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Message-ID: <174428358226.31282.6409810067635972823.tip-bot2@tip-bot2>
Date: Thu, 10 Apr 2025 11:13:02 -0000
From: "tip-bot2 for David Woodhouse" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: David Woodhouse <dwmw@...zon.co.uk>, Ingo Molnar <mingo@...nel.org>,
Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
Brian Gerst <brgerst@...il.com>, Juergen Gross <jgross@...e.com>,
"H. Peter Anvin" <hpa@...or.com>,
Linus Torvalds <torvalds@...ux-foundation.org>,
Josh Poimboeuf <jpoimboe@...hat.com>, Kees Cook <keescook@...omium.org>,
Ard Biesheuvel <ardb@...nel.org>, x86@...nel.org,
linux-kernel@...r.kernel.org
Subject: [tip: x86/asm] x86/kexec: Add 8250 MMIO serial port output
The following commit has been merged into the x86/asm branch of tip:
Commit-ID: 7516e7216bdfb9e2fab0a0ca3bd23cb2e61e46ed
Gitweb: https://git.kernel.org/tip/7516e7216bdfb9e2fab0a0ca3bd23cb2e61e46ed
Author: David Woodhouse <dwmw@...zon.co.uk>
AuthorDate: Wed, 26 Mar 2025 14:16:02
Committer: Ingo Molnar <mingo@...nel.org>
CommitterDate: Thu, 10 Apr 2025 12:17:14 +02:00
x86/kexec: Add 8250 MMIO serial port output
This supports the same 32-bit MMIO-mapped 8250 as the early_printk code.
It's not clear why the early_printk code supports this form and only this
form; the actual runtime 8250_pci doesn't seem to support it. But having
hacked up QEMU to expose such a device, early_printk does work with it,
and now so does the kexec debug code.
Signed-off-by: David Woodhouse <dwmw@...zon.co.uk>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
Cc: Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
Cc: Brian Gerst <brgerst@...il.com>
Cc: Juergen Gross <jgross@...e.com>
Cc: H. Peter Anvin <hpa@...or.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Josh Poimboeuf <jpoimboe@...hat.com>
Cc: Kees Cook <keescook@...omium.org>
Cc: Ard Biesheuvel <ardb@...nel.org>
Link: https://lore.kernel.org/r/20250326142404.256980-3-dwmw2@infradead.org
---
arch/x86/include/asm/kexec.h | 1 +
arch/x86/kernel/early_printk.c | 3 +++
arch/x86/kernel/machine_kexec_64.c | 17 +++++++++++++++++
arch/x86/kernel/relocate_kernel_64.S | 22 ++++++++++++++++++++++
4 files changed, 43 insertions(+)
diff --git a/arch/x86/include/asm/kexec.h b/arch/x86/include/asm/kexec.h
index 9601094..f2ad779 100644
--- a/arch/x86/include/asm/kexec.h
+++ b/arch/x86/include/asm/kexec.h
@@ -65,6 +65,7 @@ extern unsigned long kexec_pa_swap_page;
extern gate_desc kexec_debug_idt[];
extern unsigned char kexec_debug_exc_vectors[];
extern uint16_t kexec_debug_8250_port;
+extern unsigned long kexec_debug_8250_mmio32;
#endif
/*
diff --git a/arch/x86/kernel/early_printk.c b/arch/x86/kernel/early_printk.c
index acb7d05..9e8707d 100644
--- a/arch/x86/kernel/early_printk.c
+++ b/arch/x86/kernel/early_printk.c
@@ -333,6 +333,9 @@ static __init void early_pci_serial_init(char *s)
/* WARNING! assuming the address is always in the first 4G */
early_serial_base =
(unsigned long)early_ioremap(bar0 & PCI_BASE_ADDRESS_MEM_MASK, 0x10);
+#if defined(CONFIG_KEXEC_CORE) && defined(CONFIG_X86_64)
+ kexec_debug_8250_mmio32 = bar0 & PCI_BASE_ADDRESS_MEM_MASK;
+#endif
write_pci_config(bus, slot, func, PCI_COMMAND,
cmdreg|PCI_COMMAND_MEMORY);
}
diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
index cc73f97..ecb0da5 100644
--- a/arch/x86/kernel/machine_kexec_64.c
+++ b/arch/x86/kernel/machine_kexec_64.c
@@ -76,6 +76,19 @@ map_acpi_tables(struct x86_mapping_info *info, pgd_t *level4p)
static int map_acpi_tables(struct x86_mapping_info *info, pgd_t *level4p) { return 0; }
#endif
+static int map_mmio_serial(struct x86_mapping_info *info, pgd_t *level4p)
+{
+ unsigned long mstart, mend;
+
+ if (!kexec_debug_8250_mmio32)
+ return 0;
+
+ mstart = kexec_debug_8250_mmio32 & PAGE_MASK;
+ mend = (kexec_debug_8250_mmio32 + PAGE_SIZE + 23) & PAGE_MASK;
+ pr_info("Map PCI serial at %lx - %lx\n", mstart, mend);
+ return kernel_ident_mapping_init(info, level4p, mstart, mend);
+}
+
#ifdef CONFIG_KEXEC_FILE
const struct kexec_file_ops * const kexec_file_loaders[] = {
&kexec_bzImage64_ops,
@@ -285,6 +298,10 @@ static int init_pgtable(struct kimage *image, unsigned long control_page)
if (result)
return result;
+ result = map_mmio_serial(&info, image->arch.pgd);
+ if (result)
+ return result;
+
/*
* This must be last because the intermediate page table pages it
* allocates will not be control pages and may overlap the image.
diff --git a/arch/x86/kernel/relocate_kernel_64.S b/arch/x86/kernel/relocate_kernel_64.S
index 21011cd..8808cfc 100644
--- a/arch/x86/kernel/relocate_kernel_64.S
+++ b/arch/x86/kernel/relocate_kernel_64.S
@@ -39,6 +39,7 @@ SYM_DATA(kexec_va_control_page, .quad 0)
SYM_DATA(kexec_pa_table_page, .quad 0)
SYM_DATA(kexec_pa_swap_page, .quad 0)
SYM_DATA_LOCAL(pa_backup_pages_map, .quad 0)
+SYM_DATA(kexec_debug_8250_mmio32, .quad 0)
SYM_DATA(kexec_debug_8250_port, .word 0)
.balign 16
@@ -413,6 +414,22 @@ pr_char_null:
ret
SYM_CODE_END(pr_char_8250)
+SYM_CODE_START_LOCAL_NOALIGN(pr_char_8250_mmio32)
+ UNWIND_HINT_FUNC
+ ANNOTATE_NOENDBR
+.Lxmtrdy_loop_mmio:
+ movb (LSR*4)(%rdx), %ah
+ testb $XMTRDY, %ah
+ jnz .Lready_mmio
+ rep nop
+ jmp .Lxmtrdy_loop_mmio
+
+.Lready_mmio:
+ movb %al, (%rdx)
+ ANNOTATE_UNRET_SAFE
+ ret
+SYM_CODE_END(pr_char_8250_mmio32)
+
/*
* Load pr_char function pointer into %rsi and load %rdx with whatever
* that function wants to see there (typically port/MMIO address).
@@ -423,6 +440,11 @@ SYM_CODE_END(pr_char_8250)
testw %dx, %dx
jnz 1f
+ leaq pr_char_8250_mmio32(%rip), %rsi
+ movq kexec_debug_8250_mmio32(%rip), %rdx
+ testq %rdx, %rdx
+ jnz 1f
+
leaq pr_char_null(%rip), %rsi
1:
.endm
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