensure that the dimm is plugged in */
> > + if (!drc->dev) {
> > + return H_HARDWARE;
>
> H_HARDWARE doesn't seem right - it's the guest that has chosen to
> attempt this on an unplugged LMB, not the (virtual) hardware's fault.
>
Yes. As already suggested, simply do the same as in other hcall
implementations in this file, e.g. from h_scm_bind_mem() :
if (!drc || !drc->dev ||
spapr_drc_type(drc) != SPAPR_DR_CONNECTOR_TYPE_PMEM) {
return H_PARAMETER;
}
> > + }
> > +
> > + nvdimm = NVDIMM(drc->dev);
> > +
> > + args[0] = 0;
> > + /* Check if the nvdimm is unarmed and send its status via health
> > bitmaps */
Not sure this comment is super useful.
> > + if (object_property_get_bool(OBJECT(nvdimm), NVDIMM_UNARMED_PROP,
> > NULL)) {
> > + args[0] |= PAPR_PMEM_UNARMED;
> > + }
> > +
> > + /* Update the health bitmap with the applicable mask */
> > + args[1] = PAPR_PMEM_UNARMED_MASK;
I still think this is a misuse of PAPR_PMEM_UNARMED_MASK... The
meaning of args[1] is "health-bit-valid-bitmap indicate which
bits in health-bitmap are valid" according to the documentation.
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/Documentation/powerpc/papr_hcalls.rst#n228
Without any further detail, I tend to consider this as a hint
to the guest on the bits supported by the hypervisor. Since
we can only set PAPR_PMEM_UNARMED, for now, args[1] should
be set to just that bit PAPR_PMEM_UNARMED. Other bits can
be added later if QEMU supports more of them.
> > +
> > + return H_SUCCESS;
> > +}
> > +
> > static void spapr_scm_register_types(void)
> > {
> > /* qemu/scm specific hcalls */
> > @@ -475,6 +512,7 @@ static void spapr_scm_register_types(void)
> > spapr_register_hypercall(H_SCM_BIND_MEM, h_scm_bind_mem);
> > spapr_register_hypercall(H_SCM_UNBIND_MEM, h_scm_unbind_mem);
> > spapr_register_hypercall(H_SCM_UNBIND_ALL, h_scm_unbind_all);
> > + spapr_register_hypercall(H_SCM_HEALTH, h_scm_health);
> > }
> >
> > type_init(spapr_scm_register_types)
> > diff --git a/include/hw/ppc/spapr.h b/include/hw/ppc/spapr.h
> > index 47cebaf3ac..6e1eafb05d 100644
> > --- a/include/hw/ppc/spapr.h
> > +++ b/include/hw/ppc/spapr.h
> > @@ -538,8 +538,9 @@ struct SpaprMachineState {
> > #define H_SCM_BIND_MEM 0x3EC
> > #define H_SCM_UNBIND_MEM 0x3F0
> > #define H_SCM_UNBIND_ALL 0x3FC
> > +#define H_SCM_HEALTH 0x400
> >
> > -#define MAX_HCALL_OPCODE H_SCM_UNBIND_ALL
> > +#define MAX_HCALL_OPCODE H_SCM_HEALTH
> >
> > /* The hcalls above are standardized in PAPR and implemented by pHyp
> > * as well.
>
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- Re: [PATCH v2] ppc/spapr: Add support for implement support for H_SCM_HEALTH,
Greg Kurz <=