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

[Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>]

Wei Liu <wei.liu2@xxxxxxxxxx> wrote:
>Some firmware, such as OVMF relies on this value to get the size of
>extra memory above 4GB.
>
>Seabios in Xen doesn't need this as it gets e820 directly from Xen.
>Rombios doesn't read this value.

I was looking at this some time ago for the GPU. I think a better way is to 
take advantage that the e820 can be retrieved from the hypervisor (used to be 
only for PV - but with thr PVH patches it works on HVM too). There is code from 
Gordan that also takes advantage of e820_hole.

Anyhow why don't we plumb in the libxl the standard memory layout and query for 
that?

Or use xenstore?
>
>Signed-off-by: Wei Liu <wei.liu2@xxxxxxxxxx>
>---
> tools/firmware/hvmloader/hvmloader.c |   15 +++++++++++++++
> 1 file changed, 15 insertions(+)
>
>diff --git a/tools/firmware/hvmloader/hvmloader.c
>b/tools/firmware/hvmloader/hvmloader.c
>index 1cc8cf2..327dffd 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 +176,11 @@ 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));
>+
>+    /* Some BIOSes: 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));
> }
> 
> /*



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