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Message-ID: <556AEA3D.4000502@suse.com>
Date: Sun, 31 May 2015 13:02:21 +0200
From: Juergen Gross <jgross@...e.com>
To: Borislav Petkov <bp@...en8.de>
CC: Andrew Morton <akpm@...ux-foundation.org>,
Andy Lutomirski <luto@...capital.net>, arnd@...db.de,
Elliott@...com, hch@....de, hmh@....eng.br,
"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
konrad.wilk@...cle.com, linux-mm <linux-mm@...ck.org>,
linux-nvdimm@...ts.01.org, "Luis R. Rodriguez" <mcgrof@...e.com>,
stefan.bader@...onical.com, Thomas Gleixner <tglx@...utronix.de>,
Toshi Kani <toshi.kani@...com>, x86-ml <x86@...nel.org>,
yigal@...xistor.com, lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/4] x86/pat: Merge pat_init_cache_modes() into its caller
On 05/31/2015 12:23 PM, Borislav Petkov wrote:
> On Sun, May 31, 2015 at 11:48:04AM +0200, Borislav Petkov wrote:
>> From: Borislav Petkov <bp@...e.de>
>>
>> This way we can pass pat MSR value directly.
>
> This breaks xen as that function is used there, doh. :-\
>
> Jürgen,
>
> can you check the enlighten.c changes below please?
Acked-by: Juergen Gross <jgross@...e.com>
>
> I'm reading xen's PAT config from MSR_IA32_CR_PAT and handing it down to
> pat_init_cache_modes(). That shouldn't change current behavior AFAICT
> because pat_init_cache_modes() did it itself before.
>
> Right?
>
> Thanks.
>
> ---
> Author: Borislav Petkov <bp@...e.de>
> Date: Sat May 30 13:09:55 2015 +0200
>
> x86/pat: Emulate PAT when it is disabled
>
> 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 <bp@...e.de>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Andy Lutomirski <luto@...capital.net>
> Cc: arnd@...db.de
> Cc: Elliott@...com
> Cc: hch@....de
> Cc: hmh@....eng.br
> Cc: H. Peter Anvin <hpa@...or.com>
> Cc: Ingo Molnar <mingo@...hat.com>
> Cc: jgross@...e.com
> Cc: konrad.wilk@...cle.com
> Cc: linux-mm <linux-mm@...ck.org>
> Cc: linux-nvdimm@...ts.01.org
> Cc: Luis R. Rodriguez <mcgrof@...e.com>
> Cc: stefan.bader@...onical.com
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Toshi Kani <toshi.kani@...com>
> Cc: x86-ml <x86@...nel.org>
> Cc: yigal@...xistor.com
>
> diff --git a/arch/x86/include/asm/pat.h b/arch/x86/include/asm/pat.h
> index cdcff7f7f694..ca6c228d5e62 100644
> --- a/arch/x86/include/asm/pat.h
> +++ b/arch/x86/include/asm/pat.h
> @@ -6,7 +6,7 @@
>
> bool pat_enabled(void);
> extern void pat_init(void);
> -void pat_init_cache_modes(void);
> +void pat_init_cache_modes(u64);
>
> extern int reserve_memtype(u64 start, u64 end,
> enum page_cache_mode req_pcm, enum page_cache_mode *ret_pcm);
> 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 476d0780560f..6dc7826e4797 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
> @@ -177,14 +175,12 @@ static enum page_cache_mode pat_get_cache_mode(unsigned pat_val, char *msg)
> * configuration.
> * Using lower indices is preferred, so we start with highest index.
> */
> -void pat_init_cache_modes(void)
> +void pat_init_cache_modes(u64 pat)
> {
> - int i;
> enum page_cache_mode cache;
> char pat_msg[33];
> - u64 pat;
> + int i;
>
> - rdmsrl(MSR_IA32_CR_PAT, pat);
> pat_msg[32] = 0;
> for (i = 7; i >= 0; i--) {
> cache = pat_get_cache_mode((pat >> (i * 8)) & 7,
> @@ -198,24 +194,33 @@ void pat_init_cache_modes(void)
>
> static void pat_bsp_init(u64 pat)
> {
> + u64 tmp_pat;
> +
> if (!cpu_has_pat) {
> pat_disable("PAT not supported by CPU.");
> 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);
>
> - pat_init_cache_modes();
> +done:
> + pat_init_cache_modes(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
> @@ -231,25 +236,45 @@ 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);
> diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
> index 46957ead3060..53233a9beea9 100644
> --- a/arch/x86/xen/enlighten.c
> +++ b/arch/x86/xen/enlighten.c
> @@ -1467,6 +1467,7 @@ asmlinkage __visible void __init xen_start_kernel(void)
> {
> struct physdev_set_iopl set_iopl;
> unsigned long initrd_start = 0;
> + u64 pat;
> int rc;
>
> if (!xen_start_info)
> @@ -1574,8 +1575,8 @@ asmlinkage __visible void __init xen_start_kernel(void)
> * Modify the cache mode translation tables to match Xen's PAT
> * configuration.
> */
> -
> - pat_init_cache_modes();
> + rdmsrl(MSR_IA32_CR_PAT, pat);
> + pat_init_cache_modes(pat);
>
> /* keep using Xen gdt for now; no urgent need to change it */
>
>
>
--
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