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extend MTRRs to above 4G (Alex Williamson)
When I try to boot guests using a recent Linux kernel (2.6.26+), memory
above 3.5G gets thrown away with an error like this:
WARNING: BIOS bug: CPU MTRRs don't cover all of memory, losing 4608MB of RAM
This extends MTRRs to cover all of memory.
Signed-off-by: Alex Williamson <alex.williamson@hp.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Index: bochs/bios/rombios32.c
===================================================================
--- bochs.orig/bios/rombios32.c
+++ bochs/bios/rombios32.c
@@ -427,6 +427,7 @@ uint32_t cpuid_signature;
uint32_t cpuid_features;
uint32_t cpuid_ext_features;
unsigned long ram_size;
+uint64_t above4g_ram_size;
uint8_t bios_uuid[16];
#ifdef BX_USE_EBDA_TABLES
unsigned long ebda_cur_addr;
@@ -561,6 +562,14 @@ void setup_mtrr(void)
wrmsr_smp(MTRRphysMask_MSR(i), (~vmask & 0xfffffff000ull) | 0x800);
vbase += vmask + 1;
}
+ for (vbase = 1ull << 32; i < vcnt && vbase < above4g_ram_size; ++i) {
+ vmask = (1ull << 40) - 1;
+ while (vbase + vmask + 1 > above4g_ram_size)
+ vmask >>= 1;
+ wrmsr_smp(MTRRphysBase_MSR(i), vbase | 6);
+ wrmsr_smp(MTRRphysMask_MSR(i), (~vmask & 0xfffffff000ull) | 0x800);
+ vbase += vmask + 1;
+ }
wrmsr_smp(MSR_MTRRdefType, 0xc00);
}
@@ -572,11 +581,19 @@ void ram_probe(void)
else
ram_size = (cmos_readb(0x30) | (cmos_readb(0x31) << 8)) * 1024 +
1 * 1024 * 1024;
+ if (cmos_readb(0x5b) | cmos_readb(0x5c) | cmos_readb(0x5d))
+ above4g_ram_size = ((uint64_t)cmos_readb(0x5b) << 16) |
+ ((uint64_t)cmos_readb(0x5c) << 24) | ((uint64_t)cmos_readb(0x5d) << 32);
+
+ if (above4g_ram_size)
+ above4g_ram_size += 1ull << 32;
+
BX_INFO("ram_size=0x%08lx\n", ram_size);
#ifdef BX_USE_EBDA_TABLES
ebda_cur_addr = ((*(uint16_t *)(0x40e)) << 4) + 0x380;
BX_INFO("ebda_cur_addr: 0x%08lx\n", ebda_cur_addr);
#endif
+ BX_INFO("top of ram %ldMB\n", above4g_ram_size >> 20);
setup_mtrr();
}
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