Messages in this thread | | | Date | Wed, 10 Sep 2014 06:41:27 +0200 | From | Juergen Gross <> | Subject | Re: [PATCH V2 1/3] x86: Make page cache mode a real type |
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On 09/09/2014 07:24 PM, Toshi Kani wrote: > On Mon, 2014-09-08 at 10:01 +0200, Juergen Gross wrote: >> At the moment there are a lot of places that handle setting or getting >> the page cache mode by treating the pgprot bits equal to the cache mode. >> This is only true because there are a lot of assumptions about the setup >> of the PAT MSR. Otherwise the cache type needs to get translated into >> pgprot bits and vice versa. >> >> This patch tries to prepare for that by introducing a seperate type >> for the cache mode and adding functions to translate between those and >> pgprot values. >> >> To avoid too much performance penalty the translation between cache mode >> and pgprot values is done via tables which contain the relevant >> information. Write-back cache mode is hard-wired to be 0, all other >> modes are configurable via those tables. For large pages there are >> translation functions as the PAT bit is located at different positions >> in the ptes of 4k and large pages. >> >> Signed-off-by: Stefan Bader <stefan.bader@canonical.com> >> Signed-off-by: Juergen Gross <jgross@suse.com> > > I have two minor comments (which I should have caught before)... Other > wise, the changes look good to me > > Reviewed-by: Toshi Kani <toshi.kani@hp.com> > > >> /* >> diff --git a/arch/x86/include/asm/fb.h b/arch/x86/include/asm/fb.h >> index 2519d06..0902a50 100644 >> --- a/arch/x86/include/asm/fb.h >> +++ b/arch/x86/include/asm/fb.h >> @@ -8,8 +8,12 @@ >> static inline void fb_pgprotect(struct file *file, struct vm_area_struct *vma, >> unsigned long off) >> { >> + unsigned long prot; >> + >> + prot = pgprot_val(vma->vm_page_prot) & ~_PAGE_CACHE_MASK; >> if (boot_cpu_data.x86 > 3) >> - pgprot_val(vma->vm_page_prot) |= _PAGE_PCD; >> + pgprot_val(vma->vm_page_prot) = >> + prot | cachemode2protval(_PAGE_CACHE_MODE_UC); > > This should be _PAGE_CACHE_MODE_UC_MINUS as the original code only sets > the PCD bit.
Okay.
> >> diff --git a/drivers/video/fbdev/gbefb.c b/drivers/video/fbdev/gbefb.c >> index 4aa56ba..b1cc7a6 100644 >> --- a/drivers/video/fbdev/gbefb.c >> +++ b/drivers/video/fbdev/gbefb.c >> @@ -54,7 +54,8 @@ struct gbefb_par { >> #endif >> #endif >> #ifdef CONFIG_X86 >> -#define pgprot_fb(_prot) ((_prot) | _PAGE_PCD) >> +#define pgprot_fb(_prot) (((_prot) & ~_PAGE_CACHE_MASK) | \ >> + cachemode2protval(_PAGE_CACHE_MODE_UC)) > > Ditto.
Yep.
Thanks,
Juergen
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