From 262bd5724afdefd4c48a260d6100e78cc43ee06b Mon Sep 17 00:00:00 2001 From: Arvind Sankar Date: Fri, 27 Nov 2020 12:13:24 -0500 Subject: x86/cpu/amd: Remove dead code for TSEG region remapping Commit 26bfa5f89486 ("x86, amd: Cleanup init_amd") moved the code that remaps the TSEG region using 4k pages from init_amd() to bsp_init_amd(). However, bsp_init_amd() is executed well before the direct mapping is actually created: setup_arch() -> early_cpu_init() -> early_identify_cpu() -> this_cpu->c_bsp_init() -> bsp_init_amd() ... -> init_mem_mapping() So the change effectively disabled the 4k remapping, because pfn_range_is_mapped() is always false at this point. It has been over six years since the commit, and no-one seems to have noticed this, so just remove the code. The original code was also incomplete, since it doesn't check how large the TSEG address range actually is, so it might remap only part of it in any case. Hygon has copied the incorrect version, so the code has never run on it since the cpu support was added two years ago. Remove it from there as well. Committer notes: This workaround is incomplete anyway: 1. The code must check MSRC001_0113.TValid (SMM TSeg Mask MSR) first, to check whether the TSeg address range is enabled. 2. The code must check whether the range is not 2M aligned - if it is, there's nothing to work around. 3. In all the BIOSes tested, the TSeg range is in a e820 reserved area and those are not mapped anymore, after 66520ebc2df3 ("x86, mm: Only direct map addresses that are marked as E820_RAM") which means, there's nothing to be worked around either. So let's rip it out. Signed-off-by: Arvind Sankar Signed-off-by: Borislav Petkov Link: https://lkml.kernel.org/r/20201127171324.1846019-1-nivedita@alum.mit.edu --- arch/x86/kernel/cpu/amd.c | 21 --------------------- arch/x86/kernel/cpu/hygon.c | 20 -------------------- 2 files changed, 41 deletions(-) diff --git a/arch/x86/kernel/cpu/amd.c b/arch/x86/kernel/cpu/amd.c index 1f71c7616917..f8ca66f3d861 100644 --- a/arch/x86/kernel/cpu/amd.c +++ b/arch/x86/kernel/cpu/amd.c @@ -23,7 +23,6 @@ #ifdef CONFIG_X86_64 # include -# include #endif #include "cpu.h" @@ -509,26 +508,6 @@ static void early_init_amd_mc(struct cpuinfo_x86 *c) static void bsp_init_amd(struct cpuinfo_x86 *c) { - -#ifdef CONFIG_X86_64 - if (c->x86 >= 0xf) { - unsigned long long tseg; - - /* - * Split up direct mapping around the TSEG SMM area. - * Don't do it for gbpages because there seems very little - * benefit in doing so. - */ - if (!rdmsrl_safe(MSR_K8_TSEG_ADDR, &tseg)) { - unsigned long pfn = tseg >> PAGE_SHIFT; - - pr_debug("tseg: %010llx\n", tseg); - if (pfn_range_is_mapped(pfn, pfn + 1)) - set_memory_4k((unsigned long)__va(tseg), 1); - } - } -#endif - if (cpu_has(c, X86_FEATURE_CONSTANT_TSC)) { if (c->x86 > 0x10 || diff --git a/arch/x86/kernel/cpu/hygon.c b/arch/x86/kernel/cpu/hygon.c index dc0840aae26c..ae59115d18f9 100644 --- a/arch/x86/kernel/cpu/hygon.c +++ b/arch/x86/kernel/cpu/hygon.c @@ -14,9 +14,6 @@ #include #include #include -#ifdef CONFIG_X86_64 -# include -#endif #include "cpu.h" @@ -203,23 +200,6 @@ static void early_init_hygon_mc(struct cpuinfo_x86 *c) static void bsp_init_hygon(struct cpuinfo_x86 *c) { -#ifdef CONFIG_X86_64 - unsigned long long tseg; - - /* - * Split up direct mapping around the TSEG SMM area. - * Don't do it for gbpages because there seems very little - * benefit in doing so. - */ - if (!rdmsrl_safe(MSR_K8_TSEG_ADDR, &tseg)) { - unsigned long pfn = tseg >> PAGE_SHIFT; - - pr_debug("tseg: %010llx\n", tseg); - if (pfn_range_is_mapped(pfn, pfn + 1)) - set_memory_4k((unsigned long)__va(tseg), 1); - } -#endif - if (cpu_has(c, X86_FEATURE_CONSTANT_TSC)) { u64 val; -- cgit v1.2.3