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x86/kexec: Eliminate writes through kernel mapping of relocate_kernel page

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All writes to the relocate_kernel control page are now done *after* the
%cr3 switch via simple %rip-relative addressing, which means the DATA()
macro with its pointer arithmetic can also now be removed.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: Baoquan He <bhe@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Eric Biederman <ebiederm@xmission.com>
Cc: Ard Biesheuvel <ardb@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Link: https://lore.kernel.org/r/20241205153343.3275139-12-dwmw2@infradead.org
This commit is contained in:
David Woodhouse 2024-12-05 15:05:17 +00:00 committed by Ingo Molnar
parent b3adabae8a
commit b7155dfd49
1 changed files with 14 additions and 15 deletions
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29
arch/x86/kernel/relocate_kernel_64.S
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@ -61,21 +61,24 @@ SYM_CODE_START_NOALIGN(relocate_kernel)
pushq %r15
pushf
movq %rsp, saved_rsp(%rip)
movq %cr0, %rax
movq %rax, saved_cr0(%rip)
movq %cr3, %rax
movq %rax, saved_cr3(%rip)
movq %cr4, %rax
movq %rax, saved_cr4(%rip)
/* Save CR4. Required to enable the right paging mode later. */
movq %rax, %r13
/* zero out flags, and disable interrupts */
pushq $0
popfq
/* Switch to the identity mapped page tables */
movq %cr3, %rax
movq kexec_pa_table_page(%rip), %r9
movq %r9, %cr3
/* Save %rsp and CRs. */
movq %rsp, saved_rsp(%rip)
movq %rax, saved_cr3(%rip)
movq %cr0, %rax
movq %rax, saved_cr0(%rip)
/* Leave CR4 in %r13 to enable the right paging mode later. */
movq %cr4, %r13
movq %r13, saved_cr4(%rip)
/* Save SME active flag */
movq %r8, %r12
@ -85,10 +88,6 @@ SYM_CODE_START_NOALIGN(relocate_kernel)
/* Save the preserve_context to %r11 as swap_pages clobbers %rcx. */
movq %rcx, %r11
/* Switch to the identity mapped page tables */
movq kexec_pa_table_page(%rip), %r9
movq %r9, %cr3
/* Physical address of control page */
movq %rsi, %r8