Messages in this thread Patch in this message | | | Date | Thu, 19 Aug 2021 17:29:26 +0100 | From | Marc Zyngier <> | Subject | Re: [PATCH net-next] stmmac: align RX buffers |
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On Thu, 12 Aug 2021 12:18:48 +0100, Matteo Croce <mcroce@linux.microsoft.com> wrote: > > [1 <text/plain; UTF-8 (7bit)>] > On Thu, Aug 12, 2021 at 1:05 PM Marc Zyngier <maz@kernel.org> wrote: > > > > On Thu, 12 Aug 2021 11:18:35 +0100, > > Matteo Croce <mcroce@linux.microsoft.com> wrote: > > > > > > On Thu, 12 Aug 2021 10:48:03 +0200 > > > Eric Dumazet <eric.dumazet@gmail.com> wrote: > > > > > > > > > > > > > > > On 8/11/21 4:16 PM, Marc Zyngier wrote: > > > > > On Wed, 11 Aug 2021 13:53:59 +0100, > > > > > Eric Dumazet <eric.dumazet@gmail.com> wrote: > > > > > > > > > >> Are you sure you do not need to adjust stmmac_set_bfsize(), > > > > >> stmmac_rx_buf1_len() and stmmac_rx_buf2_len() ? > > > > >> > > > > >> Presumably DEFAULT_BUFSIZE also want to be increased by NET_SKB_PAD > > > > >> > > > > >> Patch for stmmac_rx_buf1_len() : > > > > >> > > > > >> diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c > > > > >> b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c index > > > > >> 7b8404a21544cf29668e8a14240c3971e6bce0c3..041a74e7efca3436bfe3e17f972dd156173957a9 > > > > >> 100644 --- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c +++ > > > > >> b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c @@ -4508,12 > > > > >> +4508,12 @@ static unsigned int stmmac_rx_buf1_len(struct > > > > >> stmmac_priv *priv, /* First descriptor, not last descriptor and > > > > >> not split header */ if (status & rx_not_ls) > > > > >> - return priv->dma_buf_sz; > > > > >> + return priv->dma_buf_sz - NET_SKB_PAD - > > > > >> NET_IP_ALIGN; > > > > >> plen = stmmac_get_rx_frame_len(priv, p, coe); > > > > >> > > > > >> /* First descriptor and last descriptor and not split > > > > >> header */ > > > > >> - return min_t(unsigned int, priv->dma_buf_sz, plen); > > > > >> + return min_t(unsigned int, priv->dma_buf_sz - NET_SKB_PAD > > > > >> - NET_IP_ALIGN, plen); } > > > > >> > > > > >> static unsigned int stmmac_rx_buf2_len(struct stmmac_priv *priv, > > > > > > > > > > Feels like a major deficiency of the original patch. Happy to test a > > > > > more complete patch if/when you have one. > > > > > > > > I wont have time in the immediate future. > > > > > > > > Matteo, if you do not work on a fix, I suggest we revert > > > > a955318fe67ec0d962760b5ee58e74bffaf649b8 stmmac: align RX buffers > > > > > > > > before a more polished version can be submitted. > > > > > > > > > > Better to use stmmac_rx_offset() so to have the correct length when > > > using XDP. Also, when XDP is enabled, the offset was > > > XDP_PACKET_HEADROOM (i.e. 256 bytes) even before the change, so it > > > could be already broken. Mark, can you try on the Jetson TX2 by > > > attaching an XDP program and see if it works without my change? > > > > Sorry, you'll have to hold my hand here, as I know exactly nothing > > about XDP.... > > > > Attach the attached object with: > > ip link set eth0 xdp object passall.o > > This is an empty XDP program, its source: > > __attribute__((section("prog"), used)) > int xdp_main(struct xdp_md *ctx) > { > return XDP_PASS; > } > > Every packet will pass untouched, but the offset will be shifted from > 0 to 256 bytes, which could trigger the problem anyway:
Nope. On 5.13, which doesn't have the issue, adding this payload doesn't result in any problem and the whole thing is rock solid.
> > > > A possible fix, which takes in account also the XDP headroom for > > > stmmac_rx_buf1_len() only could be (only compile tested, I don't have > > > the hardware now): > > > > However, this doesn't fix my issue. I still get all sort of > > corruption. Probably stmmac_rx_buf2_len() also need adjusting (it has > > a similar logic as its buf1 counterpart...) > > > > Unless you can fix it very quickly, and given that we're towards the > > end of the cycle, I'd be more comfortable if we reverted this patch. > > > > Can it be that the HW can't do DMA on an address which is not word aligned? > What if you replace NET_SKB_PAD with, let's say, 8?
With this:
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac.h b/drivers/net/ethernet/stmicro/stmmac/stmmac.h index fcdb1d20389b..244aa6579ef4 100644 --- a/drivers/net/ethernet/stmicro/stmmac/stmmac.h +++ b/drivers/net/ethernet/stmicro/stmmac/stmmac.h @@ -341,7 +341,7 @@ static inline unsigned int stmmac_rx_offset(struct stmmac_priv *priv) if (stmmac_xdp_is_enabled(priv)) return XDP_PACKET_HEADROOM + NET_IP_ALIGN; - return NET_SKB_PAD + NET_IP_ALIGN; + return 8 + NET_IP_ALIGN; } void stmmac_disable_rx_queue(struct stmmac_priv *priv, u32 queue); I don't see the system corrupting packets anymore. Is that exactly what you had in mind? This really seems to point to a basic buffer overflow.
Thanks,
M.
-- Without deviation from the norm, progress is not possible.
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