The following commit has been merged into the x86/boot branch of tip: Commit-ID: b7155dfd4999211247cce40be2665c71235ab094 Gitweb: https://git.kernel.org/tip/b7155dfd4999211247cce40be2665c71235ab094 Author: David Woodhouse <dwmw@xxxxxxxxxxxx> AuthorDate: Thu, 05 Dec 2024 15:05:17 Committer: Ingo Molnar <mingo@xxxxxxxxxx> CommitterDate: Fri, 06 Dec 2024 10:42:00 +01:00 x86/kexec: Eliminate writes through kernel mapping of relocate_kernel page 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@xxxxxxxxxxxx> Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> Cc: Baoquan He <bhe@xxxxxxxxxx> Cc: Vivek Goyal <vgoyal@xxxxxxxxxx> Cc: Dave Young <dyoung@xxxxxxxxxx> Cc: Eric Biederman <ebiederm@xxxxxxxxxxxx> Cc: Ard Biesheuvel <ardb@xxxxxxxxxx> Cc: "H. Peter Anvin" <hpa@xxxxxxxxx> Link: https://lore.kernel.org/r/20241205153343.3275139-12-dwmw2@xxxxxxxxxxxxx --- arch/x86/kernel/relocate_kernel_64.S | 29 +++++++++++++-------------- 1 file changed, 14 insertions(+), 15 deletions(-) diff --git a/arch/x86/kernel/relocate_kernel_64.S b/arch/x86/kernel/relocate_kernel_64.S index d52c3bb..739041c 100644 --- a/arch/x86/kernel/relocate_kernel_64.S +++ b/arch/x86/kernel/relocate_kernel_64.S @@ -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
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