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[Xen-devel] Re: [PATCH 00 of 36] x86/paravirt: groundwork for 64-bit Xen support

Ingo Molnar wrote:
* Jeremy Fitzhardinge <jeremy@xxxxxxxx> wrote:

It quickly broke the build in testing:

 include/asm/pgalloc.h: In function âparavirt_pgd_free':
 include/asm/pgalloc.h:14: error: parameter name omitted
arch/x86/kernel/entry_64.S: In file included from arch/x86/kernel/traps_64.c:51:include/asm/pgalloc.h: In function âparavirt_pgd_free':
 include/asm/pgalloc.h:14: error: parameter name omitted
No, looks like my fault. The non-PARAVIRT version of paravirt_pgd_free() is:

static inline void paravirt_pgd_free(struct mm_struct *mm, pgd_t *) {}

but C doesn't like missing parameter names, even if unused.

This should fix it:

that fixed the build but now we've got a boot crash with this config:

 time.c: Detected 2010.304 MHz processor.
 spurious 8259A interrupt: IRQ7.
 BUG: unable to handle kernel NULL pointer dereference at  0000000000000000
 IP: [<0000000000000000>]
 PGD 0
 Thread overran stack, or stack corrupted
 Oops: 0010 [1] SMP
 CPU 0



Blerg, a contextless NULL rip. Have you done any bisection on it? Could you try again with the same config, but with "CONFIG_PARAVIRT_DEBUG" enabled as well? That will BUG if it turns out to be trying to call a NULL paravirt-op

I'll try to repro here anyway.

i've pushed out the current tip/xen-64bit branch, so that you can see how things look like at the moment, but i cannot put it into tip/master yet.

Yeah, I was expecting things to break somewhere with this lot :/

Could you add this patch? I don't think it will help this case, but it's a bugfix.


Subject: x86_64: use SWAPGS_UNSAFE_STACK in ia32entry.S

Use SWAPGS_UNSAFE_STACK in ia32entry.S in the places where the active
stack is the usermode stack.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@xxxxxxxxxx>
arch/x86/ia32/ia32entry.S |    4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

--- a/arch/x86/ia32/ia32entry.S
+++ b/arch/x86/ia32/ia32entry.S
@@ -98,7 +98,7 @@
        CFI_DEF_CFA     rsp,0
        CFI_REGISTER    rsp,rbp
-       SWAPGS
        movq    %gs:pda_kernelstack, %rsp
        addq    $(PDA_STACKOFFSET),%rsp 
@@ -210,7 +210,7 @@
        CFI_REGISTER    rip,rcx
        /*CFI_REGISTER  rflags,r11*/
-       SWAPGS
        movl    %esp,%r8d
        CFI_REGISTER    rsp,r8
        movq    %gs:pda_kernelstack,%rsp

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