Re: [PATCH v4 2/5] vpci: fix deferral of long operations

[Paul Durrant <Paul.Durrant@citrix.com>]

> -----Original Message-----
> From: Roger Pau Monne [mailto:roger.pau@citrix.com]
> Sent: 14 November 2018 11:58
> To: xen-devel@lists.xenproject.org
> Cc: Roger Pau Monne <roger.pau@citrix.com>; Paul Durrant
> <Paul.Durrant@citrix.com>; Jan Beulich <jbeulich@suse.com>; Andrew Cooper
> <Andrew.Cooper3@citrix.com>; Wei Liu <wei.liu2@citrix.com>; George Dunlap
> <George.Dunlap@citrix.com>; Ian Jackson <Ian.Jackson@citrix.com>; Julien
> Grall <julien.grall@arm.com>; Konrad Rzeszutek Wilk
> <konrad.wilk@oracle.com>; Stefano Stabellini <sstabellini@kernel.org>; Tim
> (Xen.org) <tim@xen.org>
> Subject: [PATCH v4 2/5] vpci: fix deferral of long operations
> 
> Current logic to handle long running operations has two flaws:
> 
>  - hvm_io_pending is only used by Intel code, fix this by moving the
>    call to vpci_process_pending into handle_hvm_io_completion.
>  - Raise a scheduler softirq when preemption is required. The
>    do_softirq calls in the SVM/VMX guest entry points will make sure
>    the guest vcpu is not restarted until all the pending work is
>    finished.
> 
> Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>

Reviewed-by: Paul Durrant <paul.durrant@citrix.com>

> ---
> Cc: Paul Durrant <paul.durrant@citrix.com>
> Cc: Jan Beulich <jbeulich@suse.com>
> Cc: Andrew Cooper <andrew.cooper3@citrix.com>
> Cc: Wei Liu <wei.liu2@citrix.com>
> Cc: George Dunlap <George.Dunlap@eu.citrix.com>
> Cc: Ian Jackson <ian.jackson@eu.citrix.com>
> Cc: Julien Grall <julien.grall@arm.com>
> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> Cc: Stefano Stabellini <sstabellini@kernel.org>
> Cc: Tim Deegan <tim@xen.org>
> ---
> Changes since v3:
>  - Don't use a tasklet.
> ---
>  xen/arch/x86/hvm/ioreq.c  | 6 +++---
>  xen/drivers/vpci/header.c | 4 ++++
>  2 files changed, 7 insertions(+), 3 deletions(-)
> 
> diff --git a/xen/arch/x86/hvm/ioreq.c b/xen/arch/x86/hvm/ioreq.c
> index e2e755a8a1..4c4b33e220 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 +183,9 @@ 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) )
> +        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 162d51f7e2..720dec07fa 100644
> --- a/xen/drivers/vpci/header.c
> +++ b/xen/drivers/vpci/header.c
> @@ -127,7 +127,10 @@ bool vpci_process_pending(struct vcpu *v)
>          int rc = rangeset_consume_ranges(v->vpci.mem, map_range, &data);
> 
>          if ( rc == -ERESTART )
> +        {
> +            raise_softirq(SCHEDULE_SOFTIRQ);
>              return true;
> +        }
> 
>          spin_lock(&v->vpci.pdev->vpci->lock);
>          /* Disable memory decoding unconditionally on failure. */
> @@ -182,6 +185,7 @@ 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_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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