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spapr: Improve handling of memory unplug with old guests

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Since commit 1e8b5b1aa1 ("spapr: Allow memory unplug to always succeed")
trying to unplug memory from a guest that doesn't support it (eg. rhel6)
no longer generates an error like it used to. Instead, it leaves the
memory around : only a subsequent reboot or manual use of drmgr within
the guest can complete the hot-unplug sequence. A flag was added to
SpaprMachineClass so that this new behavior only applies to the default
machine type.

We can do better. CAS processes all pending hot-unplug requests. This
means that we don't really care about what the guest supports if
the hot-unplug request happens before CAS.

All guests that we care for, even old ones, set enough bits in OV5
that lead to a non-empty bitmap in spapr->ov5_cas. Use that as a
heuristic to decide if CAS has already occured or not.

Always accept unplug requests that happen before CAS since CAS will
process them. Restore the previous behavior of rejecting them after
CAS when we know that the guest doesn't support memory hot-unplug.

This behavior is suitable for all machine types : this allows to
drop the pre_6_0_memory_unplug flag.

Fixes: 1e8b5b1aa1 ("spapr: Allow memory unplug to always succeed")
Signed-off-by: Greg Kurz <groug@kaod.org>
Message-Id: <161012708715.801107.11418801796987916516.stgit@bahia.lan>
Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
This commit is contained in:
Greg Kurz 2021-01-08 18:31:27 +01:00 • committed by David Gibson
parent f17969db71
commit 73598c75df
5 changed files with 23 additions and 14 deletions
Download patch file Download diff file Expand all files Collapse all files

2
include/hw/ppc/spapr.h
View file

@ -142,7 +142,6 @@ struct SpaprMachineClass {
hwaddr rma_limit; /* clamp the RMA to this size */
bool pre_5_1_assoc_refpoints;
bool pre_5_2_numa_associativity;
bool pre_6_0_memory_unplug;
bool (*phb_placement)(SpaprMachineState *spapr, uint32_t index,
uint64_t *buid, hwaddr *pio,
@ -950,4 +949,5 @@ bool spapr_check_pagesize(SpaprMachineState *spapr, hwaddr pagesize,
void spapr_set_all_lpcrs(target_ulong value, target_ulong mask);
hwaddr spapr_get_rtas_addr(void);
bool spapr_memory_hot_unplug_supported(SpaprMachineState *spapr);
#endif /* HW_SPAPR_H */

1
include/hw/ppc/spapr_ovec.h
View file

@ -71,6 +71,7 @@ void spapr_ovec_cleanup(SpaprOptionVector *ov);
void spapr_ovec_set(SpaprOptionVector *ov, long bitnr);
void spapr_ovec_clear(SpaprOptionVector *ov, long bitnr);
bool spapr_ovec_test(SpaprOptionVector *ov, long bitnr);
bool spapr_ovec_empty(SpaprOptionVector *ov);
SpaprOptionVector *spapr_ovec_parse_vector(target_ulong table_addr, int vector);
int spapr_dt_ovec(void *fdt, int fdt_offset,
SpaprOptionVector *ov, const char *name);