Re: [PATCH v6 32/33] nvdimm acpi: support _FIT method

From: Xiao Guangrong <guangrong.xiao@linux.intel.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: pbonzini@redhat.com, imammedo@redhat.com, gleb@kernel.org,
	mtosatti@redhat.com, stefanha@redhat.com, rth@twiddle.net,
	ehabkost@redhat.com, dan.j.williams@intel.com,
	kvm@vger.kernel.org, qemu-devel@nongnu.org
Subject: Re: [PATCH v6 32/33] nvdimm acpi: support _FIT method
Date: Mon, 9 Nov 2015 14:37:14 +0800	[thread overview]
Message-ID: <56403F1A.1000305@linux.intel.com> (raw)
In-Reply-To: <20151108175031.GA26082@redhat.com>

On 11/09/2015 01:50 AM, Michael S. Tsirkin wrote:
> On Fri, Oct 30, 2015 at 01:56:26PM +0800, Xiao Guangrong wrote:
>> FIT buffer is not completely mapped into guest address space, so a new
>> function, Read FIT, function index 0xFFFFFFFF, is reserved by QEMU to
>> read the piece of FIT buffer. The buffer is concatenated before _FIT
>> return
>>
>> Refer to docs/specs/acpi-nvdimm.txt for detailed design
>>
>> Signed-off-by: Xiao Guangrong <guangrong.xiao@linux.intel.com>
>> ---
>>   hw/acpi/nvdimm.c | 168 +++++++++++++++++++++++++++++++++++++++++++++++++++++--
>>   1 file changed, 164 insertions(+), 4 deletions(-)
>>
>> diff --git a/hw/acpi/nvdimm.c b/hw/acpi/nvdimm.c
>> index f8d7d19..3f35220 100644
>> --- a/hw/acpi/nvdimm.c
>> +++ b/hw/acpi/nvdimm.c
>> @@ -384,6 +384,18 @@ static void nvdimm_build_nfit(GSList *device_list, GArray *table_offsets,
>>       g_array_free(structures, true);
>>   }
>>
>> +/*
>> + * define UUID for NVDIMM Root Device according to Chapter 3 DSM Interface
>> + * for NVDIMM Root Device - Example in DSM Spec Rev1.
>> + */
>> +#define NVDIMM_DSM_ROOT_UUID "2F10E7A4-9E91-11E4-89D3-123B93F75CBA"
>> +
>> +/*
>> + * Read FIT Function, which is a QEMU internal use only function, more detail
>> + * refer to docs/specs/acpi_nvdimm.txt
>> + */
>> +#define NVDIMM_DSM_FUNC_READ_FIT 0xFFFFFFFF
>> +
>>   /* define NVDIMM DSM return status codes according to DSM Spec Rev1. */
>>   enum {
>>       /* Common return status codes. */
>> @@ -420,6 +432,11 @@ struct NvdimmFuncInSetLabelData {
>>   } QEMU_PACKED;
>>   typedef struct NvdimmFuncInSetLabelData NvdimmFuncInSetLabelData;
>>
>> +struct NvdimmFuncInReadFit {
>> +    uint32_t offset; /* fit offset */
>> +} QEMU_PACKED;
>> +typedef struct NvdimmFuncInReadFit NvdimmFuncInReadFit;
>> +
>>   struct NvdimmDsmIn {
>>       uint32_t handle;
>>       uint32_t revision;
>> @@ -429,6 +446,7 @@ struct NvdimmDsmIn {
>>           uint8_t arg3[0];
>>           NvdimmFuncInSetLabelData func_set_label_data;
>>           NvdimmFuncInGetLabelData func_get_label_data;
>> +        NvdimmFuncInReadFit func_read_fit;
>>       };
>>   } QEMU_PACKED;
>>   typedef struct NvdimmDsmIn NvdimmDsmIn;
>> @@ -450,13 +468,71 @@ struct NvdimmFuncOutGetLabelData {
>>   } QEMU_PACKED;
>>   typedef struct NvdimmFuncOutGetLabelData NvdimmFuncOutGetLabelData;
>>
>> +struct NvdimmFuncOutReadFit {
>> +    uint32_t status;    /* return status code. */
>> +    uint32_t length;    /* the length of fit data we read. */
>> +    uint8_t fit_data[0]; /* fit data. */
>> +} QEMU_PACKED;
>> +typedef struct NvdimmFuncOutReadFit NvdimmFuncOutReadFit;
>> +
>>   static void nvdimm_dsm_write_status(GArray *out, uint32_t status)
>>   {
>>       status = cpu_to_le32(status);
>>       build_append_int_noprefix(out, status, sizeof(status));
>>   }
>>
>> -static void nvdimm_dsm_root(NvdimmDsmIn *in, GArray *out)
>> +/* Build fit memory which is presented to guest via _FIT method. */
>> +static void nvdimm_build_fit(AcpiNVDIMMState *state)
>> +{
>> +    if (!state->fit) {
>> +        GSList *device_list = nvdimm_get_plugged_device_list();
>> +
>> +        nvdimm_debug("Rebuild FIT...\n");
>> +        state->fit = nvdimm_build_device_structure(device_list);
>> +        g_slist_free(device_list);
>> +    }
>> +}
>> +
>> +/* Read FIT data, defined in docs/specs/acpi_nvdimm.txt. */
>> +static void nvdimm_dsm_func_read_fit(AcpiNVDIMMState *state,
>> +                                     NvdimmDsmIn *in, GArray *out)
>> +{
>> +    NvdimmFuncInReadFit *read_fit = &in->func_read_fit;
>> +    NvdimmFuncOutReadFit fit_out;
>> +    uint32_t read_length = TARGET_PAGE_SIZE - sizeof(NvdimmFuncOutReadFit);
>> +    uint32_t status = NVDIMM_DSM_ROOT_DEV_STATUS_INVALID_PARAS;
>> +
>> +    nvdimm_build_fit(state);
>> +
>> +    le32_to_cpus(&read_fit->offset);
>> +
>> +    nvdimm_debug("Read FIT offset %#x.\n", read_fit->offset);
>> +
>> +    if (read_fit->offset > state->fit->len) {
>> +        nvdimm_debug("offset %#x is beyond fit size (%#x).\n",
>> +                     read_fit->offset, state->fit->len);
>> +        goto exit;
>> +    }
>> +
>> +    read_length = MIN(read_length, state->fit->len - read_fit->offset);
>> +    nvdimm_debug("read length %#x.\n", read_length);
>> +
>> +    fit_out.status = cpu_to_le32(NVDIMM_DSM_STATUS_SUCCESS);
>> +    fit_out.length = cpu_to_le32(read_length);
>
> Is array always empty at this point?
> If yes, better assert this here to make sure guest can not
> use unlimited memory.

It's unnecessary. At the end of dsm handler, we have asserted it that the
memory size can not beyond the size of dsm memory region:

static uint64_t
nvdimm_dsm_read(void *opaque, hwaddr addr, unsigned size)
{
    ......
exit:
     assert(out->len <= memory_region_size(dsm_ram_mr));

     /* Write output result to dsm memory. */
     memcpy(dsm_ram_addr, out->data, out->len);
     memory_region_set_dirty(dsm_ram_mr, 0, out->len);

     buf_size = cpu_to_le32(out->len);
     ......
}

>
>> +    g_array_append_vals(out, &fit_out, sizeof(fit_out));
>> +
>> +    if (read_length) {
>> +        g_array_append_vals(out, state->fit->data + read_fit->offset,
>> +                            read_length);
>> +    }
>> +    return;
>> +
>> +exit:
>> +    nvdimm_dsm_write_status(out, status);
>> +}
>> +
>> +static void nvdimm_dsm_root(AcpiNVDIMMState *state, NvdimmDsmIn *in,
>> +                            GArray *out)
>>   {
>>       uint32_t status = NVDIMM_DSM_STATUS_NOT_SUPPORTED;
>>
>> @@ -475,6 +551,10 @@ static void nvdimm_dsm_root(NvdimmDsmIn *in, GArray *out)
>>           return;
>>       }
>>
>> +    if (in->function == NVDIMM_DSM_FUNC_READ_FIT /* FIT Read */) {
>> +        return nvdimm_dsm_func_read_fit(state, in, out);
>> +    }
>> +
>>       nvdimm_debug("Return status %#x.\n", status);
>>       nvdimm_dsm_write_status(out, status);
>>   }
>> @@ -710,7 +790,7 @@ nvdimm_dsm_read(void *opaque, hwaddr addr, unsigned size)
>>
>>       /* Handle 0 is reserved for NVDIMM Root Device. */
>>       if (!in->handle) {
>> -        nvdimm_dsm_root(in, out);
>> +        nvdimm_dsm_root(state, in, out);
>>           goto exit;
>>       }
>>
>> @@ -925,8 +1005,88 @@ static void nvdimm_build_acpi_devices(GSList *device_list, Aml *sb_scope)
>>        */
>>       BUILD_DSM_METHOD(dev, method,
>>                        0 /* 0 is reserved for NVDIMM Root Device*/,
>> -                     "2F10E7A4-9E91-11E4-89D3-123B93F75CBA"
>> -                     /* UUID for NVDIMM Root Devices. */);
>> +                     NVDIMM_DSM_ROOT_UUID /* UUID for NVDIMM Root Devices. */);
>> +
>> +    method = aml_method("RFIT", 1);
>> +    {
>> +        Aml *ret, *pckg, *ifcond, *ifctx, *dsm_return = aml_local(0);
>> +
>> +        aml_append(method, aml_create_dword_field(aml_buffer(4, NULL),
>> +                                                  aml_int(0), "OFST"));
>
> Creating new names within method is problematic: will
> lead to crashes if method is called multiple times.

I did the test that let _FIT read 8 bytes per time then this method will be called multiple
times, it worked well. The case can cause the problem is the while loop:

| Creation of a named object more than once in a given scope is not allowed. As such,
| unconditionally creating named objects within a While loop must be avoided. A fatal error will be
| generated on the second iteration of the loop, during the attempt to create the same named object
| a second time.

[ 19.6.143 While (Conditional Loop) in ACPI 6.0 ]

That is why i made it as a separate method and split it from the loop in _FIT method.

>
>
>
>> +
>> +        /* prepare NvdimmFuncInReadFit.offset */
>> +        aml_append(method, aml_store(aml_arg(0), aml_name("OFST")));
>> +        pckg = aml_package(1);
>> +        aml_append(pckg, aml_name("OFST"));
>> +
>> +        ret = aml_call4("_DSM",
>> +                        aml_touuid(NVDIMM_DSM_ROOT_UUID) /* Root Device UUID */,
>> +                        aml_int(1) /* Revision 1 */,
>> +                        aml_int(NVDIMM_DSM_FUNC_READ_FIT) /* Read FIT
>> +                                                             Function Index */,
>> +                        pckg);
>> +        aml_append(method, aml_store(ret, dsm_return));
>> +
>> +        aml_append(method, aml_create_dword_field(dsm_return,
>> +                                          aml_int(0) /* offset at byte 0 */,
>> +                                          "STAU"));
>> +        /* if something is wrong during _DSM. */
>> +        ifcond = aml_equal(aml_int(NVDIMM_DSM_STATUS_SUCCESS),
>> +                           aml_name("STAU"));
>> +        ifctx = aml_if(aml_lnot(ifcond));
>> +        {
>> +            aml_append(ifctx, aml_return(aml_buffer(0, NULL)));
>> +        }
>> +        aml_append(method, ifctx);
>> +
>> +        aml_append(method, aml_create_dword_field(dsm_return,
>> +                                          aml_int(4) /* offset at byte 4. */,
>> +                                          "BFSZ"));
>> +        /* if we read the end of fit. */
>> +        ifctx = aml_if(aml_equal(aml_name("BFSZ"), aml_int(0)));
>> +        {
>> +            aml_append(ifctx, aml_return(aml_buffer(0, NULL)));
>> +        }
>> +        aml_append(method, ifctx);
>> +
>> +        aml_append(method, aml_store(aml_shiftleft(aml_name("BFSZ"),
>> +                                                   aml_int(3)), aml_local(6)));
>> +        aml_append(method, aml_create_field(dsm_return,
>> +                            aml_int(8 * BITS_PER_BYTE), /* offset at byte 8.*/
>> +                            aml_local(6), "BUFF"));
>
> Same here.
>
> Additionally, using named constants for things like BFSZ etc
> will help name sure they match.

Okay, will change it to:

aml_append(method, aml_store(aml_shiftleft(aml_name("BFSZ"),
                                            aml_int(3)), aml_name("BFSZ")));
aml_append(method, aml_create_field(dsm_return,
                             aml_int(8 * BITS_PER_BYTE), /* offset at byte 8.*/
                             aml_name("BFSZ"), "BUFF"));

By the way, Michael, what's your idea on this thread:
       http://marc.info/?l=kvm&m=144671750722962&w=2

Thanks!