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

[Igor Mammedov <imammedo@redhat.com>]

On Mon, 9 Dec 2019 17:39:15 +0000
Shameerali Kolothum Thodi <shameerali.kolothum.thodi@huawei.com> wrote:

> 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.
Sorry, I don't have capacity to debug this right now,
but I'd prefer if 'why' question was answered first.

Anyways, if something is unclear in how concrete AML code is build/works,
feel free to ask and I'll try to explain and guide you.

> Thanks,
> Shameer
> 
> 
>