From mboxrd@z Thu Jan 1 00:00:00 1970 From: Borislav Petkov Subject: [PATCH 3/4] x86/pat: Emulate PAT when it is disabled Date: Sun, 31 May 2015 11:48:05 +0200 Message-ID: <1433065686-20922-3-git-send-email-bp@alien8.de> References: <20150531094655.GA20440@pd.tnic> <1433065686-20922-1-git-send-email-bp@alien8.de> Return-path: In-Reply-To: <1433065686-20922-1-git-send-email-bp@alien8.de> Sender: linux-kernel-owner@vger.kernel.org To: LKML Cc: Andrew Morton , Andy Lutomirski , arnd@arndb.de, Elliott@hp.com, hch@lst.de, hmh@hmh.eng.br, "H. Peter Anvin" , Ingo Molnar , jgross@suse.com, konrad.wilk@oracle.com, linux-mm , linux-nvdimm@lists.01.org, "Luis R. Rodriguez" , stefan.bader@canonical.com, Thomas Gleixner , Toshi Kani , x86-ml , yigal@plexistor.com List-Id: linux-mm.kvack.org From: Borislav Petkov In the case when PAT is disabled on the command line with "nopat" or when virtualization doesn't support PAT (correctly) - see 9d34cfdf4796 ("x86: Don't rely on VMWare emulating PAT MSR correctly"). we emulate it using the PWT and PCD cache attribute bits. Get rid of boot_pat_state while at it. Based on a conglomerate patch from Toshi Kani. Signed-off-by: Borislav Petkov Cc: Andrew Morton Cc: Andy Lutomirski Cc: arnd@arndb.de Cc: Elliott@hp.com Cc: hch@lst.de Cc: hmh@hmh.eng.br Cc: H. Peter Anvin Cc: Ingo Molnar Cc: jgross@suse.com Cc: konrad.wilk@oracle.com Cc: linux-mm Cc: linux-nvdimm@lists.01.org Cc: Luis R. Rodriguez Cc: stefan.bader@canonical.com Cc: Thomas Gleixner Cc: Toshi Kani Cc: x86-ml Cc: yigal@plexistor.com --- arch/x86/mm/init.c | 6 ++--- arch/x86/mm/pat.c | 72 +++++++++++++++++++++++++++++++++++++----------------- 2 files changed, 52 insertions(+), 26 deletions(-) diff --git a/arch/x86/mm/init.c b/arch/x86/mm/init.c index 1d553186c434..8533b46e6bee 100644 --- a/arch/x86/mm/init.c +++ b/arch/x86/mm/init.c @@ -40,7 +40,7 @@ */ uint16_t __cachemode2pte_tbl[_PAGE_CACHE_MODE_NUM] = { [_PAGE_CACHE_MODE_WB ] = 0 | 0 , - [_PAGE_CACHE_MODE_WC ] = _PAGE_PWT | 0 , + [_PAGE_CACHE_MODE_WC ] = 0 | _PAGE_PCD, [_PAGE_CACHE_MODE_UC_MINUS] = 0 | _PAGE_PCD, [_PAGE_CACHE_MODE_UC ] = _PAGE_PWT | _PAGE_PCD, [_PAGE_CACHE_MODE_WT ] = 0 | _PAGE_PCD, @@ -50,11 +50,11 @@ EXPORT_SYMBOL(__cachemode2pte_tbl); uint8_t __pte2cachemode_tbl[8] = { [__pte2cm_idx( 0 | 0 | 0 )] = _PAGE_CACHE_MODE_WB, - [__pte2cm_idx(_PAGE_PWT | 0 | 0 )] = _PAGE_CACHE_MODE_WC, + [__pte2cm_idx(_PAGE_PWT | 0 | 0 )] = _PAGE_CACHE_MODE_UC_MINUS, [__pte2cm_idx( 0 | _PAGE_PCD | 0 )] = _PAGE_CACHE_MODE_UC_MINUS, [__pte2cm_idx(_PAGE_PWT | _PAGE_PCD | 0 )] = _PAGE_CACHE_MODE_UC, [__pte2cm_idx( 0 | 0 | _PAGE_PAT)] = _PAGE_CACHE_MODE_WB, - [__pte2cm_idx(_PAGE_PWT | 0 | _PAGE_PAT)] = _PAGE_CACHE_MODE_WC, + [__pte2cm_idx(_PAGE_PWT | 0 | _PAGE_PAT)] = _PAGE_CACHE_MODE_UC_MINUS, [__pte2cm_idx(0 | _PAGE_PCD | _PAGE_PAT)] = _PAGE_CACHE_MODE_UC_MINUS, [__pte2cm_idx(_PAGE_PWT | _PAGE_PCD | _PAGE_PAT)] = _PAGE_CACHE_MODE_UC, }; diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c index 4d28759f5a1a..62171cb2b0cb 100644 --- a/arch/x86/mm/pat.c +++ b/arch/x86/mm/pat.c @@ -68,8 +68,6 @@ static int __init pat_debug_setup(char *str) } __setup("debugpat", pat_debug_setup); -static u64 __read_mostly boot_pat_state; - #ifdef CONFIG_X86_PAT /* * X86 PAT uses page flags WC and Uncached together to keep track of @@ -178,6 +176,7 @@ static void pat_bsp_init(u64 pat) { enum page_cache_mode cache; char pat_msg[33]; + u64 tmp_pat; int i; if (!cpu_has_pat) { @@ -185,14 +184,18 @@ static void pat_bsp_init(u64 pat) return; } - rdmsrl(MSR_IA32_CR_PAT, boot_pat_state); - if (!boot_pat_state) { + if (!pat_enabled()) + goto done; + + rdmsrl(MSR_IA32_CR_PAT, tmp_pat); + if (!tmp_pat) { pat_disable("PAT MSR is 0, disabled."); return; } wrmsrl(MSR_IA32_CR_PAT, pat); +done: pat_msg[32] = 0; /* @@ -209,6 +212,9 @@ static void pat_bsp_init(u64 pat) static void pat_ap_init(u64 pat) { + if (!pat_enabled()) + return; + if (!cpu_has_pat) { /* * If this happens we are on a secondary CPU, but switched to @@ -224,25 +230,45 @@ void pat_init(void) { u64 pat; - if (!pat_enabled()) - return; - - /* - * Set PWT to Write-Combining. All other bits stay the same: - * - * PTE encoding used in Linux: - * PAT - * |PCD - * ||PWT - * ||| - * 000 WB _PAGE_CACHE_WB - * 001 WC _PAGE_CACHE_WC - * 010 UC- _PAGE_CACHE_UC_MINUS - * 011 UC _PAGE_CACHE_UC - * PAT bit unused - */ - pat = PAT(0, WB) | PAT(1, WC) | PAT(2, UC_MINUS) | PAT(3, UC) | - PAT(4, WB) | PAT(5, WC) | PAT(6, UC_MINUS) | PAT(7, UC); + if (!pat_enabled()) { + /* + * No PAT. Emulate the PAT table that corresponds to the two + * cache bits, PWT (Write Through) and PCD (Cache Disable). This + * setup is the same as the BIOS default setup when the system + * has PAT but the "nopat" boot option has been specified. This + * emulated PAT table is used when MSR_IA32_CR_PAT returns 0. + * + * PTE encoding used: + * + * PCD + * |PWT PAT + * || slot + * 00 0 WB : _PAGE_CACHE_MODE_WB + * 01 1 WT : _PAGE_CACHE_MODE_WT + * 10 2 UC-: _PAGE_CACHE_MODE_UC_MINUS + * 11 3 UC : _PAGE_CACHE_MODE_UC + * + * NOTE: When WC or WP is used, it is redirected to UC- per + * the default setup in __cachemode2pte_tbl[]. + */ + pat = PAT(0, WB) | PAT(1, WT) | PAT(2, UC_MINUS) | PAT(3, UC) | + PAT(4, WB) | PAT(5, WT) | PAT(6, UC_MINUS) | PAT(7, UC); + } else { + /* + * PTE encoding used in Linux: + * PAT + * |PCD + * ||PWT + * ||| + * 000 WB _PAGE_CACHE_WB + * 001 WC _PAGE_CACHE_WC + * 010 UC- _PAGE_CACHE_UC_MINUS + * 011 UC _PAGE_CACHE_UC + * PAT bit unused + */ + pat = PAT(0, WB) | PAT(1, WC) | PAT(2, UC_MINUS) | PAT(3, UC) | + PAT(4, WB) | PAT(5, WC) | PAT(6, UC_MINUS) | PAT(7, UC); + } if (!boot_cpu_done) { pat_bsp_init(pat); -- 2.3.5