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[3/3] x86: allow load initrd below 4G for recent linux

Message ID 1542008730-6375-3-git-send-email-lizhijian@cn.fujitsu.com (mailing list archive)
State New, archived
Headers show
Series [1/3] unify len and addr type for memory/address APIs | expand

Commit Message

Li Zhijian Nov. 12, 2018, 7:45 a.m. UTC 
a new field xloadflags was added to recent x86 linux, and BIT 1:
XLF_CAN_BE_LOADED_ABOVE_4G is used to tell bootload that where initrd can be
loaded saftly.

Current QEMU always load initrd below below_4g_mem_size which always
less than 4G, so here limit initrd_max to 4G - 1 simply is enough if
this bit is set.

CC: Paolo Bonzini <pbonzini@redhat.com>
CC: Richard Henderson <rth@twiddle.net>
CC: Eduardo Habkost <ehabkost@redhat.com>
CC: "Michael S. Tsirkin" <mst@redhat.com>
CC: Marcel Apfelbaum <marcel.apfelbaum@gmail.com>
Signed-off-by: Li Zhijian <lizhijian@cn.fujitsu.com>
---
 hw/i386/pc.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)
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Patch

diff --git a/hw/i386/pc.c b/hw/i386/pc.c
index f095725..5e2f83c 100644
--- a/hw/i386/pc.c
+++ b/hw/i386/pc.c
@@ -92,6 +92,7 @@ 
 #define FW_CFG_HPET (FW_CFG_ARCH_LOCAL + 4)
 
 #define E820_NR_ENTRIES		16
+#define XLF_CAN_BE_LOADED_ABOVE_4G_MASK (1 << 1)
 
 struct e820_entry {
     uint64_t address;
@@ -916,6 +917,17 @@  static void load_linux(PCMachineState *pcms,
     } else {
         initrd_max = 0x37ffffff;
     }
+    if (protocol >= 0x20c) {
+        unsigned int xloadflags = lduw_p(header+0x236);
+        if (xloadflags & XLF_CAN_BE_LOADED_ABOVE_4G_MASK) {
+                /*
+                 * Although kernel allow initrd loading to above 4G, here we
+                 * limit initrd_max to 4G -1 due to current QEMU always loads
+                 * initrd below pcms->below_4g_mem_size
+                 */
+                initrd_max = UINT32_MAX;
+        }
+    }
 
     if (initrd_max >= pcms->below_4g_mem_size - pcmc->acpi_data_size) {
         initrd_max = pcms->below_4g_mem_size - pcmc->acpi_data_size - 1;