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Date: Fri, 24 Oct 2014 06:08:48 +0200 From: Juergen Gross <jgross@...e.com> To: hpa@...or.com, x86@...nel.org, tglx@...utronix.de, mingo@...hat.com CC: stefan.bader@...onical.com, toshi.kani@...com, linux-kernel@...r.kernel.org, xen-devel@...ts.xensource.com, konrad.wilk@...cle.com, ville.syrjala@...ux.intel.com, david.vrabel@...rix.com, jbeulich@...e.com Subject: Re: [RESEND PATCH V3 0/3] x86: Full support of PAT Ping? On 10/20/2014 05:59 AM, Juergen Gross wrote: > Hi x86 maintainers, > > any reason you seem to ignore this patch series? I think I've replied > to all open issues and sent the patches more than one month ago. Each > patch has a "Reviewed-by". Is there something else missing? > > > Juergen > > On 10/13/2014 10:13 AM, Juergen Gross wrote: >> The x86 architecture offers via the PAT (Page Attribute Table) a way to >> specify different caching modes in page table entries. The PAT MSR >> contains >> 8 entries each specifying one of 6 possible cache modes. A pte >> references one >> of those entries via 3 bits: _PAGE_PAT, _PAGE_PWT and _PAGE_PCD. >> >> The Linux kernel currently supports only 4 different cache modes. The >> PAT MSR >> is set up in a way that the setting of _PAGE_PAT in a pte doesn't >> matter: the >> top 4 entries in the PAT MSR are the same as the 4 lower entries. >> >> This results in the kernel not supporting e.g. write-through mode. >> Especially >> this cache mode would speed up drivers of video cards which now have >> to use >> uncached accesses. >> >> OTOH some old processors (Pentium) don't support PAT correctly and the >> Xen >> hypervisor has been using a different PAT MSR configuration for some >> time now >> and can't change that as this setting is part of the ABI. >> >> This patch set abstracts the cache mode from the pte and introduces >> tables to >> translate between cache mode and pte bits (the default cache mode >> "write back" >> is hard-wired to PAT entry 0). The tables are statically initialized with >> values being compatible to old processors and current usage. As soon >> as the >> PAT MSR is changed (or - in case of Xen - is read at boot time) the >> tables are >> changed accordingly. Requests of mappings with special cache modes are >> always >> possible now, in case they are not supported there will be a fallback >> to a >> compatible but slower mode. >> >> Summing it up, this patch set adds the following features: >> - capability to support WT and WP cache modes on processors with full PAT >> support >> - processors with no or uncorrect PAT support are still working as >> today, even >> if WT or WP cache mode are selected by drivers for some pages >> - reduction of Xen special handling regarding cache mode >> >> Changes in V3: >> - corrected two minor nits (UC_MINUS, again) detected by Toshi Kani >> >> Changes in V2: >> - simplified handling of PAT MSR write under Xen as suggested by David >> Vrabel >> - removed resetting of pat_enabled under Xen >> - two small corrections requested by Toshi Kani (UC_MINUS cache mode in >> vermilion driver, fix 32 bit kernel build failure) >> - correct build error on non-x86 arch by moving definition of >> update_cache_mode_entry() to x86 specific header >> >> Changes since RFC: >> - renamed functions and variables as suggested by Toshi Kani >> - corrected cache mode bits for WT and WP >> - modified handling of PAT MSR write under Xen as suggested by Jan >> Beulich >> >> >> Juergen Gross (3): >> x86: Make page cache mode a real type >> x86: Enable PAT to use cache mode translation tables >> Support Xen pv-domains using PAT >> >> arch/x86/include/asm/cacheflush.h | 38 ++++--- >> arch/x86/include/asm/fb.h | 6 +- >> arch/x86/include/asm/io.h | 2 +- >> arch/x86/include/asm/pat.h | 7 +- >> arch/x86/include/asm/pgtable.h | 19 ++-- >> arch/x86/include/asm/pgtable_types.h | 96 ++++++++++++---- >> arch/x86/mm/dump_pagetables.c | 24 ++-- >> arch/x86/mm/init.c | 37 ++++++ >> arch/x86/mm/init_64.c | 9 +- >> arch/x86/mm/iomap_32.c | 15 ++- >> arch/x86/mm/ioremap.c | 63 ++++++----- >> arch/x86/mm/mm_internal.h | 2 + >> arch/x86/mm/pageattr.c | 84 ++++++++------ >> arch/x86/mm/pat.c | 181 >> +++++++++++++++++++----------- >> arch/x86/mm/pat_internal.h | 22 ++-- >> arch/x86/mm/pat_rbtree.c | 8 +- >> arch/x86/pci/i386.c | 4 +- >> arch/x86/xen/enlighten.c | 25 ++--- >> arch/x86/xen/mmu.c | 48 +------- >> arch/x86/xen/xen-ops.h | 1 - >> drivers/video/fbdev/gbefb.c | 3 +- >> drivers/video/fbdev/vermilion/vermilion.c | 6 +- >> 22 files changed, 421 insertions(+), 279 deletions(-) >> > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@...r.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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