On Wed, 17 May 2023 at 12:24, Gerd Hoffmann <kra...@redhat.com> wrote:
>
> If PcdUse1GPageTable is not enabled restrict the physical address space
> used to 1TB, to limit the amount of memory needed for identity mapping
> page tables.
>
> The same already happens in case the processor has no support for
> gigabyte pages.
>
Apologies for the noob question, but does this mean EDK2 maps the
entire address space 1:1, not just the region that as any DRAM in it?
> Signed-off-by: Gerd Hoffmann <kra...@redhat.com>
> ---
> OvmfPkg/Library/PlatformInitLib/PlatformInitLib.inf | 1 +
> OvmfPkg/Library/PlatformInitLib/MemDetect.c | 5 +++++
> 2 files changed, 6 insertions(+)
>
> diff --git a/OvmfPkg/Library/PlatformInitLib/PlatformInitLib.inf
> b/OvmfPkg/Library/PlatformInitLib/PlatformInitLib.inf
> index 86a82ad3e084..5a79d95b689c 100644
> --- a/OvmfPkg/Library/PlatformInitLib/PlatformInitLib.inf
> +++ b/OvmfPkg/Library/PlatformInitLib/PlatformInitLib.inf
> @@ -58,6 +58,7 @@ [LibraryClasses.X64]
>
> [Pcd]
> gEfiMdePkgTokenSpaceGuid.PcdPciExpressBaseAddress
> + gEfiMdeModulePkgTokenSpaceGuid.PcdUse1GPageTable
>
> [FixedPcd]
> gUefiOvmfPkgTokenSpaceGuid.PcdOvmfWorkAreaBase
> diff --git a/OvmfPkg/Library/PlatformInitLib/MemDetect.c
> b/OvmfPkg/Library/PlatformInitLib/MemDetect.c
> index acf90b4e93fd..1102b00ecbf0 100644
> --- a/OvmfPkg/Library/PlatformInitLib/MemDetect.c
> +++ b/OvmfPkg/Library/PlatformInitLib/MemDetect.c
> @@ -663,6 +663,11 @@ PlatformAddressWidthFromCpuid (
> PhysBits = 40;
> }
>
> + if (!FixedPcdGetBool (PcdUse1GPageTable) && (PhysBits > 40)) {
> + DEBUG ((DEBUG_INFO, "%a: limit PhysBits to 40 (PcdUse1GPageTable is
> false)\n", __func__));
> + PhysBits = 40;
> + }
> +
> PlatformInfoHob->PhysMemAddressWidth = PhysBits;
> PlatformInfoHob->FirstNonAddress = LShiftU64 (1,
> PlatformInfoHob->PhysMemAddressWidth);
> }
> --
> 2.40.1
>
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