From: Borislav Petkov <bp@alien8.de>
To: Juergen Gross <jgross@suse.com>
Cc: linux-kernel@vger.kernel.org, x86@kernel.org,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
"H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [PATCH v4 06/12] x86/mtrr: replace vendor tests in MTRR code
Date: Fri, 24 Mar 2023 17:56:11 +0100 [thread overview]
Message-ID: <20230324165611.GIZB3WK13NdjceLWnN@fat_crate.local> (raw)
In-Reply-To: <20230306163425.8324-7-jgross@suse.com>
On Mon, Mar 06, 2023 at 05:34:19PM +0100, Juergen Gross wrote:
> Modern CPUs all share the same MTRR interface implemented via
> generic_mtrr_ops.
>
> At several places in MTRR code this generic interface is deduced via
> is_cpu(INTEL) tests, which is only working due to X86_VENDOR_INTEL
> being 0 (the is_cpu() macro is testing mtrr_if->vendor, which isn't
> explicitly set in generic_mtrr_ops).
>
> Fix that by replacing the is_cpu(INTEL) tests with testing for mtrr_if
> to be &generic_mtrr_ops.
Two things:
* is_cpu() checks also whether mtrr_if is set. And we don't set it for
all vendors. I wanted to replace that thing with a vendor check recently
but there's that little issue.
I guess for the cases where we have the generic MTRR implementation, we
can safely assume that mtrr_if is set. Which leads me to the second
thing:
* If you're going to test for &generic_mtrr_ops, then you can just as
well do
cpu_feature_enabled(X86_FEATURE_MTRR)
which is a lot more telling.
> diff --git a/arch/x86/kernel/cpu/mtrr/mtrr.c b/arch/x86/kernel/cpu/mtrr/mtrr.c
> index 5fe62ee0361b..0c83990501f5 100644
> --- a/arch/x86/kernel/cpu/mtrr/mtrr.c
> +++ b/arch/x86/kernel/cpu/mtrr/mtrr.c
> @@ -108,14 +108,12 @@ static int have_wrcomb(void)
> /* This function returns the number of variable MTRRs */
> static void __init set_num_var_ranges(bool use_generic)
> {
> - unsigned long config = 0, dummy;
> + unsigned long config, dummy;
>
> if (use_generic)
> rdmsr(MSR_MTRRcap, config, dummy);
> - else if (is_cpu(AMD) || is_cpu(HYGON))
> - config = 2;
> - else if (is_cpu(CYRIX) || is_cpu(CENTAUR))
> - config = 8;
> + else
> + config = mtrr_if->var_regs;
>
> num_var_ranges = config & 0xff;
> }
Since you're touching this function, you might simply expand its body in
its only call site in mtrr_bp_init(), put a comment above the expanded
code and remove that function.
That is, if we're going to do the ->var_regs thing.
Thx.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
next prev parent reply other threads:[~2023-03-24 16:56 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-06 16:34 [PATCH v4 00/12] x86/mtrr: fix handling with PAT but without MTRR Juergen Gross
2023-03-06 16:34 ` [PATCH v4 01/12] x86/mtrr: split off physical address size calculation Juergen Gross
2023-03-06 16:34 ` [PATCH v4 02/12] x86/mtrr: optimize mtrr_calc_physbits() Juergen Gross
2023-03-20 12:50 ` Borislav Petkov
2023-03-06 16:34 ` [PATCH v4 03/12] x86/mtrr: support setting MTRR state for software defined MTRRs Juergen Gross
2023-03-20 12:59 ` Huang, Kai
2023-03-20 13:47 ` Juergen Gross
2023-03-20 21:34 ` Huang, Kai
2023-03-20 22:42 ` Borislav Petkov
2023-03-21 6:01 ` Juergen Gross
2023-03-20 19:05 ` Borislav Petkov
2023-03-21 6:00 ` Juergen Gross
2023-03-21 10:30 ` Borislav Petkov
2023-03-21 15:49 ` Juergen Gross
2023-03-06 16:34 ` [PATCH v4 04/12] x86/hyperv: set MTRR state when running as SEV-SNP Hyper-V guest Juergen Gross
2023-03-06 16:34 ` [PATCH v4 05/12] x86/xen: set MTRR state when running as Xen PV initial domain Juergen Gross
2023-03-07 21:47 ` Boris Ostrovsky
2023-03-23 12:43 ` Borislav Petkov
2023-03-06 16:34 ` [PATCH v4 06/12] x86/mtrr: replace vendor tests in MTRR code Juergen Gross
2023-03-24 16:56 ` Borislav Petkov [this message]
2023-03-27 5:43 ` Juergen Gross
2023-03-27 7:14 ` Borislav Petkov
2023-03-06 16:34 ` [PATCH v4 07/12] x86/mtrr: allocate mtrr_value array dynamically Juergen Gross
2023-03-20 12:25 ` Huang, Kai
2023-03-20 13:49 ` Juergen Gross
2023-03-20 15:31 ` Dave Hansen
2023-03-20 15:49 ` Juergen Gross
2023-03-26 22:05 ` Borislav Petkov
2023-03-27 5:44 ` Juergen Gross
2023-03-06 16:34 ` [PATCH v4 08/12] x86/mtrr: add get_effective_type() service function Juergen Gross
2023-03-06 16:34 ` [PATCH v4 09/12] x86/mtrr: construct a memory map with cache modes Juergen Gross
2023-03-29 12:51 ` Borislav Petkov
2023-03-29 13:39 ` Juergen Gross
2023-03-31 12:55 ` Borislav Petkov
2023-03-31 13:23 ` Juergen Gross
2023-04-01 14:24 ` Borislav Petkov
2023-04-03 6:57 ` Juergen Gross
2023-03-31 12:57 ` Borislav Petkov
2023-03-31 13:35 ` Juergen Gross
2023-04-01 14:26 ` Borislav Petkov
2023-04-03 7:02 ` Juergen Gross
2023-03-06 16:34 ` [PATCH v4 10/12] x86/mtrr: use new cache_map in mtrr_type_lookup() Juergen Gross
2023-03-06 16:34 ` [PATCH v4 11/12] x86/mtrr: don't let mtrr_type_lookup() return MTRR_TYPE_INVALID Juergen Gross
2023-03-06 16:34 ` [PATCH v4 12/12] x86/mm: only check uniform after calling mtrr_type_lookup() Juergen Gross
2023-03-07 21:09 ` [PATCH v4 00/12] x86/mtrr: fix handling with PAT but without MTRR Michael Kelley (LINUX)
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