Messages in this thread | | | Date | Mon, 16 Oct 2023 19:26:09 +0300 | From | kirill.shutemov@linux ... | Subject | Re: [PATCH v3 1/2] x86/cpu/intel: Fix MTRR verification for TME enabled platforms |
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On Mon, Oct 16, 2023 at 09:14:35AM -0700, Compostella, Jeremy wrote: > <kirill.shutemov@linux.intel.com> writes: > > > On Fri, Oct 13, 2023 at 04:03:02PM -0700, Compostella, Jeremy wrote: > >> "kirill.shutemov@linux.intel.com" <kirill.shutemov@linux.intel.com> writes: > >> > On Tue, Oct 03, 2023 at 02:06:52AM +0000, Huang, Kai wrote: > >> >> On Tue, 2023-10-03 at 01:47 +0300, kirill.shutemov@linux.intel.com wrote: > >> >> > On Fri, Sep 29, 2023 at 09:14:00AM +0000, Huang, Kai wrote: > >> >> > > On Thu, 2023-09-28 at 15:30 -0700, Compostella, Jeremy wrote: > >> >> > > > On TME enabled platform, BIOS publishes MTRR taking into account Total > >> >> > > > Memory Encryption (TME) reserved bits. > >> >> > > > > >> >> > > > generic_get_mtrr() performs a sanity check of the MTRRs relying on the > >> >> > > > `phys_hi_rsvd' variable which is set using the cpuinfo_x86 structure > >> >> > > > `x86_phys_bits' field. But at the time the generic_get_mtrr() > >> >> > > > function is ran the `x86_phys_bits' has not been updated by > >> >> > > > detect_tme() when TME is enabled. > >> >> > > > > >> >> > > > Since the x86_phys_bits does not reflect yet the real maximal physical > >> >> > > > address size yet generic_get_mtrr() complains by logging the following > >> >> > > > messages. > >> >> > > > > >> >> > > > mtrr: your BIOS has configured an incorrect mask, fixing it. > >> >> > > > mtrr: your BIOS has configured an incorrect mask, fixing it. > >> >> > > > [...] > >> >> > > > > >> >> > > > In such a situation, generic_get_mtrr() returns an incorrect size but > >> >> > > > no side effect were observed during our testing. > >> >> > > > > >> >> > > > For `x86_phys_bits' to be updated before generic_get_mtrr() runs, > >> >> > > > move the detect_tme() call from init_intel() to early_init_intel(). > >> >> > > > >> >> > > Hi, > >> >> > > > >> >> > > This move looks good to me, but +Kirill who is the author of detect_tme() for > >> >> > > further comments. > >> >> > > > >> >> > > Also I am not sure whether it's worth to consider to move this to > >> >> > > get_cpu_address_sizes(), which calculates the virtual/physical address sizes. > >> >> > > Thus it seems anything that can impact physical address size > >> >> > > could be put there. > >> >> > > >> >> > Actually, I am not sure how this patch works. AFAICS after the patch we > >> >> > have the following callchain: > >> >> > > >> >> > early_identify_cpu() > >> >> > this_cpu->c_early_init() (which is early_init_init()) > >> >> > detect_tme() > >> >> > c->x86_phys_bits -= keyid_bits; > >> >> > get_cpu_address_sizes(c); > >> >> > c->x86_phys_bits = eax & 0xff; > >> >> > > >> >> > Looks like get_cpu_address_sizes() would override what detect_tme() does. > >> >> > >> >> After this patch, early_identify_cpu() calls get_cpu_address_sizes() first and > >> >> then calls c_early_init(), which calls detect_tme(). > >> >> > >> >> So looks no override. No? > >> > >> No override indeed as get_cpu_address_sizes() is always called before > >> early_init_intel or init_intel(). > >> > >> - init/main.c::start_kernel() > >> - arch/x86/kernel/setup.c::setup_arch() > >> - arch/x86/kernel/cpu/common.c::early_cpu_init() > >> - early_identify_cpu() > >> - get_cpu_address_sizes(c) > >> c->x86_phys_bits = eax & 0xff; > >> - arch/x86/kernel/cpu/intel.c::early_init_intel() > >> - detect_tme() > >> c->x86_phys_bits -= keyid_bits; > > > > Hmm.. Do I read it wrong: > > > > static void __init early_identify_cpu(struct cpuinfo_x86 *c) > > { > > ... > > /* cyrix could have cpuid enabled via c_identify()*/ > > if (have_cpuid_p()) { > > ... > > // Here we call early_intel_init() > > if (this_cpu->c_early_init) > > this_cpu->c_early_init(c); > > ... > > } > > > > get_cpu_address_sizes(c); > > ... > > } > > > > ? > > > > As far as I see get_cpu_address_sizes() called after early_intel_init(). > > On `58720809f527 v6.6-rc6 6.6-rc6 2de3c93ef41b' is what I have: > > ,---- > | 1599 /* cyrix could have cpuid enabled via c_identify()*/ > | 1600 if (have_cpuid_p()) { > | 1601 cpu_detect(c); > | 1602 get_cpu_vendor(c); > | 1603 get_cpu_cap(c); > | 1604 get_cpu_address_sizes(c); <= called first > | 1605 setup_force_cpu_cap(X86_FEATURE_CPUID); > | 1606 cpu_parse_early_param(); > | 1607 > | 1608 if (this_cpu->c_early_init) > | 1609 this_cpu->c_early_init(c); > | 1610 > | 1611 c->cpu_index = 0; > | 1612 filter_cpuid_features(c, false); > | 1613 > | 1614 if (this_cpu->c_bsp_init) > | 1615 this_cpu->c_bsp_init(c); > | 1616 } else { > | 1617 setup_clear_cpu_cap(X86_FEATURE_CPUID); > | 1618 } > `---- > Listing 1: arch/x86/kernel/cpu/common.c > > => get_cpu_address_sizes() is called first which is also conform to my > experiments and instrumentation.
Ah. It got patched in tip tree. See commit fbf6449f84bf.
-- Kiryl Shutsemau / Kirill A. Shutemov
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