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Subject: Re: [PATCH 0/6] xen/x86: PV boot speedup
To:     Jan Beulich <jbeulich@suse.com>, Juergen Gross <jgross@suse.com>
Cc:     Stefano Stabellini <sstabellini@kernel.org>,
        lkml <linux-kernel@vger.kernel.org>,
        "xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>
References: <022b1a5e-4121-6bae-f07c-4ad5eac12481@suse.com>
From:   Boris Ostrovsky <boris.ostrovsky@oracle.com>
Message-ID: <9f49ecdb-26d3-c38d-56a4-8425a567bf0d@oracle.com>
Date:   Fri, 1 Oct 2021 20:33:58 -0400
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On 9/30/21 8:33 AM, Jan Beulich wrote:
> The observed (by the human eye) performance difference of early boot
> between native and PV-on-Xen was just too large to not look into. As
> it turns out, gaining performance back wasn't all that difficult.
>
> While the series (re)introduces a small number of PTWR emulations on
> the boot path (from phys_pte_init()), there has been a much larger
> number of them post-boot. Hence I think if this was of concern, the
> post-boot instances would want eliminating first.
>
> Some of the later changes aren'r directly related to the main goal of
> the series; these address aspects noticed while doing the investigation.
>
> 1: streamline set_pte_mfn()
> 2: restore (fix) xen_set_pte_init() behavior
> 3: adjust xen_set_fixmap()
> 4: adjust handling of the L3 user vsyscall special page table
> 5: there's no highmem anymore in PV mode
> 6: restrict PV Dom0 identity mapping


For the series:


Reviewed-by: Boris Ostrovsky <boris.ostrovksy@oracle.com>