linux-kernel - Re: [PATCH v5 1/2] x86/mm: add a function to check if a pfn is UC/UC-

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Message-ID: <2da7d38c-8135-a722-8d93-f3d1a618b12e@redhat.com>
Date:   Mon, 18 Dec 2017 13:55:30 +0100
From:   Paolo Bonzini <pbonzini@...hat.com>
To:     Haozhong Zhang <haozhong.zhang@...el.com>, kvm@...r.kernel.org,
        x86@...nel.org
Cc:     linux-kernel@...r.kernel.org, rkrcmar@...hat.com,
        Xiao Guangrong <xiaoguangrong.eric@...il.com>,
        Dan Williams <dan.j.williams@...el.com>,
        ivan.d.cuevas.escareno@...el.com, karthik.kumar@...el.com,
        Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
        Olif Chapman <olif.chapman@...cle.com>,
        Mikulas Patocka <mpatocka@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...e.de>,
        Tom Lendacky <thomas.lendacky@....com>
Subject: Re: [PATCH v5 1/2] x86/mm: add a function to check if a pfn is UC/UC-

On 08/11/2017 08:56, Haozhong Zhang wrote:
> +bool pat_pfn_is_uc_or_uc_minus(unsigned long pfn)
> +{
> +	enum page_cache_mode cm = lookup_memtype(PFN_PHYS(pfn));
> +
> +	return cm == _PAGE_CACHE_MODE_UC || cm == _PAGE_CACHE_MODE_UC_MINUS;
> +}
> +EXPORT_SYMBOL_GPL(pat_pfn_is_uc_or_uc_minus);
> +

As discussed in the reply to v2, this should include WC too.  The
function name could become something like pat_pfn_downgraded_by_uc_mtrr.

Thanks,

Paolo