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  1. Jun 20, 2021
  3. Jun 17, 2021
    • Michael Ellerman's avatar
      Merge branch 'topic/ppc-kvm' into next · 3c536423
      Michael Ellerman authored 
      Merge some powerpc KVM patches from our topic branch.

In particular this brings in Nick's big series rewriting parts of the
guest entry/exit path in C.

Conflicts:
	arch/powerpc/kernel/security.c
	arch/powerpc/kvm/book3s_hv_rmhandlers.S
      3c536423
    • Aneesh Kumar K.V's avatar
      powerpc/mm/book3s64: Fix possible build error · 07d8ad6f
      Aneesh Kumar K.V authored 
      

Update _tlbiel_pid() such that we can avoid build errors like below when
using this function in other places.

arch/powerpc/mm/book3s64/radix_tlb.c: In function ‘__radix__flush_tlb_range_psize’:
arch/powerpc/mm/book3s64/radix_tlb.c:114:2: warning: ‘asm’ operand 3 probably does not match constraints
  114 |  asm volatile(PPC_TLBIEL(%0, %4, %3, %2, %1)
      |  ^~~
arch/powerpc/mm/book3s64/radix_tlb.c:114:2: error: impossible constraint in ‘asm’
make[4]: *** [scripts/Makefile.build:271: arch/powerpc/mm/book3s64/radix_tlb.o] Error 1
m

With this fix, we can also drop the __always_inline in __radix_flush_tlb_range_psize
which was added by commit e12d6d7d ("powerpc/mm/radix: mark __radix__flush_tlb_range_psize() as __always_inline")

Signed-off-by: default avatarAneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Reviewed-by: default avatarChristophe Leroy <christophe.leroy@csgroup.eu>
Acked-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210610083639.387365-1-aneesh.kumar@linux.ibm.com
      07d8ad6f
    • Michael Ellerman's avatar
      powerpc/signal64: Don't read sigaction arguments back from user memory · a3309226
      Michael Ellerman authored 
      

When delivering a signal to a sigaction style handler (SA_SIGINFO), we
pass pointers to the siginfo and ucontext via r4 and r5.

Currently we populate the values in those registers by reading the
pointers out of the sigframe in user memory, even though the values in
user memory were written by the kernel just prior:

  unsafe_put_user(&frame->info, &frame->pinfo, badframe_block);
  unsafe_put_user(&frame->uc, &frame->puc, badframe_block);
  ...
  if (ksig->ka.sa.sa_flags & SA_SIGINFO) {
  	err |= get_user(regs->gpr[4], (unsigned long __user *)&frame->pinfo);
  	err |= get_user(regs->gpr[5], (unsigned long __user *)&frame->puc);

ie. we write &frame->info into frame->pinfo, and then read frame->pinfo
back into r4, and similarly for &frame->uc.

The code has always been like this, since linux-fullhistory commit
d4f2d95eca2c ("Forward port of 2.4 ppc64 signal changes.").

There's no reason for us to read the values back from user memory,
rather than just setting the value in the gpr[4/5] directly. In fact
reading the value back from user memory opens up the possibility of
another user thread changing the values before we read them back.
Although any process doing that would be racing against the kernel
delivering the signal, and would risk corrupting the stack, so that
would be a userspace bug.

Note that this is 64-bit only code, so there's no subtlety with the size
of pointers differing between kernel and user. Also the frame variable
is not modified to point elsewhere during the function.

In the past reading the values back from user memory was not costly, but
now that we have KUAP on some CPUs it is, so we'd rather avoid it for
that reason too.

So change the code to just set the values directly, using the same
values we have written to the sigframe previously in the function.

Note also that this matches what our 32-bit signal code does.

Using a version of will-it-scale's signal1_threads that sets SA_SIGINFO,
this results in a ~4% increase in signals per second on a Power9, from
229,777 to 239,766.

Reviewed-by: default avatarNicholas Piggin <npiggin@gmail.com>
Signed-off-by: default avatarMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210610072949.3198522-1-mpe@ellerman.id.au
      a3309226
  5. Jun 16, 2021