Check for pae and long mode using cpuid. If present also read the physical address bits. Apply some qemu sanity checks (see below). Record results in PhysBits and LongMode variables. In case we are not sure what the address space size is leave the PhysBits variable unset.
On qemu we have the problem that for historical reasons x86_64 processors advertise 40 physical address space bits by default, even in case the host supports less than that so actually using the whole address space will not work.
Because of that the code applies some extra sanity checks in case we find 40 (or less) physical address space bits advertised. Only known-good values (which is 40 for amd processors and 36+39 for intel processors) will be accepted as valid.
Recommendation is to use 'qemu -cpu ${name},host-phys-bits=on' to advertise valid physical address space bits to the guest. Some distro builds enable this by default, and most likely the qemu default will change in near future too.
Signed-off-by: Gerd Hoffmann kraxel@redhat.com --- src/fw/paravirt.h | 2 ++ src/fw/paravirt.c | 57 +++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 59 insertions(+)
diff --git a/src/fw/paravirt.h b/src/fw/paravirt.h index 4e2e993ba9d3..7ca3fdcc06d4 100644 --- a/src/fw/paravirt.h +++ b/src/fw/paravirt.h @@ -31,6 +31,8 @@ typedef struct QemuCfgDmaAccess { extern u32 RamSize; extern u64 RamSizeOver4G; extern int PlatformRunningOn; +extern u8 PhysBits; +extern int LongMode;
static inline int runningOnQEMU(void) { return CONFIG_QEMU || ( diff --git a/src/fw/paravirt.c b/src/fw/paravirt.c index c880cb10a1bc..a84968661aee 100644 --- a/src/fw/paravirt.c +++ b/src/fw/paravirt.c @@ -32,6 +32,10 @@ u32 RamSize; // Amount of continuous ram >4Gig u64 RamSizeOver4G; +// physical address space bits +u8 PhysBits; +// 64bit processor +int LongMode; // Type of emulator platform. int PlatformRunningOn VARFSEG; // cfg enabled @@ -129,6 +133,58 @@ static void kvmclock_init(void) tsctimer_setfreq(MHz * 1000, "kvmclock"); }
+static void physbits(int qemu_quirk) +{ + unsigned int max, eax, ebx, ecx, edx; + unsigned int physbits; + char signature[13]; + int pae = 0, valid = 0; + + cpuid(0, &eax, &ebx, &ecx, &edx); + memcpy(signature + 0, &ebx, 4); + memcpy(signature + 4, &edx, 4); + memcpy(signature + 8, &ecx, 4); + signature[12] = 0; + if (eax >= 1) { + cpuid(1, &eax, &ebx, &ecx, &edx); + pae = (edx & (1 << 6)); + } + + cpuid(0x80000000, &eax, &ebx, &ecx, &edx); + max = eax; + + if (max >= 0x80000001) { + cpuid(0x80000001, &eax, &ebx, &ecx, &edx); + LongMode = (edx & (1 << 29)); + } + + if (pae && LongMode && max >= 0x80000008) { + cpuid(0x80000008, &eax, &ebx, &ecx, &edx); + physbits = (u8)eax; + if (!qemu_quirk) { + valid = 1; + } else if (physbits >= 41) { + valid = 1; + } else if (strcmp(signature, "GenuineIntel") == 0) { + if ((physbits == 36) || (physbits == 39)) + valid = 1; + } else if (strcmp(signature, "AuthenticAMD") == 0) { + if (physbits == 40) + valid = 1; + } + } else { + physbits = pae ? 36 : 32; + valid = 1; + } + + dprintf(1, "%s: signature="%s", pae=%s, lm=%s, phys-bits=%d, valid=%s\n", + __func__, signature, pae ? "yes" : "no", LongMode ? "yes" : "no", + physbits, valid ? "yes" : "no"); + + if (valid) + PhysBits = physbits; +} + static void qemu_detect(void) { if (!CONFIG_QEMU_HARDWARE) @@ -161,6 +217,7 @@ static void qemu_detect(void) dprintf(1, "Running on QEMU (unknown nb: %04x:%04x)\n", v, d); break; } + physbits(1); }
static int qemu_early_e820(void);