From: "Bae, Chang Seok" <chang.seok.bae@intel.com> To: Borislav Petkov <bp@suse.de> Cc: Andy Lutomirski <luto@kernel.org>, Thomas Gleixner <tglx@linutronix.de>, "mingo@kernel.org" <mingo@kernel.org>, "x86@kernel.org" <x86@kernel.org>, "Brown, Len" <len.brown@intel.com>, "Hansen, Dave" <dave.hansen@intel.com>, "Liu, Jing2" <jing2.liu@intel.com>, "Shankar, Ravi V" <ravi.v.shankar@intel.com>, "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>, "kvm@vger.kernel.org" <kvm@vger.kernel.org> Subject: Re: [PATCH v3 06/21] x86/fpu/xstate: Calculate and remember dynamic xstate buffer sizes Date: Wed, 27 Jan 2021 01:23:35 +0000 [thread overview] Message-ID: <6811FA0A-21A6-4519-82B8-C128C30127E0@intel.com> (raw) In-Reply-To: <20210122114430.GB5123@zn.tnic> On Jan 22, 2021, at 03:44, Borislav Petkov <bp@suse.de> wrote: > On Wed, Dec 23, 2020 at 07:57:02AM -0800, Chang S. Bae wrote: >> The xstate buffer is currently in-line with static size. To accommodatea > > "in-line" doesn't fit in this context, especially since "inline" > is a keyword with another meaning. Please replace it with a better > formulation in this patch. How about ‘embedded’?, “The xstate buffer is currently embedded into struct fpu with static size." >> -extern unsigned int fpu_kernel_xstate_size; >> +extern unsigned int fpu_kernel_xstate_min_size; >> +extern unsigned int fpu_kernel_xstate_max_size; > > Is it time to group this into a struct so that all those settings go > together instead in single variables? > > struct fpu_xstate { > unsigned int min_size, max_size; > unsigned int user_size; > ... > }; > > etc. <snip> > And since we're probably going to start querying different aspects about > the buffer, instead of exporting all kinds of variables in the future, > maybe this should be a single exported function called > > get_xstate_buffer_attr(typedef buffer_attr) > > which gives you what you wanna know about it... For example: > > get_xstate_buffer_attr(MIN_SIZE); > get_xstate_buffer_attr(MAX_SIZE); > ... Okay. I will prepare a separate cleanup patch that can be applied at the end of the series. Will post the change in this thread at first. >> /* Whitelist the FPU state from the task_struct for hardened usercopy. */ >> -static inline void arch_thread_struct_whitelist(unsigned long *offset, >> - unsigned long *size) >> -{ >> - *offset = offsetof(struct thread_struct, fpu.state); >> - *size = fpu_kernel_xstate_size; >> -} >> +extern void arch_thread_struct_whitelist(unsigned long *offset, unsigned long *size); > > What's that move for? One of my drafts had some internal helper to be called in there. No reason prior to applying the get_xstate_buffer_attr() helper. But with it, better to move this out of this header file I think. >> @@ -627,13 +627,18 @@ static void check_xstate_against_struct(int nr) >> */ > > <-- There's a comment over this function that might need adjustment. Do you mean an empty line? (Just want to clarify.) >> static void do_extra_xstate_size_checks(void) >> { <snip> >> if (boot_cpu_has(X86_FEATURE_XSAVES)) > > using_compacted_format() > > FPU code needs to agree on one helper and not use both. :-\ Agreed. I will prepare a patch. At least will post the diff here. <snip> >> + /* Ensure we have the supported in-line space: */ > > Who's "we"? How about: “Ensure the size fits in the statically-allocated buffer:" >> + if (!is_supported_xstate_size(fpu_kernel_xstate_min_size)) >> + return -EINVAL; No excuse, just pointing out the upstream code has “we” there [1]. Thanks, Chang [1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/arch/x86/kernel/fpu/xstate.c#n752
next prev parent reply other threads:[~2021-01-27 4:59 UTC|newest] Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top [not found] <20201223155717.19556-1-chang.seok.bae@intel.com> 2020-12-23 15:56 ` [PATCH v3 01/21] x86/fpu/xstate: Modify initialization helper to handle both static and dynamic buffers Chang S. Bae 2021-01-15 12:40 ` Borislav Petkov 2020-12-23 15:56 ` [PATCH v3 03/21] x86/fpu/xstate: Modify address finders " Chang S. Bae 2021-01-15 13:06 ` Borislav Petkov 2020-12-23 15:57 ` [PATCH v3 04/21] x86/fpu/xstate: Modify context switch helpers " Chang S. Bae 2021-01-15 13:18 ` Borislav Petkov 2021-01-19 18:49 ` Bae, Chang Seok 2020-12-23 15:57 ` [PATCH v3 06/21] x86/fpu/xstate: Calculate and remember dynamic xstate buffer sizes Chang S. Bae 2021-01-22 11:44 ` Borislav Petkov 2021-01-27 1:23 ` Bae, Chang Seok [this message] 2021-01-27 9:38 ` Borislav Petkov 2021-02-03 2:54 ` Bae, Chang Seok 2020-12-23 15:57 ` [PATCH v3 10/21] x86/fpu/xstate: Update xstate save function to support dynamic xstate Chang S. Bae 2021-01-07 8:41 ` Liu, Jing2 2021-01-07 18:40 ` Bae, Chang Seok 2021-01-12 2:52 ` Liu, Jing2 2021-01-15 4:59 ` Bae, Chang Seok 2021-01-15 5:45 ` Liu, Jing2 2021-02-08 12:33 ` Borislav Petkov 2021-02-09 15:48 ` Bae, Chang Seok
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