[PATCH] x86/unaccepted_memory: Do not accept ranges that are no longer E820 RAM

[Pankaj Gupta]

The EFI stub builds the unaccepted memory bitmap before the kernel parses
its command line.  Option memmap=<size>$<addr> removes RAM from the E820
map while its bits are still set in the bitmap.

The removed range, such as a memmap=...$... hole, is then still treated as
unaccepted RAM and accept_memory() tries to accept it.  The hole is not
mapped, so on SEV-SNP the PVALIDATE faults and the guest crashes early in
the boot:

  BUG: unable to handle page fault for address: ffff8a14bfe00000
  RIP: 0010:pvalidate_pages+0xc0/0x250
   set_pages_state+0x41a/0x440
   snp_accept_memory+0x3e/0x50
   accept_memory+0x186/0x260
   __free_pages_core+0xd2/0x240
   memblock_free_pages+0x1b/0x30
   memblock_free_all+0x275/0x2d0

This was seen with memmap=2M$0x1ffe00000, a 2 MiB hole in RAM, on a 19 GiB
SNP guest with lazy acceptance.

Fixes: 2053bc57f367 ("efi: Add unaccepted memory support")
Signed-off-by: Pankaj Gupta <pankaj.gupta@xxxxxxx>
---
 arch/x86/include/asm/unaccepted_memory.h | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/arch/x86/include/asm/unaccepted_memory.h b/arch/x86/include/asm/unaccepted_memory.h
index f5937e9866ac..744f1a993352 100644
--- a/arch/x86/include/asm/unaccepted_memory.h
+++ b/arch/x86/include/asm/unaccepted_memory.h
@@ -2,10 +2,11 @@
 #define _ASM_X86_UNACCEPTED_MEMORY_H
 
 #include <linux/efi.h>
+#include <asm/e820/api.h>
 #include <asm/tdx.h>
 #include <asm/sev.h>
 
-static inline void arch_accept_memory(phys_addr_t start, phys_addr_t end)
+static inline void __arch_accept_memory(phys_addr_t start, phys_addr_t end)
 {
 	/* Platform-specific memory-acceptance call goes here */
 	if (cpu_feature_enabled(X86_FEATURE_TDX_GUEST)) {
@@ -18,6 +19,26 @@ static inline void arch_accept_memory(phys_addr_t start, phys_addr_t end)
 	}
 }
 
+static inline void arch_accept_memory(phys_addr_t start, phys_addr_t end)
+{
+	u32 i;
+
+	for (i = 0; i < e820_table->nr_entries; i++) {
+		struct e820_entry *entry = &e820_table->entries[i];
+		phys_addr_t s, e;
+
+		if (entry->type != E820_TYPE_RAM)
+			continue;
+
+		s = max_t(phys_addr_t, start, entry->addr);
+		e = min_t(phys_addr_t, end, entry->addr + entry->size);
+		if (s >= e)
+			continue;
+
+		__arch_accept_memory(s, e);
+	}
+}
+
 static inline struct efi_unaccepted_memory *efi_get_unaccepted_table(void)
 {
 	if (efi.unaccepted == EFI_INVALID_TABLE_ADDR)
-- 
2.34.1