[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [PATCH v2 4/8] mem/nvdimm: ensure write persistence to
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-devel] [PATCH v2 4/8] mem/nvdimm: ensure write persistence to PMEM in label emulation |
Date: |
Fri, 9 Feb 2018 14:27:40 +0000 |
User-agent: |
Mutt/1.9.2 (2017-12-15) |
On Wed, Feb 07, 2018 at 03:33:27PM +0800, Haozhong Zhang wrote:
> @@ -156,11 +157,17 @@ static void nvdimm_write_label_data(NVDIMMDevice
> *nvdimm, const void *buf,
> {
> MemoryRegion *mr;
> PCDIMMDevice *dimm = PC_DIMM(nvdimm);
> + bool is_pmem = object_property_get_bool(OBJECT(dimm->hostmem),
> + "pmem", NULL);
> uint64_t backend_offset;
>
> nvdimm_validate_rw_label_data(nvdimm, size, offset);
>
> - memcpy(nvdimm->label_data + offset, buf, size);
> + if (!is_pmem) {
> + memcpy(nvdimm->label_data + offset, buf, size);
> + } else {
> + pmem_memcpy_persist(nvdimm->label_data + offset, buf, size);
> + }
Is this enough to prevent label corruption in case of power failure?
pmem_memcpy_persist() is not atomic. Power failure can result in a mix
of the old and new label data.
If we want this operation to be 100% safe there needs to be some kind of
update protocol that makes the change atomic, like a Label A and Label B
area with a single Label Index field that can be updated atomically to
point to the active Label A/B area.
Stefan
signature.asc
Description: PGP signature
- [Qemu-devel] [PATCH v2 0/8] nvdimm: guarantee persistence of QEMU writes to persistent memory, Haozhong Zhang, 2018/02/07
- [Qemu-devel] [PATCH v2 2/8] hostmem-file: add the 'pmem' option, Haozhong Zhang, 2018/02/07
- [Qemu-devel] [PATCH v2 1/8] memory, exec: switch file ram allocation functions to 'flags' parameters, Haozhong Zhang, 2018/02/07
- [Qemu-devel] [PATCH v2 3/8] configure: add libpmem support, Haozhong Zhang, 2018/02/07
- [Qemu-devel] [PATCH v2 4/8] mem/nvdimm: ensure write persistence to PMEM in label emulation, Haozhong Zhang, 2018/02/07
- Re: [Qemu-devel] [PATCH v2 4/8] mem/nvdimm: ensure write persistence to PMEM in label emulation,
Stefan Hajnoczi <=
- [Qemu-devel] [PATCH v2 5/8] migration/ram: ensure write persistence on loading zero pages to PMEM, Haozhong Zhang, 2018/02/07
- Re: [Qemu-devel] [PATCH v2 5/8] migration/ram: ensure write persistence on loading zero pages to PMEM, Dr. David Alan Gilbert, 2018/02/07