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OvmfPkg/PlatformInitLib: add support for GuestPhysBits 

Add support for GuestPhysBits (cpuid 0x80000008, eax, bits 23:16).

GuestPhysBits is a field which can be set by the hypervisor to inform
the guest about the /usable/ physical address space bits.  This can be
smaller than the PhysBits of the CPU, for example because of nested
paging limitations.

OVMF will read GuestPhysBits, log the value, in case it is set use it
as upper limit.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
This commit is contained in:
Gerd Hoffmann 2024-03-01 11:23:58 +01:00 committed by mergify[bot]
parent 65b0d08786
commit 603ad2d6ae
1 changed files with 14 additions and 3 deletions
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17
OvmfPkg/Library/PlatformInitLib/MemDetect.c
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@ -633,6 +633,7 @@ PlatformAddressWidthFromCpuid (
{
UINT32 RegEax, RegEbx, RegEcx, RegEdx, Max;
UINT8 PhysBits;
UINT8 GuestPhysBits;
CHAR8 Signature[13];
IA32_CR4 Cr4;
BOOLEAN Valid = FALSE;
@ -655,13 +656,17 @@ PlatformAddressWidthFromCpuid (
if (Max >= 0x80000008) {
AsmCpuid (0x80000008, &RegEax, NULL, NULL, NULL);
PhysBits = (UINT8)RegEax;
PhysBits = (UINT8)RegEax;
GuestPhysBits = (UINT8)(RegEax >> 16);
} else {
PhysBits = 36;
PhysBits = 36;
GuestPhysBits = 0;
}
if (!QemuQuirk) {
Valid = TRUE;
} else if (GuestPhysBits) {
Valid = TRUE;
} else if (PhysBits >= 41) {
Valid = TRUE;
} else if (AsciiStrCmp (Signature, "GenuineIntel") == 0) {
@ -678,15 +683,21 @@ PlatformAddressWidthFromCpuid (
DEBUG ((
DEBUG_INFO,
"%a: Signature: '%a', PhysBits: %d, QemuQuirk: %a, la57: %a, Valid: %a\n",
"%a: Signature: '%a', PhysBits: %d, GuestPhysBits: %d, QemuQuirk: %a, la57: %a, Valid: %a\n",
__func__,
Signature,
PhysBits,
GuestPhysBits,
QemuQuirk ? "On" : "Off",
Cr4.Bits.LA57 ? "On" : "Off",
Valid ? "Yes" : "No"
));
if (GuestPhysBits && (PhysBits > GuestPhysBits)) {
DEBUG ((DEBUG_INFO, "%a: limit PhysBits to %d (GuestPhysBits)\n", __func__, GuestPhysBits));
PhysBits = GuestPhysBits;
}
if (Valid) {
/*
* Due to the sign extension we can use only the lower half of the