Skip to content

L
linux-davinci
An error occurred fetching the project authors.
Switch branch/tag
  1. 30 Jan, 2009 2 commits
    • Jeremy Fitzhardinge's avatar
      x86/paravirt: add register-saving thunks to reduce caller register pressure · ecb93d1c
      Jeremy Fitzhardinge authored 
      Impact: Optimization

One of the problems with inserting a pile of C calls where previously
there were none is that the register pressure is greatly increased.
The C calling convention says that the caller must expect a certain
set of registers may be trashed by the callee, and that the callee can
use those registers without restriction.  This includes the function
argument registers, and several others.

This patch seeks to alleviate this pressure by introducing wrapper
thunks that will do the register saving/restoring, so that the
callsite doesn't need to worry about it, but the callee function can
be conventional compiler-generated code.  In many cases (particularly
performance-sensitive cases) the callee will be in assembler anyway,
and need not use the compiler's calling convention.

Standard calling convention is:
	 arguments	    return	scratch
x86-32	 eax edx ecx	    eax		?
x86-64	 rdi rsi rdx rcx    rax		r8 r9 r10 r11

The thunk preserves all argument and scratch registers.  The return
register is not preserved, and is available as a scratch register for
unwrapped callee code (and of course the return value).

Wrapped function pointers are themselves wrapped in a struct
paravirt_callee_save structure, in order to get some warning from the
compiler when functions with mismatched calling conventions are used.

The most common paravirt ops, both statically and dynamically, are
interrupt enable/disable/save/restore, so handle them first.  This is
particularly easy since their calls are handled specially anyway.

XXX Deal with VMI.  What's their calling convention?
Signed-off-by: default avatarH. Peter Anvin <hpa@zytor.com>
      ecb93d1c
    • Atsushi SAKAI's avatar
      lguest: typos fix · 72410af9
      Atsushi SAKAI authored 
      3 points

lguest_asm.S => i386_head.S
LHCALL_BREAK => LHREQ_BREAK
perferred    => preferred
Signed-off-by: default avatarAtsushi SAKAI <sakaia@jp.fujitsu.com>
Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
      72410af9
  3. 13 Dec, 2008 1 commit
  5. 11 Nov, 2008 1 commit
  7. 31 Oct, 2008 2 commits
  9. 16 Oct, 2008 1 commit
    • Yinghai Lu's avatar
      x86: make 32bit support per_cpu vector · 497c9a19
      Yinghai Lu authored 
      so we can merge io_apic_32.c and io_apic_64.c

v2: Use cpu_online_map as target cpus for bigsmp, just like 64-bit is doing.

Also remove some unused TARGET_CPUS macro.

v3: need to check if desc is null in smp_irq_move_cleanup

also migration needs to reset vector too, so copy __target_IO_APIC_irq
from 64bit.

(the duplication will go away once the two files are unified.)
Signed-off-by: default avatarYinghai Lu <yhlu.kernel@gmail.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      497c9a19
  11. 28 Jul, 2008 1 commit
  13. 20 Jul, 2008 1 commit
  15. 18 Jul, 2008 2 commits
    • Suresh Siddha's avatar
      x86: apic_ops for lguest · 511d9d34
      Suresh Siddha authored 
      apic_ops for lguest.
Signed-off-by: default avatarSuresh Siddha <suresh.b.siddha@intel.com>
Acked-by: default avatarYinghai Lu <yhlu.kernel@gmail.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      511d9d34
    • Maciej W. Rozycki's avatar
      x86: APIC: remove apic_write_around(); use alternatives · 593f4a78
      Maciej W. Rozycki authored 
      Use alternatives to select the workaround for the 11AP Pentium erratum
for the affected steppings on the fly rather than build time.  Remove the
X86_GOOD_APIC configuration option and replace all the calls to
apic_write_around() with plain apic_write(), protecting accesses to the
ESR as appropriate due to the 3AP Pentium erratum.  Remove
apic_read_around() and all its invocations altogether as not needed.
Remove apic_write_atomic() and all its implementing backends.  The use of
ASM_OUTPUT2() is not strictly needed for input constraints, but I have
used it for readability's sake.

I had the feeling no one else was brave enough to do it, so I went ahead
and here it is.  Verified by checking the generated assembly and tested
with both a 32-bit and a 64-bit configuration, also with the 11AP
"feature" forced on and verified with gdb on /proc/kcore to work as
expected (as an 11AP machines are quite hard to get hands on these days).
Some script complained about the use of "volatile", but apic_write() needs
it for the same reason and is effectively a replacement for writel(), so I
have disregarded it.

I am not sure what the policy wrt defconfig files is, they are generated
and there is risk of a conflict resulting from an unrelated change, so I
have left changes to them out.  The option will get removed from them at
the next run.

Some testing with machines other than mine will be needed to avoid some
stupid mistake, but despite its volume, the change is not really that
intrusive, so I am fairly confident that because it works for me, it will
everywhere.
Signed-off-by: default avatarMaciej W. Rozycki <macro@linux-mips.org>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      593f4a78
  17. 12 Jul, 2008 1 commit
  19. 09 Jul, 2008 1 commit
  21. 08 Jul, 2008 1 commit
  23. 31 May, 2008 1 commit
  25. 30 May, 2008 1 commit
  27. 17 Apr, 2008 1 commit
  29. 28 Mar, 2008 1 commit
  31. 10 Mar, 2008 2 commits
    • Rusty Russell's avatar
      lguest: Revert 1ce70c4f, fix real problem. · 4357bd94
      Rusty Russell authored 
      Ahmed managed to crash the Host in release_pgd(), which cannot be a Guest
bug, and indeed it wasn't.

The bug was that handing a 0 as the address of the toplevel page table
being manipulated can cause the lookup code in find_pgdir() to return
an uninitialized cache entry (we shadow up to 4 top level page tables
for each Guest).

Commit 37cc8d7f introduced this
behaviour in the Guest, uncovering the bug.

The patch which he submitted (which removed the /4 from the index
calculation) simply ensured that these high-indexed entries hit the
early exit path of guest_set_pmd().  But you get lots of segfaults in
guest userspace as the PMDs aren't being updated.
Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
      4357bd94
    • Rusty Russell's avatar
      lguest: Sanitize the lguest clock. · 3fabc55f
      Rusty Russell authored 
      Now the TSC code handles a zero return from calculate_cpu_khz(),
lguest can simply pass through the value it gets from the Host: if
non-zero, all the normal TSC code applies.

Otherwise (or if the Host really doesn't support TSC), the clocksource
code will fall back to the slower but reasonable lguest clock.
Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
      3fabc55f
  33. 26 Feb, 2008 2 commits
    • Ahmed S. Darwish's avatar
      x86/lguest: fix pgdir pmd index calculation · 1ce70c4f
      Ahmed S. Darwish authored 
      Hi all,

Beginning from commits close to v2.6.25-rc2, running lguest always oopses
the host kernel. Oops is at [1].

Bisection led to the following commit:

commit 37cc8d7f

    x86/early_ioremap: don't assume we're using swapper_pg_dir

    At the early stages of boot, before the kernel pagetable has been
    fully initialized, a Xen kernel will still be running off the
    Xen-provided pagetables rather than swapper_pg_dir[].  Therefore,
    readback cr3 to determine the base of the pagetable rather than
    assuming swapper_pg_dir[].

 static inline pmd_t * __init early_ioremap_pmd(unsigned long addr)
 {
-	pgd_t *pgd = &swapper_pg_dir[pgd_index(addr)];
+	/* Don't assume we're using swapper_pg_dir at this point */
+	pgd_t *base = __va(read_cr3());
+	pgd_t *pgd = &base[pgd_index(addr)];
 	pud_t *pud = pud_offset(pgd, addr);
 	pmd_t *pmd = pmd_offset(pud, addr);

Trying to analyze the problem, it seems on the guest side of lguest,
%cr3 has a different value from &swapper_pg-dir (which
is AFAIK fine on a pravirt guest):

Putting some debugging messages in early_ioremap_pmd:

/* Appears 3 times */
[    0.000000] ***************************
[    0.000000] __va(%cr3) = c0000000, &swapper_pg_dir = c02cc000
[    0.000000] ***************************

After 8 hours of debugging and staring on lguest code, I noticed something
strange in paravirt_ops->set_pmd hypercall invocation:

static void lguest_set_pmd(pmd_t *pmdp, pmd_t pmdval)
{
	*pmdp = pmdval;
	lazy_hcall(LHCALL_SET_PMD, __pa(pmdp)&PAGE_MASK,
		   (__pa(pmdp)&(PAGE_SIZE-1))/4, 0);
}

The first hcall parameter is global pgdir which looks fine. The second
parameter is the pmd index in the pgdir which is suspectful.

AFAIK, calculating the index of pmd does not need a divisoin over four.
Removing the division made lguest work fine again . Patch is at [2].

I am not sure why the division over four existed in the first place. It
seems bogus, maybe the Xen patch just made the problem appear ?

[2]: The patch:

[PATCH] lguest: fix pgdir pmd index cacluation

Remove an error in index calculation which leads to removing
a not existing shadow page table (leading to a Null dereference).
Signed-off-by: default avatarAhmed S. Darwish <darwish.07@gmail.com>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
      1ce70c4f
    • Harvey Harrison's avatar
      lguest: include function prototypes · cbc34973
      Harvey Harrison authored 
      Added a declaration to asm-x86/lguest.h and moved the extern arrays there
as well.  As an alternative to including asm/lguest.h directly, an
include could be put in linux/lguest.h
Signed-off-by: default avatarHarvey Harrison <harvey.harrison@gmail.com>
Cc: "rusty@rustcorp.com.au" <rusty@rustcorp.com.au>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
      cbc34973
  35. 30 Jan, 2008 7 commits
  37. 05 Nov, 2007 2 commits
  39. 25 Oct, 2007 3 commits
  41. 24 Oct, 2007 1 commit
  43. 23 Oct, 2007 5 commits
    • Rusty Russell's avatar
      Revert lguest magic and use hook in head.S · 814a0e5c
      Rusty Russell authored 
      Version 2.07 of the boot protocol uses 0x23C for the hardware_subarch
field, that for lguest is "1".  This allows us to use the standard
boot entry point rather than the "GenuineLguest" string hack.

The standard entry point also clears the BSS and copies the boot parameters
and commandline for us, saving more code.
Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
      814a0e5c
    • Rusty Russell's avatar
      Lguest support for Virtio · 19f1537b
      Rusty Russell authored 
      This makes lguest able to use the virtio devices.

We change the device descriptor page from a simple array to a variable
length "type, config_len, status, config data..." format, and
implement virtio_config_ops to read from that config data.

We use the virtio ring implementation for an efficient Guest <-> Host
virtqueue mechanism, and the new LHCALL_NOTIFY hypercall to kick the
host when it changes.

We also use LHCALL_NOTIFY on kernel addresses for very very early
console output.  We could have another hypercall, but this hack works
quite well.
Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
      19f1537b
    • Rusty Russell's avatar
      Remove old lguest bus and drivers. · 0ca49ca9
      Rusty Russell authored 
      This gets rid of the lguest bus, drivers and DMA mechanism, to make
way for a generic virtio mechanism.
Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
      0ca49ca9
    • Rusty Russell's avatar
      Boot with virtual == physical to get closer to native Linux. · 47436aa4
      Rusty Russell authored 
      1) This allows us to get alot closer to booting bzImages.

2) It means we don't have to know page_offset.

3) The Guest needs to modify the boot pagetables to create the
   PAGE_OFFSET mapping before jumping to C code.

4) guest_pa() walks the page tables rather than using page_offset.

5) We don't use page_offset to figure out whether to emulate: it was
   always kinda quesationable, and won't work for instructions done
   before remapping (bzImage unpacking in particular).

6) We still want the kernel address for tlb flushing: have the initial
   hypercall give us that, too.
Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
      47436aa4
    • Rusty Russell's avatar
      Allow guest to specify syscall vector to use. · c18acd73
      Rusty Russell authored 
      (Based on Ron Minnich's LGUEST_PLAN9_SYSCALL patch).

This patch allows Guests to specify what system call vector they want,
and we try to reserve it.  We only allow one non-Linux system call
vector, to try to avoid DoS on the Host.
Signed-off-by: default avatarRusty Russell <rusty@rustcorp.com.au>
      c18acd73