Messages in this thread | | | Date | Sun, 15 Oct 2023 00:01:25 +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 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().
-- Kiryl Shutsemau / Kirill A. Shutemov
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