Messages in this thread | | | Date | Mon, 29 Jan 2018 19:19:01 +0800 | From | Baoquan He <> | Subject | Re: [PATCH] x86/kexec: Make kexec work in 5-level paging mode |
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On 01/29/18 at 02:08pm, Kirill A. Shutemov wrote: > I've missed that we need to change relocate_kernel() to set CR4.LA57 > flag if the kernel has 5-level paging enabled. > > I avoided to use ifdef CONFIG_X86_5LEVEL here and inferred if we need to > enabled 5-level paging from previous CR4 value. This way the code is > ready for boot-time switching between paging modes. > > Fixes: 77ef56e4f0fb ("x86: Enable 5-level paging support via CONFIG_X86_5LEVEL=y") > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> > Reported-by: Baoquan He <bhe@redhat.com>
Thanks, Kirill.
Tested on qemu with la57 support, kexec works well. Kdump kernel can boot into kernel, while there's a memory allocation failure during boot which I am trying to fix. The reason is kdump kernel need reserve as small memory as possible. Will post soon.
For this patch, feel free to add my Tested-by.
Tested-by: Baoquan He <bhe@redhat.com>
Thanks Baoquan > --- > arch/x86/kernel/relocate_kernel_64.S | 8 ++++++++ > 1 file changed, 8 insertions(+) > > diff --git a/arch/x86/kernel/relocate_kernel_64.S b/arch/x86/kernel/relocate_kernel_64.S > index 307d3bac5f04..11eda21eb697 100644 > --- a/arch/x86/kernel/relocate_kernel_64.S > +++ b/arch/x86/kernel/relocate_kernel_64.S > @@ -68,6 +68,9 @@ relocate_kernel: > movq %cr4, %rax > movq %rax, CR4(%r11) > > + /* Save CR4. Required to enable the right paging mode later. */ > + movq %rax, %r13 > + > /* zero out flags, and disable interrupts */ > pushq $0 > popfq > @@ -126,8 +129,13 @@ identity_mapped: > /* > * Set cr4 to a known state: > * - physical address extension enabled > + * - 5-level paging, if it was enabled before > */ > movl $X86_CR4_PAE, %eax > + testq $X86_CR4_LA57, %r13 > + jz 1f > + orl $X86_CR4_LA57, %eax > +1: > movq %rax, %cr4 > > jmp 1f > -- > 2.15.1 >
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