On Thu, 1 Jun 2023 at 10:13, Ard Biesheuvel <[email protected]> wrote:
>
> On Thu, 1 Jun 2023 at 09:57, Gerd Hoffmann <[email protected]> wrote:
> >
> > Older linux kernels have problems with phys-bits larger than 46,
> > ubuntu 18.04 (kernel 4.15) has been reported to be affected.
> >
> > Reduce phys-bits limit from 47 to 46.
> >
> > Reported-by: Fiona Ebner <[email protected]>
> > Signed-off-by: Gerd Hoffmann <[email protected]>
>
> Thanks I'll queue this up
>
Merged as #4461
> > ---
> > OvmfPkg/Library/PlatformInitLib/MemDetect.c | 9 ++++++---
> > 1 file changed, 6 insertions(+), 3 deletions(-)
> >
> > diff --git a/OvmfPkg/Library/PlatformInitLib/MemDetect.c
> > b/OvmfPkg/Library/PlatformInitLib/MemDetect.c
> > index 1102b00ecbf0..662e7e85bbc5 100644
> > --- a/OvmfPkg/Library/PlatformInitLib/MemDetect.c
> > +++ b/OvmfPkg/Library/PlatformInitLib/MemDetect.c
> > @@ -646,16 +646,19 @@ PlatformAddressWidthFromCpuid (
> > ));
> >
> > if (Valid) {
> > - if (PhysBits > 47) {
> > + if (PhysBits > 46) {
> > /*
> > * Avoid 5-level paging altogether for now, which limits
> > * PhysBits to 48. Also avoid using address bit 48, due to sign
> > * extension we can't identity-map these addresses (and lots of
> > * places in edk2 assume we have everything identity-mapped).
> > * So the actual limit is 47.
> > + *
> > + * Also some older linux kernels apparently have problems handling
> > + * phys-bits > 46 correctly, so use that as limit.
> > */
> > - DEBUG ((DEBUG_INFO, "%a: limit PhysBits to 47 (avoid 5-level
> > paging)\n", __func__));
> > - PhysBits = 47;
> > + DEBUG ((DEBUG_INFO, "%a: limit PhysBits to 46 (avoid 5-level
> > paging)\n", __func__));
> > + PhysBits = 46;
> > }
> >
> > if (!Page1GSupport && (PhysBits > 40)) {
> > --
> > 2.40.1
> >
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