linux-kernel - Re: [Xen-devel] [RFC PATCH v4 1/7] xen/pvh: Split CONFIG_XEN_PVH into CONFIG_PVH and CONFIG_XEN_PVH

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Date:   Wed, 28 Feb 2018 16:07:34 -0500
From:   Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:     Maran Wilson <maran.wilson@...cle.com>
Cc:     pbonzini@...hat.com, jgross@...e.com, boris.ostrovsky@...cle.com,
        roger.pau@...rix.com, andrew.cooper3@...rix.com, hch@...radead.org,
        JBeulich@...e.com, x86@...nel.org, xen-devel@...ts.xenproject.org,
        linux-kernel@...r.kernel.org, kvm@...r.kernel.org,
        thomas.lendacky@....com, dave.hansen@...ux.intel.com,
        rkrcmar@...hat.com, gregkh@...uxfoundation.org, mchehab@...nel.org,
        hpa@...or.com, linus.walleij@...aro.org, mingo@...hat.com,
        rdunlap@...radead.org, luto@...nel.org, jpoimboe@...hat.com,
        tglx@...utronix.de, bp@...e.de, davem@...emloft.net,
        kirill.shutemov@...ux.intel.com
Subject: Re: [Xen-devel] [RFC PATCH v4 1/7] xen/pvh: Split CONFIG_XEN_PVH
 into CONFIG_PVH and CONFIG_XEN_PVH

On Wed, Feb 28, 2018 at 10:27:57AM -0800, Maran Wilson wrote:
> In order to pave the way for hypervisors other then Xen to use the PVH
> entry point for VMs, we need to factor the PVH entry code into Xen specific
> and hypervisor agnostic components. The first step in doing that, is to
> create a new config option for PVH entry that can be enabled
> independently from CONFIG_XEN.
> 
> Signed-off-by: Maran Wilson <maran.wilson@...cle.com>
> ---
>  arch/x86/Kconfig          | 8 ++++++++
>  arch/x86/kernel/head_64.S | 4 ++--
>  arch/x86/xen/Kconfig      | 3 ++-
>  3 files changed, 12 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index eb7f43f23521..fa7cd0305125 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -791,6 +791,14 @@ config KVM_GUEST
>  	  underlying device model, the host provides the guest with
>  	  timing infrastructure such as time of day, and system time
>  
> +config PVH
> +	bool "Support for running PVH guests"
> +	depends on KVM_GUEST || XEN
> +	def_bool n
> +	---help---
> +	  This option enables the PVH entry point for guest virtual machines
> +	  as specified in the x86/HVM direct boot ABI.
> +
>  config KVM_DEBUG_FS
>  	bool "Enable debug information for KVM Guests in debugfs"
>  	depends on KVM_GUEST && DEBUG_FS
> diff --git a/arch/x86/kernel/head_64.S b/arch/x86/kernel/head_64.S
> index 0f545b3cf926..fc9f678c6413 100644
> --- a/arch/x86/kernel/head_64.S
> +++ b/arch/x86/kernel/head_64.S
> @@ -41,7 +41,7 @@
>  
>  #define pud_index(x)	(((x) >> PUD_SHIFT) & (PTRS_PER_PUD-1))
>  
> -#if defined(CONFIG_XEN_PV) || defined(CONFIG_XEN_PVH)
> +#if defined(CONFIG_XEN_PV) || defined(CONFIG_PVH)
>  PGD_PAGE_OFFSET = pgd_index(__PAGE_OFFSET_BASE)
>  PGD_START_KERNEL = pgd_index(__START_KERNEL_map)
>  #endif
> @@ -387,7 +387,7 @@ NEXT_PAGE(early_dynamic_pgts)
>  
>  	.data
>  
> -#if defined(CONFIG_XEN_PV) || defined(CONFIG_XEN_PVH)
> +#if defined(CONFIG_XEN_PV) || defined(CONFIG_PVH)
>  NEXT_PGD_PAGE(init_top_pgt)
>  	.quad   level3_ident_pgt - __START_KERNEL_map + _KERNPG_TABLE_NOENC
>  	.org    init_top_pgt + PGD_PAGE_OFFSET*8, 0
> diff --git a/arch/x86/xen/Kconfig b/arch/x86/xen/Kconfig
> index f605825a04ab..021c8591c3c0 100644
> --- a/arch/x86/xen/Kconfig
> +++ b/arch/x86/xen/Kconfig
> @@ -77,8 +77,9 @@ config XEN_DEBUG_FS
>  	  Enabling this option may incur a significant performance overhead.
>  
>  config XEN_PVH
> -	bool "Support for running as a PVH guest"
> +	bool "Support for running as a Xen PVH guest"
>  	depends on XEN && XEN_PVHVM && ACPI
>  	# Pre-built page tables are not ready to handle 5-level paging.
>  	depends on !X86_5LEVEL

Not specific to this patch, but why is this there? PVH is not using PV so
there should be no problems with 5 level paging.

Juergen, thoughts?

> +	select PVH
>  	def_bool n
> -- 
> 2.16.1
> 
> 
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@...ts.xenproject.org
> https://lists.xenproject.org/mailman/listinfo/xen-devel

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