> -----Original Message-----
> From: Jan Beulich [mailto:jbeul...@suse.com]
> Sent: 26 November 2018 11:42
> To: Paul Durrant <paul.durr...@citrix.com>
> Cc: Julien Grall <julien.gr...@arm.com>; Andrew Cooper
> <andrew.coop...@citrix.com>; Roger Pau Monne <roger....@citrix.com>; Wei
> Liu <wei.l...@citrix.com>; George Dunlap <george.dun...@citrix.com>; Ian
> Jackson <ian.jack...@citrix.com>; Stefano Stabellini
> <sstabell...@kernel.org>; xen-devel <xen-devel@lists.xenproject.org>;
> Konrad Rzeszutek Wilk <konrad.w...@oracle.com>; Tim (Xen.org)
> <t...@xen.org>
> Subject: Re: [PATCH v5 2/6] vpci: fix deferral of long operations
>
> >>> On 20.11.18 at 17:01, <roger....@citrix.com> wrote:
> > Current logic to handle long running operations is flawed because it
> > doesn't prevent the guest vcpu from running. Fix this by raising a
> > scheduler softirq when preemption is required, so that the do_softirq
> > call in the guest entry path performs a rescheduling. Also move the
> > call to vpci_process_pending into handle_hvm_io_completion, together
> > with the IOREQ code that handles pending IO instructions.
> >
> > Note that a scheduler softirq is also raised when the long running
> > operation is queued in order to prevent the guest vcpu from resuming
> > execution.
> >
> > Signed-off-by: Roger Pau Monné <roger....@citrix.com>
> > ---
> > Cc: Paul Durrant <paul.durr...@citrix.com>
> > Cc: Jan Beulich <jbeul...@suse.com>
> > Cc: Andrew Cooper <andrew.coop...@citrix.com>
> > Cc: Wei Liu <wei.l...@citrix.com>
> > Cc: George Dunlap <george.dun...@eu.citrix.com>
> > Cc: Ian Jackson <ian.jack...@eu.citrix.com>
> > Cc: Julien Grall <julien.gr...@arm.com>
> > Cc: Konrad Rzeszutek Wilk <konrad.w...@oracle.com>
> > Cc: Stefano Stabellini <sstabell...@kernel.org>
> > Cc: Tim Deegan <t...@xen.org>
> > ---
> > Changes since v4:
> > - Add a comment to clarify defer_map raising a scheduler softirq.
> > - Reword commit message.
> > - Raise the scheduler softirq in handle_hvm_io_completion rather than
> > vpci_process_pending.
> >
> > Changes since v3:
> > - Don't use a tasklet.
> > ---
> > xen/arch/x86/hvm/ioreq.c | 9 ++++++---
>
> Paul - I'll take the liberty and reinstate your v4 R-b for v5.
>
That's fine.
Paul
> Jan
>
> > xen/drivers/vpci/header.c | 5 +++++
> > 2 files changed, 11 insertions(+), 3 deletions(-)
> >
> > diff --git a/xen/arch/x86/hvm/ioreq.c b/xen/arch/x86/hvm/ioreq.c
> > index a56d634f31..71f23227e6 100644
> > --- a/xen/arch/x86/hvm/ioreq.c
> > +++ b/xen/arch/x86/hvm/ioreq.c
> > @@ -85,9 +85,6 @@ bool hvm_io_pending(struct vcpu *v)
> > struct hvm_ioreq_server *s;
> > unsigned int id;
> >
> > - if ( has_vpci(d) && vpci_process_pending(v) )
> > - return true;
> > -
> > FOR_EACH_IOREQ_SERVER(d, id, s)
> > {
> > struct hvm_ioreq_vcpu *sv;
> > @@ -186,6 +183,12 @@ bool handle_hvm_io_completion(struct vcpu *v)
> > enum hvm_io_completion io_completion;
> > unsigned int id;
> >
> > + if ( has_vpci(d) && vpci_process_pending(v) )
> > + {
> > + raise_softirq(SCHEDULE_SOFTIRQ);
> > + return false;
> > + }
> > +
> > FOR_EACH_IOREQ_SERVER(d, id, s)
> > {
> > struct hvm_ioreq_vcpu *sv;
> > diff --git a/xen/drivers/vpci/header.c b/xen/drivers/vpci/header.c
> > index 39dffb21fb..c9bdc2ced3 100644
> > --- a/xen/drivers/vpci/header.c
> > +++ b/xen/drivers/vpci/header.c
> > @@ -184,6 +184,11 @@ static void defer_map(struct domain *d, struct
> pci_dev
> > *pdev,
> > curr->vpci.mem = mem;
> > curr->vpci.cmd = cmd;
> > curr->vpci.rom_only = rom_only;
> > + /*
> > + * Raise a scheduler softirq in order to prevent the guest from
> > resuming
> > + * execution with pending mapping operations.
> > + */
> > + raise_softirq(SCHEDULE_SOFTIRQ);
> > }
> >
> > static int modify_bars(const struct pci_dev *pdev, uint16_t cmd, bool
> > rom_only)
> > --
> > 2.19.1
>
>
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