[Xen-devel] [PATCH v2] hvmloader: write extra memory in CMOS

[Wei Liu <wei.liu2@xxxxxxxxxx>]

There's a conventional protocol for virt BIOSes such as Boches, Seabios and
OVMF to have the size of extra memory above 4GB be written to certain
locations (0x5b-0x5d) in CMOS. So update these locations as well.

Note that Seabios in Xen doesn't need this as it gets e820 directly from
Xen. Rombios doesn't read this value.

Signed-off-by: Wei Liu <wei.liu2@xxxxxxxxxx>
---
 tools/firmware/hvmloader/hvmloader.c |   17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/tools/firmware/hvmloader/hvmloader.c 
b/tools/firmware/hvmloader/hvmloader.c
index 1cc8cf2..9f692fb 100644
--- a/tools/firmware/hvmloader/hvmloader.c
+++ b/tools/firmware/hvmloader/hvmloader.c
@@ -146,6 +146,7 @@ static void init_hypercalls(void)
 static void cmos_write_memory_size(void)
 {
     uint32_t base_mem = 640, ext_mem, alt_mem;
+    uint64_t extra_mem = 0;
 
     alt_mem = ext_mem = hvm_info->low_mem_pgend << PAGE_SHIFT;
     ext_mem = (ext_mem > 0x0100000) ? (ext_mem - 0x0100000) >> 10 : 0;
@@ -153,6 +154,15 @@ static void cmos_write_memory_size(void)
         ext_mem = 0xffff;
     alt_mem = (alt_mem > 0x1000000) ? (alt_mem - 0x1000000) >> 16 : 0;
 
+    /* According to hvm_info:
+     *  0x100000000 to page_to_phys(high_mem_pgend)-1:
+     *   RAM above 4GB
+     * extra_mem written to CMOS is represented as 64kb chunks
+     */
+    extra_mem = hvm_info->high_mem_pgend;
+    extra_mem = (extra_mem > 0x100000) ?
+        (((extra_mem - 0x100000) << PAGE_SHIFT) >> 16) : 0;
+
     /* All BIOSes: conventional memory (CMOS *always* reports 640kB). */
     cmos_outb(0x15, (uint8_t)(base_mem >> 0));
     cmos_outb(0x16, (uint8_t)(base_mem >> 8));
@@ -166,6 +176,13 @@ static void cmos_write_memory_size(void)
     /* Some BIOSes: alternative extended memory (64kB chunks above 16MB). */
     cmos_outb(0x34, (uint8_t)( alt_mem >> 0));
     cmos_outb(0x35, (uint8_t)( alt_mem >> 8));
+
+    /* Used by virt BIOSes such as Boches, Seabios, OVMF etc: extra
+     * memory (64kB chunks above 4GB)
+     */
+    cmos_outb(0x5d, (uint8_t)( extra_mem >> 16));
+    cmos_outb(0x5c, (uint8_t)( extra_mem >> 8));
+    cmos_outb(0x5b, (uint8_t)( extra_mem >> 0));
 }
 
 /*
-- 
1.7.10.4


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