From: Stefano Stabellini <sstabellini@kernel.org>
To: Oleksandr Tyshchenko <olekstysh@gmail.com>
Cc: xen-devel@lists.xenproject.org,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org,
Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>,
Stefano Stabellini <sstabellini@kernel.org>,
Russell King <linux@armlinux.org.uk>,
Julien Grall <julien@xen.org>
Subject: Re: [PATCH V2 2/4] arm/xen: Switch to use gnttab_setup_auto_xlat_frames() for DT
Date: Wed, 27 Oct 2021 18:28:08 -0700 (PDT) [thread overview]
Message-ID: <alpine.DEB.2.21.2110271754400.20134@sstabellini-ThinkPad-T480s> (raw)
In-Reply-To: <1635264312-3796-3-git-send-email-olekstysh@gmail.com>
On Tue, 26 Oct 2021, Oleksandr Tyshchenko wrote:
> From: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
>
> Read the start address of the grant table space from DT
> (region 0).
>
> This patch mostly restores behaviour before commit 3cf4095d7446
> ("arm/xen: Use xen_xlate_map_ballooned_pages to setup grant table")
> but trying not to break the ACPI support added after that commit.
> So the patch touches DT part only and leaves the ACPI part with
> xen_xlate_map_ballooned_pages().
>
> This is a preparation for using Xen extended region feature
> where unused regions of guest physical address space (provided
> by the hypervisor) will be used to create grant/foreign/whatever
> mappings instead of wasting real RAM pages from the domain memory
> for establishing these mappings.
>
> The immediate benefit of this change:
> - Avoid superpage shattering in Xen P2M when establishing
> stage-2 mapping (GFN <-> MFN) for the grant table space
> - Avoid wasting real RAM pages (reducing the amount of memory
> usuable) for mapping grant table space
> - The grant table space is always mapped at the exact
> same place (region 0 is reserved for the grant table)
>
> Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
> ---
> Changes RFC -> V2:
> - new patch
> ---
> arch/arm/xen/enlighten.c | 32 +++++++++++++++++++++++++-------
> 1 file changed, 25 insertions(+), 7 deletions(-)
>
> diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
> index 7f1c106b..dea46ec 100644
> --- a/arch/arm/xen/enlighten.c
> +++ b/arch/arm/xen/enlighten.c
> @@ -59,6 +59,9 @@ unsigned long xen_released_pages;
> struct xen_memory_region xen_extra_mem[XEN_EXTRA_MEM_MAX_REGIONS] __initdata;
>
> static __read_mostly unsigned int xen_events_irq;
> +static phys_addr_t xen_grant_frames;
__read_mostly
> +#define GRANT_TABLE_INDEX 0
>
> uint32_t xen_start_flags;
> EXPORT_SYMBOL(xen_start_flags);
> @@ -303,6 +306,7 @@ static void __init xen_acpi_guest_init(void)
> static void __init xen_dt_guest_init(void)
> {
> struct device_node *xen_node;
> + struct resource res;
>
> xen_node = of_find_compatible_node(NULL, NULL, "xen,xen");
> if (!xen_node) {
> @@ -310,6 +314,12 @@ static void __init xen_dt_guest_init(void)
> return;
> }
>
> + if (of_address_to_resource(xen_node, GRANT_TABLE_INDEX, &res)) {
> + pr_err("Xen grant table region is not found\n");
> + return;
> + }
> + xen_grant_frames = res.start;
> +
> xen_events_irq = irq_of_parse_and_map(xen_node, 0);
> }
>
> @@ -317,16 +327,20 @@ static int __init xen_guest_init(void)
> {
> struct xen_add_to_physmap xatp;
> struct shared_info *shared_info_page = NULL;
> - int cpu;
> + int rc, cpu;
>
> if (!xen_domain())
> return 0;
>
> if (!acpi_disabled)
> xen_acpi_guest_init();
> - else
> + else {
> xen_dt_guest_init();
>
> + if (!xen_grant_frames)
> + return -ENODEV;
maybe we can avoid this, see below
> + }
> +
> if (!xen_events_irq) {
> pr_err("Xen event channel interrupt not found\n");
> return -ENODEV;
> @@ -370,12 +384,16 @@ static int __init xen_guest_init(void)
> for_each_possible_cpu(cpu)
> per_cpu(xen_vcpu_id, cpu) = cpu;
>
> - xen_auto_xlat_grant_frames.count = gnttab_max_grant_frames();
> - if (xen_xlate_map_ballooned_pages(&xen_auto_xlat_grant_frames.pfn,
> - &xen_auto_xlat_grant_frames.vaddr,
> - xen_auto_xlat_grant_frames.count)) {
> + if (!acpi_disabled) {
To make the code more resilient couldn't we do:
if (!acpi_disabled || !xen_grant_frames) {
> + xen_auto_xlat_grant_frames.count = gnttab_max_grant_frames();
> + rc = xen_xlate_map_ballooned_pages(&xen_auto_xlat_grant_frames.pfn,
> + &xen_auto_xlat_grant_frames.vaddr,
> + xen_auto_xlat_grant_frames.count);
> + } else
> + rc = gnttab_setup_auto_xlat_frames(xen_grant_frames);
> + if (rc) {
> free_percpu(xen_vcpu_info);
> - return -ENOMEM;
> + return rc;
> }
> gnttab_init();
next prev parent reply other threads:[~2021-10-28 1:28 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-26 16:05 [PATCH V2 0/4] xen: Add support of extended regions (safe ranges) on Arm Oleksandr Tyshchenko
2021-10-26 16:05 ` [PATCH V2 1/4] xen/unpopulated-alloc: Drop check for virt_addr_valid() in fill_list() Oleksandr Tyshchenko
2021-10-28 18:57 ` Boris Ostrovsky
2021-10-26 16:05 ` [PATCH V2 2/4] arm/xen: Switch to use gnttab_setup_auto_xlat_frames() for DT Oleksandr Tyshchenko
2021-10-28 1:28 ` Stefano Stabellini [this message]
2021-11-10 22:14 ` Oleksandr
2021-11-19 0:32 ` Stefano Stabellini
2021-11-19 18:25 ` Oleksandr
2021-10-26 16:05 ` [PATCH V2 3/4] xen/unpopulated-alloc: Add mechanism to use Xen resource Oleksandr Tyshchenko
2021-10-28 16:37 ` Stefano Stabellini
2021-11-09 18:34 ` Oleksandr
2021-11-19 0:59 ` Stefano Stabellini
2021-11-19 18:18 ` Oleksandr
2021-11-20 2:19 ` Stefano Stabellini
2021-11-23 16:46 ` Oleksandr
2021-11-23 21:25 ` Stefano Stabellini
2021-11-24 9:33 ` Oleksandr
2021-11-24 5:16 ` Juergen Gross
2021-11-24 9:37 ` Oleksandr
2021-10-28 19:08 ` Boris Ostrovsky
2021-11-09 18:51 ` Oleksandr
2021-10-26 16:05 ` [PATCH V2 4/4] arm/xen: Read extended regions from DT and init " Oleksandr Tyshchenko
2021-10-28 1:40 ` Stefano Stabellini
2021-11-10 20:21 ` Oleksandr
2021-11-19 1:19 ` Stefano Stabellini
2021-11-19 20:23 ` Oleksandr
2021-11-20 2:36 ` Stefano Stabellini
2021-11-20 13:38 ` Oleksandr
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