On Thu, Nov 10, 2022 at 09:27:52AM +0800, Li, Ming wrote:
> On 11/10/2022 1:52 AM, Bjorn Helgaas wrote:
> > On Wed, Nov 09, 2022 at 10:20:44AM +0800, Li Ming wrote:
> >> The value of data object length 0x0 indicates 2^18 dwords being
> >> transferred, it is introduced in PCIe r6.0,sec 6.30.1. This patch
> >> adjusts the value of data object length for the above case on both
> >> sending side and receiving side.
> >>
> >> Besides, it is unnecessary to check whether length is greater than
> >> SZ_1M while receiving a response data object, because length from LENGTH
> >> field of data object header, max value is 2^18.
> >>
> >> Signed-off-by: Li Ming <ming4.li@xxxxxxxxx>
> >> ---
> >> drivers/pci/doe.c | 21 +++++++++++++++++----
> >> 1 file changed, 17 insertions(+), 4 deletions(-)
> >>
> >> diff --git a/drivers/pci/doe.c b/drivers/pci/doe.c
> >> index e402f05068a5..204cbc570f63 100644
> >> --- a/drivers/pci/doe.c
> >> +++ b/drivers/pci/doe.c
> >> @@ -29,6 +29,9 @@
> >> #define PCI_DOE_FLAG_CANCEL 0
> >> #define PCI_DOE_FLAG_DEAD 1
> >>
> >> +/* Max data object length is 2^18 dwords */
> >> +#define PCI_DOE_MAX_LENGTH (2 << 18)
> >> /**
> >> * struct pci_doe_mb - State for a single DOE mailbox
> >> *
> >> @@ -107,6 +110,7 @@ static int pci_doe_send_req(struct pci_doe_mb *doe_mb,
> >> {
> >> struct pci_dev *pdev = doe_mb->pdev;
> >> int offset = doe_mb->cap_offset;
> >> + u32 length;
> >> u32 val;
> >> int i;
> >>
> >> @@ -128,10 +132,12 @@ static int pci_doe_send_req(struct pci_doe_mb *doe_mb,
> >> FIELD_PREP(PCI_DOE_DATA_OBJECT_HEADER_1_TYPE, task->prot.type);
> >> pci_write_config_dword(pdev, offset + PCI_DOE_WRITE, val);
> >> /* Length is 2 DW of header + length of payload in DW */
> >> + length = 2 + task->request_pl_sz / sizeof(u32);
> >> + if (length == PCI_DOE_MAX_LENGTH)
> >> + length = 0;
> >
> > Do you check for overflow anywhere? What if length is
> > PCI_DOE_MAX_LENGTH + 1?
> >
> >> pci_write_config_dword(pdev, offset + PCI_DOE_WRITE,
> >> FIELD_PREP(PCI_DOE_DATA_OBJECT_HEADER_2_LENGTH,
> >> - 2 + task->request_pl_sz /
> >> - sizeof(u32)));
> >> + length);
> >> for (i = 0; i < task->request_pl_sz / sizeof(u32); i++)
> >> pci_write_config_dword(pdev, offset + PCI_DOE_WRITE,
> >> task->request_pl[i]);
> >> @@ -178,7 +184,10 @@ static int pci_doe_recv_resp(struct pci_doe_mb *doe_mb, struct pci_doe_task *tas
> >> pci_write_config_dword(pdev, offset + PCI_DOE_READ, 0);
> >>
> >> length = FIELD_GET(PCI_DOE_DATA_OBJECT_HEADER_2_LENGTH, val);
> >> - if (length > SZ_1M || length < 2)
> >> + /* A value of 0x0 indicates max data object length */
> >> + if (!length)
> >> + length = PCI_DOE_MAX_LENGTH;
> >> + if (length < 2)
> >> return -EIO;
> >>
> >> /* First 2 dwords have already been read */
> >> @@ -520,8 +529,12 @@ int pci_doe_submit_task(struct pci_doe_mb *doe_mb, struct pci_doe_task *task)
> >> /*
> >> * DOE requests must be a whole number of DW and the response needs to
> >> * be big enough for at least 1 DW
> >> + *
> >> + * Max data object length is 1MB, and data object header occupies 8B,
> >> + * thus request_pl_sz should not be greater than 1MB - 8B.
> >> */
> >> - if (task->request_pl_sz % sizeof(u32) ||
> >> + if (task->request_pl_sz > SZ_1M - 8 ||
> >> + task->request_pl_sz % sizeof(u32) ||
> >
> > Oh, I see, this looks like the check for overflow. It would be nice
> > if it were expressed in terms of PCI_DOE_MAX_LENGTH somehow.
> >
> > It would also be nice, but maybe not practical, to have it closer to
> > the FIELD_PREP above so it's more obvious that we never try to encode
> > something too big.
> >
> here is the beginning of a task, and starting to check
> task->request_pl_sz, so I put request_pl_sz overflow checking here.
>
> do you mean that we keep task->request_pl_sz % sizeof(u32) here and
> move request_pl_sz overflow checking to closer to the FIELD_PREP
> above?
Yes, that's what I meant.
I think the more important thing is to do the check using
PCI_DOE_MAX_LENGTH if possible so the connection is obvious and
consistent.
