Messages in this thread | | | Date | Tue, 3 Oct 2023 10:06:59 +0300 | From | "" <> | Subject | Re: [PATCH v3 1/2] x86/cpu/intel: Fix MTRR verification for TME enabled platforms |
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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?
We identify CPU twice: once via early_cpu_init() and the second time via identify_boot_cpu()/identify_secondary_cpu(). I am talking about early_cpu_init() codepath.
It might not matter in practice as of now, because it will get straight later, but CPU ident code is mess as it is. Let's not make it even worse.
-- Kiryl Shutsemau / Kirill A. Shutemov
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