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SubjectRe: [PATCH v6 11/13] x86/mm/pat: Prepare {reserve, free}_memtype() for "decoy" addresses

* Dan Williams <dan.j.williams@intel.com> wrote:

> In preparation for using set_memory_uc() instead set_memory_np() for
> isolating poison from speculation, teach the memtype code to sanitize
> physical addresses vs __PHYSICAL_MASK.
>
> The motivation for using set_memory_uc() for this case is to allow
> ongoing access to persistent memory pages via the pmem-driver +
> memcpy_mcsafe() until the poison is repaired.
>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: Ingo Molnar <mingo@redhat.com>
> Cc: "H. Peter Anvin" <hpa@zytor.com>
> Cc: Tony Luck <tony.luck@intel.com>
> Cc: Borislav Petkov <bp@alien8.de>
> Cc: <linux-edac@vger.kernel.org>
> Cc: <x86@kernel.org>
> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
> ---
> arch/x86/mm/pat.c | 16 ++++++++++++++++
> 1 file changed, 16 insertions(+)
>
> diff --git a/arch/x86/mm/pat.c b/arch/x86/mm/pat.c
> index 1555bd7d3449..6788ffa990f8 100644
> --- a/arch/x86/mm/pat.c
> +++ b/arch/x86/mm/pat.c
> @@ -512,6 +512,17 @@ static int free_ram_pages_type(u64 start, u64 end)
> return 0;
> }
>
> +static u64 sanitize_phys(u64 address)
> +{
> + /*
> + * When changing the memtype for pages containing poison allow
> + * for a "decoy" virtual address (bit 63 clear) passed to
> + * set_memory_X(). __pa() on a "decoy" address results in a
> + * physical address with it 63 set.
> + */
> + return address & __PHYSICAL_MASK;

s/it/bit

Thanks,

Ingo

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