linux-kernel - RE: [PATCH V2 1/2] x86/efi: Unmap EFI boot services code/data regions from efi

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Message-ID: <FFF73D592F13FD46B8700F0A279B802F485E101E@ORSMSX114.amr.corp.intel.com>
Date:   Mon, 29 Oct 2018 07:26:30 +0000
From:   "Prakhya, Sai Praneeth" <sai.praneeth.prakhya@...el.com>
To:     Ingo Molnar <mingo@...nel.org>
CC:     "linux-efi@...r.kernel.org" <linux-efi@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "x86@...nel.org" <x86@...nel.org>, Borislav Petkov <bp@...en8.de>,
        "Andy Lutomirski" <luto@...nel.org>,
        "Hansen, Dave" <dave.hansen@...el.com>,
        "Bhupesh Sharma" <bhsharma@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "Peter Zijlstra" <peterz@...radead.org>,
        Ard Biesheuvel <ard.biesheuvel@...aro.org>
Subject: RE: [PATCH V2 1/2] x86/efi: Unmap EFI boot services code/data
 regions from efi_pgd

> > +int kernel_unmap_pages_in_pgd(pgd_t *pgd, unsigned long address,
> > +			      unsigned long numpages)
> > +{
> > +	int retval;
> > +
> > +	/*
> > +	 * The typical sequence for unmapping is to find a pte through
> > +	 * lookup_address_in_pgd() (ideally, it should never return NULL
> because
> > +	 * the address is already mapped) and change it's protections.
> > +	 * As pfn is the *target* of a mapping, it's not useful while unmapping.
> > +	 */
> > +	struct cpa_data cpa = {
> > +		.vaddr		= &address,
> > +		.pgd		= pgd,
> > +		.numpages	= numpages,
> > +		.mask_set	= __pgprot(0),
> > +		.mask_clr	= __pgprot(_PAGE_PRESENT | _PAGE_RW),
> > +		.flags		= 0,
> > +	};
> > +
> > +	retval = __change_page_attr_set_clr(&cpa, 0);
> > +	__flush_tlb_all();
> 
> So, just to clarify, 'pfn' is kept at 0 here? Might make sense to write it out
> explicitly like 'flags', even if it's not used by __change_page_attr_set_clr().

Sure! Makes sense. I will add it.

Regards,
Sai