Re: [Qemu-devel] [PATCH] ahci.c: mask unused flags when reading size PRDT DBC

[Alexander Graf <agraf@suse.de>]

On 29.06.14 20:21, reza.jelveh@gmail.com wrote:
> From: Reza Jelveh <reza.jelveh@tuhh.de>

This is a hint that your git configuration isn't fully correct. If the 
email address git thinks you want to use is the same as the From: email 
address, it will not print this line. I suppose the problem is with the 
difference in @gmail.com and @tuhh.de?

> The data byte count(DBC) read from the description information is defined for

bits

> 21:00.

Bits

> 30:22 are reserved and

bit

> 31 is the Interrupt on Completion (I) flag.
>
> Interrupt is not implemented in QEMU.

They are implemented in QEMU, but incorrectly. We trigger a completion 
interrupt after every transaction, not every time we see the I bit in 
the PRDT.

> tbl_entry_size is a signed integer and
> improperly reading the DBC leads to a negative offset that causes sglist
> allocation to fail.
>
> Signed-off-by: Reza Jelveh <reza.jelveh@tuhh.de>
> ---
>   hw/ide/ahci.c | 12 +++++++++---
>   hw/ide/ahci.h |  2 ++
>   2 files changed, 11 insertions(+), 3 deletions(-)
>
> diff --git a/hw/ide/ahci.c b/hw/ide/ahci.c
> index 9bae22e..93aa981 100644
> --- a/hw/ide/ahci.c
> +++ b/hw/ide/ahci.c
> @@ -639,6 +639,12 @@ static void ahci_write_fis_d2h(AHCIDevice *ad, uint8_t *cmd_fis)
>       }
>   }
>   
> +static int prdt_tbl_entry_size(const AHCI_SG tbl)

The argument should still be a pointer.

> +{
> +    return (le32_to_cpu(tbl.flags_size) & AHCI_PRDT_SIZE_MASK) + 1;
> +}
> +
> +

There is still one whitespace line too much :).


Alex

>   static int ahci_populate_sglist(AHCIDevice *ad, QEMUSGList *sglist, int offset)
>   {
>       AHCICmdHdr *cmd = ad->cur_cmd;
> @@ -681,7 +687,7 @@ static int ahci_populate_sglist(AHCIDevice *ad, QEMUSGList *sglist, int offset)
>           sum = 0;
>           for (i = 0; i < sglist_alloc_hint; i++) {
>               /* flags_size is zero-based */
> -            tbl_entry_size = (le32_to_cpu(tbl[i].flags_size) + 1);
> +            tbl_entry_size = prdt_tbl_entry_size(tbl[i]);
>               if (offset <= (sum + tbl_entry_size)) {
>                   off_idx = i;
>                   off_pos = offset - sum;
> @@ -700,12 +706,12 @@ static int ahci_populate_sglist(AHCIDevice *ad, QEMUSGList *sglist, int offset)
>           qemu_sglist_init(sglist, qbus->parent, (sglist_alloc_hint - off_idx),
>                            ad->hba->as);
>           qemu_sglist_add(sglist, le64_to_cpu(tbl[off_idx].addr + off_pos),
> -                        le32_to_cpu(tbl[off_idx].flags_size) + 1 - off_pos);
> +                        prdt_tbl_entry_size(tbl[off_idx]) - off_pos);
>   
>           for (i = off_idx + 1; i < sglist_alloc_hint; i++) {
>               /* flags_size is zero-based */
>               qemu_sglist_add(sglist, le64_to_cpu(tbl[i].addr),
> -                            le32_to_cpu(tbl[i].flags_size) + 1);
> +                            prdt_tbl_entry_size(tbl[i]));
>           }
>       }
>   
> diff --git a/hw/ide/ahci.h b/hw/ide/ahci.h
> index 9a4064f..f418b30 100644
> --- a/hw/ide/ahci.h
> +++ b/hw/ide/ahci.h
> @@ -201,6 +201,8 @@
>   
>   #define AHCI_COMMAND_TABLE_ACMD            0x40
>   
> +#define AHCI_PRDT_SIZE_MASK                0x3fffff
> +
>   #define IDE_FEATURE_DMA                    1
>   
>   #define READ_FPDMA_QUEUED                  0x60