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Re: [PATCH RESEND v2] block/nvme: introduce PMR support from NVMe 1.4 sp
From: |
Andrzej Jakowski |
Subject: |
Re: [PATCH RESEND v2] block/nvme: introduce PMR support from NVMe 1.4 spec |
Date: |
Mon, 16 Mar 2020 10:10:15 -0700 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.5.0 |
On 3/16/20 4:32 AM, Stefan Hajnoczi wrote:
> On Wed, Mar 11, 2020 at 11:08:27PM -0700, Klaus Birkelund Jensen wrote:
>> On Mar 11 15:54, Andrzej Jakowski wrote:
>>> On 3/11/20 2:20 AM, Stefan Hajnoczi wrote:
>>>> Please try:
>>>>
>>>> $ git grep pmem
>>>>
>>>> backends/hostmem-file.c is the backend that can be used and the
>>>> pmem_persist() API can be used to flush writes.
>>> I've reworked this patch into hostmem-file type of backend.
>>> From simple tests in virtual machine: writing to PMR region
>>> and then reading from it after VM power cycle I have observed that
>>> there is no persistency.
> Sounds like an integration bug. QEMU's NVDIMM emulation uses
> HostMemoryBackend and file contents survive guest reboot.
>
> If you would like help debugging this, please post a link to the code
> and the command-line that you are using.
>
Code is posted here
https://github.com/AndrzejJakowski/qemu/commit/3a7762a1d13ff1543d1da430748eb24e38faab6f
QEMU command line:
# below are just relevant pieces of configuration, other stuff omitted
# tried different setting (e.g. pmem=on and pmem=off)
./x86_64-softmmu/qemu-system-x86_64 ... \
-object
memory-backend-file,id=mem1,share=off,pmem=on,mem-path=../nvme_pmr.bin,size=$((1*1024*1024))
\
-drive file=../nvme.bin,format=raw,if=none,id=nvme_emulated \
-device nvme,drive=nvme_emulated,serial="test serial",pmrdev=mem1
In VM:
My persisent memory region is exposed PCI BAR
Region 2: Memory at fe000000 (64-bit, prefetchable) [size=1M]
So I perform reads/writes from/to following adress 0xfe000000 (decimal
4261412864)
dd if=test.bin of=/dev/mem bs=1 count=30 seek=4261412864
dd if=/dev/mem of=test1.bin bs=1 count=30 skip=4261412864
On VMM I didn't observe that backing file has been updated and after power
cycling VM
I see old junk when reading PMR region.
Also from include/qemu/pmem.h it looks like pmem_persist() will cause qemu to
exit
if libpmem is not installed:
#ifndef QEMU_PMEM_H
#define QEMU_PMEM_H
#ifdef CONFIG_LIBPMEM
#include <libpmem.h>
#else /* !CONFIG_LIBPMEM */
static inline void *
pmem_memcpy_persist(void *pmemdest, const void *src, size_t len)
{
/* If 'pmem' option is 'on', we should always have libpmem support,
or qemu will report a error and exit, never come here. */
g_assert_not_reached();
return NULL;
}
static inline void
pmem_persist(const void *addr, size_t len)
{
g_assert_not_reached();
}
#endif /* CONFIG_LIBPMEM */
#endif /* QEMU_PMEM_H */
- [PATCH RESEND v2] block/nvme: introduce PMR support from NVMe 1.4 spec, Andrzej Jakowski, 2020/03/06
- Re: [PATCH RESEND v2] block/nvme: introduce PMR support from NVMe 1.4 spec, Stefan Hajnoczi, 2020/03/10
- Re: [PATCH RESEND v2] block/nvme: introduce PMR support from NVMe 1.4 spec, Andrzej Jakowski, 2020/03/10
- Re: [PATCH RESEND v2] block/nvme: introduce PMR support from NVMe 1.4 spec, Stefan Hajnoczi, 2020/03/11
- Re: [PATCH RESEND v2] block/nvme: introduce PMR support from NVMe 1.4 spec, Andrzej Jakowski, 2020/03/11
- Re: [PATCH RESEND v2] block/nvme: introduce PMR support from NVMe 1.4 spec, Andrzej Jakowski, 2020/03/11
- Re: [PATCH RESEND v2] block/nvme: introduce PMR support from NVMe 1.4 spec, Klaus Birkelund Jensen, 2020/03/12
- Re: [PATCH RESEND v2] block/nvme: introduce PMR support from NVMe 1.4 spec, Stefan Hajnoczi, 2020/03/16
- Re: [PATCH RESEND v2] block/nvme: introduce PMR support from NVMe 1.4 spec,
Andrzej Jakowski <=
- Re: [PATCH RESEND v2] block/nvme: introduce PMR support from NVMe 1.4 spec, Stefan Hajnoczi, 2020/03/17
- Re: [PATCH RESEND v2] block/nvme: introduce PMR support from NVMe 1.4 spec, Andrzej Jakowski, 2020/03/18