From: Oleksandr <olekstysh@gmail.com>
To: Stefano Stabellini <sstabellini@kernel.org>
Cc: xen-devel@lists.xenproject.org,
linux-arm-kernel@lists.infradead.org,
linux-kernel@vger.kernel.org,
Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>,
Russell King <linux@armlinux.org.uk>,
Julien Grall <julien@xen.org>
Subject: Re: [PATCH V3 2/6] arm/xen: Switch to use gnttab_setup_auto_xlat_frames() for DT
Date: Thu, 25 Nov 2021 13:41:27 +0200 [thread overview]
Message-ID: <f69cb505-d14f-c37c-cccb-49d79a66af54@gmail.com> (raw)
In-Reply-To: <alpine.DEB.2.22.394.2111241534090.1412361@ubuntu-linux-20-04-desktop>
On 25.11.21 01:35, Stefano Stabellini wrote:
Hi Stefano
> On Wed, 24 Nov 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(). Also in order to make a code more
>> resilient use a fallback to xen_xlate_map_ballooned_pages() if grant
>> table region wasn't found.
>>
>> 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
>>
>> Changes V2 -> V3:
>> - add __read_mostly specifier to xen_grant_frames
>> - retain a fallback to xen_xlate_map_ballooned_pages() if
>> xen_grant_frames is invalid
>> - process xen_events_irq before xen_grant_frames in
>> xen_dt_guest_init()
>> - update patch description
>> ---
>> arch/arm/xen/enlighten.c | 26 ++++++++++++++++++++------
>> 1 file changed, 20 insertions(+), 6 deletions(-)
>>
>> diff --git a/arch/arm/xen/enlighten.c b/arch/arm/xen/enlighten.c
>> index 7619fbf..3fb3384 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 __read_mostly phys_addr_t xen_grant_frames;
>> +
>> +#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) {
>> @@ -311,13 +315,19 @@ static void __init xen_dt_guest_init(void)
>> }
>>
>> xen_events_irq = irq_of_parse_and_map(xen_node, 0);
>> +
>> + 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;
>> }
>>
>> 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;
>> @@ -370,12 +380,16 @@ 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 || !xen_grant_frames) {
> I realize now that we only need:
>
> if (!xen_grant_frames) {
Indeed, the first part of the check looks superfluous, will do.
>
> with that:
>
> Reviewed-by: Stefano Stabellini <sstabellini@kernel.org>
Thanks!
>
>
>
>> + 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();
--
Regards,
Oleksandr Tyshchenko
next prev parent reply other threads:[~2021-11-25 11:41 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-11-24 20:53 [PATCH V3 0/6] xen: Add support of extended regions (safe ranges) on Arm Oleksandr Tyshchenko
2021-11-24 20:53 ` [PATCH V3 1/6] xen/unpopulated-alloc: Drop check for virt_addr_valid() in fill_list() Oleksandr Tyshchenko
2021-11-24 20:53 ` [PATCH V3 2/6] arm/xen: Switch to use gnttab_setup_auto_xlat_frames() for DT Oleksandr Tyshchenko
2021-11-24 23:35 ` Stefano Stabellini
2021-11-25 11:41 ` Oleksandr [this message]
2021-11-24 20:53 ` [PATCH V3 3/6] xen/balloon: Bring alloc(free)_xenballooned_pages helpers back Oleksandr Tyshchenko
2021-11-24 23:36 ` Stefano Stabellini
2021-11-24 20:53 ` [PATCH V3 4/6] xen/unpopulated-alloc: Add mechanism to use Xen resource Oleksandr Tyshchenko
2021-11-25 1:03 ` Stefano Stabellini
2021-11-25 14:01 ` Oleksandr
2021-12-07 23:36 ` Stefano Stabellini
2021-12-09 0:04 ` Oleksandr
2021-12-09 0:59 ` Stefano Stabellini
2021-11-26 15:17 ` Boris Ostrovsky
2021-11-26 15:23 ` Oleksandr
2021-11-24 20:53 ` [PATCH V3 5/6] arm/xen: Read extended regions from DT and init " Oleksandr Tyshchenko
2021-11-25 1:07 ` Stefano Stabellini
2021-11-24 20:53 ` [PATCH V3 6/6] dt-bindings: xen: Clarify "reg" purpose Oleksandr Tyshchenko
2021-11-25 1:09 ` Stefano Stabellini
2021-11-25 12:21 ` Oleksandr
2021-11-29 1:01 ` Rob Herring
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