From: Mike Travis <mike.travis@hpe.com> To: Sasha Levin <sashal@kernel.org>, Greg KH <gregkh@linuxfoundation.org> Cc: Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>, Andrew Morton <akpm@linux-foundation.org>, Borislav Petkov <bp@alien8.de>, Christoph Hellwig <hch@infradead.org>, Dimitri Sivanich <dimitri.sivanich@hpe.com>, Russ Anderson <russ.anderson@hpe.com>, Hedi Berriche <hedi.berriche@hpe.com>, Steve Wahl <steve.wahl@hpe.com>, x86@kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH 6/8] x86/platform/uv: Decode UVsystab Info Date: Thu, 5 Sep 2019 15:42:41 -0700 [thread overview] Message-ID: <9745d473-e4bc-7ae2-fc67-a898c3606088@hpe.com> (raw) In-Reply-To: <20190905214030.GE1616@sasha-vm> On 9/5/2019 2:40 PM, Sasha Levin wrote: > On Thu, Sep 05, 2019 at 04:16:34PM +0200, Greg KH wrote: >> On Thu, Sep 05, 2019 at 08:02:58AM -0500, Mike Travis wrote: >>> --- linux.orig/arch/x86/kernel/apic/x2apic_uv_x.c >>> +++ linux/arch/x86/kernel/apic/x2apic_uv_x.c >>> @@ -1303,7 +1303,8 @@ static int __init decode_uv_systab(void) >>> struct uv_systab *st; >>> int i; >>> >>> - if (uv_hub_info->hub_revision < UV4_HUB_REVISION_BASE) >>> + /* Select only UV4 (hubbed or hubless) and higher */ >>> + if (is_uv_hubbed(-2) < uv(4) && is_uv_hubless(-2) < uv(4)) > > For someone not too familiar with the code, this is completely > unreadable. There must be a nicer way to do this. > > -- > Thanks, > Sasha Hi Sasha, I can put in further explanation but first the uv() function returns 1 left shifted by the UV #: static inline int uv(int uvtype) { /* uv(0) is "any" */ if (uvtype >= 0 && uvtype <= 30) return 1 << uvtype; return 1; } The "is_uv_hubbed(x)" and "is_uv_hubless(x)" AND's the incoming arg with the actual uv type: int is_uv_hubbed(int uvtype) { return (uv_hubbed_system & uvtype); } The uv_hub{bed,less}_system is set to 1 left shifted by the UV # plus in bit 0 is a '1' to indicate "any" UV (as in "is_uv_hubbed(1)" is any UV hubbed system). Hubbed indicates a hubbed system, and hubless indicates a hubless system, it cannot be both but can be neither. > /* UV4 Hubless, (0x11:UV4+Any) */ > if (strncmp(oem_id, "NSGI4", 5) == 0) > uv_hubless_system = 0x11; > > /* UV3 Hubless, UV300/MC990X w/o hub (0x9:UV3+Any) */ > else > uv_hubless_system = 0x9; > (There are only hubbed versions of UV1 and UV2.) Lastly (-2) translates to 0xffff...fffe (note bit 0 is clear to avoid the "any" bit. So it is looking for a a hubbed or hubless UV system that is less than UV4 meaning only UV4,5,6...qualify, hence this comment: >>> + /* Select only UV4 (hubbed or hubless) and higher */ if (UV is less than UV4 either hubbed or hubless) return; /* does not have an extended UVsystab */ Have you a suggestion on what would make it more clear? Perhaps instead of -2 I should use a hex mask? Thanks, Mike
next prev parent reply other threads:[~2019-09-05 22:42 UTC|newest] Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-09-05 13:02 [PATCH 0/8] x86/platform/UV: Update UV Hubless System Support Mike Travis 2019-09-05 13:02 ` [PATCH 1/8] x86/platform/uv: Save OEM_ID from ACPI MADT probe Mike Travis 2019-09-05 13:02 ` [PATCH 2/8] x86/platform/uv: Return UV Hubless System Type Mike Travis 2019-09-05 13:02 ` [PATCH 3/8] x86/platform/uv: Add return code to UV BIOS Init function Mike Travis 2019-09-05 13:02 ` [PATCH 4/8] x86/platform/uv: Setup UV functions for Hubless UV Systems Mike Travis 2019-09-05 13:02 ` [PATCH 5/8] x86/platform/uv: Add UV Hubbed/Hubless Proc FS Files Mike Travis 2019-09-05 13:02 ` [PATCH 6/8] x86/platform/uv: Decode UVsystab Info Mike Travis 2019-09-05 14:16 ` Greg KH 2019-09-05 14:47 ` Mike Travis 2019-09-05 16:43 ` Mike Travis 2019-09-05 16:57 ` Greg KH 2019-09-05 16:56 ` Greg KH 2019-09-05 21:40 ` Sasha Levin 2019-09-05 22:42 ` Mike Travis [this message] 2019-09-05 13:02 ` [PATCH 7/8] x86/platform/uv: Check EFI Boot to set reboot type Mike Travis 2019-09-05 13:03 ` [PATCH 8/8] x86/platform/uv: Account for UV Hubless in is_uvX_hub Ops Mike Travis 2019-09-10 12:07 ` [PATCH 0/8] x86/platform/UV: Update UV Hubless System Support Miguel Ojeda 2019-09-10 15:34 ` Mike Travis 2019-09-10 16:40 ` Borislav Petkov 2019-09-10 16:57 ` Mike Travis -- strict thread matches above, loose matches on Subject: below -- 2019-09-05 18:47 Mike Travis 2019-09-05 18:47 ` [PATCH 6/8] x86/platform/uv: Decode UVsystab Info Mike Travis 2019-09-03 0:18 [PATCH 0/8] x86/platform/UV: Update UV Hubless System Support Mike Travis 2019-09-03 0:18 ` [PATCH 6/8] x86/platform/uv: Decode UVsystab Info Mike Travis 2019-09-03 6:22 ` Greg KH
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