Apply better workaround for E820 conflict

0001-xen-use-correct-end-address-of-kernel-for-conflict-c.patch

@@ -0,0 +1,40 @@
+From db85abfa44f20856320f9cf19a4b4fe6d94b30f8 Mon Sep 17 00:00:00 2001
+From: Juergen Gross <[email protected]>
+Date: Sat, 3 Aug 2024 08:01:22 +0200
+Subject: [PATCH 1/5] xen: use correct end address of kernel for conflict
+ checking
+
+When running as a Xen PV dom0 the kernel is loaded by the hypervisor
+using a different memory map than that of the host. In order to
+minimize the required changes in the kernel, the kernel adapts its
+memory map to that of the host. In order to do that it is checking
+for conflicts of its load address with the host memory map.
+
+Unfortunately the tested memory range does not include the .brk
+area, which might result in crashes or memory corruption when this
+area does conflict withe the memory map of the host.
+
+Fix the test by using the _end label instead of __bss_stop.
+
+Fixes: 808fdb71936c ("xen: check for kernel memory conflicting with memory layout")
+Signed-off-by: Juergen Gross <[email protected]>
+---
+ arch/x86/xen/setup.c | 2 +-
+ 1 file changed, 1 insertion(+), 1 deletion(-)
+
+diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
+index 806ddb2391d9..4bcc70a71b7d 100644
+--- a/arch/x86/xen/setup.c
++++ b/arch/x86/xen/setup.c
+@@ -825,7 +825,7 @@ char * __init xen_memory_setup(void)
+ 	 * to relocating (and even reusing) pages with kernel text or data.
+ 	 */
+ 	if (xen_is_e820_reserved(__pa_symbol(_text),
+-			__pa_symbol(__bss_stop) - __pa_symbol(_text))) {
++				 __pa_symbol(_end) - __pa_symbol(_text))) {
+ 		xen_raw_console_write("Xen hypervisor allocated kernel memory conflicts with E820 map\n");
+ 		BUG();
+ 	}
+-- 
+2.43.0
+

0002-xen-introduce-generic-helper-checking-for-memory-map.patch

@@ -0,0 +1,120 @@
+From c03b755e273639b865d351ba1d36625fc8b2791e Mon Sep 17 00:00:00 2001
+From: Juergen Gross <[email protected]>
+Date: Fri, 2 Aug 2024 14:11:06 +0200
+Subject: [PATCH 2/5] xen: introduce generic helper checking for memory map
+ conflicts
+
+When booting as a Xen PV dom0 the memory layout of the dom0 is
+modified to match that of the host, as this requires less changes in
+the kernel for supporting Xen.
+
+There are some cases, though, which are problematic, as it is the Xen
+hypervisor selecting the kernel's load address plus some other data,
+which might conflict with the host's memory map.
+
+These conflicts are detected at boot time and result in a boot error.
+In order to support handling at least some of these conflicts in
+future, introduce a generic helper function which will later gain the
+ability to adapt the memory layout when possible.
+
+Add the missing check for the xen_start_info area.
+
+Signed-off-by: Juergen Gross <[email protected]>
+---
+ arch/x86/xen/mmu_pv.c  |  5 +----
+ arch/x86/xen/setup.c   | 34 ++++++++++++++++++++++++++++------
+ arch/x86/xen/xen-ops.h |  3 ++-
+ 3 files changed, 31 insertions(+), 11 deletions(-)
+
+diff --git a/arch/x86/xen/mmu_pv.c b/arch/x86/xen/mmu_pv.c
+index f1ce39d6d32c..839e6613753d 100644
+--- a/arch/x86/xen/mmu_pv.c
++++ b/arch/x86/xen/mmu_pv.c
+@@ -2018,10 +2018,7 @@ void __init xen_reserve_special_pages(void)
+
+ void __init xen_pt_check_e820(void)
+ {
+-	if (xen_is_e820_reserved(xen_pt_base, xen_pt_size)) {
+-		xen_raw_console_write("Xen hypervisor allocated page table memory conflicts with E820 map\n");
+-		BUG();
+-	}
++	xen_chk_is_e820_usable(xen_pt_base, xen_pt_size, "page table");
+ }
+
+ static unsigned char dummy_mapping[PAGE_SIZE] __page_aligned_bss;
+diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
+index 4bcc70a71b7d..96765180514b 100644
+--- a/arch/x86/xen/setup.c
++++ b/arch/x86/xen/setup.c
+@@ -567,7 +567,7 @@ static void __init xen_ignore_unusable(void)
+ 	}
+ }
+
+-bool __init xen_is_e820_reserved(phys_addr_t start, phys_addr_t size)
++static bool __init xen_is_e820_reserved(phys_addr_t start, phys_addr_t size)
+ {
+ 	struct e820_entry *entry;
+ 	unsigned mapcnt;
+@@ -624,6 +624,23 @@ phys_addr_t __init xen_find_free_area(phys_addr_t size)
+ 	return 0;
+ }
+
++/*
++ * Check for an area in physical memory to be usable for non-movable purposes.
++ * An area is considered to usable if the used E820 map lists it to be RAM.
++ * In case the area is not usable, crash the system with an error message.
++ */
++void __init xen_chk_is_e820_usable(phys_addr_t start, phys_addr_t size,
++				   const char *component)
++{
++	if (!xen_is_e820_reserved(start, size))
++		return;
++
++	xen_raw_console_write("Xen hypervisor allocated ");
++	xen_raw_console_write(component);
++	xen_raw_console_write(" memory conflicts with E820 map\n");
++	BUG();
++}
++
+ /*
+  * Like memcpy, but with physical addresses for dest and src.
+  */
+@@ -824,11 +841,16 @@ char * __init xen_memory_setup(void)
+ 	 * Failing now is better than running into weird problems later due
+ 	 * to relocating (and even reusing) pages with kernel text or data.
+ 	 */
+-	if (xen_is_e820_reserved(__pa_symbol(_text),
+-				 __pa_symbol(_end) - __pa_symbol(_text))) {
+-		xen_raw_console_write("Xen hypervisor allocated kernel memory conflicts with E820 map\n");
+-		BUG();
+-	}
++	xen_chk_is_e820_usable(__pa_symbol(_text),
++			       __pa_symbol(_end) - __pa_symbol(_text),
++			       "kernel");
++
++	/*
++	 * Check for a conflict of the xen_start_info memory with the target
++	 * E820 map.
++	 */
++	xen_chk_is_e820_usable(__pa(xen_start_info), sizeof(*xen_start_info),
++			       "xen_start_info");
+
+ 	/*
+ 	 * Check for a conflict of the hypervisor supplied page tables with
+diff --git a/arch/x86/xen/xen-ops.h b/arch/x86/xen/xen-ops.h
+index 0cf16fc79e0b..9a27d1d653d3 100644
+--- a/arch/x86/xen/xen-ops.h
++++ b/arch/x86/xen/xen-ops.h
+@@ -48,7 +48,8 @@ void xen_mm_unpin_all(void);
+ void __init xen_relocate_p2m(void);
+ #endif
+
+-bool __init xen_is_e820_reserved(phys_addr_t start, phys_addr_t size);
++void __init xen_chk_is_e820_usable(phys_addr_t start, phys_addr_t size,
++				   const char *component);
+ unsigned long __ref xen_chk_extra_mem(unsigned long pfn);
+ void __init xen_inv_extra_mem(void);
+ void __init xen_remap_memory(void);
+-- 
+2.43.0
+

0003-xen-move-checks-for-e820-conflicts-further-up.patch

@@ -0,0 +1,80 @@
+From 92bea9107c776578c415c56b4f6b3c7bca90c7e9 Mon Sep 17 00:00:00 2001
+From: Juergen Gross <[email protected]>
+Date: Tue, 6 Aug 2024 09:56:48 +0200
+Subject: [PATCH 3/5] xen: move checks for e820 conflicts further up
+
+Move the checks for e820 memory map conflicts using the
+xen_chk_is_e820_usable() helper further up in order to prepare
+resolving some of the possible conflicts by doing some e820 map
+modifications, which must happen before evaluating the RAM layout.
+
+Signed-off-by: Juergen Gross <[email protected]>
+---
+ arch/x86/xen/setup.c | 44 ++++++++++++++++++++++----------------------
+ 1 file changed, 22 insertions(+), 22 deletions(-)
+
+diff --git a/arch/x86/xen/setup.c b/arch/x86/xen/setup.c
+index 96765180514b..dba68951ed6b 100644
+--- a/arch/x86/xen/setup.c
++++ b/arch/x86/xen/setup.c
+@@ -764,6 +764,28 @@ char * __init xen_memory_setup(void)
+ 	/* Make sure the Xen-supplied memory map is well-ordered. */
+ 	e820__update_table(&xen_e820_table);
+
++	/*
++	 * Check whether the kernel itself conflicts with the target E820 map.
++	 * Failing now is better than running into weird problems later due
++	 * to relocating (and even reusing) pages with kernel text or data.
++	 */
++	xen_chk_is_e820_usable(__pa_symbol(_text),
++			       __pa_symbol(_end) - __pa_symbol(_text),
++			       "kernel");
++
++	/*
++	 * Check for a conflict of the xen_start_info memory with the target
++	 * E820 map.
++	 */
++	xen_chk_is_e820_usable(__pa(xen_start_info), sizeof(*xen_start_info),
++			       "xen_start_info");
++
++	/*
++	 * Check for a conflict of the hypervisor supplied page tables with
++	 * the target E820 map.
++	 */
++	xen_pt_check_e820();
++
+ 	max_pages = xen_get_max_pages();
+
+ 	/* How many extra pages do we need due to remapping? */
+@@ -836,28 +858,6 @@ char * __init xen_memory_setup(void)
+
+ 	e820__update_table(e820_table);
+
+-	/*
+-	 * Check whether the kernel itself conflicts with the target E820 map.
+-	 * Failing now is better than running into weird problems later due
+-	 * to relocating (and even reusing) pages with kernel text or data.
+-	 */
+-	xen_chk_is_e820_usable(__pa_symbol(_text),
+-			       __pa_symbol(_end) - __pa_symbol(_text),
+-			       "kernel");
+-
+-	/*
+-	 * Check for a conflict of the xen_start_info memory with the target
+-	 * E820 map.
+-	 */
+-	xen_chk_is_e820_usable(__pa(xen_start_info), sizeof(*xen_start_info),
+-			       "xen_start_info");
+-
+-	/*
+-	 * Check for a conflict of the hypervisor supplied page tables with
+-	 * the target E820 map.
+-	 */
+-	xen_pt_check_e820();
+-
+ 	xen_reserve_xen_mfnlist();
+
+ 	/* Check for a conflict of the initrd with the target E820 map. */
+-- 
+2.43.0
+