linux-kernel - Re: [Part1 PATCH v4 10/17] x86/mm, resource: Use PAGE_KERNEL protection for ioremap of memory pages

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Date:   Sun, 17 Sep 2017 16:07:03 +0200
From:   Borislav Petkov <bp@...e.de>
To:     Brijesh Singh <brijesh.singh@....com>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org, kvm@...r.kernel.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H . Peter Anvin" <hpa@...or.com>,
        Andy Lutomirski <luto@...nel.org>,
        Tom Lendacky <thomas.lendacky@....com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Laura Abbott <labbott@...hat.com>,
        Jérôme Glisse <jglisse@...hat.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Dan Williams <dan.j.williams@...el.com>,
        Kees Cook <keescook@...omium.org>
Subject: Re: [Part1 PATCH v4 10/17] x86/mm, resource: Use PAGE_KERNEL
 protection for ioremap of memory pages

On Sat, Sep 16, 2017 at 07:34:11AM -0500, Brijesh Singh wrote:
> From: Tom Lendacky <thomas.lendacky@....com>
> 
> In order for memory pages to be properly mapped when SEV is active, we
> need to use the PAGE_KERNEL protection attribute as the base protection.
> This will insure that memory mapping of, e.g. ACPI tables, receives the
> proper mapping attributes.
> 
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: "H. Peter Anvin" <hpa@...or.com>
> Cc: Borislav Petkov <bp@...e.de>
> Cc: "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>
> Cc: Laura Abbott <labbott@...hat.com>
> Cc: Andy Lutomirski <luto@...nel.org>
> Cc: "Jérôme Glisse" <jglisse@...hat.com>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Dan Williams <dan.j.williams@...el.com>
> Cc: Kees Cook <keescook@...omium.org>
> Cc: x86@...nel.org
> Cc: linux-kernel@...r.kernel.org
> Signed-off-by: Tom Lendacky <thomas.lendacky@....com>
> Signed-off-by: Brijesh Singh <brijesh.singh@....com>
> ---
>  arch/x86/mm/ioremap.c  | 77 ++++++++++++++++++++++++++++++++++++++++++--------
>  include/linux/ioport.h |  3 ++
>  kernel/resource.c      | 19 +++++++++++++
>  3 files changed, 88 insertions(+), 11 deletions(-)
> 
> diff --git a/arch/x86/mm/ioremap.c b/arch/x86/mm/ioremap.c
> index 52cc0f4ed494..812b8a8066ba 100644
> --- a/arch/x86/mm/ioremap.c
> +++ b/arch/x86/mm/ioremap.c
> @@ -27,6 +27,11 @@
>  
>  #include "physaddr.h"
>  
> +struct ioremap_mem_flags {
> +	bool system_ram;
> +	bool desc_other;
> +};
> +
>  /*
>   * Fix up the linear direct mapping of the kernel to avoid cache attribute
>   * conflicts.
> @@ -56,19 +61,61 @@ int ioremap_change_attr(unsigned long vaddr, unsigned long size,
>  	return err;
>  }
>  
> -static int __ioremap_check_ram(unsigned long start_pfn, unsigned long nr_pages,
> -			       void *arg)
> +static int __ioremap_check_ram(struct resource *res)
>  {
> +	unsigned long start_pfn, stop_pfn;
>  	unsigned long i;
>  
> -	for (i = 0; i < nr_pages; ++i)
> -		if (pfn_valid(start_pfn + i) &&
> -		    !PageReserved(pfn_to_page(start_pfn + i)))
> -			return 1;
> +	if ((res->flags & IORESOURCE_SYSTEM_RAM) != IORESOURCE_SYSTEM_RAM)
> +		return 0;
> +
> +	start_pfn = (res->start + PAGE_SIZE - 1) >> PAGE_SHIFT;
> +	stop_pfn = (res->end + 1) >> PAGE_SHIFT;
> +	if (stop_pfn > start_pfn) {
> +		for (i = 0; i < (stop_pfn - start_pfn); ++i)
> +			if (pfn_valid(start_pfn + i) &&
> +			    !PageReserved(pfn_to_page(start_pfn + i)))
> +				return 1;
> +	}
>  
>  	return 0;

Should return bool I guess.

Btw, this whole resource code is needlessly complex. Trying to follow
through it is one sick brain-twister. One day someone should go and
clean up that silly function pointer passing.

-- 
Regards/Gruss,
    Boris.

SUSE Linux GmbH, GF: Felix Imendörffer, Jane Smithard, Graham Norton, HRB 21284 (AG Nürnberg)
--