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Date:   Mon, 10 Oct 2022 20:57:54 -0600
From:   "Jason A. Donenfeld" <Jason@zx2c4.com>
To:     Michael Ellerman <mpe@ellerman.id.au>
Cc:     Linus Torvalds <torvalds@linux-foundation.org>, ajd@linux.ibm.com,
        aneesh.kumar@linux.ibm.com, atrajeev@linux.vnet.ibm.com,
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Subject: Re: [GIT PULL] Please pull powerpc/linux.git powerpc-6.1-1 tag
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On Tue, Oct 11, 2022 at 12:53:17PM +1100, Michael Ellerman wrote:
> "Jason A. Donenfeld" <Jason@zx2c4.com> writes:
> > On Mon, Oct 10, 2022 at 01:25:25PM -0600, Jason A. Donenfeld wrote:
> >> Hi Michael,
> >> 
> >> On Sun, Oct 09, 2022 at 10:01:39PM +1100, Michael Ellerman wrote:
> >> > powerpc updates for 6.1
> >> > 
> >> >  - Remove our now never-true definitions for pgd_huge() and p4d_leaf().
> >> > 
> >> >  - Add pte_needs_flush() and huge_pmd_needs_flush() for 64-bit.
> >> > 
> >> >  - Add support for syscall wrappers.
> >> > 
> >> >  - Add support for KFENCE on 64-bit.
> >> > 
> >> >  - Update 64-bit HV KVM to use the new guest state entry/exit accounting API.
> >> > 
> >> >  - Support execute-only memory when using the Radix MMU (P9 or later).
> >> > 
> >> >  - Implement CONFIG_PARAVIRT_TIME_ACCOUNTING for pseries guests.
> >> > 
> >> >  - Updates to our linker script to move more data into read-only sections.
> >> > 
> >> >  - Allow the VDSO to be randomised on 32-bit.
> >> > 
> >> >  - Many other small features and fixes.
> >> 
> >> FYI, something in here broke the wireguard test suite, which runs the
> >> iperf3 networking utility. The full log is here [1], but the relevant part
> >> is: 
> >> 
> >> [+] NS1: iperf3 -Z -t 3 -c 192.168.241.2
> >> Connecting to host 192.168.241.2, port 5201
> >> iperf3: error - failed to read /dev/urandom: Bad address
> >> 
> >> I'll see if I can narrow it down a bit more and bisect. But just FYI, in
> >> case you have an intuition.
> >
> > Huh. From iov_iter.c:
> >
> > static int copyout(void __user *to, const void *from, size_t n)
> > {
> >         size_t before = n;
> >         if (should_fail_usercopy())
> >                 return n;
> >         if (access_ok(to, n)) {
> >                 instrument_copy_to_user(to, from, n);
> >                 n = raw_copy_to_user(to, from, n);
> >                 if (n == before)
> >                         pr_err("SARU n still %zu pointer is %lx\n", n, (unsigned long)to);
> >         }
> >         return n;
> > }
> >
> > I added the pr_err() there to catch the failure:
> > [    3.443506] SARU n still 64 pointer is b78db000
> >
> > Also I managed to extract the failing portion of iperf3 into something
> > smaller:
> >
> >         int temp;
> >         char *x;
> >         ssize_t l;
> >         FILE *f;
> >         char template[] = "/blah-XXXXXX";
> >
> >         temp = mkstemp(template);
> >         if (temp < 0)
> >                 panic("mkstemp");
> >         if (unlink(template) < 0)
> >                 panic("unlink");
> >         if (ftruncate(temp, 0x20000) < 0)
> >                 panic("ftruncate");
> >         x = mmap(NULL, 0x20000, PROT_READ|PROT_WRITE, MAP_PRIVATE, temp, 0);
> >         if (x == MAP_FAILED)
> >                 panic("mmap");
> >         f = fopen("/dev/urandom", "rb");
> >         if (!f)
> >                 panic("fopen");
> >         setbuf(f, NULL);
> >         if (fread(x, 1, 0x20000, f) != 0x20000)
> >                 panic("fread");
> 
> Does that fail for you reliably?
> 
> It succeeds for me running under qemu ppce500, though I'm not using your
> kernel config yet.

Yes, every time without fail, across two systems and two qemu builds.

Jason