[PATCHv4, REBASED 0/4] x86: Reduce code duplication on page table initialization

[PATCHv4, REBASED 0/4] x86: Reduce code duplication on page table initialization

[Kirill A. Shutemov]

Use kernel_ident_mapping_init() to initialize kernel page tables where
possible, replacing manual initialization, reducing code duplication.

v4:
 - Reviewed-bys from Kai;
 - Fix comment in acpi_mp_setup_reset() (Rafael);
v3:
 - Reviewed-bys from Tom;
 - Improve commit messages;
v2:
 - A separate patch to change what PA is mapped at relocate_kernel() VA.
 - Improve commit messages;
 - Add Reveiwed-by from Kai;

Kirill A. Shutemov (4):
  x86/mm/ident_map: Fix virtual address wrap to zero
  x86/acpi: Replace manual page table initialization with
    kernel_ident_mapping_init()
  x86/64/kexec: Map original relocate_kernel() in
    init_transition_pgtable()
  x86/64/kexec: Rewrite init_transition_pgtable() with
    kernel_ident_mapping_init()

 arch/x86/include/asm/kexec.h       |  5 +-
 arch/x86/kernel/acpi/madt_wakeup.c | 73 +++++-------------------
 arch/x86/kernel/machine_kexec_64.c | 89 +++++++++++-------------------
 arch/x86/mm/ident_map.c            | 14 +----
 4 files changed, 50 insertions(+), 131 deletions(-)

-- 
2.45.2

[PATCHv4, REBASED 1/4] x86/mm/ident_map: Fix virtual address wrap to zero

[Kirill A. Shutemov]

Calculation of 'next' virtual address doesn't protect against wrapping
to zero. It can result in page table corruption and hang. The
problematic case is possible if user sets high x86_mapping_info::offset.

The wrapping to zero only occurs if the top PGD entry is accessed.
There are no such users in the upstream. Only hibernate_64.c uses
x86_mapping_info::offset, and it operates on the direct mapping range,
which is not the top PGD entry.

Replace manual 'next' calculation with p?d_addr_end() which handles
wrapping correctly.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
---
 arch/x86/mm/ident_map.c | 14 +++-----------
 1 file changed, 3 insertions(+), 11 deletions(-)

diff --git a/arch/x86/mm/ident_map.c b/arch/x86/mm/ident_map.c
index 437e96fb4977..5872f3ee863c 100644
--- a/arch/x86/mm/ident_map.c
+++ b/arch/x86/mm/ident_map.c
@@ -101,9 +101,7 @@ static int ident_pud_init(struct x86_mapping_info *info, pud_t *pud_page,
 		pmd_t *pmd;
 		bool use_gbpage;
 
-		next = (addr & PUD_MASK) + PUD_SIZE;
-		if (next > end)
-			next = end;
+		next = pud_addr_end(addr, end);
 
 		/* if this is already a gbpage, this portion is already mapped */
 		if (pud_leaf(*pud))
@@ -154,10 +152,7 @@ static int ident_p4d_init(struct x86_mapping_info *info, p4d_t *p4d_page,
 		p4d_t *p4d = p4d_page + p4d_index(addr);
 		pud_t *pud;
 
-		next = (addr & P4D_MASK) + P4D_SIZE;
-		if (next > end)
-			next = end;
-
+		next = p4d_addr_end(addr, end);
 		if (p4d_present(*p4d)) {
 			pud = pud_offset(p4d, 0);
 			result = ident_pud_init(info, pud, addr, next);
@@ -199,10 +194,7 @@ int kernel_ident_mapping_init(struct x86_mapping_info *info, pgd_t *pgd_page,
 		pgd_t *pgd = pgd_page + pgd_index(addr);
 		p4d_t *p4d;
 
-		next = (addr & PGDIR_MASK) + PGDIR_SIZE;
-		if (next > end)
-			next = end;
-
+		next = pgd_addr_end(addr, end);
 		if (pgd_present(*pgd)) {
 			p4d = p4d_offset(pgd, 0);
 			result = ident_p4d_init(info, p4d, addr, next);
-- 
2.45.2

Re: [PATCHv4, REBASED 1/4] x86/mm/ident_map: Fix virtual address wrap to zero

[Borislav Petkov]

On Wed, Oct 16, 2024 at 02:14:55PM +0300, Kirill A. Shutemov wrote:
> Calculation of 'next' virtual address doesn't protect against wrapping
> to zero. It can result in page table corruption and hang. The
> problematic case is possible if user sets high x86_mapping_info::offset.
> 
> The wrapping to zero only occurs if the top PGD entry is accessed.
> There are no such users in the upstream. Only hibernate_64.c uses
> x86_mapping_info::offset, and it operates on the direct mapping range,
> which is not the top PGD entry.
> 
> Replace manual 'next' calculation with p?d_addr_end() which handles
> wrapping correctly.

So this is a fix for a theoretical issue as it cannot happen currently?

Can we call that out in the commit message so that the stable AI doesn't pick
it up?

And which commit is it fixing?

aece27851d44 ("x86, 64bit, mm: Add generic kernel/ident mapping helper")
perhaps?

Always add Fixes: tags when a patch is fixing something - you know that.

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

Re: [PATCHv4, REBASED 1/4] x86/mm/ident_map: Fix virtual address wrap to zero

[Kirill A. Shutemov]

On Wed, Oct 30, 2024 at 12:47:12PM +0100, Borislav Petkov wrote:
> On Wed, Oct 16, 2024 at 02:14:55PM +0300, Kirill A. Shutemov wrote:
> > Calculation of 'next' virtual address doesn't protect against wrapping
> > to zero. It can result in page table corruption and hang. The
> > problematic case is possible if user sets high x86_mapping_info::offset.
> > 
> > The wrapping to zero only occurs if the top PGD entry is accessed.
> > There are no such users in the upstream. Only hibernate_64.c uses
> > x86_mapping_info::offset, and it operates on the direct mapping range,
> > which is not the top PGD entry.
> > 
> > Replace manual 'next' calculation with p?d_addr_end() which handles
> > wrapping correctly.
> 
> So this is a fix for a theoretical issue as it cannot happen currently?

Right.

> Can we call that out in the commit message so that the stable AI doesn't pick
> it up?

Do we have magic words for that?

I tried to express that in the second paragraph: "no such users in the
upstream".

> And which commit is it fixing?
> 
> aece27851d44 ("x86, 64bit, mm: Add generic kernel/ident mapping helper")
> perhaps?

This one is closer:

e4630fdd4763 ("x86/power/64: Always create temporary identity mapping correctly")

It adds x86_mapping_info::offset.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov

Re: [PATCHv4, REBASED 1/4] x86/mm/ident_map: Fix virtual address wrap to zero

[Borislav Petkov]

On Thu, Oct 31, 2024 at 12:11:52PM +0200, Kirill A. Shutemov wrote:
> Do we have magic words for that?

No clue.

> I tried to express that in the second paragraph: "no such users in the
> upstream".

Right, so perhaps better to spell it out explicitly:

"Backporter's note:

This fixes a theoretical issue only and there's no need to backport it to
stable."

at the end of the commit message.

> > And which commit is it fixing?
> > 
> > aece27851d44 ("x86, 64bit, mm: Add generic kernel/ident mapping helper")
> > perhaps?
> 
> This one is closer:
> 
> e4630fdd4763 ("x86/power/64: Always create temporary identity mapping correctly")
> 
> It adds x86_mapping_info::offset.

But aece27851d44 has the faulty check...

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

Re: [PATCHv4, REBASED 1/4] x86/mm/ident_map: Fix virtual address wrap to zero

[Kirill A. Shutemov]

On Thu, Oct 31, 2024 at 02:59:16PM +0100, Borislav Petkov wrote:
> On Thu, Oct 31, 2024 at 12:11:52PM +0200, Kirill A. Shutemov wrote:
> > Do we have magic words for that?
> 
> No clue.
> 
> > I tried to express that in the second paragraph: "no such users in the
> > upstream".
> 
> Right, so perhaps better to spell it out explicitly:
> 
> "Backporter's note:
> 
> This fixes a theoretical issue only and there's no need to backport it to
> stable."
> 
> at the end of the commit message.

Okay.

> 
> > > And which commit is it fixing?
> > > 
> > > aece27851d44 ("x86, 64bit, mm: Add generic kernel/ident mapping helper")
> > > perhaps?
> > 
> > This one is closer:
> > 
> > e4630fdd4763 ("x86/power/64: Always create temporary identity mapping correctly")
> > 
> > It adds x86_mapping_info::offset.
> 
> But aece27851d44 has the faulty check...

It cannot be triggered without 'offset'.

I'll put both.

-- 
  Kiryl Shutsemau / Kirill A. Shutemov

[tip: x86/mm] x86/mm/ident_map: Fix theoretical virtual address overflow to zero

[tip-bot2 for Kirill A. Shutemov]

The following commit has been merged into the x86/mm branch of tip:

Commit-ID:     4f10ec03fe1ed12479134be33ddf006382744651
Gitweb:        https://git.kernel.org/tip/4f10ec03fe1ed12479134be33ddf006382744651
Author:        Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
AuthorDate:    Wed, 16 Oct 2024 14:14:55 +03:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Mon, 10 Mar 2025 20:31:30 +01:00

x86/mm/ident_map: Fix theoretical virtual address overflow to zero

The current calculation of the 'next' virtual address in the
page table initialization functions in arch/x86/mm/ident_map.c
doesn't protect against wrapping to zero.

This is a theoretical issue that cannot happen currently,
the problematic case is possible only if the user sets a
high enough x86_mapping_info::offset value - which no
current code in the upstream kernel does.

( The wrapping to zero only occurs if the top PGD entry is accessed.
  There are no such users upstream. Only hibernate_64.c uses
  x86_mapping_info::offset, and it operates on the direct mapping
  range, which is not the top PGD entry. )

Should such an overflow happen, it can result in page table
corruption and a hang.

To future-proof this code, replace the manual 'next' calculation
with p?d_addr_end() which handles wrapping correctly.

[ Backporter's note: there's no need to backport this patch. ]

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/20241016111458.846228-2-kirill.shutemov@linux.intel.com
---
 arch/x86/mm/ident_map.c | 14 +++-----------
 1 file changed, 3 insertions(+), 11 deletions(-)

diff --git a/arch/x86/mm/ident_map.c b/arch/x86/mm/ident_map.c
index 5ab7bd2..bd5d101 100644
--- a/arch/x86/mm/ident_map.c
+++ b/arch/x86/mm/ident_map.c
@@ -101,9 +101,7 @@ static int ident_pud_init(struct x86_mapping_info *info, pud_t *pud_page,
 		pmd_t *pmd;
 		bool use_gbpage;
 
-		next = (addr & PUD_MASK) + PUD_SIZE;
-		if (next > end)
-			next = end;
+		next = pud_addr_end(addr, end);
 
 		/* if this is already a gbpage, this portion is already mapped */
 		if (pud_leaf(*pud))
@@ -154,10 +152,7 @@ static int ident_p4d_init(struct x86_mapping_info *info, p4d_t *p4d_page,
 		p4d_t *p4d = p4d_page + p4d_index(addr);
 		pud_t *pud;
 
-		next = (addr & P4D_MASK) + P4D_SIZE;
-		if (next > end)
-			next = end;
-
+		next = p4d_addr_end(addr, end);
 		if (p4d_present(*p4d)) {
 			pud = pud_offset(p4d, 0);
 			result = ident_pud_init(info, pud, addr, next);
@@ -199,10 +194,7 @@ int kernel_ident_mapping_init(struct x86_mapping_info *info, pgd_t *pgd_page,
 		pgd_t *pgd = pgd_page + pgd_index(addr);
 		p4d_t *p4d;
 
-		next = (addr & PGDIR_MASK) + PGDIR_SIZE;
-		if (next > end)
-			next = end;
-
+		next = pgd_addr_end(addr, end);
 		if (pgd_present(*pgd)) {
 			p4d = p4d_offset(pgd, 0);
 			result = ident_p4d_init(info, p4d, addr, next);

[tip: x86/core] x86/mm/ident_map: Fix theoretical virtual address overflow to zero

[tip-bot2 for Kirill A. Shutemov]

The following commit has been merged into the x86/core branch of tip:

Commit-ID:     f666c92090a41ac5524dade63ff96b3adcf8c2ab
Gitweb:        https://git.kernel.org/tip/f666c92090a41ac5524dade63ff96b3adcf8c2ab
Author:        Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
AuthorDate:    Wed, 16 Oct 2024 14:14:55 +03:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Wed, 19 Mar 2025 11:12:29 +01:00

x86/mm/ident_map: Fix theoretical virtual address overflow to zero

The current calculation of the 'next' virtual address in the
page table initialization functions in arch/x86/mm/ident_map.c
doesn't protect against wrapping to zero.

This is a theoretical issue that cannot happen currently,
the problematic case is possible only if the user sets a
high enough x86_mapping_info::offset value - which no
current code in the upstream kernel does.

( The wrapping to zero only occurs if the top PGD entry is accessed.
  There are no such users upstream. Only hibernate_64.c uses
  x86_mapping_info::offset, and it operates on the direct mapping
  range, which is not the top PGD entry. )

Should such an overflow happen, it can result in page table
corruption and a hang.

To future-proof this code, replace the manual 'next' calculation
with p?d_addr_end() which handles wrapping correctly.

[ Backporter's note: there's no need to backport this patch. ]

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/20241016111458.846228-2-kirill.shutemov@linux.intel.com
---
 arch/x86/mm/ident_map.c | 14 +++-----------
 1 file changed, 3 insertions(+), 11 deletions(-)

diff --git a/arch/x86/mm/ident_map.c b/arch/x86/mm/ident_map.c
index 5ab7bd2..bd5d101 100644
--- a/arch/x86/mm/ident_map.c
+++ b/arch/x86/mm/ident_map.c
@@ -101,9 +101,7 @@ static int ident_pud_init(struct x86_mapping_info *info, pud_t *pud_page,
 		pmd_t *pmd;
 		bool use_gbpage;
 
-		next = (addr & PUD_MASK) + PUD_SIZE;
-		if (next > end)
-			next = end;
+		next = pud_addr_end(addr, end);
 
 		/* if this is already a gbpage, this portion is already mapped */
 		if (pud_leaf(*pud))
@@ -154,10 +152,7 @@ static int ident_p4d_init(struct x86_mapping_info *info, p4d_t *p4d_page,
 		p4d_t *p4d = p4d_page + p4d_index(addr);
 		pud_t *pud;
 
-		next = (addr & P4D_MASK) + P4D_SIZE;
-		if (next > end)
-			next = end;
-
+		next = p4d_addr_end(addr, end);
 		if (p4d_present(*p4d)) {
 			pud = pud_offset(p4d, 0);
 			result = ident_pud_init(info, pud, addr, next);
@@ -199,10 +194,7 @@ int kernel_ident_mapping_init(struct x86_mapping_info *info, pgd_t *pgd_page,
 		pgd_t *pgd = pgd_page + pgd_index(addr);
 		p4d_t *p4d;
 
-		next = (addr & PGDIR_MASK) + PGDIR_SIZE;
-		if (next > end)
-			next = end;
-
+		next = pgd_addr_end(addr, end);
 		if (pgd_present(*pgd)) {
 			p4d = p4d_offset(pgd, 0);
 			result = ident_p4d_init(info, p4d, addr, next);

[PATCHv4, REBASED 2/4] x86/acpi: Replace manual page table initialization with kernel_ident_mapping_init()

[Kirill A. Shutemov]

The function init_transition_pgtable() maps the page with
asm_acpi_mp_play_dead() into an identity mapping.

Replace manual page table initialization with kernel_ident_mapping_init()
to avoid code duplication. Use x86_mapping_info::offset to get the page
mapped at the correct location.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
 arch/x86/kernel/acpi/madt_wakeup.c | 73 ++++++------------------------
 1 file changed, 15 insertions(+), 58 deletions(-)

diff --git a/arch/x86/kernel/acpi/madt_wakeup.c b/arch/x86/kernel/acpi/madt_wakeup.c
index d5ef6215583b..f36f28405dcc 100644
--- a/arch/x86/kernel/acpi/madt_wakeup.c
+++ b/arch/x86/kernel/acpi/madt_wakeup.c
@@ -70,58 +70,6 @@ static void __init free_pgt_page(void *pgt, void *dummy)
 	return memblock_free(pgt, PAGE_SIZE);
 }
 
-/*
- * Make sure asm_acpi_mp_play_dead() is present in the identity mapping at
- * the same place as in the kernel page tables. asm_acpi_mp_play_dead() switches
- * to the identity mapping and the function has be present at the same spot in
- * the virtual address space before and after switching page tables.
- */
-static int __init init_transition_pgtable(pgd_t *pgd)
-{
-	pgprot_t prot = PAGE_KERNEL_EXEC_NOENC;
-	unsigned long vaddr, paddr;
-	p4d_t *p4d;
-	pud_t *pud;
-	pmd_t *pmd;
-	pte_t *pte;
-
-	vaddr = (unsigned long)asm_acpi_mp_play_dead;
-	pgd += pgd_index(vaddr);
-	if (!pgd_present(*pgd)) {
-		p4d = (p4d_t *)alloc_pgt_page(NULL);
-		if (!p4d)
-			return -ENOMEM;
-		set_pgd(pgd, __pgd(__pa(p4d) | _KERNPG_TABLE));
-	}
-	p4d = p4d_offset(pgd, vaddr);
-	if (!p4d_present(*p4d)) {
-		pud = (pud_t *)alloc_pgt_page(NULL);
-		if (!pud)
-			return -ENOMEM;
-		set_p4d(p4d, __p4d(__pa(pud) | _KERNPG_TABLE));
-	}
-	pud = pud_offset(p4d, vaddr);
-	if (!pud_present(*pud)) {
-		pmd = (pmd_t *)alloc_pgt_page(NULL);
-		if (!pmd)
-			return -ENOMEM;
-		set_pud(pud, __pud(__pa(pmd) | _KERNPG_TABLE));
-	}
-	pmd = pmd_offset(pud, vaddr);
-	if (!pmd_present(*pmd)) {
-		pte = (pte_t *)alloc_pgt_page(NULL);
-		if (!pte)
-			return -ENOMEM;
-		set_pmd(pmd, __pmd(__pa(pte) | _KERNPG_TABLE));
-	}
-	pte = pte_offset_kernel(pmd, vaddr);
-
-	paddr = __pa(vaddr);
-	set_pte(pte, pfn_pte(paddr >> PAGE_SHIFT, prot));
-
-	return 0;
-}
-
 static int __init acpi_mp_setup_reset(u64 reset_vector)
 {
 	struct x86_mapping_info info = {
@@ -130,6 +78,7 @@ static int __init acpi_mp_setup_reset(u64 reset_vector)
 		.page_flag      = __PAGE_KERNEL_LARGE_EXEC,
 		.kernpg_flag    = _KERNPG_TABLE_NOENC,
 	};
+	unsigned long mstart, mend;
 	pgd_t *pgd;
 
 	pgd = alloc_pgt_page(NULL);
@@ -137,8 +86,6 @@ static int __init acpi_mp_setup_reset(u64 reset_vector)
 		return -ENOMEM;
 
 	for (int i = 0; i < nr_pfn_mapped; i++) {
-		unsigned long mstart, mend;
-
 		mstart = pfn_mapped[i].start << PAGE_SHIFT;
 		mend   = pfn_mapped[i].end << PAGE_SHIFT;
 		if (kernel_ident_mapping_init(&info, pgd, mstart, mend)) {
@@ -147,14 +94,24 @@ static int __init acpi_mp_setup_reset(u64 reset_vector)
 		}
 	}
 
-	if (kernel_ident_mapping_init(&info, pgd,
-				      PAGE_ALIGN_DOWN(reset_vector),
-				      PAGE_ALIGN(reset_vector + 1))) {
+	mstart = PAGE_ALIGN_DOWN(reset_vector);
+	mend = mstart + PAGE_SIZE;
+	if (kernel_ident_mapping_init(&info, pgd, mstart, mend)) {
 		kernel_ident_mapping_free(&info, pgd);
 		return -ENOMEM;
 	}
 
-	if (init_transition_pgtable(pgd)) {
+	/*
+	 * Make sure asm_acpi_mp_play_dead() is present in the identity mapping
+	 * at the same place as in the kernel page tables.
+	 * asm_acpi_mp_play_dead() switches to the identity mapping and the
+	 * function must be present at the same spot in the virtual address space
+	 * before and after switching page tables.
+	 */
+	info.offset = __START_KERNEL_map - phys_base;
+	mstart = PAGE_ALIGN_DOWN(__pa(asm_acpi_mp_play_dead));
+	mend = mstart + PAGE_SIZE;
+	if (kernel_ident_mapping_init(&info, pgd, mstart, mend)) {
 		kernel_ident_mapping_free(&info, pgd);
 		return -ENOMEM;
 	}
-- 
2.45.2

[tip: x86/mm] x86/acpi: Replace manual page table initialization with kernel_ident_mapping_init()

[tip-bot2 for Kirill A. Shutemov]

The following commit has been merged into the x86/mm branch of tip:

Commit-ID:     376daf20eda4898a49a4746f225153efb4c094e7
Gitweb:        https://git.kernel.org/tip/376daf20eda4898a49a4746f225153efb4c094e7
Author:        Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
AuthorDate:    Wed, 16 Oct 2024 14:14:56 +03:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Mon, 10 Mar 2025 20:31:28 +01:00

x86/acpi: Replace manual page table initialization with kernel_ident_mapping_init()

The init_transition_pgtable() functions maps the page with
asm_acpi_mp_play_dead() into an identity mapping.

Replace open-coded manual page table initialization with
kernel_ident_mapping_init() to avoid code duplication.

Use x86_mapping_info::offset to get the page mapped at the
correct location.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/20241016111458.846228-3-kirill.shutemov@linux.intel.com
---
 arch/x86/kernel/acpi/madt_wakeup.c | 73 +++++------------------------
 1 file changed, 15 insertions(+), 58 deletions(-)

diff --git a/arch/x86/kernel/acpi/madt_wakeup.c b/arch/x86/kernel/acpi/madt_wakeup.c
index d5ef621..f36f284 100644
--- a/arch/x86/kernel/acpi/madt_wakeup.c
+++ b/arch/x86/kernel/acpi/madt_wakeup.c
@@ -70,58 +70,6 @@ static void __init free_pgt_page(void *pgt, void *dummy)
 	return memblock_free(pgt, PAGE_SIZE);
 }
 
-/*
- * Make sure asm_acpi_mp_play_dead() is present in the identity mapping at
- * the same place as in the kernel page tables. asm_acpi_mp_play_dead() switches
- * to the identity mapping and the function has be present at the same spot in
- * the virtual address space before and after switching page tables.
- */
-static int __init init_transition_pgtable(pgd_t *pgd)
-{
-	pgprot_t prot = PAGE_KERNEL_EXEC_NOENC;
-	unsigned long vaddr, paddr;
-	p4d_t *p4d;
-	pud_t *pud;
-	pmd_t *pmd;
-	pte_t *pte;
-
-	vaddr = (unsigned long)asm_acpi_mp_play_dead;
-	pgd += pgd_index(vaddr);
-	if (!pgd_present(*pgd)) {
-		p4d = (p4d_t *)alloc_pgt_page(NULL);
-		if (!p4d)
-			return -ENOMEM;
-		set_pgd(pgd, __pgd(__pa(p4d) | _KERNPG_TABLE));
-	}
-	p4d = p4d_offset(pgd, vaddr);
-	if (!p4d_present(*p4d)) {
-		pud = (pud_t *)alloc_pgt_page(NULL);
-		if (!pud)
-			return -ENOMEM;
-		set_p4d(p4d, __p4d(__pa(pud) | _KERNPG_TABLE));
-	}
-	pud = pud_offset(p4d, vaddr);
-	if (!pud_present(*pud)) {
-		pmd = (pmd_t *)alloc_pgt_page(NULL);
-		if (!pmd)
-			return -ENOMEM;
-		set_pud(pud, __pud(__pa(pmd) | _KERNPG_TABLE));
-	}
-	pmd = pmd_offset(pud, vaddr);
-	if (!pmd_present(*pmd)) {
-		pte = (pte_t *)alloc_pgt_page(NULL);
-		if (!pte)
-			return -ENOMEM;
-		set_pmd(pmd, __pmd(__pa(pte) | _KERNPG_TABLE));
-	}
-	pte = pte_offset_kernel(pmd, vaddr);
-
-	paddr = __pa(vaddr);
-	set_pte(pte, pfn_pte(paddr >> PAGE_SHIFT, prot));
-
-	return 0;
-}
-
 static int __init acpi_mp_setup_reset(u64 reset_vector)
 {
 	struct x86_mapping_info info = {
@@ -130,6 +78,7 @@ static int __init acpi_mp_setup_reset(u64 reset_vector)
 		.page_flag      = __PAGE_KERNEL_LARGE_EXEC,
 		.kernpg_flag    = _KERNPG_TABLE_NOENC,
 	};
+	unsigned long mstart, mend;
 	pgd_t *pgd;
 
 	pgd = alloc_pgt_page(NULL);
@@ -137,8 +86,6 @@ static int __init acpi_mp_setup_reset(u64 reset_vector)
 		return -ENOMEM;
 
 	for (int i = 0; i < nr_pfn_mapped; i++) {
-		unsigned long mstart, mend;
-
 		mstart = pfn_mapped[i].start << PAGE_SHIFT;
 		mend   = pfn_mapped[i].end << PAGE_SHIFT;
 		if (kernel_ident_mapping_init(&info, pgd, mstart, mend)) {
@@ -147,14 +94,24 @@ static int __init acpi_mp_setup_reset(u64 reset_vector)
 		}
 	}
 
-	if (kernel_ident_mapping_init(&info, pgd,
-				      PAGE_ALIGN_DOWN(reset_vector),
-				      PAGE_ALIGN(reset_vector + 1))) {
+	mstart = PAGE_ALIGN_DOWN(reset_vector);
+	mend = mstart + PAGE_SIZE;
+	if (kernel_ident_mapping_init(&info, pgd, mstart, mend)) {
 		kernel_ident_mapping_free(&info, pgd);
 		return -ENOMEM;
 	}
 
-	if (init_transition_pgtable(pgd)) {
+	/*
+	 * Make sure asm_acpi_mp_play_dead() is present in the identity mapping
+	 * at the same place as in the kernel page tables.
+	 * asm_acpi_mp_play_dead() switches to the identity mapping and the
+	 * function must be present at the same spot in the virtual address space
+	 * before and after switching page tables.
+	 */
+	info.offset = __START_KERNEL_map - phys_base;
+	mstart = PAGE_ALIGN_DOWN(__pa(asm_acpi_mp_play_dead));
+	mend = mstart + PAGE_SIZE;
+	if (kernel_ident_mapping_init(&info, pgd, mstart, mend)) {
 		kernel_ident_mapping_free(&info, pgd);
 		return -ENOMEM;
 	}

[tip: x86/core] x86/acpi: Replace manual page table initialization with kernel_ident_mapping_init()

[tip-bot2 for Kirill A. Shutemov]

The following commit has been merged into the x86/core branch of tip:

Commit-ID:     775d37d8f01ea1349be8bd7cc8651b51814c48df
Gitweb:        https://git.kernel.org/tip/775d37d8f01ea1349be8bd7cc8651b51814c48df
Author:        Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
AuthorDate:    Wed, 16 Oct 2024 14:14:56 +03:00
Committer:     Ingo Molnar <mingo@kernel.org>
CommitterDate: Wed, 19 Mar 2025 11:12:29 +01:00

x86/acpi: Replace manual page table initialization with kernel_ident_mapping_init()

The init_transition_pgtable() functions maps the page with
asm_acpi_mp_play_dead() into an identity mapping.

Replace open-coded manual page table initialization with
kernel_ident_mapping_init() to avoid code duplication.

Use x86_mapping_info::offset to get the page mapped at the
correct location.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: https://lore.kernel.org/r/20241016111458.846228-3-kirill.shutemov@linux.intel.com
---
 arch/x86/kernel/acpi/madt_wakeup.c | 73 +++++------------------------
 1 file changed, 15 insertions(+), 58 deletions(-)

diff --git a/arch/x86/kernel/acpi/madt_wakeup.c b/arch/x86/kernel/acpi/madt_wakeup.c
index d5ef621..f36f284 100644
--- a/arch/x86/kernel/acpi/madt_wakeup.c
+++ b/arch/x86/kernel/acpi/madt_wakeup.c
@@ -70,58 +70,6 @@ static void __init free_pgt_page(void *pgt, void *dummy)
 	return memblock_free(pgt, PAGE_SIZE);
 }
 
-/*
- * Make sure asm_acpi_mp_play_dead() is present in the identity mapping at
- * the same place as in the kernel page tables. asm_acpi_mp_play_dead() switches
- * to the identity mapping and the function has be present at the same spot in
- * the virtual address space before and after switching page tables.
- */
-static int __init init_transition_pgtable(pgd_t *pgd)
-{
-	pgprot_t prot = PAGE_KERNEL_EXEC_NOENC;
-	unsigned long vaddr, paddr;
-	p4d_t *p4d;
-	pud_t *pud;
-	pmd_t *pmd;
-	pte_t *pte;
-
-	vaddr = (unsigned long)asm_acpi_mp_play_dead;
-	pgd += pgd_index(vaddr);
-	if (!pgd_present(*pgd)) {
-		p4d = (p4d_t *)alloc_pgt_page(NULL);
-		if (!p4d)
-			return -ENOMEM;
-		set_pgd(pgd, __pgd(__pa(p4d) | _KERNPG_TABLE));
-	}
-	p4d = p4d_offset(pgd, vaddr);
-	if (!p4d_present(*p4d)) {
-		pud = (pud_t *)alloc_pgt_page(NULL);
-		if (!pud)
-			return -ENOMEM;
-		set_p4d(p4d, __p4d(__pa(pud) | _KERNPG_TABLE));
-	}
-	pud = pud_offset(p4d, vaddr);
-	if (!pud_present(*pud)) {
-		pmd = (pmd_t *)alloc_pgt_page(NULL);
-		if (!pmd)
-			return -ENOMEM;
-		set_pud(pud, __pud(__pa(pmd) | _KERNPG_TABLE));
-	}
-	pmd = pmd_offset(pud, vaddr);
-	if (!pmd_present(*pmd)) {
-		pte = (pte_t *)alloc_pgt_page(NULL);
-		if (!pte)
-			return -ENOMEM;
-		set_pmd(pmd, __pmd(__pa(pte) | _KERNPG_TABLE));
-	}
-	pte = pte_offset_kernel(pmd, vaddr);
-
-	paddr = __pa(vaddr);
-	set_pte(pte, pfn_pte(paddr >> PAGE_SHIFT, prot));
-
-	return 0;
-}
-
 static int __init acpi_mp_setup_reset(u64 reset_vector)
 {
 	struct x86_mapping_info info = {
@@ -130,6 +78,7 @@ static int __init acpi_mp_setup_reset(u64 reset_vector)
 		.page_flag      = __PAGE_KERNEL_LARGE_EXEC,
 		.kernpg_flag    = _KERNPG_TABLE_NOENC,
 	};
+	unsigned long mstart, mend;
 	pgd_t *pgd;
 
 	pgd = alloc_pgt_page(NULL);
@@ -137,8 +86,6 @@ static int __init acpi_mp_setup_reset(u64 reset_vector)
 		return -ENOMEM;
 
 	for (int i = 0; i < nr_pfn_mapped; i++) {
-		unsigned long mstart, mend;
-
 		mstart = pfn_mapped[i].start << PAGE_SHIFT;
 		mend   = pfn_mapped[i].end << PAGE_SHIFT;
 		if (kernel_ident_mapping_init(&info, pgd, mstart, mend)) {
@@ -147,14 +94,24 @@ static int __init acpi_mp_setup_reset(u64 reset_vector)
 		}
 	}
 
-	if (kernel_ident_mapping_init(&info, pgd,
-				      PAGE_ALIGN_DOWN(reset_vector),
-				      PAGE_ALIGN(reset_vector + 1))) {
+	mstart = PAGE_ALIGN_DOWN(reset_vector);
+	mend = mstart + PAGE_SIZE;
+	if (kernel_ident_mapping_init(&info, pgd, mstart, mend)) {
 		kernel_ident_mapping_free(&info, pgd);
 		return -ENOMEM;
 	}
 
-	if (init_transition_pgtable(pgd)) {
+	/*
+	 * Make sure asm_acpi_mp_play_dead() is present in the identity mapping
+	 * at the same place as in the kernel page tables.
+	 * asm_acpi_mp_play_dead() switches to the identity mapping and the
+	 * function must be present at the same spot in the virtual address space
+	 * before and after switching page tables.
+	 */
+	info.offset = __START_KERNEL_map - phys_base;
+	mstart = PAGE_ALIGN_DOWN(__pa(asm_acpi_mp_play_dead));
+	mend = mstart + PAGE_SIZE;
+	if (kernel_ident_mapping_init(&info, pgd, mstart, mend)) {
 		kernel_ident_mapping_free(&info, pgd);
 		return -ENOMEM;
 	}

[PATCHv4, REBASED 3/4] x86/64/kexec: Map original relocate_kernel() in init_transition_pgtable()

[Kirill A. Shutemov]

The init_transition_pgtable() function sets up transitional page tables.
It ensures that the relocate_kernel() function is present in the
identity mapping at the same location as in the kernel page tables.
relocate_kernel() switches to the identity mapping, and the function
must be present at the same location in the virtual address space before
and after switching page tables.

init_transition_pgtable() maps a copy of relocate_kernel() in
image->control_code_page at the relocate_kernel() virtual address, but
the original physical address of relocate_kernel() would also work.

It is safe to use original relocate_kernel() physical address cannot be
overwritten until swap_pages() is called, and the relocate_kernel()
virtual address will not be used by then.

Map the original relocate_kernel() at the relocate_kernel() virtual
address in the identity mapping. It is preparation to replace the
init_transition_pgtable() implementation with a call to
kernel_ident_mapping_init().

Note that while relocate_kernel() switches to the identity mapping, it
does not flush global TLB entries (CR4.PGE is not cleared). This means
that in most cases, the kernel still runs relocate_kernel() from the
original physical address before the change.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
---
 arch/x86/kernel/machine_kexec_64.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
index 9c9ac606893e..645690e81c2d 100644
--- a/arch/x86/kernel/machine_kexec_64.c
+++ b/arch/x86/kernel/machine_kexec_64.c
@@ -157,7 +157,7 @@ static int init_transition_pgtable(struct kimage *image, pgd_t *pgd)
 	pte_t *pte;
 
 	vaddr = (unsigned long)relocate_kernel;
-	paddr = __pa(page_address(image->control_code_page)+PAGE_SIZE);
+	paddr = __pa(relocate_kernel);
 	pgd += pgd_index(vaddr);
 	if (!pgd_present(*pgd)) {
 		p4d = (p4d_t *)get_zeroed_page(GFP_KERNEL);
-- 
2.45.2

Re: [PATCHv4, REBASED 3/4] x86/64/kexec: Map original relocate_kernel() in init_transition_pgtable()

[Borislav Petkov]

On Wed, Oct 16, 2024 at 02:14:57PM +0300, Kirill A. Shutemov wrote:
> The init_transition_pgtable() function sets up transitional page tables.
> It ensures that the relocate_kernel() function is present in the
> identity mapping at the same location as in the kernel page tables.
> relocate_kernel() switches to the identity mapping, and the function
> must be present at the same location in the virtual address space before
> and after switching page tables.
> 
> init_transition_pgtable() maps a copy of relocate_kernel() in
> image->control_code_page at the relocate_kernel() virtual address, but
> the original physical address of relocate_kernel() would also work.
> 
> It is safe to use original relocate_kernel() physical address cannot be
					^^^^^^^^^^^^^^^

something went missing here in that sentence. Reads weird.

> overwritten until swap_pages() is called, and the relocate_kernel()
> virtual address will not be used by then.

...

> diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
> index 9c9ac606893e..645690e81c2d 100644
> --- a/arch/x86/kernel/machine_kexec_64.c
> +++ b/arch/x86/kernel/machine_kexec_64.c
> @@ -157,7 +157,7 @@ static int init_transition_pgtable(struct kimage *image, pgd_t *pgd)
>  	pte_t *pte;
>  
>  	vaddr = (unsigned long)relocate_kernel;
> -	paddr = __pa(page_address(image->control_code_page)+PAGE_SIZE);
> +	paddr = __pa(relocate_kernel);
>  	pgd += pgd_index(vaddr);
>  	if (!pgd_present(*pgd)) {
>  		p4d = (p4d_t *)get_zeroed_page(GFP_KERNEL);

Such changes always make me nervous so I'd queue them only after this merge
window is over so that they can get maximal testing in next. Unless someone
objects...

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette

[PATCHv4, REBASED 4/4] x86/64/kexec: Rewrite init_transition_pgtable() with kernel_ident_mapping_init()

[Kirill A. Shutemov]

init_transition_pgtable() sets up transitional page tables. Rewrite it
using kernel_ident_mapping_init() to avoid code duplication.

Change struct kimage_arch to track allocated page tables as a list, not
linking them to specific page table levels.

Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
Reviewed-by: Tom Lendacky <thomas.lendacky@amd.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
---
 arch/x86/include/asm/kexec.h       |  5 +-
 arch/x86/kernel/machine_kexec_64.c | 89 +++++++++++-------------------
 2 files changed, 32 insertions(+), 62 deletions(-)

diff --git a/arch/x86/include/asm/kexec.h b/arch/x86/include/asm/kexec.h
index ae5482a2f0ca..7f9287f371e6 100644
--- a/arch/x86/include/asm/kexec.h
+++ b/arch/x86/include/asm/kexec.h
@@ -145,10 +145,7 @@ struct kimage_arch {
 };
 #else
 struct kimage_arch {
-	p4d_t *p4d;
-	pud_t *pud;
-	pmd_t *pmd;
-	pte_t *pte;
+	struct list_head pages;
 };
 #endif /* CONFIG_X86_32 */
 
diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
index 645690e81c2d..fb350372835c 100644
--- a/arch/x86/kernel/machine_kexec_64.c
+++ b/arch/x86/kernel/machine_kexec_64.c
@@ -134,71 +134,42 @@ map_efi_systab(struct x86_mapping_info *info, pgd_t *level4p)
 	return 0;
 }
 
+static void *alloc_transition_pgt_page(void *data)
+{
+	struct kimage *image = (struct kimage *)data;
+	unsigned long virt;
+
+	virt = get_zeroed_page(GFP_KERNEL);
+	if (!virt)
+		return NULL;
+
+	list_add(&virt_to_page(virt)->lru, &image->arch.pages);
+	return (void *)virt;
+}
+
 static void free_transition_pgtable(struct kimage *image)
 {
-	free_page((unsigned long)image->arch.p4d);
-	image->arch.p4d = NULL;
-	free_page((unsigned long)image->arch.pud);
-	image->arch.pud = NULL;
-	free_page((unsigned long)image->arch.pmd);
-	image->arch.pmd = NULL;
-	free_page((unsigned long)image->arch.pte);
-	image->arch.pte = NULL;
+	struct page *page, *tmp;
+
+	list_for_each_entry_safe(page, tmp, &image->arch.pages, lru) {
+		list_del(&page->lru);
+		free_page((unsigned long)page_address(page));
+	}
 }
 
 static int init_transition_pgtable(struct kimage *image, pgd_t *pgd)
 {
-	pgprot_t prot = PAGE_KERNEL_EXEC_NOENC;
-	unsigned long vaddr, paddr;
-	int result = -ENOMEM;
-	p4d_t *p4d;
-	pud_t *pud;
-	pmd_t *pmd;
-	pte_t *pte;
+	struct x86_mapping_info info = {
+		.alloc_pgt_page	= alloc_transition_pgt_page,
+		.context	= image,
+		.page_flag	= __PAGE_KERNEL_LARGE_EXEC,
+		.kernpg_flag	= _KERNPG_TABLE_NOENC,
+		.offset = __START_KERNEL_map - phys_base,
+	};
+	unsigned long mstart = PAGE_ALIGN_DOWN(__pa(relocate_kernel));
+	unsigned long mend = mstart + PAGE_SIZE;
 
-	vaddr = (unsigned long)relocate_kernel;
-	paddr = __pa(relocate_kernel);
-	pgd += pgd_index(vaddr);
-	if (!pgd_present(*pgd)) {
-		p4d = (p4d_t *)get_zeroed_page(GFP_KERNEL);
-		if (!p4d)
-			goto err;
-		image->arch.p4d = p4d;
-		set_pgd(pgd, __pgd(__pa(p4d) | _KERNPG_TABLE));
-	}
-	p4d = p4d_offset(pgd, vaddr);
-	if (!p4d_present(*p4d)) {
-		pud = (pud_t *)get_zeroed_page(GFP_KERNEL);
-		if (!pud)
-			goto err;
-		image->arch.pud = pud;
-		set_p4d(p4d, __p4d(__pa(pud) | _KERNPG_TABLE));
-	}
-	pud = pud_offset(p4d, vaddr);
-	if (!pud_present(*pud)) {
-		pmd = (pmd_t *)get_zeroed_page(GFP_KERNEL);
-		if (!pmd)
-			goto err;
-		image->arch.pmd = pmd;
-		set_pud(pud, __pud(__pa(pmd) | _KERNPG_TABLE));
-	}
-	pmd = pmd_offset(pud, vaddr);
-	if (!pmd_present(*pmd)) {
-		pte = (pte_t *)get_zeroed_page(GFP_KERNEL);
-		if (!pte)
-			goto err;
-		image->arch.pte = pte;
-		set_pmd(pmd, __pmd(__pa(pte) | _KERNPG_TABLE));
-	}
-	pte = pte_offset_kernel(pmd, vaddr);
-
-	if (cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT))
-		prot = PAGE_KERNEL_EXEC;
-
-	set_pte(pte, pfn_pte(paddr >> PAGE_SHIFT, prot));
-	return 0;
-err:
-	return result;
+	return kernel_ident_mapping_init(&info, pgd, mstart, mend);
 }
 
 static void *alloc_pgt_page(void *data)
@@ -299,6 +270,8 @@ int machine_kexec_prepare(struct kimage *image)
 	unsigned long start_pgtable;
 	int result;
 
+	INIT_LIST_HEAD(&image->arch.pages);
+
 	/* Calculate the offsets */
 	start_pgtable = page_to_pfn(image->control_code_page) << PAGE_SHIFT;
 
-- 
2.45.2

Re: [PATCHv4, REBASED 0/4] x86: Reduce code duplication on page table initialization

[Kirill A. Shutemov]

On Wed, Oct 16, 2024 at 02:14:54PM +0300, Kirill A. Shutemov wrote:
> Use kernel_ident_mapping_init() to initialize kernel page tables where
> possible, replacing manual initialization, reducing code duplication.
> 
> v4:
>  - Reviewed-bys from Kai;
>  - Fix comment in acpi_mp_setup_reset() (Rafael);
> v3:
>  - Reviewed-bys from Tom;
>  - Improve commit messages;
> v2:
>  - A separate patch to change what PA is mapped at relocate_kernel() VA.
>  - Improve commit messages;
>  - Add Reveiwed-by from Kai;
> 
> Kirill A. Shutemov (4):
>   x86/mm/ident_map: Fix virtual address wrap to zero
>   x86/acpi: Replace manual page table initialization with
>     kernel_ident_mapping_init()
>   x86/64/kexec: Map original relocate_kernel() in
>     init_transition_pgtable()
>   x86/64/kexec: Rewrite init_transition_pgtable() with
>     kernel_ident_mapping_init()
> 
>  arch/x86/include/asm/kexec.h       |  5 +-
>  arch/x86/kernel/acpi/madt_wakeup.c | 73 +++++-------------------
>  arch/x86/kernel/machine_kexec_64.c | 89 +++++++++++-------------------
>  arch/x86/mm/ident_map.c            | 14 +----
>  4 files changed, 50 insertions(+), 131 deletions(-)

Any feedback on this series?

-- 
  Kiryl Shutsemau / Kirill A. Shutemov

Re: [PATCHv4, REBASED 0/4] x86: Reduce code duplication on page table initialization

[Dave Hansen]

On 10/29/24 08:09, Kirill A. Shutemov wrote:
> Any feedback on this series?

It's tempting because it removes so much code, but it's also worrying
because these code paths are notoriously hard to test.

I'd be much happier if you'd send this after 6.13-rc1 drops and we give
it as much testing time as possible.

Re: [PATCHv4, REBASED 0/4] x86: Reduce code duplication on page table initialization

[Ingo Molnar]

* Kirill A. Shutemov <kirill.shutemov@linux.intel.com> wrote:

> Use kernel_ident_mapping_init() to initialize kernel page tables where
> possible, replacing manual initialization, reducing code duplication.
> 
> v4:
>  - Reviewed-bys from Kai;
>  - Fix comment in acpi_mp_setup_reset() (Rafael);
> v3:
>  - Reviewed-bys from Tom;
>  - Improve commit messages;
> v2:
>  - A separate patch to change what PA is mapped at relocate_kernel() VA.
>  - Improve commit messages;
>  - Add Reveiwed-by from Kai;
> 
> Kirill A. Shutemov (4):
>   x86/mm/ident_map: Fix virtual address wrap to zero
>   x86/acpi: Replace manual page table initialization with kernel_ident_mapping_init()
>   x86/64/kexec: Map original relocate_kernel() in init_transition_pgtable()
>   x86/64/kexec: Rewrite init_transition_pgtable() with kernel_ident_mapping_init()
> 
>  arch/x86/include/asm/kexec.h       |  5 +-
>  arch/x86/kernel/acpi/madt_wakeup.c | 73 +++++-------------------
>  arch/x86/kernel/machine_kexec_64.c | 89 +++++++++++-------------------
>  arch/x86/mm/ident_map.c            | 14 +----
>  4 files changed, 50 insertions(+), 131 deletions(-)

So looks like this series feel between the cracks during the holiday 
season.

To help move them along, I've fixed up the first patch with the review 
feedback clarification requests, and applied patch #1 and #2 to 
tip:x86/mm:

  4f10ec03fe1e ("x86/mm/ident_map: Fix theoretical virtual address overflow to zero")
  376daf20eda4 ("x86/acpi: Replace manual page table initialization with kernel_ident_mapping_init()")

Patches #3 and #4 don't apply anymore, due to interference by other 
work with commits like:

  4b5bc2ec9a23 ("x86/kexec: Allocate PGD for x86_64 transition page tables separately")

If the remaining patches are still relevant, mind porting them to 
latest -tip?

Thanks,

	Ingo