Messages in this thread | | | Subject | Re: [PATCH V3 2/6] arm/xen: Switch to use gnttab_setup_auto_xlat_frames() for DT | From | Oleksandr <> | Date | Thu, 25 Nov 2021 13:41:27 +0200 |
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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
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