This patch makes the kernel bootable again on ia32 EFI systems.
Signed-off-by: Edgar Hucek <[email protected]>
On Thu, 2 Mar 2006, Edgar Hucek wrote:
> This patch makes the kernel bootable again on ia32 EFI systems.
>
> Signed-off-by: Edgar Hucek <[email protected]>
>
spin_lock(&efi_rt_lock);
local_irq_save(efi_rt_eflags);
That looks like a race, not to mention that efi_rt_eflags is a global
variable. The same strange ordering occurs on unlock, i presume this code
'works' because it's done early during boot?
Edgar Hucek wrote:
> This patch makes the kernel bootable again on ia32 EFI systems.
>
> Signed-off-by: Edgar Hucek <[email protected]>
>
>
> ------------------------------------------------------------------------
>
> diff -uNr linux-2.6.16-rc5/arch/i386/kernel/efi.c linux-2.6.16-rc5.efi/arch/i386/kernel/efi.c
> --- linux-2.6.16-rc5/arch/i386/kernel/efi.c 2006-03-02 14:08:06.000000000 +0100
> +++ linux-2.6.16-rc5.efi/arch/i386/kernel/efi.c 2006-03-02 14:04:44.000000000 +0100
> @@ -70,7 +70,8 @@
> {
> unsigned long cr4;
> unsigned long temp;
> -
> + struct Xgt_desc_struct *cpu_gdt_descr = &per_cpu(cpu_gdt_descr, 0);
> +
> spin_lock(&efi_rt_lock);
> local_irq_save(efi_rt_eflags);
>
> @@ -103,18 +104,17 @@
> */
> local_flush_tlb();
>
> - per_cpu(cpu_gdt_descr, 0).address =
> - __pa(per_cpu(cpu_gdt_descr, 0).address);
> - load_gdt((struct Xgt_desc_struct *)__pa(&per_cpu(cpu_gdt_descr, 0)));
> + cpu_gdt_descr->address = __pa(cpu_gdt_descr->address);
> + load_gdt(cpu_gdt_descr);
> }
>
> static void efi_call_phys_epilog(void)
> {
> unsigned long cr4;
> + struct Xgt_desc_struct *cpu_gdt_descr = &per_cpu(cpu_gdt_descr, 0);
>
> - per_cpu(cpu_gdt_descr, 0).address =
> - (unsigned long)__va(per_cpu(cpu_gdt_descr, 0).address);
> - load_gdt((struct Xgt_desc_struct *)__va(&per_cpu(cpu_gdt_descr, 0)));
> + cpu_gdt_descr->address = __va(cpu_gdt_descr->address);
> + load_gdt(cpu_gdt_descr);
>
> cr4 = read_cr4();
>
I don't know if it is a race condition. At least it makes the kernel bootable agin on my box.
Any idea what i could try to make a better patch ?
cu
Edgar (gimli) Hucek
Edgar Hucek <[email protected]> wrote:
>
> This patch makes the kernel bootable again on ia32 EFI systems.
>
Argh, thanks. I'll move the per_cpu() call inside the lock, just in case
we happen to be running preemptibly there.
Zach, Matt: please review, test and ack asap?
diff -puN arch/i386/kernel/efi.c~efi-fix-gdt-load arch/i386/kernel/efi.c
--- devel/arch/i386/kernel/efi.c~efi-fix-gdt-load 2006-03-04 18:40:20.000000000 -0800
+++ devel-akpm/arch/i386/kernel/efi.c 2006-03-04 18:41:50.000000000 -0800
@@ -70,10 +70,13 @@ static void efi_call_phys_prelog(void)
{
unsigned long cr4;
unsigned long temp;
+ struct Xgt_desc_struct *cpu_gdt_descr;
spin_lock(&efi_rt_lock);
local_irq_save(efi_rt_eflags);
+ cpu_gdt_descr = &per_cpu(cpu_gdt_descr, 0);
+
/*
* If I don't have PSE, I should just duplicate two entries in page
* directory. If I have PSE, I just need to duplicate one entry in
@@ -103,18 +106,17 @@ static void efi_call_phys_prelog(void)
*/
local_flush_tlb();
- per_cpu(cpu_gdt_descr, 0).address =
- __pa(per_cpu(cpu_gdt_descr, 0).address);
- load_gdt((struct Xgt_desc_struct *)__pa(&per_cpu(cpu_gdt_descr, 0)));
+ cpu_gdt_descr->address = __pa(cpu_gdt_descr->address);
+ load_gdt(cpu_gdt_descr);
}
static void efi_call_phys_epilog(void)
{
unsigned long cr4;
+ struct Xgt_desc_struct *cpu_gdt_descr = &per_cpu(cpu_gdt_descr, 0);
- per_cpu(cpu_gdt_descr, 0).address =
- (unsigned long)__va(per_cpu(cpu_gdt_descr, 0).address);
- load_gdt((struct Xgt_desc_struct *)__va(&per_cpu(cpu_gdt_descr, 0)));
+ cpu_gdt_descr->address = __va(cpu_gdt_descr->address);
+ load_gdt(cpu_gdt_descr);
cr4 = read_cr4();
_
Zwane Mwaikambo <[email protected]> wrote:
>
> On Thu, 2 Mar 2006, Edgar Hucek wrote:
>
> > This patch makes the kernel bootable again on ia32 EFI systems.
> >
> > Signed-off-by: Edgar Hucek <[email protected]>
> >
>
> spin_lock(&efi_rt_lock);
> local_irq_save(efi_rt_eflags);
>
> That looks like a race, not to mention that efi_rt_eflags is a global
> variable. The same strange ordering occurs on unlock, i presume this code
> 'works' because it's done early during boot?
No, the code's OK. This is the prologue function. The epilogue function
does the opposite. In between, this CPU will dink around with EFI stuff.
And the order is correct too - the lock protects efi_rt_eflags.