The following commit has been merged into the x86/boot branch of tip: Commit-ID: 207bdf7f72ae8b1764de294ae59bdf5b015082bd Gitweb: https://git.kernel.org/tip/207bdf7f72ae8b1764de294ae59bdf5b015082bd Author: David Woodhouse <dwmw@xxxxxxxxxxxx> AuthorDate: Thu, 05 Dec 2024 15:05:08 Committer: Ingo Molnar <mingo@xxxxxxxxxx> CommitterDate: Fri, 06 Dec 2024 10:41:58 +01:00 x86/kexec: Clean up and document register use in relocate_kernel_64.S Add more comments explaining what each register contains, and save the preserve_context flag to a non-clobbered register sooner, to keep things simpler. No change in behavior intended. Signed-off-by: David Woodhouse <dwmw@xxxxxxxxxxxx> Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx> Acked-by: Kai Huang <kai.huang@xxxxxxxxx> 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/20241205153343.3275139-3-dwmw2@xxxxxxxxxxxxx --- arch/x86/kernel/relocate_kernel_64.S | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-) diff --git a/arch/x86/kernel/relocate_kernel_64.S b/arch/x86/kernel/relocate_kernel_64.S index 1236f25..92478e2 100644 --- a/arch/x86/kernel/relocate_kernel_64.S +++ b/arch/x86/kernel/relocate_kernel_64.S @@ -100,6 +100,9 @@ SYM_CODE_START_NOALIGN(relocate_kernel) movq %r10, CP_PA_SWAP_PAGE(%r11) movq %rdi, CP_PA_BACKUP_PAGES_MAP(%r11) + /* Save the preserve_context to %r11 as swap_pages clobbers %rcx. */ + movq %rcx, %r11 + /* Switch to the identity mapped page tables */ movq %r9, %cr3 @@ -116,6 +119,14 @@ SYM_CODE_END(relocate_kernel) SYM_CODE_START_LOCAL_NOALIGN(identity_mapped) UNWIND_HINT_END_OF_STACK + /* + * %rdi indirection page + * %rdx start address + * %r11 preserve_context + * %r12 host_mem_enc_active + * %r13 original CR4 when relocate_kernel() was invoked + */ + /* set return address to 0 if not preserving context */ pushq $0 /* store the start address on the stack */ @@ -170,8 +181,6 @@ SYM_CODE_START_LOCAL_NOALIGN(identity_mapped) wbinvd .Lsme_off: - /* Save the preserve_context to %r11 as swap_pages clobbers %rcx. */ - movq %rcx, %r11 call swap_pages /* @@ -183,13 +192,14 @@ SYM_CODE_START_LOCAL_NOALIGN(identity_mapped) movq %cr3, %rax movq %rax, %cr3 + testq %r11, %r11 /* preserve_context */ + jnz .Lrelocate + /* * set all of the registers to known values * leave %rsp alone */ - testq %r11, %r11 - jnz .Lrelocate xorl %eax, %eax xorl %ebx, %ebx xorl %ecx, %ecx
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