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Message-ID: <20200304191053.GA291311@rani.riverdale.lan>
Date: Wed, 4 Mar 2020 14:10:53 -0500
From: Arvind Sankar <nivedita@...m.mit.edu>
To: Ard Biesheuvel <ardb@...nel.org>
Cc: Arvind Sankar <nivedita@...m.mit.edu>,
Dave Hansen <dave.hansen@...ux.intel.com>,
Andy Lutomirski <luto@...nel.org>,
Peter Zijlstra <peterz@...radead.org>,
Thomas Gleixner <tglx@...utronix.de>,
Ingo Molnar <mingo@...hat.com>, Borislav Petkov <bp@...en8.de>,
"H. Peter Anvin" <hpa@...or.com>,
the arch/x86 maintainers <x86@...nel.org>,
linux-efi <linux-efi@...r.kernel.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/4] x86/mm/pat: Handle no-GBPAGES case correctly in
populate_pud
On Wed, Mar 04, 2020 at 08:04:04PM +0100, Ard Biesheuvel wrote:
> On Wed, 4 Mar 2020 at 19:50, Arvind Sankar <nivedita@...m.mit.edu> wrote:
> >
> > On Wed, Mar 04, 2020 at 07:44:50PM +0100, Ard Biesheuvel wrote:
> > >
> > > I've tried a couple of different ways, but I can't seem to get my
> > > memory map organized in the way that will trigger the error.
> >
> > What does yours look like? efi_merge_regions doesn't merge everything
> > that will eventually be mapped the same way, so if there are some
> > non-conventional memory regions scattered over the address space, it
> > might be breaking up the mappings to the point where this doesn't
> > trigger.
>
> I have a region
>
> [ 0.000000] efi: mem07: [Conventional Memory| | | | | | | |
> | |WB|WT|WC|UC] range=[0x0000000001400000-0x00000000b9855fff]
> (2948MB)
>
> which gets covered correctly
>
> [ 0.401766] 0x0000000000a00000-0x0000000040000000 1014M
> RW PSE NX pmd
> [ 0.403436] 0x0000000040000000-0x0000000080000000 1G
> RW PSE NX pud
> [ 0.404645] 0x0000000080000000-0x00000000b9800000 920M
> RW PSE NX pmd
> [ 0.405844] 0x00000000b9800000-0x00000000b9a00000 2M
> RW NX pte
> [ 0.407436] 0x00000000b9a00000-0x00000000baa00000 16M
> ro PSE x pmd
> [ 0.408591] 0x00000000baa00000-0x00000000bbe00000 20M
> RW PSE NX pmd
> [ 0.409751] 0x00000000bbe00000-0x00000000bc000000 2M
> RW NX pte
> [ 0.410821] 0x00000000bc000000-0x00000000be600000 38M
> RW PSE NX pmd
>
> However, the fact that you can provide a case where it does fail
> should be sufficient justification for taking this patch. I was just
> trying to give more than a regression-tested-by
No, this case is exactly one that should break. But I think you're
running on a processor model that _does_ support GB pages, as shown by
the "pud" mapping there for the 1G-2G range.
At least for my version of qemu, -cpu Haswell does not enable the
pdpe1gb feature. Which cpu did you specify?
Thanks.
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