BMC/Intel-BMC/linux.git/arch/x86/kernel/cpu/mtrr/generic.c, branch dev

x86/mm/mtrr: Generalize runtime disabling of MTRRs

2015-05-27T12:41:01+00:00

It is possible to enable CONFIG_MTRR and CONFIG_X86_PAT and end up with a system with MTRR functionality disabled but PAT functionality enabled. This can happen, for instance, when the Xen hypervisor is used where MTRRs are not supported but PAT is. This can happen on Linux as of commit 47591df50512 ("xen: Support Xen pv-domains using PAT") by Juergen, introduced in v3.19. Technically, we should assume the proper CPU bits would be set to disable MTRRs but we can't always rely on this. At least on the Xen Hypervisor, for instance, only X86_FEATURE_MTRR was disabled as of Xen 4.4 through Xen commit 586ab6a [0], but not X86_FEATURE_K6_MTRR, X86_FEATURE_CENTAUR_MCR, or X86_FEATURE_CYRIX_ARR for instance. Roger Pau Monné has clarified though that although this is technically true we will never support PVH on these CPU types so Xen has no need to disable these bits on those systems. As per Roger, AMD K6, Centaur and VIA chips don't have the necessary hardware extensions to allow running PVH guests [1]. As per Toshi it is also possible for the BIOS to disable MTRR support, in such cases get_mtrr_state() would update the MTRR state as per the BIOS, we need to propagate this information as well. x86 MTRR code relies on quite a bit of checks for mtrr_if being set to check to see if MTRRs did get set up. Instead, lets provide a generic getter for that. This also adds a few checks where they were not before which could potentially safeguard ourselves against incorrect usage of MTRR where this was not desirable. Where possible match error codes as if MTRRs were disabled on arch/x86/include/asm/mtrr.h. Lastly, since disabling MTRRs can happen at run time and we could end up with PAT enabled, best record now in our logs when MTRRs are disabled. [0] ~/devel/xen (git::stable-4.5)$ git describe --contains 586ab6a 4.4.0-rc1~18 [1] http://lists.xenproject.org/archives/html/xen-devel/2015-03/msg03460.html Signed-off-by: Luis R. Rodriguez Signed-off-by: Borislav Petkov Cc: Andy Lutomirski Cc: Antonino Daplas Cc: Borislav Petkov Cc: Brian Gerst Cc: Daniel Vetter Cc: Dave Airlie Cc: Dave Hansen Cc: Davidlohr Bueso Cc: Denys Vlasenko Cc: H. Peter Anvin Cc: Jean-Christophe Plagniol-Villard Cc: Juergen Gross Cc: Linus Torvalds Cc: Mel Gorman Cc: Peter Zijlstra Cc: Roger Pau Monné Cc: Stefan Bader Cc: Suresh Siddha Cc: Thomas Gleixner Cc: Tomi Valkeinen Cc: Toshi Kani Cc: Ville Syrjälä Cc: Vlastimil Babka Cc: bhelgaas@google.com Cc: david.vrabel@citrix.com Cc: jbeulich@suse.com Cc: konrad.wilk@oracle.com Cc: venkatesh.pallipadi@intel.com Cc: ville.syrjala@linux.intel.com Cc: xen-devel@lists.xensource.com Link: http://lkml.kernel.org/r/1426893517-2511-3-git-send-email-mcgrof@do-not-panic.com Link: http://lkml.kernel.org/r/1432628901-18044-12-git-send-email-bp@alien8.de Signed-off-by: Ingo Molnar

x86/mm/mtrr: Enhance MTRR checks in kernel mapping helpers

2015-05-27T12:40:58+00:00

This patch adds the argument 'uniform' to mtrr_type_lookup(), which gets set to 1 when a given range is covered uniformly by MTRRs, i.e. the range is fully covered by a single MTRR entry or the default type. Change pud_set_huge() and pmd_set_huge() to honor the 'uniform' flag to see if it is safe to create a huge page mapping in the range. This allows them to create a huge page mapping in a range covered by a single MTRR entry of any memory type. It also detects a non-optimal request properly. They continue to check with the WB type since it does not effectively change the uniform mapping even if a request spans multiple MTRR entries. pmd_set_huge() logs a warning message to a non-optimal request so that driver writers will be aware of such a case. Drivers should make a mapping request aligned to a single MTRR entry when the range is covered by MTRRs. Signed-off-by: Toshi Kani [ Realign, flesh out comments, improve warning message. ] Signed-off-by: Borislav Petkov Cc: Andrew Morton Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: Elliott@hp.com Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Luis R. Rodriguez Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: dave.hansen@intel.com Cc: linux-mm Cc: pebolle@tiscali.nl Link: http://lkml.kernel.org/r/1431714237-880-7-git-send-email-toshi.kani@hp.com Link: http://lkml.kernel.org/r/1432628901-18044-8-git-send-email-bp@alien8.de Signed-off-by: Ingo Molnar

x86/mm/mtrr: Clean up mtrr_type_lookup()

2015-05-27T12:40:57+00:00

MTRRs contain fixed and variable entries. mtrr_type_lookup() may repeatedly call __mtrr_type_lookup() to handle a request that overlaps with variable entries. However, __mtrr_type_lookup() also handles the fixed entries, which do not have to be repeated. Therefore, this patch creates separate functions, mtrr_type_lookup_fixed() and mtrr_type_lookup_variable(), to handle the fixed and variable ranges respectively. The patch also updates the function headers to clarify the return values and output argument. It updates comments to clarify that the repeating is necessary to handle overlaps with the default type, since overlaps with multiple entries alone can be handled without such repeating. There is no functional change in this patch. Signed-off-by: Toshi Kani Signed-off-by: Borislav Petkov Cc: Andrew Morton Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: Elliott@hp.com Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Luis R. Rodriguez Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: dave.hansen@intel.com Cc: linux-mm Cc: pebolle@tiscali.nl Link: http://lkml.kernel.org/r/1431714237-880-6-git-send-email-toshi.kani@hp.com Link: http://lkml.kernel.org/r/1432628901-18044-6-git-send-email-bp@alien8.de Signed-off-by: Ingo Molnar

x86/mm/mtrr: Use symbolic define as a retval for disabled MTRRs

2015-05-27T12:40:57+00:00

mtrr_type_lookup() returns verbatim 0xFF when MTRRs are disabled. This patch defines MTRR_TYPE_INVALID to clarify the meaning of this value, and documents its usage. Document the return values of the kernel virtual address mapping helpers pud_set_huge(), pmd_set_huge, pud_clear_huge() and pmd_clear_huge(). There is no functional change in this patch. Signed-off-by: Toshi Kani Signed-off-by: Borislav Petkov Cc: Andrew Morton Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: Elliott@hp.com Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Luis R. Rodriguez Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: dave.hansen@intel.com Cc: linux-mm Cc: pebolle@tiscali.nl Link: http://lkml.kernel.org/r/1431714237-880-5-git-send-email-toshi.kani@hp.com Link: http://lkml.kernel.org/r/1432628901-18044-5-git-send-email-bp@alien8.de Signed-off-by: Ingo Molnar

x86/mm/mtrr: Fix MTRR state checks in mtrr_type_lookup()

2015-05-27T12:40:56+00:00

'mtrr_state.enabled' contains the FE (fixed MTRRs enabled) and E (MTRRs enabled) flags in MSR_MTRRdefType. Intel SDM, section 11.11.2.1, defines these flags as follows: - All MTRRs are disabled when the E flag is clear. The FE flag has no affect when the E flag is clear. - The default type is enabled when the E flag is set. - MTRR variable ranges are enabled when the E flag is set. - MTRR fixed ranges are enabled when both E and FE flags are set. MTRR state checks in __mtrr_type_lookup() do not match with SDM. Hence, this patch makes the following changes: - The current code detects MTRRs disabled when both E and FE flags are clear in mtrr_state.enabled. Fix to detect MTRRs disabled when the E flag is clear. - The current code does not check if the FE bit is set in mtrr_state.enabled when looking at the fixed entries. Fix to check the FE flag. - The current code returns the default type when the E flag is clear in mtrr_state.enabled. However, the default type is UC when the E flag is clear. Remove the code as this case is handled as MTRR disabled with the 1st change. In addition, this patch defines the E and FE flags in mtrr_state.enabled as follows. - FE flag: MTRR_STATE_MTRR_FIXED_ENABLED - E flag: MTRR_STATE_MTRR_ENABLED print_mtrr_state() and x86_get_mtrr_mem_range() are also updated accordingly. Signed-off-by: Toshi Kani Signed-off-by: Borislav Petkov Cc: Andrew Morton Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: Elliott@hp.com Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Luis R. Rodriguez Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: dave.hansen@intel.com Cc: linux-mm Cc: pebolle@tiscali.nl Link: http://lkml.kernel.org/r/1431714237-880-4-git-send-email-toshi.kani@hp.com Link: http://lkml.kernel.org/r/1432628901-18044-4-git-send-email-bp@alien8.de Signed-off-by: Ingo Molnar

x86/mm/mtrr: Fix MTRR lookup to handle an inclusive entry

2015-05-27T12:40:56+00:00

When an MTRR entry is inclusive to a requested range, i.e. the start and end of the request are not within the MTRR entry range but the range contains the MTRR entry entirely: range_start ... [mtrr_start ... mtrr_end] ... range_end __mtrr_type_lookup() ignores such a case because both start_state and end_state are set to zero. This bug can cause the following issues: 1) reserve_memtype() tracks an effective memory type in case a request type is WB (ex. /dev/mem blindly uses WB). Missing to track with its effective type causes a subsequent request to map the same range with the effective type to fail. 2) pud_set_huge() and pmd_set_huge() check if a requested range has any overlap with MTRRs. Missing to detect an overlap may cause a performance penalty or undefined behavior. This patch fixes the bug by adding a new flag, 'inclusive', to detect the inclusive case. This case is then handled in the same way as end_state:1 since the first region is the same. With this fix, __mtrr_type_lookup() handles the inclusive case properly. Signed-off-by: Toshi Kani Signed-off-by: Borislav Petkov Cc: Andrew Morton Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: Elliott@hp.com Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Luis R. Rodriguez Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: dave.hansen@intel.com Cc: linux-mm Cc: pebolle@tiscali.nl Link: http://lkml.kernel.org/r/1431714237-880-3-git-send-email-toshi.kani@hp.com Link: http://lkml.kernel.org/r/1432628901-18044-3-git-send-email-bp@alien8.de Signed-off-by: Ingo Molnar

x86/mm/mtrr: Remove incorrect address check in __mtrr_type_lookup()

2015-05-11T08:38:44+00:00

__mtrr_type_lookup() checks MTRR fixed ranges when mtrr_state.have_fixed is set and start is less than 0x100000. However, the 'else if (start < 0x1000000)' in the code checks with an incorrect address as it has an extra-zero in the address. The code still runs correctly as this check is meaningless, though. This patch replaces the incorrect address check with 'else' with no condition. Signed-off-by: Toshi Kani Signed-off-by: Borislav Petkov Cc: Andrew Morton Cc: Andy Lutomirski Cc: Borislav Petkov Cc: Brian Gerst Cc: Denys Vlasenko Cc: Elliott@hp.com Cc: H. Peter Anvin Cc: Linus Torvalds Cc: Luis R. Rodriguez Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: dave.hansen@intel.com Cc: linux-mm Cc: pebolle@tiscali.nl Link: http://lkml.kernel.org/r/1427234921-19737-4-git-send-email-toshi.kani@hp.com Link: http://lkml.kernel.org/r/1431332153-18566-8-git-send-email-bp@alien8.de Signed-off-by: Ingo Molnar

x86: Store a per-cpu shadow copy of CR4

2015-02-04T11:10:42+00:00

Context switches and TLB flushes can change individual bits of CR4. CR4 reads take several cycles, so store a shadow copy of CR4 in a per-cpu variable. To avoid wasting a cache line, I added the CR4 shadow to cpu_tlbstate, which is already touched in switch_mm. The heaviest users of the cr4 shadow will be switch_mm and __switch_to_xtra, and __switch_to_xtra is called shortly after switch_mm during context switch, so the cacheline is likely to be hot. Signed-off-by: Andy Lutomirski Reviewed-by: Thomas Gleixner Signed-off-by: Peter Zijlstra (Intel) Cc: Kees Cook Cc: Andrea Arcangeli Cc: Vince Weaver Cc: "hillf.zj" Cc: Valdis Kletnieks Cc: Paul Mackerras Cc: Arnaldo Carvalho de Melo Cc: Linus Torvalds Link: http://lkml.kernel.org/r/3a54dd3353fffbf84804398e00dfdc5b7c1afd7d.1414190806.git.luto@amacapital.net Signed-off-by: Ingo Molnar

mm, x86: Account for TLB flushes only when debugging

2014-01-25T08:10:41+00:00

Bisection between 3.11 and 3.12 fingered commit 9824cf97 ("mm: vmstats: tlb flush counters") to cause overhead problems. The counters are undeniably useful but how often do we really need to debug TLB flush related issues? It does not justify taking the penalty everywhere so make it a debugging option. Signed-off-by: Mel Gorman Tested-by: Davidlohr Bueso Reviewed-by: Rik van Riel Signed-off-by: Andrew Morton Cc: Hugh Dickins Cc: Alex Shi Cc: Linus Torvalds Cc: Peter Zijlstra Link: http://lkml.kernel.org/n/tip-XzxjntugxuwpxXhcrxqqh53b@git.kernel.org Signed-off-by: Ingo Molnar

mm: vmstats: track TLB flush stats on UP too

2013-09-11T22:57:09+00:00

The previous patch doing vmstats for TLB flushes ("mm: vmstats: tlb flush counters") effectively missed UP since arch/x86/mm/tlb.c is only compiled for SMP. UP systems do not do remote TLB flushes, so compile those counters out on UP. arch/x86/kernel/cpu/mtrr/generic.c calls __flush_tlb() directly. This is probably an optimization since both the mtrr code and __flush_tlb() write cr4. It would probably be safe to make that a flush_tlb_all() (and then get these statistics), but the mtrr code is ancient and I'm hesitant to touch it other than to just stick in the counters. [akpm@linux-foundation.org: tweak comments] Signed-off-by: Dave Hansen Cc: Peter Zijlstra Cc: Ingo Molnar Cc: "H. Peter Anvin" Cc: Thomas Gleixner Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds