| Message ID | 1454045043-25545-9-git-send-email-david@gibson.dropbear.id.au (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
On 01/29/2016 10:54 AM, David Gibson wrote: > The hypervisor needs to know a guest is capable of using the HPT resizing > PAPR extension in order to make full advantage of it for memory hotplug. > > If the hypervisor knows the guest is HPT resize aware, it can size the > initial HPT based on the initial guest RAM size, relying on the guest to > resize the HPT when more memory is hot-added. Without this, the hypervisor > must size the HPT for the maximum possible guest RAM, which can lead to > a huge waste of space if the guest never actually expends to that maximum > size. > > This patch advertises the guest's support for HPT resizing via the > ibm,client-architecture-support OF interface. Obviously, the actual > encoding in the CAS vector is tentative until the extension is officially > incorporated into PAPR. For now we use bit 0 of (previously unused) byte 8 > of option vector 5. > > Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Reviewed-by: Anshuman Khandual <khandual@linux.vnet.ibm.com>
On Fri, Jan 29, 2016 at 04:24:02PM +1100, David Gibson wrote: > The hypervisor needs to know a guest is capable of using the HPT resizing > PAPR extension in order to make full advantage of it for memory hotplug. > > If the hypervisor knows the guest is HPT resize aware, it can size the > initial HPT based on the initial guest RAM size, relying on the guest to > resize the HPT when more memory is hot-added. Without this, the hypervisor > must size the HPT for the maximum possible guest RAM, which can lead to > a huge waste of space if the guest never actually expends to that maximum > size. > > This patch advertises the guest's support for HPT resizing via the > ibm,client-architecture-support OF interface. Obviously, the actual > encoding in the CAS vector is tentative until the extension is officially > incorporated into PAPR. For now we use bit 0 of (previously unused) byte 8 > of option vector 5. > > Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Reviewed-by: Paul Mackerras <paulus@samba.org>
diff --git a/arch/powerpc/include/asm/prom.h b/arch/powerpc/include/asm/prom.h index 7f436ba..ef08208 100644 --- a/arch/powerpc/include/asm/prom.h +++ b/arch/powerpc/include/asm/prom.h @@ -151,6 +151,7 @@ struct of_drconf_cell { #define OV5_XCMO 0x0440 /* Page Coalescing */ #define OV5_TYPE1_AFFINITY 0x0580 /* Type 1 NUMA affinity */ #define OV5_PRRN 0x0540 /* Platform Resource Reassignment */ +#define OV5_HPT_RESIZE 0x0880 /* Hash Page Table resizing */ #define OV5_PFO_HW_RNG 0x0E80 /* PFO Random Number Generator */ #define OV5_PFO_HW_842 0x0E40 /* PFO Compression Accelerator */ #define OV5_PFO_HW_ENCR 0x0E20 /* PFO Encryption Accelerator */ diff --git a/arch/powerpc/kernel/prom_init.c b/arch/powerpc/kernel/prom_init.c index da51925..c6feafb 100644 --- a/arch/powerpc/kernel/prom_init.c +++ b/arch/powerpc/kernel/prom_init.c @@ -713,7 +713,7 @@ unsigned char ibm_architecture_vec[] = { OV5_FEAT(OV5_TYPE1_AFFINITY) | OV5_FEAT(OV5_PRRN), 0, 0, - 0, + OV5_FEAT(OV5_HPT_RESIZE), /* WARNING: The offset of the "number of cores" field below * must match by the macro below. Update the definition if * the structure layout changes.
The hypervisor needs to know a guest is capable of using the HPT resizing PAPR extension in order to make full advantage of it for memory hotplug. If the hypervisor knows the guest is HPT resize aware, it can size the initial HPT based on the initial guest RAM size, relying on the guest to resize the HPT when more memory is hot-added. Without this, the hypervisor must size the HPT for the maximum possible guest RAM, which can lead to a huge waste of space if the guest never actually expends to that maximum size. This patch advertises the guest's support for HPT resizing via the ibm,client-architecture-support OF interface. Obviously, the actual encoding in the CAS vector is tentative until the extension is officially incorporated into PAPR. For now we use bit 0 of (previously unused) byte 8 of option vector 5. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> --- arch/powerpc/include/asm/prom.h | 1 + arch/powerpc/kernel/prom_init.c | 2 +- 2 files changed, 2 insertions(+), 1 deletion(-)