From: Vitaly Kuznetsov <vkuznets@redhat.com>
To: Wei Liu <wei.liu@kernel.org>
Cc: Wei Liu <wei.liu@kernel.org>,
Linux on Hyper-V List <linux-hyperv@vger.kernel.org>,
virtualization@lists.linux-foundation.org,
Linux Kernel List <linux-kernel@vger.kernel.org>,
Michael Kelley <mikelley@microsoft.com>,
Vineeth Pillai <viremana@linux.microsoft.com>,
Sunil Muthuswamy <sunilmut@microsoft.com>,
Nuno Das Neves <nudasnev@microsoft.com>,
Lillian Grassin-Drake <ligrassi@microsoft.com>,
"K. Y. Srinivasan" <kys@microsoft.com>,
Haiyang Zhang <haiyangz@microsoft.com>,
Stephen Hemminger <sthemmin@microsoft.com>,
Thomas Gleixner <tglx@linutronix.de>,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
"maintainer\:X86 ARCHITECTURE \(32-BIT AND 64-BIT\)"
<x86@kernel.org>, "H. Peter Anvin" <hpa@zytor.com>
Subject: Re: [PATCH RFC v1 06/18] x86/hyperv: allocate output arg pages if required
Date: Wed, 16 Sep 2020 18:10:26 +0200 [thread overview]
Message-ID: <87zh5phfd9.fsf@vitty.brq.redhat.com> (raw)
In-Reply-To: <20200916154200.7nf74vjmqu3f6sfq@liuwe-devbox-debian-v2>
Wei Liu <wei.liu@kernel.org> writes:
> On Tue, Sep 15, 2020 at 12:43:18PM +0000, Wei Liu wrote:
>> On Tue, Sep 15, 2020 at 12:16:58PM +0200, Vitaly Kuznetsov wrote:
>> > Wei Liu <wei.liu@kernel.org> writes:
>> >
>> > > When Linux runs as the root partition, it will need to make hypercalls
>> > > which return data from the hypervisor.
>> > >
>> > > Allocate pages for storing results when Linux runs as the root
>> > > partition.
>> > >
>> > > Signed-off-by: Lillian Grassin-Drake <ligrassi@microsoft.com>
>> > > Co-Developed-by: Lillian Grassin-Drake <ligrassi@microsoft.com>
>> > > Signed-off-by: Wei Liu <wei.liu@kernel.org>
>> > > ---
>> > > arch/x86/hyperv/hv_init.c | 45 +++++++++++++++++++++++++++++----
>> > > arch/x86/include/asm/mshyperv.h | 1 +
>> > > 2 files changed, 41 insertions(+), 5 deletions(-)
>> > >
>> > > diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c
>> > > index cac8e4c56261..ebba4be4185d 100644
>> > > --- a/arch/x86/hyperv/hv_init.c
>> > > +++ b/arch/x86/hyperv/hv_init.c
>> > > @@ -45,6 +45,9 @@ EXPORT_SYMBOL_GPL(hv_vp_assist_page);
>> > > void __percpu **hyperv_pcpu_input_arg;
>> > > EXPORT_SYMBOL_GPL(hyperv_pcpu_input_arg);
>> > >
>> > > +void __percpu **hyperv_pcpu_output_arg;
>> > > +EXPORT_SYMBOL_GPL(hyperv_pcpu_output_arg);
>> > > +
>> > > u32 hv_max_vp_index;
>> > > EXPORT_SYMBOL_GPL(hv_max_vp_index);
>> > >
>> > > @@ -75,14 +78,29 @@ static int hv_cpu_init(unsigned int cpu)
>> > > u64 msr_vp_index;
>> > > struct hv_vp_assist_page **hvp = &hv_vp_assist_page[smp_processor_id()];
>> > > void **input_arg;
>> > > - struct page *pg;
>> > > + struct page *input_pg;
>> > >
>> > > input_arg = (void **)this_cpu_ptr(hyperv_pcpu_input_arg);
>> > > /* hv_cpu_init() can be called with IRQs disabled from hv_resume() */
>> > > - pg = alloc_page(irqs_disabled() ? GFP_ATOMIC : GFP_KERNEL);
>> > > - if (unlikely(!pg))
>> > > + input_pg = alloc_page(irqs_disabled() ? GFP_ATOMIC : GFP_KERNEL);
>> > > + if (unlikely(!input_pg))
>> > > return -ENOMEM;
>> > > - *input_arg = page_address(pg);
>> > > + *input_arg = page_address(input_pg);
>> > > +
>> > > + if (hv_root_partition) {
>> > > + struct page *output_pg;
>> > > + void **output_arg;
>> > > +
>> > > + output_pg = alloc_page(irqs_disabled() ? GFP_ATOMIC :
>> > > GFP_KERNEL);
>> >
>> > To simplify the code, can we just rename 'input_arg' to 'hypercall_args'
>> > and do alloc_pages(rqs_disabled() ? GFP_ATOMIC : GFP_KERNEL, 1) to
>> > allocate two pages above?
>>
>> It should be doable, but I need to code it up and test it to be 100%
>> sure.
>>
>
> I switch to alloc_pages to allocate an order of 2 page if necessary, but
> I keep input_arg and output_arg separate because I want to avoid code
> churn in other places.
>
My idea was that we're free to choose how to use these pages, e.g. with
two pages allocated we can now do a hypercall which takes two pages of
input and produces no output other than the return value. This doesn't
contradict your suggestion to keep input_arg/output_arg as these are
just pointers to the continuous space, we can still do the trick.
I don't feel strong about this and you probably have more patches in
your stash, no need for massive re-work I believe.
--
Vitaly
next prev parent reply other threads:[~2020-09-16 16:26 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-14 11:27 [PATCH RFC v1 00/18] Introducing Linux root partition support for Microsoft Hypervisor Wei Liu
2020-09-14 11:27 ` [PATCH RFC v1 01/18] asm-generic/hyperv: change HV_CPU_POWER_MANAGEMENT to HV_CPU_MANAGEMENT Wei Liu
2020-09-14 11:27 ` [PATCH RFC v1 02/18] x86/hyperv: detect if Linux is the root partition Wei Liu
2020-09-14 11:27 ` [PATCH RFC v1 03/18] Drivers: hv: vmbus: skip VMBus initialization if Linux is root Wei Liu
2020-09-14 11:27 ` [PATCH RFC v1 04/18] iommu/hyperv: don't setup IRQ remapping when running as root Wei Liu
2020-09-18 9:12 ` Joerg Roedel
2020-09-14 11:27 ` [PATCH RFC v1 05/18] clocksource/hyperv: use MSR-based access if " Wei Liu
2020-09-15 10:10 ` Vitaly Kuznetsov
2020-09-15 10:32 ` Wei Liu
2020-09-14 11:27 ` [PATCH RFC v1 06/18] x86/hyperv: allocate output arg pages if required Wei Liu
2020-09-15 10:16 ` Vitaly Kuznetsov
2020-09-15 12:43 ` Wei Liu
2020-09-16 15:42 ` Wei Liu
2020-09-16 16:10 ` Vitaly Kuznetsov [this message]
2020-09-14 11:27 ` [PATCH RFC v1 07/18] x86/hyperv: extract partition ID from Microsoft Hypervisor if necessary Wei Liu
2020-09-15 10:27 ` Vitaly Kuznetsov
2020-09-16 16:32 ` Wei Liu
2020-10-27 12:19 ` Wei Liu
2020-09-14 11:27 ` [PATCH RFC v1 08/18] x86/hyperv: handling hypercall page setup for root Wei Liu
2020-09-15 10:32 ` Vitaly Kuznetsov
2020-09-15 10:37 ` Wei Liu
2020-09-15 11:02 ` Vitaly Kuznetsov
2020-09-15 11:16 ` Wei Liu
2020-09-15 11:23 ` Vitaly Kuznetsov
2020-09-15 11:27 ` Wei Liu
2020-09-16 21:34 ` [EXTERNAL] " Sunil Muthuswamy
2020-09-17 11:06 ` Vitaly Kuznetsov
2020-09-14 11:59 ` [PATCH RFC v1 09/18] x86/hyperv: provide a bunch of helper functions Wei Liu
2020-09-15 11:00 ` Vitaly Kuznetsov
2020-10-27 13:10 ` Wei Liu
2020-09-14 11:59 ` [PATCH RFC v1 10/18] x86/hyperv: implement and use hv_smp_prepare_cpus Wei Liu
2020-09-15 11:14 ` Vitaly Kuznetsov
2020-10-27 13:47 ` Wei Liu
2020-10-27 13:56 ` Wei Liu
2020-09-14 11:59 ` [PATCH RFC v1 11/18] asm-generic/hyperv: update hv_msi_entry Wei Liu
2020-09-14 11:59 ` [PATCH RFC v1 12/18] asm-generic/hyperv: update hv_interrupt_entry Wei Liu
2020-10-01 14:33 ` Rob Herring
2020-09-14 11:59 ` [PATCH RFC v1 13/18] asm-generic/hyperv: introduce hv_device_id and auxiliary structures Wei Liu
2020-09-15 11:16 ` Vitaly Kuznetsov
2020-09-15 11:59 ` Wei Liu
2020-09-14 11:59 ` [PATCH RFC v1 14/18] asm-generic/hyperv: import data structures for mapping device interrupts Wei Liu
2020-09-14 11:59 ` [PATCH RFC v1 15/18] x86/apic/msi: export pci_msi_get_hwirq Wei Liu
2020-09-14 11:59 ` [PATCH RFC v1 16/18] x86/hyperv: implement MSI domain for root partition Wei Liu
2020-09-14 11:59 ` [PATCH RFC v1 17/18] x86/ioapic: export a few functions and data structures via io_apic.h Wei Liu
2020-09-14 11:59 ` [PATCH RFC v1 18/18] x86/hyperv: handle IO-APIC when running as root Wei Liu
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