RE: [PATCH 0/5] ARM virt: Add NVDIMM support

[Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com>]

Hi Igor/ xiaoguangrong,

> -----Original Message-----
> From: Shameerali Kolothum Thodi
> Sent: 28 November 2019 12:36
> To: 'Igor Mammedov' <imammedo@redhat.com>;
> xiaoguangrong.eric@gmail.com
> Cc: peter.maydell@linaro.org; drjones@redhat.com;
> shannon.zhaosl@gmail.com; qemu-devel@nongnu.org; Linuxarm
> <linuxarm@huawei.com>; Auger Eric <eric.auger@redhat.com>;
> qemu-arm@nongnu.org; xuwei (O) <xuwei5@huawei.com>;
> lersek@redhat.com
> Subject: RE: [PATCH 0/5] ARM virt: Add NVDIMM support
> 
> 
> 
> > -----Original Message-----
> > From: Qemu-devel
> >
> [mailto:qemu-devel-bounces+shameerali.kolothum.thodi=huawei.com@nongn
> > u.org] On Behalf Of Igor Mammedov
> > Sent: 26 November 2019 08:57
> > To: Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com>
> > Cc: peter.maydell@linaro.org; drjones@redhat.com;
> > xiaoguangrong.eric@gmail.com; shannon.zhaosl@gmail.com;
> > qemu-devel@nongnu.org; Linuxarm <linuxarm@huawei.com>; Auger Eric
> > <eric.auger@redhat.com>; qemu-arm@nongnu.org; xuwei (O)
> > <xuwei5@huawei.com>; lersek@redhat.com
> > Subject: Re: [PATCH 0/5] ARM virt: Add NVDIMM support
> 
> [..]
> 
> > > > 0xb8 Dirty No.  -->Another read is attempted
> > > > > [Qemu]NVDIMM:nvdimm_dsm_func_read_fit: read_fit_out buf size 0x8
> > > > func_ret_status 3  --> Error status returned
> > > >
> > > > status 3 means that QEMU didn't like content of NRAM, and there is only
> > > > 1 place like this in nvdimm_dsm_func_read_fit()
> > > >     if (read_fit->offset > fit->len) {
> > > >         func_ret_status = NVDIMM_DSM_RET_STATUS_INVALID;
> > > >         goto exit;
> > > >     }
> > > >
> > > > so I'd start looking from here and check that QEMU gets expected data
> > > > in nvdimm_dsm_write(). In other words I'd try to trace/compare
> > > > content of DSM buffer (from qemu side).
> > >
> > > I had printed the DSM buffer previously and it looked same, I will double
> check
> > > that.
> 
> Tried printing the buffer in both Qemu/AML code.
> 
> On Amr64,

[...]
 
> Attached the SSDT.dsl used for debugging. I am still not clear why on ARM64,
> 2nd iteration case, the created buffer size in NCAL and RFIT methods have
> additional 4 bytes!.
> 
>     CreateField (ODAT, Zero, Local1, OBUF)
>     Concatenate (Buffer (Zero){}, OBUF, Local7)
> 
> Please let me know if you have any clue.
> 

I couldn't figure out yet, why this extra 4 bytes are added by aml code on ARM64
when the nvdimm_dsm_func_read_fit() returns NvdimmFuncReadFITOut without
any FIT data. ie, when the FIT buffer len (read_len) is zero.

But the below will fix this issue,

diff --git a/hw/acpi/nvdimm.c b/hw/acpi/nvdimm.c
index f91eea3802..cddf95f4c1 100644
--- a/hw/acpi/nvdimm.c
+++ b/hw/acpi/nvdimm.c
@@ -588,7 +588,7 @@ static void nvdimm_dsm_func_read_fit(NVDIMMState *state, NvdimmDsmIn *in,
     nvdimm_debug("Read FIT: offset %#x FIT size %#x Dirty %s.\n",
                  read_fit->offset, fit->len, fit_buf->dirty ? "Yes" : "No");

-    if (read_fit->offset > fit->len) {
+    if (read_fit->offset >= fit->len) {
         func_ret_status = NVDIMM_DSM_RET_STATUS_INVALID;
         goto exit;
     }


This will return error code to aml in the second iteration when there is no further
FIT data to report. But, I am not sure why this check was omitted in the first place.

Please let me know if this is acceptable and then probably I can look into a v2 of this
series.

Thanks,
Shameer